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Open Access
Irrigation scheduling and water stress mitigation strategies in upland rice (Oryza sativa L.)
(Department of Agronomy, College of Agriculture, Vellayani, 2021) Gritta, Elizabeth Jolly; KAU; Sajitha Rani, T
The study entitled “Irrigation scheduling and water stress mitigation strategies in upland rice (Oryza sativa L.)” was carried out as two field experiments at the Instructional Farm, College of Agriculture, Vellayani from 2017 to 2020 to identify a suitable variety and irrigation method for upland rice, to standardize irrigation scheduling and to assess the effect of moisture stress mitigation strategies on the growth, yield and economics of upland rice. Experiment I entitled “Identification of suitable variety and standardization of irrigation method” was conducted from January 2019 to May 2019. The experiment was laid out in split plot design with five main plot treatments and two sub plot treatments, in four replications. The treatments included sprinkler irrigation at 100% PE, sprinkler irrigation at 75% PE, drip irrigation at 100% PE, drip irrigation at 75% PE and hose irrigation (farmer’s practice-irrigation given thrice in a week) as main plot treatments and rice varieties Uma and Prathyasa as sub-plot treatments. The height of the plant, number of tillers m -2 , leaf area index and dry matter production were observed to be significantly the highest for the variety Prathyasa irrigated using sprinkler irrigation at 100% PE and hose irrigation was significantly inferior to all other methods of irrigation. The variety Prathyasa irrigated using sprinkler irrigation at 100% PE also recorded the highest number of panicles m -2 (226.00), number of grains per panicle (159.75) and grain yield (4.37 Mg ha -1 ). The highest RLWC and consumptive use (434.25 mm) by the crop was observed in the variety Uma irrigated using sprinkler at 100% PE, followed by drip irrigated plots at 100% PE. The highest crop water use efficiency (1.53 kg m -3 ) was observed in the variety Prathyasa irrigated using hose method and the highest field water use efficiency (0.95 kg m -3 ) was observed in the variety Prathyasa irrigated using sprinkler at 100% PE. 282The economics of cultivation in terms of net returns ( ₹ 1,32,465.50 ha -1 ) and B:C ratio (2.67) were observed to be the highest in the variety Prathyasa irrigated using sprinkler irrigation plots at 100% PE, followed by the variety Prathyasa irrigated using drip irrigation at 100% PE. Field experiment II entitled “Standardization of irrigation scheduling and moisture stress mitigation strategies for upland rice” was conducted during January 2020 to April 2020. The experiment was laid out in split plot design with four main plot treatments and five sub plot treatments in five replications (the best treatment from the experiment I - sprinkler method of irrigation at 100% PE and the variety Prathyasa were used for the experiment II). The main plot treatments included approaches of scheduling irrigation: IW/CPE of 0.8, critical growth stage approach, irrigation to maintain soil moisture at 100% FC and irrigation to maintain soil moisture at 75% FC. The sub-plot treatments included field application of hydrogel polymer (20 kg ha -1 ), seed treatment with hydrogel polymer (10 g kg -1 ), hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10g kg -1 ), foliar application of PPFM (1%) and absolute control. The plant height, number of tillers m -2 , leaf area index and dry matter production were observed to be significantly higher in the plots irrigated at 100% FC, treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10 g kg -1 ), which was followed by the plots irrigated to maintain 2 cm depth of water at critical stages of crop growth. The number of days for 50% flowering, the number of panicles m -2 (233.20), length of panicle (20.36 cm), weight of panicle (3.07 g), number of grains panicle -1 (169.20), grain yield (5.00 Mg ha -1 ) and straw yield (8.07 Mg ha -1 ) were the highest in the plots irrigated at 100% FC and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10g kg -1 . . The consumptive use by the crop was significantly the highest in the plots irrigated at 100% FC (1265.60 mm) and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ).The crop water use efficiency recorded the highest value (0.69 kg m -3 ) in the plots irrigated at IW/CPE 283of 0.8 and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ) and a significantly higher field water use efficiency (0.58) was recorded in the plots irrigated at IW/CPE of 0.8 and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ) The highest B: C ratio (2.92) and net returns ( ₹ 1,58,000.00 ha -1 ) were obtained from the plots irrigated at 100% FC and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 . The results of the study revealed suitability of the variety Prathyasa, irrigated using sprinkler irrigation at 100% PE for higher yield and monetary returns under upland conditions. It also reflected the suitability of irrigating upland rice at 100 % FC as an effective approach of scheduling irrigation, along with the application of hydrogel polymer (field application @ 2.5kg ha -1 + seed treatment @ 10 g kg -1 ) as the most suitable moisture stress mitigation strategy for upland rice cultivation for enhanced yield and economic returns under water stress conditions.
Open Access
Productivity enhancement of blackgram (Vigna mungo (L.) Hepper) intercropped in coconut gardens
(Department of Agronomy, College of Agriculture,Vellayani, 2021) Pooja, A P; KAU; Ameena, M
The research work entitled ‘Productivity enhancement of blackgram (Vigna mungo (L.) Hepper) intercropped in coconut gardens’ was undertaken at College of Agriculture, Vellayani during 2018-2021. The study aimed to identify shade tolerant blackgram varieties suitable for coconut gardens, to study the effect of foliar nutrition and plant growth regulators on growth and yield of the shade tolerant blackgram varieties intercropped in coconut garden and to work out the economics of cultivation. The investigation was carried out as two experiments: (i) screening of blackgram varieties for shade tolerance, and (ii) performance evaluation of shade tolerant varieties under foliar application of nutrients and growth regulators in rainfed coconut garden. The first experiment was conducted during Rabi 2019-20 in coconut garden having a light intensity equivalent to 50 per cent of that under open condition (56.25 klux), planted at a spacing of 7.6 m x 7.6 m. Seeds of 12 promising blackgram varieties collected from different research stations of south India (Sumanjana, DU 1, DBGV 5, VBN 5, VBN 6, VBN 8, Rashmi, CO 6, TAU 1, TAU 2, Blackgold and AKU 15) and three cultures (Culture 4.5.8, Culture 4.5.18 and Culture 4.6.1), were raised in micro plots laid out in randomized block design with three replications. The crop was raised as per KAU package of practices. The results of the study revealed significant variation in growth characters among the varieties screened for shade tolerance under partial shade in coconut garden. Plants of DBGV 5 were significantly taller (96.89 cm) with higher initial number of leaves at all the stages and was on par with Sumanjana and CO 6. Higher leaf area index (LAI) and leaf area duration were recorded in CO 6 (5.77, 65.66 days) and DBGV 5 (5.36, 58.40 days) followed by Sumanjana. Early flowering was observed in Sumanjana (34.33 days) and DBGV 5 (36.33 days). The variety DBGV 5 had the highest photosynthetic rate and resulted in significantly more pods per plant (23.67) which was on par with CO 6, VBN 5, VBN 6, Sumanjana and Rashmi. DBGV 5 produced the highest seed yield per plant (5.44 g) followed by VBN 5 and Sumanjana. Haulm yield per plant was higher for DBGV 5 (19 g) and was on par with VBN 5, Sumanjana and CO 6. The variety DBGV 5 produced the highest seed yield (1183 kg ha-1 ) followed by VBN 5, Sumanjana and CO 6. A higher harvest index of 0.24 was recorded by Sumanjana which was on par with DBGV 5 and VBN 6. Among the varieties screened, five varieties which performed better in terms of yield per unit area under the partial shade in coconut garden viz., DBGV 5, VBN 5, Sumanjana, CO 6 and VBN 6 were selected for experiment II undertaken in summer 2020 followed by the confirmatory trial during Rabi 2020 -21. The experiment was laid out in split plot design with five varieties (v1 - Sumanjana, v2 - DBGV 5,v3 - VBN 5,v4 - VBN 6,v5 - CO 6) as main plot treatments and six foliar sprays of nutrients and plant growth regulators as subplot treatments (f1: 19:19:19 (1%) at 45 and 60 DAS, f2: SOP (0.5%) at 45 and 60 DAS, f3: NAA 40 mg L-1 and salicylic acid 100 mg L-1 at pre-flowering (30-45 DAS) and 15 days later, f4: f3 + f1, f5: f3 + f2 and f6: Control - KAU POP). Among the varieties, Sumanjana (v1) grew taller during both the seasons and was comparable with CO 6 and DBGV 5 at harvest. Sumanjana produced higher number of branches with more number of leaves during both the seasons. At flowering, higher LAI, number and dry weight of nodules per plant were realized by Sumanjana and was on par with CO 6 (v5) in summer and DBGV 5 (v2) in Rabi. Sumanjana exhibited the highest crop growth rate (CGR) and relative growth rate (RGR) during both the seasons at 45-60 DAS. However, DBGV 5 recorded the highest net assimilation rate (NAR) between 30-45 DAS and 45-60 DAS during both the seasons. The highest chlorophyll content was recorded by DBGV 5 (1.96 mg g-1 fresh tissue) during summer and by Sumanjana (2.36 mg g-1 fresh tissue) during Rabi. The highest stomatal conductance (30.22 m moles m-2 s -1 and 28.34 m moles m-2 s -1 ) and lower stomatal index (15.16% and 13.34%) were recorded in Sumanjana during both the seasons. The variety Sumanjana flowered earlier compared to other varieties during both the seasons and produced the highest number of pods per plant (27.30 and 26.54). Hundred seed weight was significantly higher for DBGV 5 (5.01 g and 4.92 g) and remained at par with Sumanjana (4.99 g and 4.88 g) during both the seasons. Seed yield, haulm yield and total dry matter production (TDMP) were higher for Sumanjana and comparable with DBGV 5 during both the seasons. Sumanjana recorded higher NPK uptake during both the seasons followed by DBGV 5. The subplot factor foliar spray had significant effect on growth, physiological and yield attributes of blackgram varieties. Foliar spray of 19:19:19 (1%) at 45 and 60 DAS + foliar spray of NAA 40 mg L-1 and SA 100 mg L-1 at pre-flowering and 15 days later (f4) resulted in significantly taller plants, more number of branches and leaves. The highest CGR, RGR (at 45-60 DAS), LAI, number and dry weight of nodules per plant at flowering were recorded in f4 during both the seasons. During summer, f3, f4 and f5 recorded higher NAR between 45-60 DAS. Higher chlorophyll content and stomatal conductance were recorded by f4 during both the seasons. Plants supplied with f3 attained 50 per cent flowering earlier and was on par with f5 during both the seasons. Highest number of pods per plant, 100 seed weight, seed yield, haulm yield and TDMP were recorded by f4 during both seasons. The grain protein content was improved by f4 and was on par with f3, f1 and f5. The NPK uptake was higher in f4 and was on par with f3 and f5 during summer. Significantly higher organic carbon, available N and P was recorded in f4. Among the treatment combinations, Sumanjana (v1) with f4 produced taller plants at two months after sowing (MAS), higher number of branches and leaves per plant during summer and Rabi. Leaf area index, number of nodules and dry weight of nodules at flowering were higher for v1f4 followed by v2f4. Sumanjana in combination with f4 measured significantly higher CGR and RGR (at active growth stages), highest chlorophyll content, stomatal conductance and lower stomatal index during both the seasons. The variety Sumanjana with f4 produced superior number of pods per plant (30.24 and 29.40) and hundred seed weight during summer and Rabi. A higher seed yield was realized in v1f4 (1750 kg ha-1 ) which was on par with v2f4 (1713 kg ha-1 ) during summer. Seed yield was the highest (1700 kg ha-1 ) in v1f4 during Rabi. Haulm yield and TDMP recorded were higher for v1f4 and was on par with v2f4 during both the seasons. The available N status in soil was higher during both the seasons in v1f4 with the highest NPK uptake during Rabi. Sumanjana and DBGV 5 with f4 realized higher mean net income (₹ 70411 ha-1 and ₹ 61256 ha-1 ) and mean B: C ratio (2.04 and 1.95). The present study identified DBGV 5 and Sumanjana as shade tolerant blackgram varieties with superior growth and yield attributes under partial shade and could be recommended for intercropping in coconut garden. Further, the yield of the shade tolerant varieties could be enhanced by recommended dose of nutrients as per KAU package supplemented with foliar spray of 19:19:19 (1%) at 45 and 60 DAS + foliar spray of NAA 40 mg L-1 and SA 100 mg L-1 at preflowering (35 DAS) and 15 days later. Sumanjana and DBGV 5 raised under partial shade in coconut garden with recommended dose of nutrients supplemented with the above said foliar spray realized higher mean net income and mean B: C ratio.
Open Access
Input optimization for short duration Red gram [Cajanus cajan (L.) Millsp.]
(Department of Agronomy, College of Agriculture,Vellayani, 2021) Anjana Devaraj, G; KAU; Sheeba, Rebecca Isaac
The study entitled “Input optimization for short duration red gram [Cajanus cajan (L.) Millsp.]” was conducted at College of Agriculture, Vellayani during 2017 - 2020 with the objectives, to assess the suitability of two short duration varieties of red gram, standardize the spacing and nutrient management practices for short duration red gram and to examine the legume effect on succeeding fodder maize crop. The investigation was done as three experiments (i) assessment of the suitability of two short duration varieties and standardization of spacing and nutrient levels (ii) assessment of legume effect on fodder maize and (iii) nutrient scheduling in red gram. The experiment I was laid out in randomized block design (RBD) with three replications during Rabi season (November to March) in 2018 - 2019 and the confirmatory experiment, during 2019 - 2020. The treatments included combinations of varieties [v1: APK 1; v2: Vamban (Rg) 3], spacings [s1: 40 cm x 20 cm; s2: 60 cm x 30 cm] and nutrient levels [ n1: 40:80:40, n2: 30:60:30; n3: 20:40:20 kg NPK ha-1 ]. Half nitrogen (N), potassium (K) and full phosphorus (P) were given basally, remaining as top dressing, 30 days after sowing (DAS). Farmyard manure (FYM) was applied uniformly @ 12. 5 t ha-1 . The varieties, spacings and nutrient levels had significant influence on the growth characters of red gram at the different stages of observation. Variety Vamban (Rg) 3 (v2) recorded significantly taller plants, higher number of branches and root parameters compared to APK1 (v1) during both the years of experimentation. The wider spacing, s2 (60 cm x 30 cm), the highest nutrient level, n1 (40:80:40 kg NPK ha-1 ) and the combination, v2s2n1 resulted in superior values for plant height, number of branches per plant, root volume and root dry weight, while narrow spacing (40 cm x 20 cm) recorded the highest number and weight of nodules per plant. The interactions also exerted significant influence on growth parameters with the interactions involving v2, s2 and n1 recording higher values. The variety APK 1 showed earliness in flowering with significantly higher average pod weight, 100 seed weight, seed yield (1.04 t ha-1 ) and haulm yield (3.70 t ha-1 ). Narrow spacing and the highest nutrient level recorded superior values for average pod weight, seed and haulm yields. The interactions also resulted in significant variations in yield attributes and yield. Pooled analysis of yield data of the two years registered the highest seed yield (1.38 t ha-1 ) in v1s1n1 (APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 ). Maximum dry matter production (DMP), crop growth rate (CGR) and seed protein content were recorded in APK 1 and at the highest nutrient level. Among the spacings tried, wider spacing resulted in the highest DMP and seed protein, while CGR was higher in the narrow spacing. The partial factor productivity (PFP) for N, P and K were superior in the combination v1s1n1 in both years. Individual effects of the variety APK 1, narrow spacing and the highest nutrient level recorded maximum nutrient uptake and in the combinations of APK 1 or Vamban (Rg) 3 with 40 cm x 20 cm and 40:80:40 kg NPK ha-1 . Available soil N and microbial counts assessed after the experiment were the highest after APK 1. Wider spacing and the highest NPK level recorded maximum soil available nutrient status, while microbial counts, at narrow spacing. Soil nutrient balance sheet computed for N was positive during both years. The balance sheet for P was positive for all the treatment combinations involving wider spacing during the first year. During the second year, all treatments showed positive balance for P except v1s1n1, v1s1n2, v1s2n2 and v2s2n3. Nutrient balance for K was positive in treatments v1s1n1, v1s2n1 and v2s1n1 during the both years. Pooled mean of the economics of cultivation during the two years revealed maximum net returns per hectare (₹ 88621/-) and B:C ratio (2.03) in v1s1n1 (APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 ). The legume effect of red gram on fodder maize was assessed during Kharif season, June to August 2019. Crop residues (root + shoot + fallen leaves) of red gram were incorporated in situ and allowed to decompose for two months. The maximum quantity of residues (4.83 tha-1 ) was generated in the treatment combination T7, Vamban (Rg) 3 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 imposed in red gram, which was on par with T1, the combination, APK 1 + 40 cm x 20 cm + 40:80:40 kg NPK ha-1 (4.75 tha-1 ). There were no marked variations in the biochemical characters of residues, while C: N ratio was significantly narrower in T1 (18.2: 1) and T7 (18.9:1). Residue incorporation improved the soil chemical properties and at 60 days after residue incorporation (DAI), maximum soil pH and C pool (total organic carbon and labile carbon) were estimated in treatment T7, and recalcitrant organic carbon, in T1. Soil available N, P status and dehydrogenase activity were higher in T1, and available K, in T7 at 60DAI. Fodder maize seeds (variety, African tall) were sown during the third week of June in the residue incorporated plots. Green and dry fodder yields (33.61 and 11.37 t ha-1 respectively) were the highest in the treatment T7 which was on par with T1 (32.85 and 11.08 t ha-1 respectively). Soil available NPK status were found to decline from the initial status with fodder maize cultivation. The nutrient scheduling experiment was conducted during Rabi season, 2019 - 2020, in RBD with nine treatments and three replications. The variety APK 1, spacing 40 cm x 20 cm and nutrient level 40:80:40 kg NPK ha-1 found superior in Experiment I were adopted. The integrated nutrient management (INM) practices evaluated were T1: 100 % NPK as chemical fertilizers, T2: 100 % N + 50 % P + 100 % K + P solubiliser, T3: 100 % N + 100 % P + 50 % K + K solubiliser, T4: 100 % N + 50 % P + 50 % K + P solubiliser + K solubiliser, T5: T1 (50 % N foliar), T6: T2 (50 % N foliar), T7 : T3 (50 % N foliar), T8 : T4 (50 % N foliar) and T9 : Absolute control: No fertilizers. The entire dose of N was given as soil application in T1 to T4 and foliar spray of 50 per cent N in T5 to T8 with urea (2 %) at 30 and 45 DAS. Phosphorus and K solubilisers (Bacillus megaterium and Bacillus sporothermodurans respectively) were mixed with powdered FYM in the ratio 1: 50 separately, and 10 g of each mixture was added in soil one week after basal fertilizer application. The INM practice of 100 per cent N + 50 per cent P + 50 per cent K along with P and K solubilisers (T4) recorded significantly taller plants (109.70 cm), maximum number of branches (6.5) at harvest, whereas weight of nodules per plant at flowering (0.59 g) and root parameters were significantly the highest in treatment T8. Average pod weight (0.62 g) and seed yield (1.48 t ha-1 ) were superior in T4 and on par with the combination involving foliar nutrition, T8 (1.46 t ha-1 ). Integration of P and K solubilisers with chemical fertilizers (100 % N and 50 % P and K), registered 50 per cent higher yield than the absolute control. Among the agronomic indices, DMP at 100 DAS (34.18 g plant-1 ), CGR at 80 - 100 DAS (3.44 g m-2 day-1 ) were the highest in T4, and RGR, in T2 followed by T4. Substitution of 50 per cent Pand K with biofertilizers recorded maximum uptake of N, P and K and physiological efficiencies for the nutrients. Computation of nutrient balances with the INM practices adopted revealed the highest positive balance for N in T8, P in T4 and for K in T7. Economic analysis showed the treatment T to record the highest net return per hectare (₹ 94722 /-) and B: C ratio (2.05). Based on the results it could be concluded that the short duration red gram varieties, APK 1 and Vamban (Rg) 3 are suitable for cultivation in the southern laterites of Kerala. The variety APK 1 was superior in terms of yield and profit and can be recommended for planting at a spacing of 40 cm x 20 cm and an NPK dose of 40:80:40 kg ha-1 based on the soil test results. Evaluation of the legume effect of red gram revealed significant increases in soil fertility status with residue incorporation. Among the treatments imposed in red gram, irrespective of the variety, the residual effect realized with red gram planted at 40 cm x 20 cm spacing and fertilized with 40:80:40 kg NPK ha-1 was found to be superior in terms of fodder yield in the succeeding crop of maize. The integrated nutrient management practice that proved profitable in APK 1 involved application of 40:40:20 kg NPK ha-1 as chemical fertilizers along with P and K solubilisers, the entire dose in soil.
Open Access
Bio-efficacy of tank mixed herbicides and urea in wet seeded rice
(Department of Agronomy, College of Agriculture, Vellanikkara, 2021) Thumu, Venkateswara Reddy; KAU; Meera, V Menon
The use of herbicides has become an indispensable part of agriculture, particularly in rice cultivation, where weeds are the most harmful of the biotic constraints to production. A usual practice among rice farmers in the Kole lands of Kerala is the tank mixing of herbicides, for a broader spectrum of weed control, enhanced weed control efficiency and reduction in the cost of application. However, mixing of herbicides is done without any knowledge of the probable synergistic or antagonistic interactions on weed flora. Herbicides are also mixed with fertilizers like urea under the common belief that herbicidal efficiency is enhanced by this practice. Application of herbicides may affect various plant pathogens and microbial bioagents which occur naturally in the rice ecosystem. Information of the effect on main disease causing as well as beneficial microorganisms would help in selecting appropriate herbicides. Hence the major objectives of the research programme entitled “Bio-efficacy of tank mixed herbicides and urea in wet seeded rice” were to study the synergistic or antagonistic effect of tank mixing of commonly used herbicides, and to evaluate the efficiency of these herbicides on mixing with urea, on major weeds of rice. The effect of these herbicides on beneficial and pathogenic microorganisms were also investigated. Two field experiments were conducted at Alappad padasekharam in the Kole lands of Thrissur from October to January 2019-20 and 2020-21. The soil of experimental field was clayey in texture, high in organic carbon (1.1-1.3%), low available nitrogen (180-188 kg/ha), and medium phosphorus (20-21.5 kg/ha) and potash (152-159 kg/ha), with a soil pH of 4.5-4.7. The feasibility of mixing herbicides was evaluated in experiment I (Bio-efficacy of tank mixed herbicide combinations in wet seeded rice). There were fourteen treatments and they included tank mixtures and sequential applications of five herbicides viz., fenoxaprop-p-ethyl (0.06 kg/ha), (chlorimuron-ethyl + metsulfuron-ethyl) (0.004 kg/ha), carfentrazone ethyl (0.02 ii kg/ha), bispyribac-sodium (0.025 kg/ha), and (cyhalofop-butyl + penoxsulam) (0.15 kg/ha). These were compared with two broad spectrum herbicides, bispyribac-sodium (0.025 kg/ha) and (cyhalofop-butyl + penoxsulam) (0.15 kg/ha), as well hand weeded and unweeded controls. In experiment II (Bio-efficacy of tank mixed herbicides and urea in wet seeded rice), there were twelve treatments. Six herbicides, viz., cyhalofop butyl (0.08 kg/ha), (cyhalofop butyl + penoxsulam) (0.15 kg/ha), bispyribac-sodium (0.025 kg/ha), fenoxaprop-p-ethyl (0.06 kg/ha), carfentrazone ethyl (0.02 kg/ha) and (chlorimuron ethyl + metsulfuron methyl) (0.004 kg/ha) were applied with and without urea (1%) mixing. Hand weeded and unweeded controls were also included for comparison. Randomized Block Design with three replications was adopted for both experiments. Wet seeding of rice at the seed rate of 100 kg/ha was done. Nitrogen, phosphorus and potassium @ 90:35:45 kg/ha were supplied through urea, factomphos and muriate of potash (KAU, 2016). In experiment III (In vitro evaluation of herbicides on beneficial and pathogenic microorganisms) treatments included the effect of herbicides mentioned in experiment II which were evaluated under in vitro conditions with recommended, higher and lower doses on beneficial microbial bioagents (Trichoderma viride and Pseudomonas fluorescens) and pathogenic microorganisms (Rhizoctonia solani, Pyricularia oryzae and Xanthomonas oryzae pv. oryzae). Factorial Completely Randomized Block Design was adopted with 18 treatments and three replications each. Tank mixing of herbicides was found to be more effective than their sequential application for most of the combinations. Tank mixed combination of (cyhalofopbutyl + penoxsulam) with (chlorimuron-ethyl + metsulfuron-methyl) showed synergistic effect and had lowest weed density (32, 16 and 20 nos./m2 ), lowest weed dry matter production (14.68, 50.50 and 88.95 kg/ha), and highest weed control efficiency (91, 88, and 82%) at 15, 30 and 60 days after application respectively. The number of tillers per sq. m (411), number of panicles per sq. m (288), number of grains per panicle (103), percentage of filled grain (91.6) at harvest, nutrient uptake by rice at 60 DAS (105.06, 14.32 and 74.28 kg/ha of N, P and K respectively), grain iii yield (3.97 t/ha), net returns (Rs.71,406/ha) and benefit: cost ratio (2.25) were highest in the same treatment. The next best treatment was fenoxaprop-p-ethyl + bispyribac sodium. On tank mixing of herbicides with urea, bispyribac-sodium and urea interacted synergistically, resulting in highest weed control efficiency (82.5 and 78% at 15 and 30 days after application respectively), highest grain yield (5.03 t/ha), and profitability (Rs. 93,509/ha) over the other treatments. Mixing of (cyhalofop-butyl + penoxsulam) with urea could also be recommended for good results (grain yield of 4.94 t/ha and net returns of Rs.87,463/ha). In vitro evaluation of herbicides revealed that bispyribac-sodium and (cyhalofop-butyl + penoxsulam) had greatest inhibitory effect on pathogenic microorganisms Rhizoctonia solani and Pyricularia oryzae, but showed no effect on Xanthomonas oryzae pv. oryzae, and were less harmful to biocontrol agents Trichoderma viride and Pseudomonas fluorescens at recommended doses. Tank mix combination of (cyhalofop-butyl + penoxsulam) with (chlorimuronethyl + metsulfuron-methyl) was the best treatment with compatibility, efficient weed control, high grain yield and net returns. Tank mixing of bispyribac-sodium with urea 1% had synergistic effect resulting in highest weed control efficiency, production and profitability over the other treatments. Mixing of (cyhalofop-butyl + penoxsulam) with urea 1% could also be recommended for good results. Bispyribac-sodium and (cyhalofop-butyl + penoxsulam) were the best herbicides on in vitro evaluation in their effect on pathogenic microorganisms Rhizoctonia solani and Pyricularia oryzae, and at recommended doses were compatible with biocontrol agents Trichoderma viride and Pseudomonas flourescens.
Open Access
Resource management for source- sink modulation in chinese potato[Plectranthus rotundifolius (Poir.) Spreng.]
(Department of Agronomy, College of Agriculture Vellayani, 2021) Arunjith, P; KAU; Sheeba, Rebecca Isaac
The research work entitled ‘Resource management for source-sink modulation in Chinese potato [Plectranthus rotundifolius (Poir.) Spreng.]’ was undertaken at College of Agriculture, Vellayani during 2018 – 2021. The main objectives were to study the influence of planting methods, nutrient management practices and growth promoters on source-sink relationship, tuber yield and quality in Chinese potato, to assess the growth and yield responses of the crop to carbon dioxide (CO2) fertilization and to work out the economics. The investigation was carried out as two experiments: i) influence of planting methods, nutrient management practices and growth promoters on source - sink relationship, tuber yield and quality and ii) influence of CO2 fertilization on growth and yield responses in Chinese potato. The photo insensitive variety Suphala, released by Kerala Agricultural University (KAU), was used for the study. Experiment I was conducted during October 2019- February 2020 and repeated during 2020-2021 for confirmation. It was laid out in split plot design with five methods of planting as main plots and six combinations of two nutrient management practices and three growth promoters as sub plot treatments, in four replications. The methods of planting included were m1: bed method (30 cm x 15 cm), m2: bed method (30 cm x 30 cm), m3: ridge method (30 cm x 15 cm), m4: ridge method (30 cm x 30 cm) and m5: mound method (30 cm x 30 cm). The combinations comprised nutrient management practices (n1: 60:30:120 kg NPK ha-1 + PGPR Mix 1, n2: 60:30:120 kg NPK ha-1) and growth promoters (g1: humic acid @ 5 g L-1, g2: benzyl adenine @ 50 mg L-1 and g3: water spray). PGPR Mix 1 (2 %) was applied @ 5 g per plant, thrice, at the time of planting, 30 DAP and 60 DAP in n1 and growth promoters were sprayed 45 and 75 DAP. Other cultural operations were done as per package of practices of KAU. Bed method of planting at 30 cm x 15 cm (m1) produced significantly taller plants with higher leaf area index (LAI), dry matter production (DMP) and crop growth rate (CGR) in both the years. Planting at the wider spacing (30 cm x 30 cm) on beds (m2) or ridges (m4) resulted in higher and comparable values for number of branches and plant spread (N-S and E-W), while m2 showed superiority in the number of leaves and leaf area per plant at 45 and 90 DAP. The wider spacing, irrespective of the method of planting, revealed markedly higher relative growth rate (RGR) during 45-90 DAP and the trend remained similar in both years. Significantly higher net assimilation rate (NAR) between 45-90 and 90-135 DAP, and chlorophyll content were noted in m2. Higher chlorophyll content in m2 was on par with m4 during second year. Per plant tuber attributes (number of tubers, tuber yield, marketable tuber yield and average tuber weight) were found superior in bed planting at 30 cm x 30 cm. But, average tuber weight was comparable with m4 in the first year and with m4 and m5 in the second year. Per hectare tuber yields were significantly the highest in the bed method of planting at 30 cm x 15 cm spacing, during both the years with a pooled mean of 20.93 t ha-1. The treatment also showed the maximum uptake of N, P and K. Soil available N, P and K status were the highest in mound method at 30 cm x 30 cm (m5) and on par with m4 and m2. Bacterial, fungal and actinomycete population and dehydrogenase activity were higher in the bed/ridge method of planting at 30 cm x 15 cm spacing (m1 and m3). The combination of 60:30:120 kg NPK ha-1 + PGPR Mix 1 + humic acid (n1g1) resulted in significantly higher growth attributes (plant height, number of branches and plant spread) while at 135 DAP, n1g2 recorded the maximum number of leaves, leaf area per plant, LAI and delayed senescence in both the years. Physiological parameters (DMP, CGR, RGR, NAR) yield attributes, per hectare tuber yield, marketable tuber yield, percentage marketable tuber yield, N, P, K uptake, starch and protein content were superior in n1g1. The tuber yield and marketable tuber yield (pooled) were 21.10 and 18.34 t ha-1 respectively. Soil available N, P, K status, microbial count and dehydrogenase activity were markedly higher in treatments involving PGPR Mix 1 (n1) compared to that without PGPR Mix 1, nevertheless, remained comparable among n1g1, n1g2 and n1g3. Land configuration (bed/ridge) with planting at wider spacing and inclusion of PGPR and humic acid proved superior with respect to the number of branches, leaves per plant and leaf area. Leaf area index was significantly the highest in m3n1g1 in the first year and m1n1g1 in the second year at 90 DAP. The combination m4n1g1, produced the maximum number of tubers per plant (23.8) in the first year on par with m2n1g1 (23.6), whereas during the second year it was the highest (25.0) in m2n1g1. Maximum per plant tuber yield (189.48 and 198.95 g), marketable tuber yield (170.37 and 179.45 g) and percentage of marketable tubers (73.06 and 70.67) were noted in m2n1g1 during both years. The treatment combination m1n1g1 recorded the highest DMP and per hectare tuber yield with a pooled mean of 23.38 t ha-1. The percentage of marketable tuber yields increased by nearly 10 per cent over m1n2g3 in the two years. Potassium uptake was the highest in m1n1g1 and remained comparable with m1n1g2 in the second year. Irrespective of growth promoters applied, inclusion of PGPR Mix 1 (n1) resulted in higher soil available P and K status in the widely spaced planting and the maximum dehydrogenase activity and microbial counts were enumerated in the closely spaced planting on beds (m1). Bed method of planting at 30 cm x 15 cm spacing along with application of 60:30:120 kg NPK ha-1 + PGPR Mix 1 + humic acid (m1n1g1) was the most profitable resource management practice, pooled mean of economics of cultivation revealed maximum net returns and BCR of ₹ 651296 ha-1 and 3.83 respectively. The CO2 fertilization study was conducted in trenches (2 m x 1 m x 1 m) in completely randomized design with six treatments (substrates for CO2 evolution) replicated thrice, during November 2019- July 2020 and October 2020- March 2021. The treatments included, s0: no substrate, s1: cow dung, s2: coir pith, s3: cow dung + coir pith (2:1), s4: s2 + Pleurotus 1g kg-1 + N + P (2% w/w) and s5: s3 + Pleurotus 1g kg-1 + N + P (2% w/w). Cuttings of Chinese potato were planted directly in soil in the first year and in grow bags during the second year. Organic substrates (as per treatment) were spread at the trench base to a thickness of 5 cm, taking precautions to avoid direct contact of the substrates with the cuttings planted directly in soil. The trenches were kept covered with a dome prepared of 200 μ uv stabilised polythene sheet fixed on a metal frame, daily from 4.00 pm to 10.30 am. In all the substrate applied treatments, maximum release of CO2 (501 to 858 ppm) occurred during the first two weeks of application and thereafter it declined. The highest peak of CO2 concentration (858 ppm) at two weeks of application was observed in s5 followed by s3, (752 ppm). Relatively higher air and soil temperatures were observed in trenches during both the years of study. Significantly higher growth attributes at 30 DAP were observed in plants grown in the trench filled with cow dung and coir pith in 2:1 ratio (s3) comparable with treatments containing cow dung and additives (s5). The superiority of s5 on growth attributes were evident at the later stages of growth. Chlorophyll contents (1.147 and 1.193 mg g-1) were maximum in s3 applied trenches at 45 DAP, whereas s5 recorded superior values at 90 DAP (1.153 and 1.193 mg g-1). Initiation of senescence was significantly earlier in CO2 fertilized plants and the highest biomass per plant was recorded in s5. Nevertheless, despite an increased above ground biomass with elevated CO2, tuber development was not observed in any of the treatments. Based on the results of the experiments, it could be concluded that bed/ ridge method of land preparation with planting at 30 cm x 30 cm spacing in combination with an NPK dose of 60:30:120 kg ha-1 + PGPR Mix 1 + humic acid significantly improved the growth parameters (source) and yield attributes (sink) in Chinese potato. A closer planting (30 cm x 15 cm) on beds and application of 60:30:120 kg NPK ha-1 through chemical fertilizers, PGPR Mix 1 (2 %) @ 5 g per plant thrice, as basal, 30 and 60 DAP along with foliar sprays of humic acid @ 5 g L-1 (45 and 75 DAP) can be recommended for superior marketable tuber yields, higher net returns and B: C ratio. The results of the CO2 fertilization study indicated that elevated CO2 enhanced the vegetative growth in Chinese potato at the expense of tuber development.
Open Access
Germination ecology and management of chinese sprangletop [Leptochloa chinensis (L.) Nees.] in wet seeded rice
(Department of Agronomy, College of Agriculture, Vellayani, 2021) Lekshmi, Sekhar; KAU; Ameena, M
An investigation entitled ‘Germination ecology and management of Chinese sprangletop [Leptochloa chinensis (L.) Nees.] in wet seeded rice’ was undertaken at the College of Agriculture, Vellayani during 2017-2020. The objectives were to study the habitat, germination ecology and distribution of Leptochloa chinensis in major rice growing tracts of Kerala; to test the efficacy of tank mix combinations of herbicides for the management of the weed; to test the sensitivity of the weed to herbicide combinations and to assess the mode of action of the herbicide combinations. The phytosociological survey was conducted to document the habitat, composition and distribution of L. chinensis in different rice tracts of Kerala viz., Palakkad, Kole and Kuttanad after selecting three severely infested padasekharams in each tract during 2018 and 2019. L. chinensis was found to occur in all the major rice growing tracts of Kerala and registered summed dominance ratio of 13.05, 12.40 and 17.49, respectively in Kuttanad, Kole and Palakkad (Kharif). Appraisal of weed vegetation analysis indices displayed the highest weed species richness (17) and Simpson’s diversity index in Kole and the lowest Shannon Wiener diversity index (2.09) in Palakkad. L. chinensis was the dominant weed in all these tracts with an abundance of 17.33, 17.0 and 16.36, respectively and the weed inhabited both upland and lowland situations, either in crop lands, field bunds, stream banks or waterways. Profuse growth of the weed was observed along the inner bunds separating individual fields. The weed was a prolific seed producer with seed production potential ranging from 7400-33,941 seeds per plant across the surveyed locations. Germination ecology experiments encompassed studies on weed phenology and germination of Chinese sprangletop. L. chinensis is an erect or creeping, annual or perennial grass that can grow upto a height of 120-150 cm, propagates both by seed and slips with very minute seeds (thousand seed weight of 0.10-0.18 g). The weed was noticed to develop through five phenological stages, viz., emergence, tillering, heading, flowering and maturity with an average duration of 10.6, 41.5, 73.5, 78.5 and 95 days, respectively. Investigations on germination ecology revealed that light was not an absolute requirement for germination of seeds of L. chinensis, but stimulated germination by 23 per cent. When exposed to alternating temperatures in light/dark, seeds germinated at 15°C to 35°C. The highest germination occurred at 25/15°C (87.2%), while at 35/25°C it was only 70.31 per cent. Germination of L. chinensis was significantly influenced by moisture regime; with zero germination under continuous flooding or with thin layer of water (3 cm) and 70 per cent germination on irrigating at alternate days. Seedling emergence was also significantly affected by seed burial depth. Seedling emergence was high (85%) for seeds placed on the soil surface, while no emergence was observed at burial depths of 2 cm or beyond. Slips placed at the surface recorded 100 per cent sprouting and the time taken for 50 per cent emergence increased with increase in burial depth. The seeds germinated upto nine months after harvest with the germination declining over time. The field experiments on management of L. chinensis were conducted during 2018 and 2019 Kharif at Integrated Farming System Research Station, Karamana. The experiment was laid out in randomized block design with 10 treatments and three replications. The treatments included T1: cyhalofop butyl @ 0.08 kg ha-1 , T2: penoxsulam + cyhalofop butyl (6% OD) @ 0.15 kg ha-1 , T3: cyhalofop butyl + carfentrazone ethyl @ 0.08 + 0.02 kg ha-1 , T4: bispyribac sodium @ 0.025 kg ha-1 , T5: bispyribac sodium + cyhalofop butyl @ 0.025 + 0.08 kg ha-1 , T6: bispyribac sodium + fenoxaprop-p-ethyl @ 0.025 + 0.06 kg ha-1 , T7: fenoxaprop-p-ethyl @ 0.06 kg ha-1 , T8: stale seedbed followed by (fb) glyphosate + oxyfluorfen @ 0.8 + 0.15 kg ha-1 at 15-20 days after land preparation fb cyhalofop butyl + carfentrazone ethyl @ 0.08 + 0.02 kg ha-1 , T9: unweeded control and T10: hand weeding twice at 20 and 45 days after sowing (DAS). The weed management practices had significant influence on L. chinensis count, dry matter production, control efficiency and nutrient removal at different stages of observation. Count of L. chinensis was zero in T6, T7, T8 and T10 at 15 days after treatment application (DATA) during both the years. The lowest count and dry matter production and the highest pooled control efficiency of L. chinensis (97.55 and 96.78 per cent, respectively at 30 and 45 DATA) was registered in T7. It was statistically on par with all other treatments except T4 and T9. Bispyribac sodium was not effective in controlling L. chinensis and resulted in lower control efficiency of 52.63, 38.68 and 42.43 per cent, respectively at 15, 30 and 45 DATA. However, its combination with fenoxaprop-p-ethyl (T6) or cyhalofop butyl (T5) resulted in higher control efficiency of L. chinensis at all stages of observation and recorded 100, 96.06 and 95.96 and 97.23, 92.37 and 94.55 per cent, respectively at 15, 30 and 45 DATA. Among the herbicide treatments, T6 registered the least total weed dry matter production at all stages and resulted in the highest pooled weed control efficiency of 98.20 and 89.70 per cent which was on par with T2 (96.61 and 83.86%) and T5 (95.40 and 84.81%) respectively at 30 and 45 DATA. The highest pooled grain yield (5.03 t ha-1 ) also was registered in T6 which was on par with T2 and T5 with 4.79 and 4.76 t ha-1 . Pooled data revealed that season long weed competition in wet seeded rice (WSR) with L. chinensis as a major weed caused a yield reduction of 59.95 per cent. Compared to the unweeded control, herbicidal treatments enhanced grain yield by 23.89-58.84 per cent, whereas herbicide combinations increased grain yield by 56-59 per cent in WSR. Pooled mean of the economics of cultivation registered maximum net returns per hectare (₹ 63,657 ha-1 ) and B:C ratio (1.81) in T6 followed by T2 (₹ 56,995 ha-1 and 1.73) and T5 (₹ 56,044 ha-1 and 1.72). The sensitivity of L. chinensis to herbicide combinations was tested at the field recommended dose and its lower doses using whole plant bioassay technique after identifying best combinations viz., bispyribac sodium + fenoxaprop-p-ethyl @ 0.025 + 0.06 kg ha-1 , bispyribac sodium + cyhalofop butyl @ 0.025 + 0.08 kg ha-1 , penoxsulam + cyhalofop butyl @ 0.15 kg ha-1 and cyhalofop butyl + carfentrazone ethyl @ 0.08 + 0.02 kg ha-1 . The experiment was laid out in completely randomized design (CRD) with eight treatments and three replications. Lower dose of bispyribac sodium + fenoxaprop-p-ethyl @ 0.020 + 0.04 kg ha-1 recorded the least survival (0%) of L. chinensis whereas, bispyribac sodium + cyhalofop butyl @ 0.020 + 0.06 kg ha-1 , cyhalofop butyl + carfentrazone ethyl @ 0.06 + 0.01 kg ha-1 and penoxsulam + cyhalofop butyl @ 0.10 kg ha-1 registered 26.66, 30.0 and 86.66 per cent survival, respectively. The experiment on mode of action of tank mix herbicide combination was laid out in CRD with four treatments and five replications. The treatments included T1: ALS inhibitor alone (bispyribac sodium @ 0.025 kg ha-1 ), T2: ACCase inhibitor alone (fenoxaprop-p-ethyl @ 0.06 kg ha-1 ), T3: ALS + ACCase inhibitor (bispyribac sodium @ 0.025 kg ha-1 + fenoxaprop-p-ethyl @ 0.06 kg ha-1 ) and T4: Control. Treatment T3 recorded lower amino acid content (0.1775 mg mL-1 ) than T1 (0.2904 mg mL-1 ) confirming that the combined application of an ALS + ACCase inhibitor could provide better control of L. chinensis compared to sole application of ALS inhibitor. The experiment on assessing the differential response of L. chinensis and Echinochloa colona to the broad-spectrum herbicide bispyribac sodium, revealed that amino acid content of L. chinensis was not influenced by the increasing concentration of bispyribac sodium. High content of amino acid was registered in L. chinensis (0.2904 and 0.3234 mg mL-1 ) compared to E. colona irrespective of the concentration of bispyribac sodium. However, in E. colona, the amino acid content (0.1520 and 0.0627 mg mL-1 ) was found to decrease with increasing concentration of bispyribac sodium. The present study identified L. chinensis as a major weed in all the major rice growing tracts of Kerala indicating its invasive potential under diverse environmental conditions owing to its prolific seed production, sprouting from weed slips on soil surface, extended period of seed viability and different mode of propagation. The results revealed that early and continuous flooding, deep tillage for burial of seeds and slips into the soil beyond 5 cm could suppress its emergence. The study identified fenoxaprop-p-ethyl @ 0.06 kg ha-1 as the most effective herbicide against L. chinensis to be sprayed at 15-18 DAS in WSR. In areas where L. chinensis is a dominant weed in the WSR, tank mix application of bispyribac sodium @ 0.025 kg ha-1 + fenoxapropp-ethyl @ 0.06 kg ha-1 at 15-18 DAS could be recommended for broad spectrum weed management. Whole plant bioassay of the above combination proved effective at its still lower dose and the differential response of L. chinensis to bispyribac sodium indicated herbicide combinations for managing the complex spectrum of weeds in wet seeded rice.
Open Access
Conservation agriculture practices for upland rice based cropping system
(Department of Agronomy, College of Agriculture, Vellanikkara, 2021) Durga, C; KAU; Anitha, S
Conservation agriculture (CA) is an approach to manage agro-ecosystems for improved and sustained productivity, increased profits and food security while preserving and enhancing the resource base, which emphasize minimum soil disturbance, permanent soil cover and diversified crop rotation. In India and Kerala, there is dearth of information on resource-conserving techniques, for productivity, profitability and soil health. Hence the present study entitled “Conservation agriculture practices for upland rice based cropping system” was carried out at Agronomy Farm, College of Agriculture, Vellanikkara from May 2019 to March 2021 to develop a conservation agricultural practices for upland rice-okra-green manure cropping system. Rice–okra-green manure cropping system with conservation practices were compared with rice–okra-green manure cropping system without conservation practices. The experiment was laid out in RBD with 10 treatments replicated thrice and was repeated for two years keeping the same layout. The treatments consisted of Direct seeding rice (DSR) in flat bed (FB) + brown manuring (BM)- okra+ green manuring (GM)-cowpea, DSR in FB+ BM- okra + crop residue mulch (CRM)- cowpea, DSR in FB+ GM- okra + GM-cowpea, DSR in FB+ GM- okra + CRMcowpea, DSR in raised bed(RB) + BM- okra + GM-cowpea, DSR in RB+ BM-okra+ CRM-cowpea, DSR in RB+ GM- okra + GM-cowpea, DSR in RB+ GM- okra+ CRMcowpea, DSR in FB – okra-fallow, DSR in RB- okra-fallow. Conservation treatments had significant influence on growth, yield parameters and yield of rice. Growth and yield attributes were highest in direct seeding rice in flat bed + green manuring which had an yield increment of 49 % compared to control ie., direct seeding rice in flat bed without any conservation agriculture practice. Raising rice crop in raised bed without cowpea intercropping also resulted in 23 % higher rice yield compared to rice grown alone in flat bed. Conservation treatments had significant influence on weed suppression. Growing of cowpea as an intercrop in rice and its incorporation at 25 DAS either by cutting it and spreading as mulch (green manuring) or decomposing it using 2-4-D application (brown manuring) either in flat bed and raised bed resulted in 58-73% reduction of weeds in upland situation. Physiological parameters like leaf area index, crop growth rate, relative growth rate and net assimilation rate were found higher in direct seeding rice in flat bed+green manuring. Significantly higher values of nutrient uptake, resource use efficiencies such as water use efficiency, partial factor productivity of NPK, net returns and B:C ratio in direct seeding rice in flat bed + green manuring proved the superiority of this conservation practice in rice over conventional DSR-okra-cowpea. Okra crop was raised in sequence with rice in the same field keeping the layout undisturbed. Field was made weed free before sowing with minimum soil disturbance using brush cutter after harvest of rice. Conservation agriculture practices applied to both rice and okra had significant influence in the growth and yield performance of okra. From the results it was observed that growth and yield parameters were higher when okra was raised on flat bed with the application of previous crops residue as mulch. DSR in FB+GM–okra+ CRM recorded the highest okra yield of 16.47 t/ha with 71-83 % reduction in weeds compared to control ie DSR in flat bed - okra. Physiological parameters like leaf area index, crop growth rate, relative growth rate and net assimilation rate were found higher in conservation treatments compared to non-conservation treatments. The highest NPK uptake, resource use efficiencies such as water use efficiency, partial factor productivity of NPK and high B:C ratio were recorded in DSR in FB +GM –okra + CRM. Cowpea was raised after okra by keeping the same layout in all conservation treatments and the field was kept as fallow in non-conservation agriculture treatments. The highest biomass yield of 1920.22 kg/ha was recorded in DSR in FB +GM –okra + CRM -cowpea at 45 DAS. While assessing the whole cropping system, conservation treatments recorded 72.60 % land use efficiency and 300 % multiple cropping index but whereas non conservation treatments recorded 60.27 % land use efficiency and 200 % multiple cropping index. Among the different conservation agriculture practices applied to rice –okra-green manure cropping system, DSR in FB +GM –okra + CRM –cowpea recorded the highest cropping system resource use efficiency, net profit and and a B:C ratio. Soil physical, chemical and biological properties were improved due to the effect of conservation treatments over non conservation treatments. Water holding capacity was increased by 31.96 %, porosity by 16.66 % and the soil moisture by 39.83 % in DSR in FB +GM–okra + CRM–cowpea over the non conservation method.The highest soil carbon stock and sequestration at 0-15 and 15-30 cm soil depth were recorded in DSR in FB +GM –okra + CRM–cowpea. At 45 cm only a meagre storage was recorded in DSR in FB +BM –okra + CRM –cowpea. The treatments without conservation agriculture practices ie DSR in FB–okra-fallow showed a negative value for sequestration. It indicates the loss of carbon in conventional method. A slow increase in sequestration after each crops clearly indicated that conservation agriculture practices for a long run will sequester the carbon to entire soil profile. The result of the present two years study indicated that in a rice-okra-green manure cropping system in upland, direct seeding rice in flat bed with green manuring followed by okra with crop residue mulch of previous crop followed by cowpea as green manure can be recommended as a cost effective and sustainable conservation agriculture practice as it resulted in higher system yield, better weed control, sustained the soil health and higher B:C ratio.
Open Access
Nutrients and tillage interactions in rice fallow cowpea (Vigna unguiculata L. Walp.) production
(Department of Agronomy, College of Agriculture, Vellanikkara, 2020) Vandana, G Pai; KAU; Prameela, P
An experiment entitled “Nutrients and tillage interactions in rice fallow cowpea production” was conducted during 2017-2019 at College of Horticulture, Vellanikkara of Kerala Agricultural University, Thrissur. The study consisted of two experiments. Experiment-1 was a pot culture study undertaken during 2017, to find out optimum dose of potassium and magnesium sulphate for cowpea. The experiment was laid out in CRD with 14 treatments and three replications. The treatments included three levels of K2O (10, 20 and 40 kg/ha), and four levels of MgSO4 (40, 60, 80 and 100 kg/ha). Apart from K: MgSO4 @ 10:80 kg/ha (KAU package of practices) and soil test based nutrition (K: MgSO4 @12:80 kg/ha) were also included. Nitrogen and P2O5 were applied at the rate of 20 and 30 kg/ha, respectively, uniformly to all pots. A bush type variety of cowpea Anaswara released from Kerala Agricultural University was used in the study. In the pot culture experiment, application of K2O: MgSO4 @ 40: 40 kg/ha and 40:100 kg/ha resulted in taller plants. At 60 DAS, POP based nutrient application registered more number of branches (12.7 /plant), which was on par with K2O: MgSO4 @ 10:60 (T2), 20:40 (T5), 20:100 (T8), 40:40 (T9), 40:80 (T11), 40:100 (T12) kg/ha as well as to soil test based nutrition (T14). Highest number of root nodules (201) and higher dry matter production at harvest (44 g/plant) was observed in application of K: MgSO4 @ 40:100 kg/ha (T12). An increase in dry matter production of cowpea was observed with magnesium sulphate nutrition. Various levels of K and Mg resulted in significant variation in chlorophyll a and total chlorophyll content. Application of potassium and MgSO4 @ 40:60 kg/ha resulted in higher number of pods and grain yield (40.3 g/plant) and it was statistically comparable to T11 and T12 (K2O: MgSO4 @ 40:80 & 40:100 kg/ha). Based on grain yield, treatments K: MgSO4 @ 20:60 kg/ha, 20:80 kg/ha, 40:60 kg/ha, 40:80 kg/ha were selected for field trial along with soil test based nutrition as control. The second experiment aimed at assessing the effect of various tillage practices, and varied doses of potassium and MgSO4 on growth and yield of cowpea and to work out economic viability. Field experiments were undertaken in rice fallow during 2017 and 2018 (November/December - March/April). Soil of the filed was high in organic carbon, available N, but deficient in available P, K, and Mg. The experiment was laid out in RBD and the treatments were factorial combinations of three types of tillage and varied doses of potassium and magnesium sulphate and it was replicated thrice. Zero tillage (ZT- M1), minimum tillage (MT- M2) and conventional tillage (CT- M3) were the major factors and five nutrient doses (S1-S5) were soil test based nutrition (S1- 11-13 kg K2O/ha along with 80 kg MgSO4/ha), 20 kg K2O/ha along with 60 kg/ 80 kg MgSO4/ha (S2 & S3) and 40 kg K2O/ha along with 60 kg/ 80 kg MgSO4/ha (S4 & S5). N and P2O5 were applied at the rate of 20 kg/ha and 30 kg/ha in all plots. Seeds were dibbled at spacing of 30 cm x 15 cm. In zero tillage, herbicide glyphosate was sprayed @ 0.85 kg/ha two weeks before sowing. In minimum tillage, strip tillage using spade was adopted at a spacing of 30 cm. In conventional tillage, land was ploughed twice followed by formation of small ridges and furrows at a spacing of 30 cm. The plot size was 6 m x 4.2 m. Germination percentage of cowpea (at 7 DAS) was significantly higher in conventional tillage (79 %), whereas, it was very low in zero till (44 %) and intermediate in MT (58 %). Tillage systems and potassium, magnesium sulphate doses had no significant effect on plant height of cowpea, and at 60 DAS average height was 47.5 cm, 52.9 cm and 48.4 cm under zero tillage, minimum tillage and conventional tillage, respectively. At 45 DAS and 60 DAS minimum tillage resulted in higher number of branches per plant whereas, plants in conventional tillage showed earliness in 50 % flowering. Significantly higher LAI was recorded in zero tillage, followed by minimum and conventional tillage. Application of K: MgSO4 @ 40:80 kg/ha also resulted in higher LAI. Zero tillage along with K: MgSO4 @ 40:80 kg/ha (M1S5) recorded the highest LAI. Tillage had no significant effect on chlorophyll a, chlorophyll b, and total chlorophyll content and on chlorophyll a/b ratio. Whereas, potassium and magnesium sulphate application had significant effect on chlorophyll content. Application of K: MgSO4 @ 20:60 kg/ha and K: MgSO4 @ 40:80 kg/ha resulted in higher as well as comparable chlorophyll a and total chlorophyll content. Among interactions ZT with K: MgSO4 @ 12:80 kg/ha (soil test) and CT along with K: MgSO4 @ 20:60 kg/ha higher chlorophyll a content. Dry matter production at early growth stage was higher under conventional tillage, followed by minimum tillage and zero tillage. Whereas, at 75 DAS, highest dry matter was registered under minimum tillage (3240 kg/ha). However, at 90 DAS, both minimum and conventional tillage resulted in higher as well as comparable dry matter (2043 kg/ha and 2085 kg/ha). Root length and root spread were higher under zero tillage followed by MT and CT. Application of K: MgSO4 @ 40:60 kg/ha also resulted in higher root spread. Zero tillage with K: MgSO4 @ 40:60 kg/ha (45.2 cm) resulted in longest roots and higher root spread (2695 cm2). Conventional tillage along with supply of K and MgSO4@ 40 and 80 kg /ha registered shortest roots and lower root spread. Pooled analysis showed that, among various tillage systems, significantly higher grain yield was realized under minimum tillage (735 kg/ha). This was followed by conventional tillage (648 kg/ha) and zero tillage (618 kg/ha) which were on par. Among varied potassium and magnesium doses, application of K: MgSO4 @ 40:60 kg/ha was found to be the best (grain yield of 806 kg/ha). Hence combination of minimum tillage along with K: MgSO4 @ 40:60 kg/ha resulted in the highest grain yield (915 kg/ha). Uptake of nutrients at 30 DAS followed the order of CT>MT>ZT. At harvest, higher uptake of potassium, and magnesium was noted in K: MgSO4 @ 40:60 kg/ha under minimum tillage. There was no significant variation with respect to grain protein content of cowpea due to various tillage practices whereas higher content was registered with application of K: MgSO4 @ 40:80 kg/ha (26.2 %).
Open Access
Organic nutrition in taro (Colocasia esculenta (L.) Schott)
(Department of Agronomy, College of Agriculture, Vellayani, 2022) Limisha, N P; KAU; Rajasree, G
The study entitled “Organic nutrition in taro (Colocasia esculenta (L.) Schott)” was conducted at College of Agriculture, Vellayani, Thiruvananthapuram, Kerala to investigate the effect of organic nutrition on growth, yield, quality, soil organic carbon build up and economics of cultivation of taro and to study rooting and tuberisation pattern of taro under organic nutrition. The experiment was conducted in the farmer’s field at Peringamala, Thiruvananthapuram from June 2019 to January 2020 and June 2020 to January 2021. The investigation comprised two separate experiments: (1) Organic nutrition in taro (field experiment) and (2) Rooting and tuberisation pattern study in taro (pot culture). The first experiment was laid out in randomized block design with three replications. The treatments comprised six organic sources (s1- FYM + wood ash; s2- FYM + wood ash +PGPR mix I; s3- FYM + wood ash + PGPR mix I + vermiwash; s4- poultry manure + wood ash ; s5- poultry manure + wood ash + PGPR mix I; s6- poultry manure + wood ash + PGPR mix I + vermiwash) and two in situ green manuring (g1- in situ green manuring with cowpea; g2- in situ green manuring with daincha) with three controls (C1- nutrient management through chemical fertilizers as per KAU POP (80 : 25: 100 kg ha-1 ); C2 - nutrient management as per KAU organic POP (Ad hoc); C3 - absolute control). The tuberization study was laid out as completely randomized design as pot culture with the six organic sources (s1 to s6 used in field experiment) as treatments (T1 to T6) together with three controls, and were replicated thrice. The recommended dose of NPK for colocasia @ 80: 25: 100 kg ha-1 was applied through organic sources on N equivalent basis as per the treatments. Application of FYM + wood ash +PGPR mix I (s2) took less number of days (24.33 days) for 50 per cent sprouting of seed corm during first year. Application of poultry manure along with wood ash, PGPR mix I and vermiwash (s6) and in situ green manuring with daincha (g2) found superior with respect to growth characters such as plant height, number of leaves per plant, leaf area and leaf area index (LAI). The interaction s6g2 recorded taller plants, higher leaf area and LAI during both the years. Taller plants were produced by s6g2 at 4 MAP and s6g1 at harvest compared to C1 (151.48 cm) during first year. Organic treatments performed better than C2 and C3 with respect to all growth parameters. FYM + wood ash and poultry manure + wood ash recorded the highest number of cormels per plant during first and second year respectively. Mean weight of cormel was higher in s6 (34.86 g) during first year and in s3 (26.01 g) during second year. The application of poultry manure along with wood ash, PGPR mix I and vermiwash (s6) recorded the highest cormel yield (18.68 t ha-1 ) and corm yield (12.21 t ha-1 ) under pooled analysis. Organic treatment s5 recorded the highest cormel to corm ratio (1.80) during second year. In situ green manuring with daincha (g2) recorded the highest mean cormel weight during both the years while cormel and corm yield in pooled analysis were also the highest with this treatment. The treatment s3g2 recorded the highest mean weight of cormel and the treatment s6g2 recorded the highest cormel yield under pooled analysis (19.02 t ha-1 ). The treatment s5g1 registered the highest cormel to corm ratio during second year. The organic treatments s3g2, s5g1, s5g2, s6g1 and s6g2 were found to be equally effective as C1 in case of corm and cormel yield of taro. The treatment s6g2 recorded a 0.90 percentage increase of cormel yield over chemical nutrient management during first year and a 2.67 percentage increase of corm yield over chemical nutrient management for pooled mean. The treatment combinations s3g2, s5g1, s5g2, s6g1 and s6g2 were found superior to C2 in case of corm yield, cormel yield and mean cormel weight. The treatment s6g2 recorded a 37.83 percentage and 27.82 percentage increase of cormel yield and corm yield respectively over KAU organic POP for pooled mean. The treatments s3g2, s4g2, s6g1 and s6g2 during first year and s3g2, s5g2 and s6g2 during second year recorded significantly higher mean weight of cormel than C3. All the treatment combinations in case of corm yield and all the treatment combinations except s1g1 in case of cormel yield recorded significantly higher value than C3. During second year, the treatments s5g1 and s2g2 recorded the highest harvest index (0.60) and were significantly superior to C2 (0.47). The organic source s6 and in situ green manuring g2 recorded the highest dry matter production (DMP). Treatment combination s6g2 (8.37 t ha-1 ) during first year and s3g2 (6.55 t ha-1 ) during second year recorded the highest DMP. Except s1g1, s1g2 and s4g2, all other treatment combinations resulted in significantly higher DMP compared to C2. All organic treatments were significantly superior to C3 with respect to DMP during both the years. The organic source s6 and in situ green manuring g2 were found superior in improving quality characters of cormel. The higher N and K content and uptake were noticed in organic source s6, while P uptake was higher in s3. In situ green manuring g2 resulted in higher NPK contents and uptake. The highest N (149.03 kg ha-1 ) and K (232.80 kg ha-1 ) uptakes were recorded with treatment combination s6g2 during second year. During first year, the treatment s3g2 recorded the highest tuber P content and P uptake (35.12 kg ha-1 ). The treatment combination s6g2 was significantly superior to C1 in case of K uptake during first year. The treatment combinations s2g1, s2g2, s3g1, s3g2, s5g1, s5g2, s6g1 and s6g2 were found superior to C2 in nutrient content and uptake. The organic treatments were superior to absolute control in nutrient contents and uptake. The organic source s5 recorded the lowest EC during second year. The organic sources s5 and s6 resulted in higher organic carbon and available N content in soil while available P content of soil was the highest with s3. In situ green manuring with daincha found superior in organic carbon, available N and available P content of soil. Available N content in soil was the highest in s6g2 during first year. The treatments s2g2 and s3g2 were found to be significantly superior to C1 and C2 during second year with respect to available P status. The organic treatments were found superior to C3 in case of pH, organic carbon and available NPK. The organic sources s5, s3, s6 and in situ green manuring g2 resulted in higher total organic carbon and recalcitrant carbon, labile carbon and water soluble carbon content of soil. All organic nutrition treatments were found superior to control treatments in soil organic carbon buildup. Balance sheet of K was positive for s3g1, s5g1, s6g1, s6g2 and C1 after first year of experiment and the N balance was positive for absolute control after second year. The organic source s6 and in situ green manuring g2 registered the highest net income and BCR. Treatment combination s6g2 resulted in the highest net income (₹737241 ha-1 ) and BCR (2.82). All the treatments except s1g1 and s2g1 recorded higher net income and the treatments s4g1, s5g1, s6g1 and s6g2 resulted in higher BCR than C1. The treatment s6g2 recorded a 43.96 percentage and 6.02 percentage increase of net income and BCR respectively over chemical nutrient management for mean. All treatment combinations except s1g1 and s2g1 recorded higher net income and all except s1g1, s2g1 and s3g1 recorded higher BCR compared to C2. The treatment s6g2 recorded a 54.71 percentage and 19.49 percentage increase of net income and BCR respectively over KAU organic POP for mean. All organic nutrition treatments recorded higher net income and all treatments except s2g1 and s3g1 recorded higher BCR compared to absolute control. In pot culture study, the treatments T6 and T5 in case of pH, absolute control in case of EC, T2 and T3 in case of organic carbon and available P and T6 and C1 in case of available N and K were found superior throughout the growing period. The higher microbial population was observed with organic sources T6, T5, T3 and T2. The organic sources T5 and T3 recorded the highest dehydrogenase activity. The treatments T6, T3 and T5 excelled in rooting pattern and root anatomical characters. Significant and positive correlation was observed between nutrient uptake and root apex diameter, late metaxylem number, early metaxylem number and stele diameter. Corm initiation was early (between 1 MAP and 2 MAP) in treatments C1 and T6 while it was between 2 MAP and 3 MAP in all other treatments. Control C1 and T6 recorded the highest corm and cormel weight per plant during initial stages and later stages respectively. The highest values of cormel bulking rate were observed between 3 MAP and 4 MAP. The treatment T6 recorded the highest bulking rate during 3-4 MAP, T3 and T5 during 4-5 MAP and T2 during 5-6 MAP. The study revealed that application of poultry manure, wood ash, PGPR mix I and vermiwash, along with in situ green manuring of daincha in taro resulted in higher growth, yield, quality, net returns and BCR under organic nutrition and hence can be recommended for its organic nutrient management. All the organic nutrient management practices were found to improve soil organic carbon build up. Application of poultry manure, wood ash, PGPR mix I and vermiwash as organic sources was also found to promote the rooting and tuberisation in taro.

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