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Central Agricultural University, College of Post Graduate Studies in Agricultural Sciences, Umiam

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  • ThesisItemOpen Access
    Development of native Rhizobium compatible enriched compost for use in Lentil (Lens culinaris Medik.) grown in Acid Soil.
    (College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2018-09) Sangma, Christy Berylnight K.; Thakuria, Dwipendra
    The benefit of Rhizobium inoculation in pulse crops grown near neutral to slightly acidic soils is well known. The promotion of pulse crops, especially lentil (Lens culinaris Medik.) in acid soils of North East India is very challenging due to poor nodulation efficiency and nitrogen fixation in strongly acid soils. Out of several causes, the development of acidity tolerant Rhizobium strain and build-up of Rhizobium population near the germinating seeds (spermosphere) in acid soils are challenging tasks. This investigation aimed at the development of effective native Rhizobium leguminosarum strain tolerant to acid soil and delivery of the effective Rhizobium strain through enriched compost to the soil. In order to prepare enriched compost, effective cellulose degrading bacteria (CDB) were screened and the most effective one used for preparation of compost followed by its enrichment by application of efficient Rhizobium strain and phosphate solubilising bacteria (PSB) along with rock phosphate (RP). Cellulose degrading bacteria were isolated from the forest floor litters of jhum cycles 2, 5, 10, and 20 years using cellulose agar medium (CAM) and were screened for cellulase activity in agar plates containing carboxy-methyl-cellulose (CMC) as substrate. Out of 32 CDB isolates, the most effective one (CDM-C1) was used for enrich compost preparation. Pea plant grown in 4 soil types (organic farm plot of ICAR, Umiam; Monabari, Garo Hills; Soils from Upland Lowland of CPGS farm fields) were screened for nodules. R. leguminosarum bv. viceae isolates were grow non Yeast Extract Mannitol Agar (YEMA). R. leguminosarum isolates were further confirmed on CRYEMA containing congo red. Four native Rhizobium isolates (NR1, NR2, NR3 and NR4) including one reference exotic strain (ER), Rhizobium leguminosarum CK1 (obtained from AINP Solan Centre, Dr. YSPUH & F, Solan, HP,India) were screened for nodulation efficiency and yield enhancement on lentil crop grown in a pot experiment using an acid soil (pH 5.25). The treatment combinations of the pot experiment were: (1) SRE 1: negative control (no Rhizobium inoculation)+50%RDF (@ 10:30:10 kg N-P-K ha-1), (2) SRE 2: positive control(CK1)+50% RDF, (3) SRE 3: NR1+50%RDF, (4) SRE 4: NR2+50%RDF, (5) SRE 5:NR3+50%RDF and (6) SRE 6: NR4+50%RDF. The treatment SRE4 (native Rhizobium NR2) performed best in terms of plant height, no. of branches, nodulation efficiency and yield compared to other treatments (P≤0.05, one-way ANOVA). Inoculum of the most effective CDM-C1 isolate was applied into mixed biomass (Eupatorium spp., Ambrosia spp. and broom grass and crop residues like rice straw, maize stalk and banana leaves) for preparation of compost in standard pits (each pit size was 1m x 1m × 1m) by imposing 5 treatments: (1) Normal compost 1 (EC1), (2) enriched compost (EC 2): RP+PSB compost, (3) enriched compost (EC 3): NR2 compost (4) enriched compost (EC 4): RP+PSB+NR2 compost, and (5) enriched compost (EC 5): RP+PSB+ER(CK1) compost. The compost quality and nutrient contents (E4/E6, ash content and alkalinity, germination percentage and index, N, Pand K content, pH and EC) values indicated that EC4 and EC5 composts were better than EC1 and other enriched compost. A field experiment on lentil crop (variety PL-8)was conducted in the ICAR Experimental Farm, Umiam with 9 treatments combination:T1: 100% RDF (@20:60:20 kg N-P-K ha-1), T2: 50% RDF, T3: seed inoculation (SI) with NR2+EC 1+50% RDF, T4: SI with ER (CK1)+EC 1+50% RDF, T5: SI with NR2+EC 2+50% RDF, T6: SI with ER (CK1)+EC 2+50% RDF, T7: SI with NR2+EC 4+50% RDF, T8: SI with ER (CK1)+EC 5+50% RDF, T9: SI with NR2+ EC 3+50% RDF. The nodulation efficiency was the highest in T5 followed by T7. Pod and seed yield were the highest in T5 followed by T7 and these treatments received enriched compost amended with native Rhizobium (NR2), PSB and RP. Overall, it can be concluded that enriched compost amended with native Rhizobium, PSB and RP showed great potential in supporting higher nodulation efficiency and yield of lentil crop grown under acid soil. Key words: Cellulose decomposer; Jhum; native Rhizobium; Acid soil; Pulse promotion; Lentil.
  • ThesisItemOpen Access
    Effecy of nitrogen application through urea and azolla on growth, yield of rice (Oryza Sativa L.) and temporal soil phosphorus availability
    (College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) Singh, Shubham; Swami, Sanjay
    Phosphorus (P) deficiency occurs widely in lowland soils having high native P-fixing capacity, especially in acidic soils of Northeast region of India. It is very much important to ensure availability of P throughout the crop growing period to synchronize with crop demand. Combined application of organic and chemical sources of nutrients is necessary for sustainable agriculture to ensure food production with high quality. Therefore, a field experiment was conducted at Research Farm of CPGS, CAU, Umiam, Meghalaya during kharif season of 2017 to investigate the effects of azolla incorporation and nitrogen fertilization through urea and azolla on growth and yield of rice (Oryza sativa L.) cv. Shasharang, and also to study the temporal P availability in soil. The treatment combination consist of T1- control, T2- azolla incorporation @ 16000 kg ha-1, T3- 30 kg N ha-1 through urea, T4- 60 kg N ha-1 through urea, T5- 30 kg N ha-1 through urea + azolla incorporation @ 16000 kg ha-1 and T6- 60 kg N ha-1 through urea+ azolla incorporation @ 16000 kg ha-1. The treatments were replicated four times in Randomised Block Design. The experimental soil was sandy clay loam in texture having pH 5.1, bulk density 1.36 g cc-1 and organic carbon 1.75 per cent. The available N, P and K was 288.62, 17.23 and 201.46 kg ha-1, respectively. The result indicated that highest plant height, grain and straw yield was obtained in T6 (60 kg N ha-1 through urea + azolla incorporation @ 16000 kg ha-1) which was higher to the tune of 19.94, 53.84 and 31.28 per cent, respectively over T1 (control). Further, it was also observed that the plant height, plant dry matter production, grain and straw yield obtained in T2 was statistically at par with T3, and following the same trend, all these parameters in T4 was statistically at par with T5. The magnitude of increase in N, P and K concentration and uptake in grain was 28.57, 97.02; 26.09, 84.21 and 15.69, 76.47 per cent in T6 over T1. The concentration and uptake of N, P and K in grain and straw was statistically at par in T2 and T3 as well as in T4 and T5. The soil available P and K contents were recorded higher in the treatments with azolla incorporation (T2, T5 and T6) as compared to the sole application of urea/control treatments (T1, T3 and T4) at different time interval of crop growth i.e. 30, 60, 90 DAT and at maturity. The soil available P and K content increased significantly in T6 over T1 in respective time interval of crop growth. However, the temporal availability of P decreased with advances in crop growth period in respective treatments. The highest availability of P in soil was recorded in T6 (24.13 kg ha-1) at 30 Days after paddy transplanting whereas the lowest available P in soil was found in T1 (14.91 kg ha-1) at maturity stage. The OC data followed the same trends.The soil available N content increased significantly in T6 over T1 in respective time interval of crop growth period. However, the temporal availability of N decreases with advances in crop growth period in respective treatments. The analysis of soil acidity indices indicated that highest improvement in pH was observed in T2 over all the treatments. Further, it is also observed that pH increased significantly in the treatments receiving azolla incorporation (T2, T5 and T6) compared with the sole application of urea/control (T1, T3 and T4). The exchangeable calcium and magnesium (meq100g-1), CEC (meq100g-1) and base saturation percentage also showed the same trends and the highest values were observed as 1.92, 7.90 and 24.30 in T2. However, in contrast to this, the lowest values of exchangeable aluminium, exchangeable acidity and acidity saturation percentage were observed in T2 indicating that the sole application of azolla improved soil acidity indices. It may be concluded from present study that application of 60 kg N ha-1 through urea in combination with incorporation of azolla @ 16000 kg ha-1 is the best suitable option for getting optimum production of rice and sustainability of soil health in low land acid soil of Meghalaya. Moreover, the farmers can manage around 30 kg N through incorporation of azolla @ 16000 kg ha-1 in rice crop instead of supplying this through nitrogenous fertilizers.
  • ThesisItemOpen Access
    Screening of rice endophytes for ACC-deaminase activity and rice growth promotion under acidity stress
    (College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) Devi, Shamulailatpam Shidayaichenbi; Thakuria, Dwipendra
    Soil acidity is well known constraint of higher crop productivity especially in tropics and sub-tropical humid climate. To overcome the barrier of soil acidity related stresses, application of microbial bioinoculants tolerant to abiotic stresses is one of the most discussed topics on plant-microbe interactions in the recent years. The ability of plant growth-promoting (PGP) bacteria that produce 1-aminocyclopropane-1-carboxylate deaminase (ACCD) to lower ethylene levels in plants under stress condition is a key mechanism of bacteria to help its host plant for habitat-adaptive fitness. The information on +ACCD bacteria associated with rice plant in response to acidity stress is seldom reported. To address this issue the present investigation was formulated with three objectives were: (1) to screen bacteria associated with rice plant for ACC-deaminase activity, (2) to determine in-vitro PGP activity of screened bacteria under pH stress condition, (3) to assess comparative efficiency of ACC-deaminase positive and negative bacteria on rice growth under pH stress condition. Altogether 70 pure isolates of rice plant associated bacteria were screened for ACCD activity and 20 isolates showed ACCD activity higher than 20 M of α-ketoglutarate mg-1 protein h-1 and these isolates were referred as +ACCD group. The isolate 52E showed exceptional higher (191 -M of α-ketoglutarate mg-1 protein h-1) ACCD activity followed by appreciable ACCD activity by isolates 69E and 47E. From rest of 50 isolates, 20 isolates were randomly selected and referred as –ACCD group. Both +ACCD and –ACCD groups (total 40 isolates) were screened for PGP-traits viz. IAA-production, dissolution of Ca3 (PO4)2, FePO4, AlPO4, and Zn3 (PO)4, and mineralization of Na-phytate. Then isolates were scored individually based on 6 traits and the sum of scores for each isolate was assigned as the total score. Incase of higher amount of dissolution of AlPO4 by bacterial isolates was found to be in order of pH 6.8 > pH 4.0 > pH 5.5. There was no significant effect of pH on the ability of bacterial isolates for dissolution of Ca3 (PO4)2. The +ACCD and –ACCD groups didn’t differ significantly in terms of in terms of their abilities for IAA production, dissolution of FePO4, AlPO4, and and mineralization of Na-phytate. However, -ACCD group dissolved significant higher quantity of Ca3 (PO4)2 as compared to that of +ACCD group. The interaction (pH level X ACCD trait) effects on all PGP traits of bacteria were non-significant; with only exception in the significant higher mineralization of Na-phytate by +ACCD group at higher pH. The effects of ACCD trait and interaction (ACCD trait x pH level) were non-significant on the total score of bacterial isolates; whereas the effect of pH was significant indicating higher scores in order of pH 6.8 > pH 4.0 >pH 5.5. On basis of higher total scores, 11 isolates representing +ACCD and –ACCD groups (top 3 scorers from the respective ACCD group at each pH level) were used to inoculate sterile dehusked rice seeds (CAU-R1) for rice plant growth enhancement study at pH levels 6.8, 5.5and 4.0 under axenic rice culture experiment. Findings indicated that the pH level had the significant impact on dry plant biomass and shoot biomass indicating higher values in order of pH 5.5 > pH 6.8 > pH 4.0 and pH 6.8 > pH 5.5 > pH 4.0, respectively. However, the dry root biomass was significantly higher at pH 5.5 followed by pH 4.0 and the lowest at pH 6.8. The effect of ACCD trait and interaction (pH level x ACCD trait) on dry plant biomass and root biomass were non-significant; whereas, the significant effect was on dry shoot biomass. The effects of pH level, ACCD trait and their interaction were found to be significant on dry root to plant biomass ratio indicating higher values in order of pH 5.5 > pH 4.0 > pH 6.8 and +ACCDgroup > -ACCD group. The pH level x ACCD trait interaction effect indicated that +ACCD group maintained lower dry root to plant biomass ratio at lower pH as compared to that of –ACCD group. In conclusion, the PGP traits of bacterial inoculants significantly reduced under higher acidity stress, but such stress induced negative effect was comparatively lesser in +ACCD group compared to –ACCD group. Besides, the benefits of bacterial inoculation to rice crop was more prominent under higher acidity stress and the dependency of rice plant to microbial inoculation gradually decreased with the reduction in acidity stress.
  • ThesisItemOpen Access
    Land use effects on aggregation of acid soils under humid sub-tropics
    (College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University, Imphal, 2018) Chanu, Pukhrambam Helena; Bora, Pradip Kumar
    The traditional and subsistence farming system of crop production which is accompanied with huge loss and burning of phyto-biomass in the North-East Hill (NEH) Region of India requires improvement in production technology and soil health. The land use is an important factor affecting soil organic carbon (SOC) accumulation and storage in soils, which controls the magnitude of SOC stock and also greatly influences the composition and quality of organic matter in soils. Soil organic carbon is an essential component and takes a main role in soil fertility and crop production. Its content varies with the topography, soil erosion and subsistence nature of farming. It takes a major role in the soil aggregate formation on different land use type. Aggregate formation increases moisture-holding capacity of soil and reduces erosion. It also maintains sufficient cohesion in the soil to give anchorage to plant, yet sufficient incoherence to facilitate root penetration and emergence of seedlings. So, an experiment was conducted at two different areas, Bhoirymbong and Umsning of Ri-Bhoi District, Meghalaya in eight (8) different land use system for better understanding on the relationship among the landscape, land use, soil texture and soil aggregation.The soils were collected from two different depths i.e., 0-10 cm and 10-20 cm and four composite sample per each depth. The pH is moderately acidic in nature ranging from 5.26-6.42 (Bhoirymbong) and strongly acidic ranging from 4.85-5.85 (Umsning). The amount of clay content was highest in Umsning area ranging from 46.6-26.9% and lower at Bhoirymbong area with 46.3-25.9% where the highest clay content was obtained in Rice-Rice system at both depth (Umsning); and Pineapple system (0-10cm) and Terrace Rice system (10-20 cm) obtained the highest in Bhoirymbong area. TN was found comparatively higher in Umsning area (4939-3379 kg/ha) than in Bhoirymbong area ranging from 4939-2744 kg/ha. MWD is found highest in Upland Rice (2mm) and Terrace Rice (1.72mm) at 0-10 cm and 10-20 cm depth, respectively in both the study areas. SMBC, POM, HWEC, Glomalin protein, Exchangeable Ca+++Mg++, Clay and OC show significant (p≤ 0.05) and strong positive correlation with MWD at both depth in both the study sites. At 0-10 cm depth, highest positive correlation with MWD is shown in HWEC (Bhoirymbong) and OC (Umsning). And, at10-20 cm depth, highest positive correlation with MWD is shown in SMBC in both areas. Higher MWD in surface soil was obtained from upland rice which indicated that as the Upland rice cultivation is traditionally a mono-culture activity without much soil manipulation the aggregation might not have broken in the cultivation process. Findings on each aggregating element and the combined variabilities of all aggregating elements explained in PCA plot clearly demonstrated that the land use system had significant influence on the aggregating elements. Moreover, the influenced of land use system on aggregating elements varied according to land use type. Thus, the findings of this study clearly traced upon the proper selection of landuse according to the state of soil aggregating elements for better soil sustainability.
  • ThesisItemOpen Access
    Development of soil erodibility index map for Ri-Bhoi district of Meghalaya / by
    (College of Post Graduate Studies in Agricultural Sciences, CAU , Imphal, 2018) Olaniya, Manish; Bora, P. K.
    In the Revised Universal Soil Loss Equation (RUSLE), erodibility accounts for the influence of soil properties on soil loss during storm events in upland areas, which are represented by the soil erodibility factor (K). K-factor values were best obtained from long-term direct measurements on natural run off plots; however, in the absence of field tests, these values can be estimated using relationships based on physico-chemical soil properties. Soil erosion by water is a major concern in Meghalaya, and the application of models such as Universal Soil Loss Equation (USLE) or RUSLE is limited due to the lack of information about erodibility factors. The K factors once determined are generally given in nomograph or map form so that the values can be picked up easily for estimating soil erosion. The present study was therefore planned to determine the erodibility factor of Ri-Bhoi district of Meghalaya based on soil’s physico-chemical properties and to prepare the erodibility map on GIS platform. The objectives of the study were: i) to determine the soil erodibility index for Ri-Bhoi District of Meghalaya and ii) to prepare the erodibility Index map for estimation of soil erosion. Ri-Bhoi district has primarily four dominant land uses viz., agriculture, jhum, forestry and waste land apart from the built-up areas. Hundred sampling points were taken according to the land uses, taking 25 sampling points for each land use, and the exact locations of the sampling points were recorded with GPS. The sampling points were than plotted on the map of Ri-Bhoi in the GIS. The K factor for each of the sampling points have been determined and recorded. In agriculture land use system (LUS) K factor values were observed in the range of 0.08 - 0.41 with an average of 0.24, jhum LUS 0.08 - 0.42 with an average of 0.19, forest LUS 0.09 - 0.40 with an average of 0.22, in waste land 0.10 - 0.34 with an average value of 0.22 and final map of soil erodibility was generated using Geographical Information System (GIS) tools for the spatial representation of the soil erodibility in the study area. Arc-GIS was used to interpolate the data.
  • ThesisItemOpen Access
    Effect of organic and inorganic nutrient sources on performance of cabbage (Brassica oleracea L. var capitata) in inceptisol
    (College of Post Graduate Studies in Agricultural Sciences, CAU, Imphal, 2018) Konyak, Chingak P.W.; Swami, Sanjay
    Chemical fertilizers alone are unable to maintain the long-term soil health and sustain crop productivity. Cabbage is one of the most popularly grown vegetables in India with second highest in production (209 Mt) after China while Meghalaya stand with just 39.49 tonnes per annum. Among the many constraints for low productivity of cabbage, unbalance nutrition is found to be the main limiting factor besides deteriorating the soil physical and biological properties. The present investigation was undertaken during rabi 2017-18 to study the effect of organic and inorganic nutrient sources on performance of cabbage (Brassica oleracea L. varcapitata) in Inceptisol. Two organic sources of nutrients viz., vermicompost (VC) and farm yard manure (FYM) were used in different 8 combinations with and without graded recommended doses of chemical fertilizers (RDF) as T1- Control, T2- 100% NPKRDF, T3- 100% N FYM, T4- 100% N VC, T5- 50% NPK RDF+50% N FYM, T6- 25% NPKRDF+75% N FYM, T7- 50% NPK RDF+50% N VC and T8- 25% NPK RDF+75% N VC.The experiment was laid out in RBD and replicated thrice. The cabbage cv. Wonder Ball as test crop was raised following all the package of practices. The experimental soil was sandy clay loam in texture with pH 4.87, organic carbon 1.24 per cent, and available N, P, K, and S with 260.0, 18.6, 238.4, and 17.3 kg/ha, respectively. The FYM and VC used in this study contain N (0.55, 2.1), P (0.24, 1.22) and K (0.52, 1.53) percent, respectively. The experimental results revealed that the highest head compactness was observed in T7 followed by T5 which were 10.89 and 9.688 higher respectively over T2 (6.22). The head shape index was observed higher in combined application of organic and inorganic sources as compare to sole application of inorganic fertilizer (T2). The head yield of cabbage was obtained highest in T7 which was 12.09 per cent higher over T2. Further, the yield obtained in T2 was significantly higher over control by 57.38 per cent. The similar trend was observed with sole application of organic manure; however the degree of response was of lower order as compared to sole inorganic treatment. The treatment T7 and T5 with VC were found superior as compared to T7 and T6 with FYM, respectively. The concentration and uptake of N, P and K in cabbage was found significantly higher in T7 over T2. The degree of increase in concentration and uptake of respective nutrient was found to be 5.32 and 17.20, 8.06 and 18.43, and 3.03 and 13.76 per cent. The same trend was observed in case of micronutrient concentration in cabbage. Further, T2 showed significant higher concentration and uptake of N, P and K over control. The treatmentT7 and T5 with VC were found superior as compare to T8 and T6 with FYM, respectively.Contrary to this, the concentration of sulphur was found highest in T2 with 5.97 per centincrease over T7. The soil organic carbon was found significantly higher in T3 over T2 by 41.88 per cent and T2 was higher over T1 by 2.63. Among the organic treatment, FYM treated plot yielded higher soil organic carbon than VC treatment plot in all the combinations. The increase in exchangeable calcium and magnesium was observed T3 over T2 by 27.50 per cent but in T2, it was recorded higher over T1 by 12.14 per cent.The soil available N, P, K, and micronutrients were found significantly higher in T7 over T2, whereas T2 showed significant higher availability of all nutrients over control. The treatment T7 and T5 with VC were found superior as compared to T8 and T6 with FYM, respectively. The available sulphur showed reverse trend with significant higher concentration and uptake in T2 over T7. The soil microbial biomass carbon, dehydrogenase activity and soil moisture were observed significantly higher in T3 over T2 while values in T2 were higher over control. Soil pH increased in T3 then rest of the treatments. From this study, it may be concluded that for acid Inceptisol soils of Meghalaya, T7- 50% RDF+50% N VC is best option for obtaining optimum production of cabbage with superior quality while maintaining soil health.
  • ThesisItemOpen Access
    Phosphorus fixation capacity and release pattern in dominant soil orders of North east India
    (College of Post Graduate Studies in Agricultural Sciences, CAU, Imphal, 2018) Borpatragohain, Bidisha; Thakuria, Dwipendra
    Phosphorus (P) deficiency is wide spread in approximately 42% of arable lands in India. In North East India, approximately 95% soils are acidic, and nearly 65% soils are suffering from strong acidity (pHAlfisol (84.5) >Inceptisol (74.2) >Entisol (49.2). The bulk density (BD), maximum water holding capacity (MWHC) and clay content ranged from 0.91 to1.37 g cc-1, 32.7 to 55.5% and 3.7 to 55%, respectively among twelve soil profiles. The content of soil organic carbon (SOC), soil available nitrogen, phosphorus and potassium (Avl.N, Avl.P and Avl.K, respectively) ranged from 0.50 to 2.00%, 122 to 301 kg ha-1, 6.6to 62.1 kg ha-1 and 115 to 220 kg ha-1, respectively. Soil pH, exchangeable aluminium (Ex.Al), readily soluble aluminium (RS.Al), exchangeable calcium+magnesium (Ex.Ca+Mg) and base saturation (BS) ranged from 4.22 to 7.74, 0.09 to 3.5 meq 100-1 g soil, 18.4 to 384 mg kg-1 soil, 1.7 to 12.9 meq 100-1 g soil, 16.2 to 71%, respectively. In laboratory soil column study, six P sources imposed were: (1) control (no P addition), (2) phosphate solubilizing bacteria (PSB), (3) organic manure (OM), (4) rock phosphate (RP), (5) single superphosphate (SSP) and (6) RP+PSB. The PRP was studied in soil columns by extracting solution phase P with distilled water (5 ml) at 6 time points (0, 5, 15, 30, 45, 60 days). The amount of released Pi was dependent soil orders, whereas the pattern of released Pi was highly influenced by P sources across soil orders.Within 15 days of incubation, SSP addition caused the highest amount of released Pi and thereafter the released Pi gradually decreased.On the other hand, the amount of released Pi was increasing gradually with progression of incubation duration beyond 15 days for PSB, OM, RP and RP+PSB sources. Among the latter four P sources, application of RP+PSB could release significant higher quantity of Pi as compared to their single application.The significant higher correlation of PFC with RS.Al, Clay, Ex.Al, Avl.P, Ex.Ca+Mg, pH, BS and SOC indicated the need for formulation of suitable management practices that can improve the status of these soil attributes so as to reduce PFC of soils. The application of OM, RP and PSB showed significant positive effects on the PRP of acid soils. So, it can be suggested that PFC and PRP behaviours of acid soils of NE India are important factors to be considered while formulating P nutrition management practices.
  • ThesisItemOpen Access
    Performance of pea (Pisum sativum L.) under phytoremediated heavy metal polluted soil with residual phosphorus
    (College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2019) Sailo, Vanlalmalsawmi; Swami, Sanjay
    Due to extensive coal mining in Meghalaya, large areas of Jaintia Hills district had turned into heavy metal polluted land, creating unfavourable condition for plant growth. In acid soils, the residual effects of P fertilizer can persist for as long as 5–10 years (or more), depending on the initial P fertilizer rate applied, crop removal and soil buffering capacity, therefore, a pot culture experiment was carried out during rabi 2017-18 utilizing the heavy metals polluted soil but phytoremediated by maize (Zea mays) to assess the performance of pea (Pisum sativum L.) cv. Arkel with eleven residual phosphorus levels applied to preceding maize crop viz. 0, 10, 20, 30, 40, 50, 60, 60, 80, 90 and 100 mg kg-1 soil under completely randomized design and replicated thrice. The experimental results revealed that plant height, number of pods plant-1, number of seeds pod-1 and fresh seed weight of pea is markedly increased with the increasing levels of residual P up to the highest level of previously applied P. The lowest plant height (25.50 cm), number of pods plant-1 (3.03), number of seeds pod-1 (2.9) and fresh seed weight (5.35 g plant-1) was observed under no residual P which significantly improved by 39, 76, 56 and 78%, respectively in the highest level of previously applied P (100 mg P kg-1 soil). The highest dry seed (16.8 g) and straw weight (44.24 g) was observed under highest residual P, which were 11 and 10 fold more in comparison to that received with lowest residual P. The P concentration in pea straw ranged from 0.03 to 0.12% while it ranged from 0.07 to 0.21% in seed maintaining increasing order with the increased residual P, whereas the concentration of Cr, Cd, Ni, Pb and Co followed the reverse trend and it decreased with each increasing level of residual P. The uptake of Cr and Ni increased with the increasing level of residual P up to highest residual P whereas the uptake of Cd in both seed and straw of pea increased up to 60 mg applied P kg-1 soil and thereafter showed decreasing trend. The Pb uptake in pea straw increased up to 50 mg applied P kg-1 soil whereas in seed, it showed increasing trend up to 60 mg applied P kg-1 soil and thereafter decreased up to highest residual P level (100 mg P kg-1). In case of Co, the uptake in straw increased up to 50 mg residual P kg-1 whereas the seed uptake increased up to 70 mg residual P kg-1 and declined thereafter. The P content in soil after harvest of pea ranged from 0.11 to 1.83 mg kg-1 indicating increased availability of P with each successive increased level of previously applied P, whereas a reverse trend was observed in case of heavy metals and the lowest contents were observed at highest level of 100 mg P kg-1 soil. It may be concluded from the present investigation that the increasing soil available P maintained by higher P application rates for preceding phytoremediating crop may efficiently be utilized to phytoremediate the remaining heavy metals contents of the coal mined heavy metals polluted soil and almost normal yield levels of pea cv. Arkel can be achieved with 100 mg kg-1 soil level of residual P.
  • ThesisItemOpen Access
    Temporal soil nitrogen availability and its influence on rapeseed (Brassica campestrisL.) under varying nitrogen sources
    (College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2019) Sowjanya T V; Singh, Naorem Janaki
    The rapeseed-mustard (Brassica campestris and B. juncea) is an indispensable part of food as leafy vegetables or cooking oil in North East India. The production in the region is far below the national average production and therefore could not meet the population demand. A proper scientific intervention with understanding the interaction effect between the soil N, crop uptake and added N during crop growing is the time of hours for sustainable crop production and improving soil fertility. Therefore, a study was carried out to understand the N availability pattern at different time intervals during crop growing at college research farm with the treatments such as T0- Control, T1- 100% N (inorganic), T2- 100% N (organic), T3- 50% N (inorganic) + 50% N (organic), T4- 75% N (inorganic) + 25% N (organic) in randomized block design (RBD) design with four replications using a test crop Brassica campestris L. (variety M27). The results revealed that soil bulk density (BD), moisture content, pH and electrical conductivity (EC) were not significantly influenced by the treatments. The soil organic carbon (SOC) was significantly higher in T2 (1.74, 1.24, 1.10 and 0.81% at 0- 15, 15-30, 30-45 and 45-60 cm respectively). The treatments T1, T2, T3 and T4 had a similar effect on the soil ammonical nitrogen (NH+4-N), nitrate nitrogen (NO3--N), available nitrogen (Avl. N), total nitrogen (TN), available phosphorus (Avl. P) and potassium (Avl. K) at different growth stages. The T4 showed the highest soil NH+ 4-N as 50.25 mg kg-1 in 0-15 cm and 47.25 mg kg-1 in 15-30 cm at 20 DAS, and 47.34 mg kg-1 in 0-15 cm and 45.05 mg kg-1 in 15-30 cm at 40 DAS, whereas T2 showed the highest NH+4-N as 48.29, 47.69 and 40.03 mg kg-1 in 0-15 cm at 60, 80 DAS and harvest, respectively, and 45.45, 43.86 and 42.84 mg kg-1 in 15-30 cm at 60, 80 DAS and harvest, respectively. Similarly, the highest NO3--N under T4 was 35.93 in 0-15 cm and 39.16 mg kg-1 in 15-30 cm at 20 DAS and 34.45 mg kg-1 in 0-15 cm and 37.21 mg kg-1 in 15-30 cm soil depth at 40 DAS. The treatment T2 showed the highest NO3--N as 36.03, 31.11 and 25.50 mg kg-1 in 0-15 cm at 60, 80 DAS and harvest, respectively, and 37.25, 32.85 and 26.54 mg kg-1 in 15-30 cm soil depth at 60, 80 DAS and harvest, respectively. There was no significant effect of treatments on TN and K content in the soil during the growth stages, however, at 20 and 40 DAS, T4 was found the highest Avl. N, P and K in both the soil depths, whereas T2 showed the highest TN content in soil. At 60, 80 DAS and harvest T2 showed the highest Avl. N, P, K and TN in both the soil depths. With soil depths, the soil BD, pH and NO3--N were increased, however, EC, SOC, TN, NH4+-N, Avl. N, P and K content were decreased with soil depths. The highest dry matter production (at 40, 60, 80 DAS and at harvest), yield attributes (number of seeds siliqua-1, number of siliqua plant-1 and grain yield plant-1), yield (grain, straw, biological yield and harvest index), N content and uptake were recorded in T4 which was at par with T3. The dry matter production at 20 DAS and yield attributes such as length of siliqua and test weight were not significantly influenced by the treatments. It was concluded that the treatments T4 and T3 were the best among the treatments to produce significantly higher yield attributes and yield and also to improve the soil fertility status in acid Inceptisols of Meghalaya. The application of T4 could substitute the 25% nitrogen of RDF by organic sources and increased the available (solution N + exchangeable N + labile organic N) N fractions.