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Central Agricultural University, College of Post Graduate Studies in Agricultural Sciences, Umiam
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ThesisItem Open 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, DwipendraThe 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.ThesisItem Open Access Impact of slash-burning and plant species on soil microbial community and processes in Jhum agro-ecosystem(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2020-07) Zothansiami, Carolyn; Thakuria, DwipendraTerrestrial ecosystem supports the above- and below-ground biota communities that interact to influence ecosystem-level processes and functions. Soil acts as the most important medium for linking the above- and below-ground communities which are very sensitive to any external disturbances. To study the effect of above- and below-ground linkages on soil microbial community composition and soil processes, the short jhum cycle can be considered as important experimental plot in farmers’ field. Because the above ground plant biomass generated during fallow phase of the jhum cycle gradually rejuvenate the degraded soil system and upon burning of such biomass suddenly breakdown the linkages between above-ground and below-ground community linkages. In this study, a jhum field (approximate 1.5 ha) during fallow phase of 5 year cycle was considered from Muallungthu village, Aizawl, Mizoram and the one half part of the field was slashed and burned and the other half part of the field was kept unburnt. The bulk quantity (800 kg) of soil (0-10 cm depth) from 4 random spots (1 sqm per spot) was collected immediately next morning of burning night from the burnt field and similar way 800 kg soil from unburnt field were collected and carried to the CPGS Farm Field for setting up of mesocosm (pot) experiments under 4 conditions viz. burnt and unburnt soils in presence of rice crop and without rice crop. Under each of 4 conditions, 6 microbial inoculation (MI) treatments were imposed maintaining 6 replicated pots. Each pot contained 4 kg soil. Altogether 144 pots were maintained (4 conditions x 6 MI treatments x 6 replications = 144). The MI treatments were: (T1) PSB+Fungi, (T2) N2-Fixer+Fungi, (T3) CDB+Fungi, (T4) PSB+N2-Fixer+CDB+ Fungi, (T5) No bacteria + Fungi and (T6) No inoculation. The rice crop used was a jhum rice landrace Khawlian Buh. The crop was maintained till harvest within a plastic shade house. The study reveals that the soil bacterial community composition altered significantly due to burning of slashed biomass on soil surface. The introduction of rice crop also altered the bacterial community composition in burnt/unburnt which shows a distinct cluster within the soil type. The Alpha proteobacterial communities of burnt and unburnt without rice crop clustered together and distinctly separated from the clusters of burnt and unburnt soil with rice crop at 45 days of rice growth and at 90 days of rice growth the impact of rice crop on composition of Alpha and beta proteobacterial community was more consicious in burnt soil then in unburnt soil. The beta proteobacterial community of burnt and unburnt soil cluster together in absence of rice crop and there cluster was distinctly separated from the cluster due to cultivation. With the progress of time (90 days of rice growth) the effect of rice crop on beta proteobacterial community was more prominent than compared to burnt unburnt factor. Burning had significant negative effect on the activity of DHA, GSA, PHA, SOC, pMN, POM, and MBC except ASA indicating higher activity in burnt soil. Introduction of rice crop had significant positive influence on the activity of soil enzymes and soil process indicators. There was significant positive interaction on burning and cropping on soil enzymes activities soil process indicators. There was a significant difference in the activity of soil enzymes and soil process indicators among the microbial inoculants treatment soil process indicators. There was significant positive interaction between burnt and microbial inoculants or cropping and microbial inoculants. The change in bacterial community composition due to burning and cropping factor significantly influence soil process indicator such as ASA, DHA, pMN, POM, and MBC as evident from analysis result of Multi dimensional Scale (MDS) 1 and 2. The change in alpha and beta proteobacterial community composition due to burning and cropping factor significantly influence soil process indicator like PHA, ASA, DHA, pMN, POM, SOC and MBC as evident from their significant correlation with MDS 1 and 2. Burning had significant positive influence on rice growth yield. This study indicated that introduction of crop in burn soil along with microbial inoculation may positively influenced soil processes as well as crop growth.ThesisItem Open Access Hyperspectral spectroscopic study of soil properties in acid soils of North East India.(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2020-11) Gowami, Chandan; Singh, N. JanakiPeriodic monitoring of soil nutrient status for crop production is vital for growing population. The conventional soil analysis has several disadvantages which may be overcome by using real time optical remote sensing data. However, interpretation of nutrient content of soil is difficult using few wide spectral bands (5-10 bands). On the contrary, a large number of narrow spectral bands (350 to 2500 nm) are used in hyperspectral remote sensing. With these advantages, it is attempted to study spectral signature of soil and their relationship with soil attributes and to develop spectral indices using hyperspectral spectroscopy in acid soils of Ri Bhoi district of Meghalaya, India. Spatial stratification of 21 different classes was generated from Land Use Land Cover (LULC) map prepared by National Remote Sensing Centre and soil order map prepared by National Bureau of Soil Survey and Land Use Planning. Five random soil sampling sites were selected from each stratum and recorded the spectral signature of soil in-situ. A composite soil sample at 0-10 cm depth was made from 10 random soil samples from each stratum. Soil attributes viz. pH, soil organic carbon (SOC), available nitrogen (N), available phosphorus (P2O5), available potassium (K2O), available zinc (Zn), sand, silt, clay and moisture were estimated using standard procedures. Field spectra were recorded using field portable spectroradiometer and laboratory soil spectra were recorded using contact probe. Suitable bands for each soil attribute were identified using Variable Importance in Prediction (VIP). Four commonly used indices such as Simple Ratio Index (SRI), Normalized Difference Index (NDI), Renormalized Difference Index (RDI) and Modified Simple Ratio Index (MSRI) were used for development of spectral indices for soil attributes. Soil attributes were also predicted using Partial Least Square Regression (PLSR) models. Highest and lowest field spectral reflectance was found in Kharif Crop (0.03 to 0.27) & Double Crop (0.02 to 0.14) under Alfisols, Wastelands (0.04 to 0.34) and Deciduous Forest (0.02 to 0.16) under Inceptisols and Double Crop (0.04 to 0.31) & Abandoned Jhum (0.02 to 0.22) under Ultisols,respectively. Again, highest and lowest reflectance of field spectra was observed in Inceptisols (0.03 to 0.30) & Ultisols (0.02 to 0.22) under Abandoned Jhum, Ultisols (0.03 to 0.26) & Inceptisols (0.02 to 0.25) under Current Jhum, Ultisols (0.04 to 0.28) & Inceptisols (0.02 to 0.16) under Deciduous Forest, Ultisols (0.04 to 0.31) & Alfisols (0.02 to 0.14) under Double Crop, Alfisols (0.02 to 0.29) & Ultisols (0.01 to 0.29) under Evergreen Forest, Inceptisols (0.03 to 0.30) & Ultisols (0.02 to 0.25) under Kharif Crop and Inceptisols (0.04 to 0.34) & Alfisols (0.02 to 0.18) under Wastelands. On the other hand, highest and lowest laboratory spectral reflectance values were recorded in Kharif Crop (0.10 to 0.62) & Deciduous Forest (0.09 to 0.49) in Alfisols, Evergreen Forest (0.10 to 0.62) & Current Jhum (0.09 to 0.51) in Inceptisols and Double Crop (0.09 to 0.62) & Deciduous Forest (0.09 to 0.54) in Ultisols. Again, highest and lowest laboratory spectral reflectance were recorded in Ultisols (0.09 to 0.58) & Alfisols (0.08 to 0.55) under abandoned jhum, Alfisols (0.09 to 0.57) & Inceptisols (0.09 to 0.51) under current jhum, Inceptisols (0.09 to 0.55) & Alfisols (0.09 to 0.49) under deciduous forest, Ultisols (0.09 to 0.62) & Alfisols (0.10 to 0.57) under Double Crop, Inceptisols (0.01 to 0.62) & Ultisols (0.08 to 0.55) under Evergreen Forest, Alfisols (0.10 to 0.62) & Inceptisols (0.11 to 0.58) under Kharif Crop and Alfisols (0.10 to 0.59) & Inceptisols (0.09 to 0.54) under wastelands. Descriptive statistics of the soil attributes showed medium level of variability ( madian) and normal distribution of the data (skewness < 3.0). VIP score for pH (2.65), SOC (2.87), N (2.75), P2O5 (2.41), K2O (2.19) Zn (2.93), sand (3.59), silt (2.44), clay (3.29), and moisture (3.15) has been found in 1383 nm, 1368 nm, 1391 nm, 1417 nm, 1417 nm, 1368 nm, 1368 nm, 1368 nm, 1368 nm and 1417 nm field spectra. Again, Highest VIP score for pH (2.03), SOC (1.80), N (1.73), P2O5 (2.12), K2O (2.39) Zn (2.38), sand (2.21), silt (2.69) and clay (1.89) has been found in 2203 nm, 2386 nm, 2205 nm, 2205 nm, 2396 nm, 2206 nm, 2205 nm, 2205 nm and 2267 nm laboratory spectra. Ratio of Prediction to Deviation (RPD) value derived from field spectra was found to be highest in RDI (1697 nm, 1751 nm) for pH (1.06), SRI (615 nm, 628 nm) for SOC (1.11), RDI (413 nm, 2178 nm) for N (1.07), RDI (852 nm, 903 nm) for P2O5 (1.16), RDI (2246 nm, 2353 nm) for K2O (1.07), SRI (2445 nm, 2458 nm) for Zn (1.06), SRI (2369 nm, 2135 nm) for sand (1.10), RDI (776 nm, 779 nm) for silt (1.07), RDI (2089 nm, 2333 nm) for clay (1.15) and MSRI (2358 nm, 2005 nm) for moisture (1.07). Again, RPD value derived from laboratory spectra was found to be highest in SRI (1416 nm, 1394 nm) for pH (1.09), RDI (423 nm, 424 nm) for SOC (1.09), SRI (1994 nm, 1995 nm) for N (1.08), SRI (414 nm, 403 nm) for P2O5 (1.10), SRI (414 nm, 403 nm) for K2O (1.12), SRI (2445 nm, 2458 nm) for Zn (1.06), SRI (2410 nm, 2369 nm) for sand (1.08), RDI (1514 nm, 1515 nm) for silt (1.07) and RDI (2457 nm, 2459 nm) for clay (1.07). Soil attributes predicted by PLSR model using field spectra showed highest RPD value in clay (1.60) which was followed by K2O (1.57), pH (1.56), soil moisture (1.42), P2O5 (1.41), sand (1.40), SOC (1.34), N (1.27), Zn (1.33) and silt (1.32). Again, Soil attributes predicted by PLSR model using laboratory spectra showed highest RPD value in soil pH (2.01) which was followed by Zn (1.83), sand (1.77), SOC (1.76), clay (1.62), silt (1.60), N (1.59), P2O5 (1.56) and K2O (1.54). Spectral signature of soil was different under selected LULC. VIP has been found to be useful in studying the relationship of spectral reflectance with soil attributes. Spectral indices were found to poorly predict soil attributes in field as well as laboratory spectra. Soil pH, P2O5, K2O, sand, clay and moisture could be fairly predicted by PLSR models using field spectra. SOC, N and silt could be fairly predicted by PLSR model using laboratory spectra. Good quantitative prediction could be achieved for Zn through PLSR model using laboratory spectra. Again, very good quantitative prediction could be achieved for soil pH through PLSR model using laboratory spectra.ThesisItem Open Access Effect of amelioration practices on soil productivity of coal mine affected lowland fields(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2020-11) Lyngdoh, Markynti S.; Singh, N. JanakiReckless mining of coal has often impaired the ecosystem of plant and soil resulting in various scarcities of the environmental bio-resources that ultimately will haunt the living population in a long run. Often mining activities in relation to agriculture has been through encroachment activities accompanied with natural drainage that perpetuate into agricultural lands and resulted in damaging the soil functionality to reach to most of it toxic levels that growth establishment becomes a mere illusion and if not improvise it may further pose a serious implication to the agricultural scenario of the region. Additionally, the stoppage of the unscientific activities during these current times provides opportunity to employ the technology for improvisation so as to make the visibility for better environmental sustainability. Under such circumstances, the need to ameliorate these soil and identification of the suitable management practices for such high acidified regions soils become imperative. Keeping this in regard, present investigation was conducted at the most well-known coal mining location of Khliehriat block, East Jaintia Hills, Meghalaya involving the categorization of ten potential adjacent coal mine affected paddy soils on the basis of their acidity indices followed by the pot experimentation using Rice var. CAU-R3 on the type of acidity categories identified, that consist of a completely randomised block design (5 nos. replicates) with ameliorating assessments effect of poultry manure (PM), compost (C), lime (L), paper mill sludge (PMS) and microbial consortium (MC) on soil chemical properties and effects of their combinations on soil productivity and rice yield at College of Post Graduate Studies in Agricultural Science, Umiam, followed by field trials at Khliehriat, Meghalaya. The factors were PM (5 t ha-1) and C (10 t ha-1), L as CaCO3 and PMS (250 and 500 kg ha-1), and MC applied as root dip before transplanting were incorporated at appropriate rates. Results revealed that on categorization, two locations were found to exhibit extremely pH acid soil (pH 4.51 ± 0.51) i.e., Moonlakhep and ultra pH soil (pH 3.14 ± 0.23) i.e., Ladrymbai. Integration of practices showed significant increase in soil acidic indices such as soil pH by 0.7% to 23% at Moonlakhep and 0.3% to 17% at Ladrymbai, slight increase in base saturation and significant decrease in exchangeable acidity by 0.48% to 49% at Moonlakhep and 0% to 28% at Ladrymbai with T4 (PM+L@500 kg/ha+ MC) being superior at both locations. Confined increases of soil organic carbon were noticed by 90% at Moonlakhep and 70% at Ladrymbai with enhanced available soil nutrients by 30- 40% on incorporating T4. Sulphur (16% to 30%), Fe (22% to 27%) and Zn (9-14%) were decreased with the addition of poultry manure+lime@500kg/ha+ MC at both sites. Soil microbial biomass (SMB) carbon was greater enhanced with substantial increase in SMB Nitrogen and SMB Phosphorus. Enzymes activities were also seen to be improved with the application of the amelioration practices at both locations' soils. Yield attributes were significantly influenced by different treatments. Highest plant height (83.58 cm and 81.32 cm), Grain yield (3.61 t ha-1 and 2.88t ha-1) were recorded under the practices of T4. However, stover yield (7.88 t ha-1) was noticed in T8 (PM+PMS @500kg/ha+ MC) at Moonlakhep while in Ladrymbai it was maximum at T4 (7.42 t ha-1). Field trials studies however revealed that the effectiveness of the amelioration practices was less and indicates long term experimentation. The performance these amelioration practices were better in extremely acid soil of Moonlakhep than the ultra-acid soil of Ladrymbai, with slight improvement of both highly acidic soils.ThesisItem Open Access Soil organic carbon mapping and carbon sequestration of hill agro-ecosystems of Ri-Bhoi district, Meghalaya.(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2020-09) Deb Barma, Kabir; Singh, N. JanakiThe experiment conducted in Ri-Bhoi, Meghalaya which lies between 91°20'30" - 92°17'00" E longitude and 25°40' - 26°20' N latitude with 951 m altitude above the mean sea level covering 2448 km2 geographical area (10.92% of state geographical area).Six images of Resoursecat-2 LISS III acquired on 26th October, 2015 (kharif season), 8th December, 2015 (rabi season), 23rd February, 2016 (rabi season), 18th March, 2016 (zaid season), 1st January, 2016 (rabi season) and 17th April 2016 (zaid season) from National Remote Sensing Centre (NRSC), Hyderabad .The DEM (Digital elevation model) data of Ri-Bhoi district, Meghalaya was downloaded from bhuvan (https://bhuvan.nrsc.gov.in). Out of 21 land use land cover 6 agro ecological land use has been taken for creating land use/land cover and slope intersection map using ARC-GIS 10.2. There were 39 strata in the final image and each strata has its own acreage distribution. The maximum area found in tree clad area- closed (32.78%) followed by tree clad area-open (25.96%). The minimum area found in river/stream-dry (0.001%) followed by barren rocky/stony (0.005%). The maximum area of strata were found in S5T2 (22.59%) followed by S4T2 (16.10%) and the minimum found in S7OS1 (0.01%) and S7OS2 (0.01%). The none transformation model was the best transformation model. The SOC interpolated with ordinary kriging prediction exponential model. The nugget/sill ratio of found strong to moderate. In the whole observation (1-12) a positive significant correlation found between slope (1-3) and SOC content and negative significant correlation found between S5,S6,S7 and SOC content at both the depth (0-15cm) and (15-30cm) .In per hectare basis the SOC stock of each strata at 0-15cm soil depth were found maximum in S1T2 (3.72 Mg/ha/month) followed by S2T2 (3.66 Mg/ha/month) and minimum in S7OS1 (2.72 Mg/ha/month) followed by S7OS2 (2.78 Mg/ha/month). The SOC stock of different strata at 15-30cm depth were found maximum in S1T2 (3.49 Mg/ha/month) followed by S2T2 (3.30 Mg/ha/month) and minimum in S7OS1 (2.49 Mg/ha/month) followed by S7OS2 (2.52 Mg/ha/month). On land cover area basis, SOC stock at 0-15 cm depth were found maximum in S5T2 (78.18 Gg/total area (ha)/month) followed by S3T2 (59.27 Gg/total area (ha)/month) and minimum in S7OS1 (0.02 Gg/total area (ha)/month) followed by S7OS1 (0.02 Gg/total area (ha)/month). Similarly, at 15-30 cm depth were found maximum in S5T2 (64.09 Gg/total area (ha)/month) followed by S3T2 (51.88 Gg/total area (ha)/month) and minimum in S7OS1 and S7OS2 (0.02 Gg/total area (ha)/month) and S7OS1 (0.02 Gg/total area (ha)/month). SOC has shown positive and significant correlation with avl. N, silt, MWD, negative and significant with BD, sand, positive but no significant with clay.ThesisItem Open Access Phytoremediation of heavy metal polluted soils of coal mine areas of Jaintia Hills and determination of critical limit of phosphorus for maize (Zea mays L.)(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2019-08) Lyngdoh, Euwanrida Adleen Shylla; Swami, SanjayTo investigate the phytoremediation effect on heavy metals polluted soils of coal mine areas of Jaintia Hills of Meghalaya, and to determine the critical limits of available phosphorus for maize (Zea mays), two pot culture experiments were conducted at school of NRM, CPGS-AS, Umiam during 2017. Bulk surface soil sample (0-15 cm) was collected from heavy metals polluted soil of coal mine area of Sutnga in East Jaintia Hills. The experimental soil was having pH, texture, EC, BD, OC values 3.93, sandy clay loam, 0.08 dSm-1, 2.2 g/cc, 0.83 per cent, respectively. The available N, P, K content was recorded 259, 21.03 and 166 kg ha-1, respectively whereas Cr, Cd, Pb, Ni and Co was 95.393, 25.936, 17.410, 51.127 and 6.462 mg kg-1, respectively. In the first pot culture experiment, asparagus (Vigna ungniculata) and sunflower (Helainthus annuus) were raised using processed heavy metals polluted soil for phytoremediation with a no crop treatment and replicated 33 times. The dry matter yield of sunflower was 5.08 g pot-1 and the concentration of heavy metals in the plant tissues was 10.22 (Cr), 2.99 (Cd), 2.07 (Pb), 6.15 (Ni) and 1.13 mg kg-1 (Co), and uptake was 51.83 (Cr), 15.05 (Cd), 10.40 (Pb), 30.88 (Ni) and 5.68 μg pot-1 (Co). Whereas the dry matter yield of asparagus was 11.79 g pot-1 which was higher than sunflower however the heavy metals concentration in the plant tissues of asparagus recorded as 3.67 (Cr), 1.22 (Cd), 0.78 (Pb), 1.83 (Ni) and 0.35 mg kg-1 (Co) and the uptake was 42.98 (Cr), 14.30 (Cd), 9.20 (Pb), 21.43 (Ni) and 4.06 μg pot-1 (Co) depicting lower uptake for each heavy metal as compared to sunflower. The amount of heavy metals left in the soil after harvest of crops was found higher in asparagus remediated soil and lower in sunflower remediated soil indicating superiority of sunflower over asparagus in phytoremediating potential. In the second pot culture experiment, the non-phytoremediated and phytoremediated soils from first experiment were used to raise maize (Zea mays) as test crop superimposing eleven P doses (0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 mg P kg- 1 soil through SSP) and replicated thrice in factorial CRD. After 28 days of incubation of applied P doses, soil samples were drawn from each pot for analysis of available P by four different soil test methods viz., Bray-1, Bray-2, Mehlich-1 and Mehlich-3. The highest amount of P was recorded in Bray-2 method followed by Bray-1, Mehlich-1 and Mehlich-3 in non-phytoremediated as well as phytoremediated soils. There was a significant interaction between P test methods and P levels. The mean dry matter yield of maize grown in non-phytoremediated soil increased significantly with increasing doses of P up to highest dose of applied P i.e. 100 mg P kg-1 soil. The per cent increase in mean dry matter yield with the application of 50 and 100 mg P kg–1 soil over control was 118 and 182 per cent, respectively. The dry matter yield of maize grown in asparagus and sunflower remediated soil increased significantly with increasing levels of P up to 90 mg kg-1 and 80 mg kg-1, respectively. The mean dry matter yield of maize produced in asparagus and sunflower remediated soil significantly increased by 20 and 45 per cent, respectively over maize grown in non-phytoremediated soil. The interaction between PXS was also found to be significant. The mean P concentration increased significantly with increasing doses of applied P in non-phytoremediated as well as remediated soils. The per cent increase in mean P concentration with the application of 50 and 100 mg P kg–1 soil over control was 30 and 60 per cent, respectively. The mean P concentration of maize produced in asparagus and sunflower remediated soil significantly increased to about 10 and 27 per cent, respectively over P concentration of non-phytoremediated maize. Heavy metals concentration in maize decreased with increasing doses of P in non-phytoremediated soil as well as in phytoremediated soils. The lowest mean Cr concentration i.e. 1.29 mg Cr kg-1 was recorded in sunflower remediated soil, which was followed by asparagus remediated soil and the highest value of Cr concentration was recorded in non-remediated soil (2.91 mg Cr kg-1). The similar trend was observed for Cd, Pb, Ni and Co. The interaction between PXS was also found to be significant. The highest concentration and uptake of heavy metals in maize was recorded in non-phytoremediated soil followed by asparagus and sunflower remediated soil. To find out the most suitable soil test method of available P, the correlation coefficients between the available P determined by different soil test methods with dry matter yield and P uptake by maize were calculated for non-phytoremediated and phytoremediated soils. The highest r value was observed in case of Bray-1 for dry matter as well as P uptake which was comparable with Mehlich-1 followed by Bray-2 and Mehlich-3. However, as Bray-1 method is more suitable for acidic soils hence this method was adjudged to be the best method for assessing the P status of soil and to predict the response of applied P in maize owing to its highest degree of correlation coefficients with dry matter yield. The critical limits of available P for maize in asparagus and sunflower remediated soils were established by LRP model as 26.0 and 21.9 kg P ha-1, respectively. However, in case of non-phytoremediated soil, no plateau stage was achieved therefore no critical limit was defined for this soil indicating that this soil require P dose more than 100 mg kg-1 soil. Heavy metals content in soil after harvest of maize crop decreased significantly with increasing doses of P. The magnitude of decrease in mean Cr content with the application of 50 and 100 mg P kg-1 soil over control was 34 and 60 per cent, respectively. The lowest mean Cr content i.e. 17.96 mg kg-1 was recorded in sunflower remediated soil, which was followed by asparagus remediated soil and the highest value of Cr was recorded in non-phytoremediated soil (46.23 mg kg-1). The similar pattern was observed in case of Cd, Pb, Ni and Co. The interaction between PXS was also found to be significant. However, the heavy metals content in the soil decreased in the descending order of non-phytoremediated soil > asparagus remediated soil > sunflower remediated soil.ThesisItem Open 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, DwipendraThe 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.ThesisItem Open Access Effect of phosphorus, zinc and silicon amended root-dip methods on rice in acid soils.(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2018-05) Devi, Mayanglambam Homeshwari; Thakuria, DwipendraApproximately 100 million-hectare of land suitable for rice production is currently under utilised because of the soil-related constraints. One of such constraints is high acidity induced limitation of essential nutrients for plant growth and development. Phosphorus (P) and Zinc (Zn) deficiency are widespread in approximately 42% and 43%, respectively of the arable lands in India. Phosphorus is not only deficient in rice soils but also finite in source (natural stock can support P fertilizer supply only for 105 to 470 years). Soil application of Zn often results in complexation with available P fractions in soil leading poor use efficiency of P and Zn. Silicon (Si) plays important beneficial roles especially in rice nutrition in terms of enhanced tolerance to abiotic and biotic stresses. However, soil application of Si is quite expensive for resource poor farmers. So, nutrient management approach should consider the principle of efficient utilization of applied nutrients ensuring maximum availability during critical periods of crop growth and minimizing the quantity to be applied. In the recent years, seedling root-dip (SRD) method is being increasing recognized as one of the efficient rhizosphere-based nutrient management approaches in terms of enhanced nutrient use efficiency and sustaining grain yield of rice in acid soil. The objectives of the present study were: (1) to determine uptake pattern of P, Zn and Si in SRD of rice cultivars (HYV, Hybrid and Traditional), (2) To find out the optimum doses of P, Zn and Si and their combinations in SRD methods, and (3) To compare the effectiveness of SRD method relative to soil and foliar application (SA and FA) of P, Zn and Si. The incubation experiments on SRD in soil slurry amended with P, Zn and Si (either alone or in combination) for three rice types (HYV- Ranjit, Hybrid – Arize 6444 and Traditional- Mendri) using two distinct acid soils (sandy clay loam, SCL, pH 4.98 and clay loam,CL, pH 4.52) was carried out. Results indicated that the optimum doses of P in soil slurry for SRD were 62, 88 and 138 mg kg-1 soil for traditional, HYV and Hybrid rice, respectively in SCL, and in CL soil, 88 mg kg-1 soil for both traditional and HYV rice and 112 mg kg-1 soil for Hybridrice. The optimum doses of Zn in soil slurry were 0.22 mg kg-1 soil for traditional and HYV riceand 0.78 mg kg-1 soil for Hybrid in SCL and 0.72, 1.24 and 1.72 mg kg-1 soil for traditional rice, HYV rice and Hybrid rice, respectively in CL. The optimum doses of Si in soil slurry were 225 mg kg-1 for traditional and HYV rice and 275 mg kg-1 for Hybrid rice in SCL and 175, 225 and325 mg kg-1 soil for traditional rice, HYV rice and Hybrid rice, respectively in CL. Results on the combination of two nutrients (P+Zn, P+Si, and Zn+Si) and three nutrients (P+Zn+Si) applied through SRD methods indicated that P+Zn and Zn+Si root-dipmethods showed the negative response in terms of nutrient content and their uptake inseedling biomass compared to that of their respective individual SRD method. Root-dip onP+Si added soil slurry showed the positive response of Hybrid rice in both soil types and HYVin CL soil. Root-dip on P+Zn+Si amended soil slurry also showed the negative response interms of P content and uptake in seedling biomass for all rice types in SCL and traditional ricein CL soil. However, it gave positive response in HYV and Hybrid rice in CL soil. The comparative effectiveness of SRD method relative to SA of P-Zn-Si and P+MCRD+50%RDP+foliar application (FA) of Zn and Si was evaluated on two field experiments (Kharif, 2015 at CPGS research Farm, Meghalaya and Kharif, 2016 at farmer’sfield, Kakching, Manipur). Soils of both experimental sites were acidic (Kharif, 2015 experimentwas SCL with pH 4.85 and Kharif, 2016 experiments was CL with pH 5.56). In the Kharif, 2015 experiment HYV rice variety CAU-R1 was used, and six nutrient treatments were allocated asper Randomized Block Design (RBD) with four replications. The treatments were: (1) control (no P input), (2) Microbial consortium root-dip (MCRD), (3) Multi-nutrients (P, Zn and Si) rootdip (MNRD), (4) MN+MCRD, (5) soilapplication of P, Zn and Si (SA of P-Zn-Si), and (6) P+MCRD+50%RDP+FA of Zn-Si. In the Kharif, 2016 experiment HYV rice variety CAU-R1 wasused and four nutrient treatments were allocated as per RBD design with 5 replications. The treatments were: (1) 100%RDP, (2) MNRD+50%RDP, (3) MN+MCRD+50%RDP, and (4)P+MCRD+50%RDP+FA of Zn-Si. In Kharif, 2015 experiment, the content and uptake of P, Zn and Si in shoot and root at different growth stages (30, 60 and 90 DAT), straw and grain at harvest and grain yield of rice were significantly higher in SA of P-Zn-Si treatment followed by P+MCRD+50%RDP+FA of Zn-Si as compared to that in other treatments. In the Kharif, 2016 experiment, the content and uptake of P, Zn and Si in shoot and root at 50 DAT were significantly higher in SRD treatments as compared to that in 100% RDP treatment. However, grain yield of rice among four treatments were comparable. In conclusion, the critical doses of P, Zn and Si in soil slurry for SRD method according to rice types (traditional, HYV and hybrid rice) for acidic SCL and CL soils were reported for the first time. The critical doses of P, Zn and Si in soil slurry SRD method for rice crop were in increasing order of Hybrid rice > HYV rice ≥ traditional rice. TheP+MCRD+50%RDP+FA of Zn-Si method was comparable to 100% RDP in terms of grain yield, harvest index and uptake of N, P, Zn and Si. The half quantity of the recommended P fertilizer dose can be reduced by adopting P+MC RD+50%RDP+FA of Zn-Si method in acid soil without compromising yield and approximate 2 times higher P use efficiency. Hence, P+MCRD+50%RDP+FA of Zn-Si method is recommended for enhancing nutrient use efficiency and sustaining higher yield of rice in acid soils.ThesisItem Open Access Plant litter–soil enzyme interactions and biochemical index of soil fertility in Jhum Agroecosystem(College of Post Graduate Studies in Agricultural Sciences, CAU-Imphal, Umiam, 2016-03) Saplalrinliana, Henry; Thakuria, DwipendraThis study assessed whether the slash-burn practice (jhum) induced disturbance on the above-ground biological inputs (plant and leaf litters) had any influence on the soil biochemical processes in terms of soil enzyme activities and thereby framing up biochemical index of soil fertility. The jhum cycles of 5 yr, 10 yr and 15 yr from Mizoram and 5 yr, 10 yr and 20 yr from Nagaland were selected. Litter (adjacent fallow stands/secondary forest) and soil samples (burnt and unburnt cropping phase) were collected from three slopes (upper, middle and lower) from each site and were analyzed for chemical and biochemical properties. Two microcosm experiments were conducted using jhum soils (before and after burnt and unburnt from 5 yr and 10 yr fallows) to investigate the effect of different forest floor litter types on stress physiology of jhum rice, soil chemical and biochemical processes, and also to compare the effects of litter amendment (LA), microbial consortium (MC), LA+MC, ash amendment (AA) and no input on physiology and growth of jhum rice and soil biochemical properties. Forest floor litter (FFL) accumulation significantly increases with the increasing fallow length and accumulation dynamics showed an increasing trend in the order of January> April> August> November. Quality of FFL (N, P, Ca, Mg and Zn contents) varied significantly among fallow lengths with maximum contents in the longer fallows (P0.05, Kruskal-Wallis H-test). Higher content of Carbohydrate, Cellulose, Hemicelulose, Pectin and Lignin in FLL was in the order of 20yr & 15yr > 10yr > 5yr and effects were significant. Soil chemical and biochemical properties varied significantly between burnt and unburnt or among fallow periods (P0.05, Kruskal - Wallis test). In microcosm experiment-I, there was significantly positive influence on reducing physiological stress and root growth of jhum rice due to burning or longer fallow lengths or types of FFL (5, 10 and 15 yr FFL). The extent of positive influence of FFL addition on rice grain was more pronounced under burning situation. The extent of grain yield enhancement decreased with the increasing complexity of the litter types. However, such influence was nullified under 10 yr burnt situation. In microcosm experiment II, the extent of physiological stress in jhum rice was the minimum in LA+MC followed by MC and AA. Application of LA+MC and MC supported better soil enzyme activities (AMY, ASA, DHA, GSA, PHA and PRO) in both 5yr and 10 yr burnt jhum soils as compared to other LA and AA alone applied pots. The extent of change of soil biochemical attributes, SOC and Avl P relative to reference site (reserve forest) were more pronounced due to burning as well as fallow lengths. Among soil enzymes, PRO, PHA and DHA were more sensitive to burning. Soil BD seems to be more sensitive to burning than fallow lengths. Higher fallow lengths reflected higher SQI. The differences in SQI among fallow lengths were significant under unburnt situation. In general, SQI values were higher in unburnt compared to their respective burnt situations. In conclusion, burning of biomass releases a higher quantum of plant available nutrients in jhum soils momentarily, which can support better crop growth under longer fallow lengths. However, burning negatively impacted the biochemical quality of jhum soils. Thus, it indicates that burning gradually decrease the inherent nutrient cycling potentials of jhum soils. Application of less complex litter materials along with native microbial consortium as biological inputs can rejuvenate the biochemical and biological activities of jhum soils. The SQI index values of different fallow lengths under burnt situation indicated that jhum soils seem to attain a new threshold limit of soil quality at approximate 10 yr fallow length, where SQI value was comparable with the SQI values of 15 yr and 20 yr fallows.
