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The present study was carried out at Dr. Rajendra Prasad Central Agricultural University, Samastipur, Bihar during 2021–2023 to focus on examining alterations in SOC pools resulting from conservation agriculture (CA) practices in R-W system in the eastern IGP, following the collection of soil samples from a long-term trial that was initiated in rainy (kharif) season 2006. The trial included eight combinations, namely: conventional tilled rice (Oryza sativa L.) and wheat (Triticum aestivum L.) (CTR-CTW); CT rice and zero till wheat (CTR-ZTW); direct seeded rice (DSR) and wheat on permanent raised beds (PBDSR-PBW); ZTDSR and CT Wheat (ZTDSR-CTW); ZTDSR and ZT wheat without residue (ZTDSR-ZTW -R); ZTDSR-ZT wheat with residue (ZTDSR-ZTW +R); unpuddled transplanted rice- ZTW (UpTR-ZTW) and ZTDSR-sesbania brown manure-ZTW (ZTDSR-S-ZTW). Results revealed that implementing zero tillage (ZT) combined with residue retention in rice and wheat cultivation led to enhanced levels of soil organic carbon (SOC) across all four fractions, namely very labile (CVL), labile (CL), less labile (CLL), and non-labile (CNL), in comparison to the continuous and rotational tillage practices. The tillage and residue management options significantly affected the lability index (LI) and C pool index (CPI), with zero-tillage and residue retention leading to lower LI and higher CPI values. The management practices significantly affected the C management index (CMI), with zero-tillage and residue retention showing the highest CMI values. Findings showed the potential of CA practices for enhancing soil C quality as well as C sequestration in soil of the Eastern IGP of India.

Copper (Cu) and manganese (Mn) are two most important micronutrients, essential to living organisms through their involvement in different enzymes and other biologically active molecules. An experiment was conducted at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to investigate the impact of various fertilizers and manurial treatments on DTPA-extractable Cu and Mn in soil and their concentration in grain and straw of wheat (Triticum aestivum L.) after 46 years of continuous cropping. The soil and plants samples were collected at wheat harvest during April, 2018 and April, 2019 following fertilizers and manurial treatments: control, N alone, NP, NPK, 150% NPK, NPK+Zn and NPK+FYM. Results revealed that DTPA-extractable Cu did not show any significant variation among the various treatments except control but DTPA-Mn was highest under FYM treated plot. In addition, nutrient management options such as 150% NPK, NPK+FYM and NPK+Zn were equally effective in enhancing the yield of wheat. The concentration of Cu and Mn in grain varied from 5.25–7.63 and 28.5–36.4 mg/kg, respectively under different nutrient management options. Highest uptake of Cu and Mn was obtained under NPK+FYM treatment while control showed the lowest, indicating importance of organic manures for improving the nutritional quality of food grains. Transfer coefficient (indicating transfer nutrients from vegetative tissue to grain) of Cu did not change by fertilization and manuring to a significant level whereas balance and integrated use of fertilizers and manure significantly increased the transfer of Mn from straw to grains.

Zinc (Zn) is one of the seventeen essential nutrients required for proper growth and development of plants. Majority of soils of India (about 43% of its cultivated soil) are deficient in Zn. Long-term fertilizer experiments (LTFE) are the perfect platform to investigate the impact of integrated nutrient management (INM) over a long period of time on Zn availability and uptake by crops. With this aim, soil samples were collected from an on-going 47 year-old longterm fertilizer experiment at ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi after harvesting of wheat during April, 2018. The selected fertilizer and manurial treatments includes control, N alone, NP, NPK, 150% NPK, NPK+Zn and NPK+FYM were studied. Results of the study reveal that yield of wheat, Zn content and uptake varied from 1.95-5.58 t/ha, 29.8-42.3 mg/kg, and 96.5-368 g/ha, respectively, across the nutrient management practices. It was also found that residual Zn was the major fraction in soil which accounted for 86-90% of the total Zn followed by oxide bound Zn (5.4-9.2%), organically bound Zn (1.9-3.8%), carbonate bound Zn (0.34-0.82%) and water soluble plus exchangeable Zn (0.26-0.58%). Grain yield of wheat was at par in NPK+Zn and NPK+FYM indicating that similar response of the applied Zn as compared to integrated nutrient management. Thus, NPK+Zn are the best option for producing Zn-fortified grains and sustainable crop production.

Present study was under taken to evaluate the impact of long-term application of fertilizers and lime on fluorescein diacetate (FDA) activity, and their resistance and resilience against heat stress (48°C for 24 h) in acidic Alfisol. To accomplish this, soil samples (0-15 cm depth) were collected from seven treatments (control, 100% N, 100% NP, 100% NPK, 100% NPK+ handweeding, 100% NPK+FYM and 100% NPK+lime) from soybean crop under long-term fertiliser experiment (LTFE) at Birsa Agricultural University, Ranchi (2018). Resistance and resilience capacity of FDA were analyzed at 1, 15, 30 and 60 days after heat stress (DAS). FDA in soil was significantly higher in NPK+FYM (747 μg fluorescein g/soil/h) followed by100% NPK+hand weeding, 100% NPK+lime, 100% NPK, 100% NP, 100% N and control treatment. At 1 DAS, maximum reduction (69%) of FDA was noticed under 100% NP alone plots followed by 100% N (64%) treatments over initial value. Treatment 100% NPK+FYM had highest resistance index (0.33) with lowest resistance (0.19) was noticed in 100% NP alone treatment. Recovery rate of most of the treatments was higher during 15 to 30 DAS and almost 100 % recovery at 60 DAS. In nutshell, FDA emerged as a good indicator to assess resistance, resilience and functional behavior of soil against abiotic stress.

A field experiment was conducted to evaluate the long-term sewage sludge (SS) and fertilizer impact on yield and farm profitability in maize (Zea mays L.) grown at the ICAR-IARI, New Delhi during 2014-17. The experiment was laid out in a randomized complete block design with eight different treatment combinations comprising of different levels of sludge and fertilizer as follows: T1= control (no sludge and NPK fertilizer), T2= 100% recommended dose of NPK (NPK), T3= 25% N substituted by sludge +75% N + PK, T4= 50% N substituted by sludge + 50% N + PK, T5= 100% N substituted by sludge + PK, T6= Two times of sludge as applied in T5 + PK, T7= Three times of sludge as applied in T5 + PK and T8= NPK+2.5 t sludge/ha. Results revealed that the combined application of sludge @ 2.5 t/ha along with NPK (T8) showed highest grain yield of maize i.e. 5.93 t/ha. Total P, K and micronutrients uptake by straw and grain of maize were found to be highest in T7 treated plot. The maximum gross return, net return and B:C ratio were recorded under NPK along with 2.5 SS t/ha. Application of sludge not only enhanced the crop productivity of maize by supplying major and micronutrients, but also enriched maize grain with micronutrients like Zn and Fe throughout the treatments. Finally, it can be concluded that the treatment T8 i.e. NPK+2.5 SS t/ha could be an effective option for getting higher profitability and better quality yield of maize.

Field experiment was conducted during rabi season for two years (2014-15 and 2015-16) on wheat cultivar HD- 2967 in a sandy loam soil (Inceptisol) for simulation of evapotranspiration, crop water use efficiency (WUE) and yield of wheat under different tillage (Conventional tillage (CT) and no tillage (NT)), residue (maize residue @ 5 t ha-1 (R+) and without residue (R0)) and nitrogen (60, 120 and 180 kg N ha-1, representing 50% (N60), 100% (N120) and 150% (N180) of the recommended dose of nitrogen for wheat (Triticum aestivum L.), respectively management practices using DSSAT (v 4.6) model. Experimental data of the years 2014-15 and 2015-16 was used for the calibration and validation of the model, respectively. The results showed no significant difference in grain and biomass yield due to tillage and crop residue mulch but it increased significantly with increase in the N levels. The WUE of wheat was also not influenced by tillage but increased significantly with the increase in N levels. The DSSAT model could satisfactorily simulate grain yield (R2 = 0.759), biomass yield (R2= 0.728) and seasonal ET (R2= 0.904) in wheat but simulation of WUE (R2= 0.414) was not significant under different tillage, residue and nitrogen management with acceptable level of accuracy.

A study was conducted on a semi-arid climate and sandy loam soils of Indian Agricultural Research Institute farm, New Delhi to evaluate the short-term (5 years) interactions of tillage, residue and nitrogen management on soil physical properties, root growth and yield of wheat (Triticum aestivum L.) in a maize-wheat cropping system in a split-split plot design comprising two tillage (No tillage and conventional tillage), two residue levels (no residue, maize residue @ 5 t ha-1) and three nitrogen doses (N60, N120 and N180) as the main plot, sub plot and sub subplot treatments, respectively. It was observed that bulk density (up to 45 cm), penetration resistance (10-27 cm depth) reduced under no tillage and residue applied plots while the porosity (15-60 cm), mean weight diameter (0-15 cm), organic carbon (0-15 cm) improved in these treatments. The hydraulic conductivity was significantly enhanced due to residue applications in the surface layers (0-15cm). Root growth parameters were improved under no tillage and crop residue mulching. Although neither tillage nor residue mulching could significantly influence the grain and biomass yield of wheat on two years of study (2017-18, 2018-19), yield increased significantly with increasing nitrogen doses. Thus no tillage, residue mulching with 150% recommended dose of nitrogen can be practised for maintaining a better soil physical health, root growth without any significant reduction in crop productivity compared to conventional tillage.

Soil organic carbon (SOC) is the center of all physical, chemical and biological properties of soils, its maintenance and buildup in soils is necessary to sustain the intensive cereal-based cropping system of Indo Gangetic plains. Intensive tillage, residue removal and indiscriminate use of fertilizers led to a continuous deterioration of soil health in Indo Gangetic parts of the country. Under this context, a field experiment on conservation agriculture (CA) was conducted at Taroari, Karnal, comprising four combinations of tillage and residue management [i.e. conventional tillage (CT) with complete residue removal (CT-RR), CT with 20% residue incorporation of wheat, 50% residue incorporation of maize and incorporation of green gram residue (CT+RI+GI), permanent beds (PB) with 20% residue retention of wheat and 50% residue retention of maize (PB+RR), and PB with 20% residue retention of wheat, 50% residue retention of maize and retention of green gram residue (PB+RR+GR)] and three nutrient management options [viz. farmers fertilization practice (FFP), recommended fertilizer dose (RDF) and site-specific nutrient management (SSNM)]. The results showed that, there was an increase in SOC mainly the active SOC pools, permanganate oxidizable-C (1.70 g/kg), hot water extractable-C (0.32 g/kg) and soil microbial biomass C (310 mg/kg) under CA-based treatment (PB+RR+GR) compared to CT (0.58, 0.23 g/kg, 183 mg/kg, respectively). Also, the mineral N was invariably greater under residue treatments. Therefore, crops residue retention as well as balanced fertilization (RDF and SSNM) under CA helped in improving SOC; mineral N and soil aggregation stability which can lead to increased sustainability under cereal-based intensive cropping systems.

An experiment was carried out on basmati rice (Oryza sativa, var. Pusa Basmati 1121) using IARI soil to assess the effect of applied sludge on different soil properties, metals content in rice grain and computed hazard quotient for suitability of rice grain for human consumption. The different doses of sludge were used as treatments 0, 10, 20, 30, 40 and 50 g/kg.The results indicated that applied sludge @ (50 g/kg) reduced the pH from 7.98 (control) to 7.21 of sludge amended soil. Whereas, the EC increased from 0.22 (control) to 1.33 dS/m under applied @ 50 g sludge/kg of soil. The organic carbon content and cation exchange capacity were found highest in 50 g sludge/ kg soil treatment as compared to control. DTPA Extractable metals in post- harvest soil were significantly higher in sludge application @ ≥ 30 g/kg treatments. The value of HQ ranged from 0.05 to 0.49 and 0.02 to 0.09 for Pb and Cd, respectively across the various treatments of sludge addition. It can be concluded that risk assessment for intake of metals through consumption of rice by human indicated that application of sludge should be restricted up to 20 g/ kg unfit for rice cultivation.

The present study was performed to evaluate the effect of lime, poultry manure and farmyard manure (FYM) application on the immobilization of soil iron (Fe) under both submergence and alternate wetting-drying (AWD) soil moisture regimes. Effect of soil amendments (organic and inorganic) and soil moisture regimes on the dry matter yield, total Fe content in plant, the DTPA-extractable soil Fe and the distribution of Fe in various chemical fractions of contaminated soil was explored in the greenhouse pot experiment during 2018 at IARI, New Delhi. Results indicated that the mean DTPA-extractable Fe content in post-harvest soil was found significantly lower under AWD (84.8 mg/ kg) as compared to submergence (118 mg/kg). The mean DTPA-extractable Fe was significantly reduced by 14.7% due to the application of lime over control. Poultry manure and FYM application were ineffective in altering the mean DTPA-extractable Fe. Water soluble and exchangeable Fe content in post-harvest soil was decreased significantly by 17.7% under AWD compared with submergence and it was reduced significantly by 25.2% due to the lime application over control. Whereas, carbonate bound Fe content was increased significantly by 8.0% due to the lime application over control while it was decreased significantly by 5.3% due the poultry manure over control. Therefore, lime application under AWD soil moisture regime was the best practice for remediation of metal contaminated soil and poultry manure and FYM could be include in management practices for improving crop yield.

A pot experiment was conducted in acid soil (Alfisol) using four levels of lime (CaCO3) based on lime requirement (LR), viz. 0, 1/3, 2/3, and 1 and four levels of boron (B), viz. 0, 1.0, 1.5 and 2 mg/kg to evaluate the effect of applied calcium (Ca) and boron (B) on biomass yield, nutrient uptake of tomato (Solanum lycopersicum L.) and soil properties. The results indicated that application of Ca @ 2/3 LR and 1 LR significantly increased biomass yield of tomato by 21% and 16%, respectively over control. Boron application @ 1.0 mg/kg recorded highest biomass yield (19.6 g/pot) of tomato as compared to other boron treatments. Applied Ca @ 2/3 LR significantly increased the uptake of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), zinc (Zn) and copper (Cu), whereas iron (Fe), manganese (Mn) and B uptake increased only up to Ca @ 1/3 LR treatment. Application of B increased the nutrients uptake over control, whereas it was observed significantly higher with B @ 1.5 mg/kg treatment. Applied Ca significantly enhanced the pH and available Ca in post-harvest soil, whereas salicylic acid extractable boron (SAE-B) was declined. The combined application of calcium @ 2/3 LR and B @ 1.5 mg/kg was most effective in enhancing the yield and nutrient uptake of tomato.

The efficient (site-specific) management of soil nutrients is possible by understanding the spatial variability in distribution of phyto-available nutrients (here after called available nutrients) and identifying the soil management zones (MZs) of agricultural landscapes. There is need for delineating soil MZs of agricultural landscapes of the world for efficient management of soil nutrients in order to obtain sustainability in crop yield. The present study was, therefore, undertaken to understand the spatial distribution pattern of available micronutrients (zinc (Zn), boron (B), iron (Fe), manganese (Mn) and copper (Cu)), available sulphur (S), and soil properties (soil acidity (pH), electrical conductivity (EC) and organic carbon (SOC) content) in soils of intensively cultivated Indo-Gangetic Plain (IGP) of India and to delineate soil MZs for efficient management of soil nutrients. Totally, 55101 soil samples from 0-15 cm depth were obtained from 167 districts of IGP during 2014 to 2017 and were analysed for different soil parameters. Soil pH, EC and SOC content varied from 4.44 to 9.80, 0.02 to 2.13 dS m-1 and 0.10 to 1.99%, respectively. The concentration of available Zn, B, Fe, Mn, Cu and S varied from 0.01 to 3.27, 0.01 to 3.51, 0.19 to 55.7, 0.05 to 49.0, 0.01 to 5.29 and 1.01 to 108 mg kg-1, respectively. Geostatistical analysis resulted in varied distribution pattern of studied soil parameters with moderate to strong spatial dependence. The extent (% area) of nutrient deficiencies in IGP followed the order: S > Zn > B > Mn > Cu > Fe. Principal component analysis and fuzzy c-means clustering produced six distinctly different soil MZs of IGP for implementation of zone-specific soil nutrient management strategies for attaining sustainability in crop yield. The developed MZ maps could also be utilized for prioritization and rationalization of nutrients supply in IGP of India.

A long-term field experiment on conservation agriculture (CA) was initiated in sandy loam soil of Indo-Gangetic plain in 2008 at Research Farm of ICAR-IARI, New Delhi with 3 tillage practices, i.e. permanent bed (PB), zero-tillage (ZT) and conventional tillage (CT) in main plots and four maize-based cropping systems, i.e. maize-wheat-mungbean (MWMb), maize-chickpea-sesbania (MCS), maize-mustard-mungbean (MMuMb), maize-maize-sesbania (MMS) in sub-plots, in a split- plot design with three replications to evaluate the long-term effects of CA practices on maize yield and soil fertility under maize-based cropping systems. The current study was undertaken in kharif maize 2015 after completion of seven years of experimentation. Soil fertility parameters like mineral nitrogen (N) (NO3 – and NH4 +), available phosphorus (P), potassium (K), sulphur (S) and micronutrients (Zn, Fe, Mn, Cu) were determined from 0–5, 5–15 and 15–30 cm of soil depths. The available macronutrients (N, P, K and S) and micronutrients (Zn, Fe, Mn, Cu) were higher under PB and ZT compared with CT. Among the cropping systems, MCS and MWMb performed equally in relation to nutrient availability. The grain yield of maize was significantly higher under PB (5.55 t/ha) and ZT (5.49 t/ha) as compared to CT (4.81 t/ha), whereas MCS and MWMb performed better in term of maize productivity as compared with MMuMb and MMS. Thus, the long-term study suggested that ZT and PB under diversified cropping systems such as MWMb and MCS could be the best agricultural practices for sustainable production as well as nutrient availability in maize-based cropping systems.

Effect of long-term fertilization and manuring on soil potassium (K) fractions in black soil (Vertisol) was investigated after 42 years of cultivation. Soils from 6 treatments, viz. control (unfertilized), N (100% of recommended N fertilizer), NP (N+ 100% of recommended P fertilizer), NPK (NP+ 100% of recommended K fertilizer), 150% NPK (150% of recommended N, P and K fertilizer), NPK+FYM (NPK+ farm yard manure), and adjacent uncultivated land were collected from 0–15 and 15–30 cm depths. Water soluble K (WSK), exchangeable K (EK) and non-exchangeable K (NEK) in soil; grain yields and K uptakes of soybean and wheat; and annual apparent K balances for different treatments were determined. Long-term variation in fertilization significantly altered the WSK, EK and NEK fractions in the soil. Cropping with K fertilizer resulted in higher WSK and EK than cropping without K fertilizer. Non-exchangeable K estimated by boiling nitric acid extraction showed higher values than that extracted by sodium tetraphenyl boron for five minutes. Wheat grain yield and total K uptake by the two crops showed positive response to K fertilization. Apparent annual K balances for 2013-14 crop cycle were negative irrespective of nutrient supply options. In general, all the K fractions and especially the exchangeable and interlayer K showed decline over uncultivated (or initial) soil. Findings of the present study, thus, highlight the need to develop a more pragmatic K fertilization approach based on exchangeable and non-exchangeable K reserves so as to minimize the decline in soil K-fertility under intensive cultivation.

A field experiment was conducted between 2012-14 to investigate the effect of different phosphorus levels (control-no P, 33% P, 50% P, 100% P and 100% P in 3-splits of the recommended dose of P) and microbial inoculants (un-inoculated control, arbuscular mycorrhizal fungi, AM phosphate solubilising bacteria, PSB and AM+PSB) in maize-wheat system. The study revealed that the maize and wheat grain yields were increased by 20% and 40%, respectively, under 100% P which were significantly higher over control. The total P uptake by maize and wheat varies from 11.7–20.7 kg/ha and 17.7–32.4 kg/ha, respectively. The highest apparent recovery (AR) in both the crops was recorded when 50% P was added with AM+PSB inoculation whereas, a significant reduction in AR was recorded with increase in fertilizer P beyond 50% of recommended P. Agronomic efficiency was highest under 50% P averaged across microbial inoculants in both maize (32.5 kg grain/kg P) and wheat (78.5 kg grain/kg P). Grain yield of both maize and wheat was significantly and positively correlated with Olsen P content at tasseling (r = 0.30*) and panicle emergence (r = 0.35**). The higher P use-efficiency under 50% recommended P along with microbial inoculants suggests applying lower doses of P fertilizer along with microbial inoculants to achieve optimum yield in maize-wheat system without any adverse impact on soil fertility.

Limited information is available on the impacts of long-term organic nutrient management practices on different nitrogen pools and urease enzyme activity. Hence, the major objective of this study was to evaluate long-term (12 years) organic nutrient management practices’ impact on different nitrogen pools and urease activity. Treatments were two cropping systems, viz. rice (Oryza sativa L.) –wheat (Triticum aestivum L.)-mungbean [Vigna radiata (L.) Wilczek] (RWMCS) and rice-wheat (RWCS) in strips and seven nutrient combinations, i.e. FYM equivalent to 60kg N/ha, VC equivalent to 60 kg N/ha, FYM + crop residue (CR) of preceding crop @ 3 t/ha for each rice, wheat and mungbean, VC+CR, FYM+CR+BF and VC+CR+BF and control under sub-plots. Available N, microbial biomass N (MBN), mineral N, potential mineralizable (PMN), total N and urease enzyme assay were analysed in 0-15 cm soil depth. Results showed that FYM+CR+BF recorded 5.5% and 7.7% higher available N as compared to the FYM alone in both RWMCS and RWCS, respectively. Similarly, an increment of 4.0% and 7.5% in available N was observed with VC+CR+BF over VC alone in both the cropping systems, respectively. MBN ranged from 47.1 mg/kg (control) to 69.6mg/kg (FYM) under RWMCS and 43.2 mg/kg (control) to 67.6 mg/kg (FYM) under RWCS. Treatments FYM+CR and FYM+CR+BF showed 5.0% and 30% lower ammonical N as compared to FYM alone treatments in RWMCS. Concurrently, in case of RWCS, the magnitude of decrease in ammonical N content was similar (21.1%) both in FYM+CR and FYM+CR+BF. The total mineral nitrogen (NH4+ -N+ NO 3 - -N) content was significantly influenced by the application of organic manures, crop residues and biofertilizers in both RWMCS and RWCS and their interaction effects. The FYM+CR+BF treatment recorded highest (56.4 mg/kg) potential mineralizable N (PMN) among all the treatments with an increment of 86.4% and 104% the over control in RWMCS and RWCS, respectively. The VC+CR showed 6.1% and 5.5% higher total N content over the control in RWMCS and RWCS, respectively. The content of urease enzyme ranged from 155.1 μg urea/g soil/h (control) to 230.4 μg urea/g soil/h (VC+CR) and 144.3 μg urea/g soil/h (control) to 233.6 μg urea/g soil/h (FYM+CR) in RWMCS and RWCS, respectively

An attempt was made to evaluate simple techniques for extraction of soil solution for predicting uptake of Zn, Cu, Ni, Pb and Cd by spinach (Beta vulgaris L. var. All Green) grown on metal contaminated soils under modelling framework. Twenty-eight surface soil samples (0-15 cm) with heterogeneous chemical properties were collected. A pot experiment was conducted using spinach as a test crop. The leachate from experimental pots was collected with the help of plastic container installed below the pots. The 1:2 and 1:5 soil: water ratio was used for soil solution extraction. The total concentration of Zn, Cu, Ni, Pb, and Cd in soil solution was determined using ICP-MS. Harvested plant sample was analyzed for total Zn, Cu, Ni, Pb, and Cd using ICP-MS. For predicting metal uptake by spinach free ion activity model (FIAM) was used and total metal concentration in soil solution was used as an input of FIAM. Higher concentration of all metal in 1:5 soil-water ratio were recorded than that in 1:2 soil-water ratio. The free ion activity model as a function of total metal concentration in soil solution, as measured by 1:5 soil: water extraction, could explain the variability in metal content in spinach to the extent of 94% for Zn, 67% for Cu, 80% for Ni, 50% for Pb and 75% for Cd, respectively. Extraction of soil with 1:5 soil-water ratio is more efficient and suitable for predicting metal uptake by spinach as compared to that of 1:2 and leachate extraction.