This study assessed spatiotemporal water quality, hydrogeochemical characteristics, and heavy metal contamination level of anthropogenically impacted an ancient artificial freshwater wetland, Bhojtal, India, which is crucial for drinking water supply and aquatic biodiversity. The study revealed significant (p < 0.05) seasonal variations in pH, magnesium, and dissolved oxygen levels exceeding permissible limits. Hydrogeochemical classification indicated Cl‒-Ca2+/Mg2+ facies dominance post-monsoon. Entropy-based WQI results showed excellent water quality during the monsoon, which declined to good (67

This study was undertaken to address how near-surface soil water content (SWC) patterns have varied across diverse agroecological regions (AERs) of mainland India from 1979 to 2022 (44 years) and how these variations relate to environmental factors. Grid-wise trend analysis using the Mann–Kendall (MK) trend test and Sen’s slope was conducted to determine the trends and their magnitudes. Additionally, we used Spearman’s rank correlation (ρ) to explore the relationships of ESA CCI’s near-surface SWC data with key environmental variables, including rainfall, temperature, actual evapotranspiration, and the normalized difference vegetation index (NDVI). The results revealed significant variations in SWC patterns and trends across different AERs and months. The MK trend test indicated that 17.96% of the area exhibited a significantly increasing trend (p < 0.1), while7.6% showed a significantly decreasing trend, with an average annual Sen’s slope of 0.9 × 10−4 m3 m−3 year−1 for mainland India. Areas with the highest decreasing trends were AER-16 (warm per-humid with brown and red hill soils), AER-15 (hot subhumid to humid with alluvium-derived soils), and AER-17 (warm per-humid with red and lateritic soils). In contrast, increasing trends were the most prominent in AER-5 (hot semi-arid with medium and deep black soils), AER-6 (hot semi-arid with shallow and medium black soils), and AER-19 (hot humid per-humid with red, lateritic, and alluvium-derived soils). Significant increasing trends were more prevalent during monsoon and post-monsoon months while decreasing trends were noted in pre-monsoon months. Correlation analysis showed strong positive correlations of SWC with rainfall (ρ = 0.70), actual evapotranspiration (ρ = 0.74), and NDVI (ρ = 0.65), but weak or negative correlations with temperature (ρ = 0.12). This study provides valuable insights for policymakers to delineate areas based on soil moisture availability patterns across seasons, aiding in agricultural and water resource planning under changing climatic conditions.

Keywords: climate change, nitrogen limitation, physiological response, photosynthesis, soil nutrient pool

Optimum soil moisture and high crop residue return (RR) can increase the active pool of soil organic carbon and nitrogen, thus modulating the magnitude of greenhouse gas (GHG) fluxes. To determine the effect of soil moisture on the threshold level of RR for the wheat production system, we analyzed the relationship between GHG fluxes and RR at four levels, namely 0, 5, 10, and 15 Mg ha−1 (R0, R5, R10, and R15) under two soil moisture content (80% FC and 100% FC) and three levels of nutrient management (NS0: no nutrient; NS1, NS2= 3x NS1). Nutrient input (N and P) in NS1 balanced the residue C/nutrient stoichiometry to achieve 30% stabilization of the residue C input in RR (R5). All RR treatments (cf. R0) were found to significantly reduce N2O emission in moderate soil moisture content (80% FC) by 22–56% across nutrient management due to enhanced soil C mineralization, microbial biomass carbon, and N immobilization. However, averaged across nutrient management, a linear increase in N2O emission was observed with increasing RR under 100% FC soil moisture. A significant decrease in CH4 emission by ca. 46% in most RR treatments was observed in 100% FC compared with the R0. The N2O emission was negatively correlated (p = <0.001) with nutrient stoichiometry. Partial least square (PLS) regression indicated that GHG emissions were more responsive (values > 0.8) to management variables (RR rate, nitrogen (N) input rate, soil moisture, and nutrient stoichiometry of C: N) and post-incubation soil properties (SMBC and NO3-N) in Alfisols. This study demonstrated that the mechanisms responsible for RR effects on soil N2O, CH4 fluxes, and carbon mineralization depend on soil moisture and nutrient management, shifting the nutrient stoichiometry of residue C: N: P.

Years of chemical-intensive agricultural practices following the Green Revolution in the late 1960s have led to extensive soil degradation in India. This has implications for food security, farmers’ incomes, and the country's economy. However, domestic top-down policy mandates in recent times have favoured practices like natural farming with a view to slow down and eventually halt soil degradation. This is in line with the international Sustainable Development Goals (SDGs), one of which is focused on restoring degraded lands (SDG 15.3 aims to strive achieve land degradation neutrality). Taking cue from recent policy mandates on soil and land, this chapter posits the historical significance of the Panchayat — a village-level administrative institution in India — and argues for its involvement in policy implementation for soil rehabilitation at the village level, The article also makes a case for the introduction of an overarching National Soil Policy to encourage natural farming practices and biofertilizer use.

Evaluating the impacts of high temperature-mediated changes in soil-plant systems is crucial in sustaining the productivity of heat-sensitive crops like chickpea (Cicer arietinum L.). Currently, the impact of a high temperature environment on soil processes and crop nutrition, particularly phosphorus (P), remains uncertain in tropical alkaline soils. Therefore, an open-top chamber-based experiment with ambient temperature [a(Temp)] and elevated temperature [e(Temp)] (+2 degrees C over ambient) aimed to investigate the impacts of high temperature environment on plant physiology, soil plant P dynamics, and yield of chickpea in a moderately-alkaline Vertisol of sub-tropical climate. The e(Temp) reduced Olsen-P (available-P) and NaHCO3-Pi at the flowering stage by 12% and 32%, respectively, as compared to a(Temp) treatment. The e(Temp) treatment markedly reduced KMnO4-oxidizable carbon (-25% to 42%), but did not alter water-soluble carbon. Alkaline phosphatase and ss-glucosidase activities were reduced under the e(Temp) treatment, while acid phosphatase activity remained unchanged. The elevated temperature had a significant impact on chlorophyll-b content (+18%), stomatal conductance (+5%), transpiration rate (+8%), and photosynthetic rate (-22%). The e(Temp) treatment did not alter total P uptake rather altered its distribution in grain (-16%) and stover (+17%) parts, resulting in a lower internal P use efficiency (-12%) and P harvest index (+15%). The e(Temp) treatment caused 12% yield loss compared to a(Temp) treatment. Therefore, this is concluded that retardation in P-mineralization along with terminal heat stress could impair P nutrition, physiological activity, and yield of chickpea.

Although crop residue returns are extensively practiced in agriculture, large uncertainties remain about greenhouse gas (GHG) emissions and global warming potential (GWP) responses to residue return (RR) rates under different residue placements and nutrient supplements. We conducted a laboratory mesocosm experiment in Alfisol in central India to investigate the responses of soil GHG emissions (CO2, N2O, and CH4) and the global warming potential to four wheat RR rates (R0: no residue; R5: 5 Mg/ha; R10: 10 Mg/ha; R15: 15 Mg/ha) and two placements (surface [Rsur] and incorporated [Rinc]) under three nutrient supplement levels (NSLs) (NS0: no nutrients, NS1: nutrients (N and P) added to balance the stoichiometry of C:N:P to achieve 30% humification in RR at 5 t/ha, NS2: 3 × NS1). The results demonstrated a significant (p < 0.05) interaction effect of RR × NSL × residue placement on N2O emission. However, CH4 and GWP responses to the RR rate were independent of NSL. N2O fluxes ranged from −2.3 µg N2O-N kg−1 soil (R5 NS0 Rsur) to 43.8 µg N2O-N kg−1 soil (R10 NS2 Rinc). A non-linear quadratic model yielded the best fit for N2O emissions with RR rate (R2 ranging from 0.55 to 0.99) in all NSLs and residue placements. Co-applying wheat residue at 10 and 15 Mg/ha at NS1 reduced CH4 and N2O emissions (cf. R0 at NS1). However, increasing NSLs in NS2 reduced the nutrient stoichiometry to < 12:1 (C:N) and < 50:1 (C:P), which increased N2O emissions in all RR rates (cf. R0) across all residue placements. Averaged across nutrient levels and residue placements, the order of the effects of RR rates on CH4 emissions (µg C kg−1 soil) was R10 (5.5) > R5 (3.8) > R15 (2.6) > R0 (1.6). Our results demonstrated a significant linear response of total GWP to RR rates R15 > R10 > R5 > R0, ranging from 201.4 to 1563.6 mg CO2 eq kg−1 soil. In conclusion, quadratic/linear responses of GHGs to RR rates underscore the need to optimize RR rates with nutrient supplements and residue placement to reduce GHG emissions and GWP while ensuring optimal soil health and crop productivity.

Greenhouse gas emissions from agricultural production systems are a major area of concern in mitigating climate change. Therefore, a study was conducted to investigate the effects of crop residue, nutrient management, and soil moisture on methane (CH4) emissions from maize, rice, soybean, and wheat production systems. In this study, incubation experiments were conducted with four residue types (maize, rice, soybean, wheat), seven nutrient management treatments {N0P0K0 (no nutrients), N0PK, N100PK, N150PK, N100PK + manure@ 5 Mg ha−1, N100PK + biochar@ 5 Mg ha−1, N150PK+ biochar@ 5 Mg ha−1}, and two soil moisture levels (80% FC, and 60% FC). The results of this study indicated that interactive effects of residue type, nutrient management, and soil moisture significantly affected methane (CH4) fluxes. After 87 days of incubation, the treatment receiving rice residue with N100PK at 60% FC had the highest cumulative CH4 mitigation of −19.4 µg C kg−1 soil, and the highest emission of CH4 was observed in wheat residue application with N0PK at 80% FC (+12.93 µg C kg−1 soil). Nutrient management had mixed effects on CH4 emissions across residue and soil moisture levels in the following order: N150PK > N0PK > N150PK + biochar > N0P0K0 > N100PK + manure > N100PK + biochar > N100PK. Decreasing soil moisture from 80% FC to 60% FC reduced methane emissions across all residue types and nutrient treatments. Wheat and maize residues exhibited the highest carbon mineralization rates, followed by rice and soybean residues. Nutrient inputs generally decreased residue carbon mineralization. The regression analysis indicated that soil moisture and residue C mineralization were the two dominant predictor variables that estimated 31% of soil methane fluxes in Vertisols. The results of this study show the complexity of methane dynamics and emphasize the importance of integrated crop, nutrient, and soil moisture (irrigation) management strategies that need to be developed to minimize methane emissions from agricultural production systems to mitigate climate change.

Developing successful mitigation strategies for greenhouse gases (GHGs) from crop residue returned to the soil can be difficult due to an incomplete understanding of factors controlling their magnitude and direction. Therefore, this study investigates the effects of varying levels of wheat residue (WR) and nutrient management on GHGs emissions (CO2, N2O, and CH4) across three soil types: Alfisol, Vertisol, and Inceptisol. A combination of laboratory-based measurements and a variety of data analysis techniques was used to assess the GHG responses under four levels of WR inputs (0, 5, 10, and 15 Mg/ha; WR0, WR5, WR10, and WR15) and three levels of nutrient (NP0: no nutrient, NP1: nutrients (N and P) were added to balance the residue C/nutrient stoichiometry of C/N/P= 100: 8.3: 2.0 to achieve 30% stabilization of added residue C input at 5 Mg/ha (R5), and NP2: 3 × NP1). The results of this study clearly showed that averaged across residue and nutrient input, Inceptisol showed negative N2O flux, suggesting consumption which was supported by its high legacy phosphorus (19.7 mg kg⁻1), elevated pH (8.49), and lower clay content (13%), which reduced microbial activity, as indicated by lower microbial biomass carbon (MBC) and alkaline phosphatase (Alk-P) levels. N2O emissions were more responsive to nutrient inputs, particularly in Vertisol under high WR (15 Mg/ha) input, while CH4 fluxes were significantly reduced under high residue inputs, especially in Vertisol and Inceptisol. Alfisol exhibited the highest total carbon mineralization and GWP, with cumulative GWP being 1.2 times higher than Vertisol and 1.4 times higher than Inceptisol across residue and nutrient input. The partial least square (PLS) regression revealed that anthropogenic factors significantly influenced CO2 and N2O fluxes more than CH4. The anthropogenic drivers contributed 62% and 44% of the variance explained for N2O and CH4 responses. Our study proves that different biogeochemical mechanisms operate simultaneously depending on the stoichiometry of residue C and nutrients influencing soil GHG responses. Our findings provide insight into the relative contribution of anthropogenic and natural drivers to agricultural GHG emissions, which are relevant for developing process-based models and addressing the broader challenge of climate change mitigation through crop residue management.

Information on the fate of micronutrients in plant tissue and total uptake from soil upon exposure to elevated carbon dioxide (CO2) is meager. Hence, this field study was conducted in open top field chambers to investigate the effects of elevated CO2 and applied nitrogen (N) on partitioning and uptake of zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn) in soybean crop under two CO2 and four N levels during 2016 and 2018 crop seasons. The two CO2 concentrations were ambient and elevated (similar to 550 mu mol mol(-1)). Nitrogen treatments included application at 0, 50, 100, and 150% of the recommended dose. Significant effects of CO2 and N were observed on grain yield, biomass and uptake of the four micronutrients. Seed Fe concentration was significantly increased by 12% under CO2 enrichment. Tukey's post-hoc test revealed significantly higher grain yield, biomass and uptake of micronutrients in seed and straw under CO2 elevation and at higher N application. Uptake of Fe, Zn, Cu, and Mn increased by 53, 42, 36, and 41%, respectively, in seed and by 25, 26, 31, and 18% in straw under elevated CO2. Total uptake of Fe, Zn, Cu, and Mn increased by 39, 38, 34, and 29%, respectively. Nitrogen at 100% level enhanced uptake of Fe, Zn, Cu, and Mn by 25, 20, 32, and 28%. The study bears implications in micronutrient management for sustaining soil health under changing climate.

The usefulness of the soil quality index (SQI) as a tool to evaluate management options has mostly been studied within the boundaries of a crop or experimental field, calling for the need to enhance its utility in regional-scale soil health assessment. Thus, four quantitative approaches for computing the SQI were evaluated with samples collected from 0 to 15 and 15 to 30 cm depths at 156 points from the Trans-Gangetic Plains of North India. Principal component analysis (PCA) and soil function (SF)-based approaches were used to select the minimum dataset from 18 soil parameters and assign weights to key indicators. In both approaches, two different data transformation methods were followed: 1) routine method with maximum or minimum values of indicator parameters and 2) percentile method with the 90th or 10th percentile value as the denominator or numerator for “more is better” and “less is better” scoring functions, respectively. The PCA output with factor loadings from the varimax rotation showed six principal components accounting for 75% of the total variance, with PC1 explaining the highest variance (26.8%) followed by PC2 (16%). The SF-based approach was better than PCA in terms of a higher correlation of SQI with rice and wheat yields. The percentile method showed a higher correlation in both PCA and SF methods. The SQI computed from 0 to 30 cm soil data did not show any superiority over that from 0 to 15 cm soil. Thus, the soil function–based approach with the percentile method of data transformation proved better to compute the SQI and establish a relationship with production function.

Conservation tillage has proven advantageous in improving soil health and productivity. However, the greenhouse gases (GHGs) emission and intensity from different conservation tillage and nutrient management systems under Indian conditions are less understood. Therefore, here, we compared the effect of tillage and nutrient management on GHGs emissions, net global warming potential (NGWP), and greenhouse gas intensity (GHGI) from a field experiment under five years in a soybean-wheat cropping system in the Vertisols. The tillage treatments comprised of reduced tillage (RT) and no tillage (NT). The three nutrient management treatments included application of 100% NPK (T-1), 100% NPK + 1.0 Mg FYM-C ha(-1) (T-2), 100% NPK + 2.0 Mg FYM-C ha(-1) (T-3). The results showed significantly higher SOC sequestration under NT (1388 kg ha(-1) yr(-1)) followed by RT (1134 kg ha(-1) yr(-1)) with application of FYM (2.0 Mg C ha(-1)) (T-3) every year. Across tillage, integrated nutrient management (T-2 and T-3) lowered NGWP and GHGI compared to NPK (T-1). The GHGI of NT system was less by 33% compared to RT. The results suggest that GHGs mitigation and sustained food production in the soybean-wheat system can be achieved in NT and RT with integrated use of organic and inorganic fertilizer as the major component of nutrient management.

Soil erosion and associated loss of soil nutrients and organic carbon are one of the major reasons for low crop productivity in major cotton (Gossypium hirsutum L.) growing areas of India. This calls for designing acceptable and low-cost bioengineering measures to enhance system productivity and soil health. Thus, a field study was conducted at Vasad, Gujarat, India from 2014 to 2017 to evaluate the efficacy of selected bioengineering treatments on cotton crop production and runoff and soil loss. The eight experimental treatments consisted of bio-filters of three grass species, viz.Para (Brachiaria mutica), Guinea (Megathyrsus maximus),and Napier (Pen-nisetum purpureum) at two strip widths (1 m and 2 m), field bund, and the conventional system as practiced by the farmers of the region. The treatments were tested in 45 x 10 m plots having the gauging facility for recording runoff and soil loss data. Rainfall, runoff, sediment concentration, soil loss, organic carbon, nutrient loss, and growth and yield parameters of grass barrier species and the cotton crop were recorded and analysed. The filter strip of Guinea sp. at 2 m width was most effective, reducing runoff by 30%, soil loss by 66%, nutrients loss by 69%, sediment concentration to 1/3rd, and soil organic carbon loss by 65%. The lowest runoff coefficient value of 0.209 observed among the filter strips in this treatment, indicated about 79% of rainwater was conserved in situ. The available soil nutrients increased by up to 42% and SOC concentration by 61%, and cotton equivalent yield by 25% than that of the conventional system. We concluded that Guinea grass filter strips of 2 m width planted at 45 m spacing in cultivable lands having 2% slope minimized runoff, soil loss, nutrient loss, improved soil fertility and enhanced cotton productivity.

The increasing atmospheric [CO2] would alter soil–plant nutrient dynamics depending on crop species, soil type, and climate. Insights on the impacts of the predicted level of elevated [CO2] (e[CO2]) on the soil–plant-environment system are, therefore, important for strategic nutrient management for future environments. The impacts of e[CO2] environment on soil phosphorus (P) bioavailability and soil–plant P dynamics in chickpea are uncertain in tropical alkaline Vertisols. An open-top chamber–based experiment with e[CO2] (570 ± 30 ppmv) and ambient [CO2] treatments aimed to investigate the impacts of e[CO2] on soil–plant P dynamics, physiology, and yield of chickpea in a moderately alkaline Vertisol of subtropical central India. Experimental findings revealed that the e[CO2] treatment increased Olsen P at flowering stage (+ 13%, p < 0.05), water-soluble carbon (11–14%), and KMnO4-C (5–14%) at both branching and flowering stages (p < 0.05). Results demonstrated that the increased mobilization of dissolved non-reactive P (NaHCO3-Po, NaOH-Po) (from branching to flowering) and competitive sorption with higher soluble carbon possibly contributed to the higher available P (Olsen P) under the e[CO2] environment. The e[CO2] treatment had a significant impact on photosynthetic rate (+ 5.3%), stomatal conductance (− 16.5%), and leaf chlorophyll content (+ 5.1%) over the ambient (p < 0.05) but did not alter leaf nitrate reductase activity. The e[CO2] treatment increased plant biomass (+ 25%) and productivity (+ 11.6%), P uptake (+ 16.6%), and physiological P use efficiency (+ 7.1%) (p < 0.05). Thus, it can be concluded that e[CO2] (~ 570 ppmv) could enhance P availability in alkaline Vertisols of subtropical regions favoring P nutrition, physiological activity, and yield of chickpea.

Crop residues as key organic carbon inputs have the potential for soil carbon sequestration. However, previous studies have shown an inconsistent effect of residue return on the direction and magnitude of soil nitrous oxide (N 2 O) emission. We used a laboratory-based soil incubation study to test the response of N 2 O emission to crop residue type, soil moisture, and how nutrient management modulates these responses. In this study, we incorporated crop residues with different qualities (wheat, rice, soybean, and maize) at two soil moisture contents {80% field capacity (FC) and 60% FC} and under seven nutrient levels: N0P0K0 (no nutrients), N0PK, N100PK, N150PK, N100PK + manure@ 5 Mg ha −1 , N100PK + biochar@ 5 Mg ha −1 , and N150PK + biochar@ 5 Mg ha −1 . The results demonstrated significant ( p < 0.01) differences in the magnitude of N 2 O emissions among treatments. However, only the interaction effect of residue × nutrient and nutrient × moisture was significant ( p < 0.05). N100PK and N150PK at 80% FC mitigated N 2 O emission by approximately 20% in wheat residue-amended soil ( cf . control soil without residue). In contrast, maize residue amendment ( cf. control soil) increased N 2 O emission by 130% under N0P0K0 and 80% FC. Residue effects were negatively correlated with the C:N ratio, and a strong positive correlation ( p < 0.01) was obtained between N 2 O emission and CO 2 respiration, labile carbon, mineral N, and residue total nitrogen (TN). When no nutrients were added, N 2 O emission was higher in residue returned soil. However, cumulative fluxes of N 2 O decreased by 6–17% when maize and wheat residues ( cf. control soil) were applied with nutrients. Negative fluxes of N 2 O indicating consumption were observed in every treatment after 57 days of incubation and were most pronounced in control soil without residue and nutrients. Decreasing the soil moisture from 80% FC to 60% FC, the N 2 O consumption rate increased by 6.6 times across residue types and nutrient management. The regression analysis and structural equation modeling (SEM) results showed that residue TN, soil CO 2 emission, NO 3 -N, and labile SOC were the key predictor variables and could explain 82% variability in the soil N 2 O emission in the Vertisols of Central India. The results suggested that nutrient addition (NPK) could alter the magnitude and direction of soil N 2 O flux by residue type and soil moisture by influencing the underlying soil microbial processes of the C and N cycle in the Vertisol of subtropical India.

Despite several implications of excessive nitrogen (N) use on environment, information on effect of elevated carbon dioxide (CO2) and/or temperature on recovery and use efficiency of applied N are limited. Hence, this field study was carried out for three consecutive seasons of wheat crop during 2016-17 to 2018-19 in Open Top Field chambers (OTCs) under four climate conditions, viz. ambient, elevated CO2 (similar to 550 mu mol mol(-1)), elevated temperature (similar to 2.0 degrees C above ambient) and co-elevation of both CO2 and temperature. Interaction of climate and year was found non-significant (P > 0.05) for the studied parameters, but, significant effect of climate was observed in most of the parameters except straw N uptake. Pooled data analysis of three consecutive crop years indicated CO2 elevation significantly enhancing above ground biomass and grain yield and also N uptake in grain. The CO2 mediated grain yield response was to the extent of 15% (P < 0.0001) as compared to ambient, however, the yield advantage was partly offset with co-elevation of temperature. Elevation in CO2 produced 16% higher total N uptake than ambient. Co-elevation of CO2 and temperature showed a higher N uptake by about 10% as compared to ambient. In absolute terms, 25 and 15 kg ha(-1) of additional N uptake was observed under elevation of CO2, and with co-elevation of temperature, respectively. Agronomic (AE(N)) and physiological N use efficiency (PEN), recovery of applied fertilizer N (REN) and partial factor productivity (PFPN) were significantly higher under CO2 elevation. Co-elevation of temperature caused significant depletion in REN and PFPN compared to CO2 elevation. The three years' study clearly indicated significant advantage in yield and recovery of applied fertilizer N with CO2 elevation, at the cost of significantly higher N uptake. Significantly higher N removal and trend of declining soil mineral N content under elevated CO2 indicates possible N mining and N limitations may constrain the long-term plant response to CO2 elevation. The study has significance in N management for sustaining productivity and maintaining soil nutrient pool under changing climate.

Atmospheric carbon dioxide (CO2) concentration, temperature and nitrogen (N) are the key regulators of productivity and water use of plants under the changing climate. However, field scale studies on the interactive effect of the three above critical inputs are limited. Hence, this field study was conducted with three climate treatments (ambient (AC), elevated CO2 (eC, similar to 550 mu mol mol(-1)) and co-elevation of both CO2 and temperature (eCeT, similar to 550 mu mol mol(-1) and temperature similar to 2 degrees C above ambient)) and four N treatments (0%, 50%, 100% and 150% of recommended N dose of 120 kg N ha(-1)). The experiment was carried out in open top field chambers to study the effects of climate and N application on grain yield, evapotranspiration (ET) and water use efficiency (WUE) in wheat crop. Crop ET was estimated by field water balance method and WUE by taking the ratio of grain yield to crop ET. Elevation of CO2 showed 9% yield gain over ambient (averaged across N levels), whereas, coelevation of temperature reduced the yield gain to 4%. Further, N application significantly altered the level of CO2 response. Under CO2 enriched environment, the yield gain was 15% with N-100 as compared to 2% and 4% under N-0 and N-50, respectively, indicating CO2 enrichment benefits in grain yield was N dependent. The three years' pooled data showed significant effect of climate, N and their interaction on profile water storage, evapotranspiration and WUE. Elevation of CO2 alone or with co-elevation of temperature resulted in significant decline in crop ET by 4-11 mm and significant increase in profile soil moisture and WUE. The WUE improved significantly, by 12% under eC and by 4% under eCeT, respectively, with the increase, more attributed to gain in grain yield. Quantitative derivation from the three years' field experimentation could establish that under elevated CO2 scenario (550 mu mol mol(-1)), an additional 1 degrees C rise in temperature would result in enhanced crop ET by 5 mm and yield loss of about 4%. This study thus revealed that limited N and increased temperature would potentially restrict the CO2 mediated benefits in wheat yield and water use under the changing climate.

The annual fertilizer use would increase by 50% in India to increase crop production by 20% from current level to feed 1.7 billion people by 2050. While increasing crop production by 20% to feed the growing population remains a priority, the fertilizer industry has also prioritized climate-smart agriculture to minimize the impact on the environment. Without the reduction in emission intensity, increases in productivity cannot be sustainable over the long term. Reconciling the goals of increasing food demands together with reduced GHG emission from increased fertilizer use requires adoption of good practice guidelines of fertilizer use. It is thus important to consider which technologies and practices can be applied that meet not only adaptation needs, but also mitigation needs. Thus, management practices need to be identified to better utilize fertilizer, while at the same time safeguarding the environment. Therefore, this book chapter aims to discuss the effect of natural and management factors that influence the biochemical and physical processes that determine GHGs emission from fertilizer use.

Rising concentration of atmospheric carbon dioxide (CO2) is reported to cause fertilization effect resulting in enhanced crop biomass and yields and may alter the water use of plants. However, factors like air temperature and nitrogen (N) management could modify the feedbacks of CO2 on crop water use. Hence, this field study was carried out in open top field chambers (OTC) for two crop seasons to investigate the interactive effects of climate and N on evapotranspiration, yield and water use efficiency in soybean (Glycine max L.). Soybean crop was grown under three climate conditions (ambient : AC, elevated CO2 : eC, and co-elevation of both CO2 and temperature : eCeT) and four N treatments during July to October 2016 and 2018. Elevation of CO2 was done to the level of 535-540 mu mol mol(-1), and temperature was elevated by about 2 degrees C above ambient. The four N levels were N-0, N-50, N-100 and N-150 referring to 0, 50, 100 and 150% of recommended N dose (30 kg N ha(-1)). Crop evapotranspiration (ET) was computed by soil water balance method. The two years' field study indicated eC and eCeT showed significant yield advantage to the extent of 32-47% over ambient. Significant effect (P < 0.05) of climate was observed on crop ET, profile water storage and water use efficiency (WUE) during both the study years. The effect of N application on these three parameters was significant only in 2016 crop year. Averaged across N treatments, profile soil water storage at harvest was higher by about 5% in 2016 and by 9% in 2018 crop season under eC and eCeT treatments as compared to AC. The crop ET was significantly lower under eC and eCeT in both the years, with significantly higher WUE. The WUE varied from 2.99 to 4.48 kg ha(-1) mm(-1) in 2016 and from 4.62 to 6.42 kg ha(-1) mm(-1) in 2018 crop year. Stomatal conductance during major growth period reduced by 21-42% under eC and by 19-31% under eCeT, though it did not reflect in reduced transpiration. The study indicated significantly higher leaf area contributing to reduced soil water evaporation is the major mechanism explaining higher soil water profile under eC and eCeT. Over ambient, the WUE was higher by 48-50% in 2016 and by 37-39% in 2018 under eC and eCeT treatments, which was mostly attributed to higher grain yield.