Modeling maize growth and nitrogen dynamics using CERES-Maize (DSSAT) under diverse nitrogen management options in a conservation agriculture-based maize-wheat system.

Agricultural field experiments are costly and time-consuming, and often struggling to capture spatial and temporal variability. Mechanistic crop growth models offer a solution to understand intricate crop-soil-weather system, aiding farm-level management decisions throughout the growing season. The objective of this study was to calibrate and the Crop Environment Resource Synthesis CERES-Maize (DSSAT v 4.8) model to simulate crop growth, yield, and nitrogen dynamics in a long-term conservation agriculture (CA) based maize system. The model was also used to investigate the relationship between, temperature, nitrate and ammoniacal concentration in soil, and nitrogen uptake by the crop. Additionally, the study explored the impact of contrasting tillage practices and fertilizer nitrogen management options on maize yields. Using field data from 2019 and 2020, the DSSAT-CERES-Maize model was calibrated for plant growth stages, leaf area index-LAI, biomass, and yield. Data from 2021 were used to evaluate the model's performance. The treatments consisted of four nitrogen management options, viz., N0 (without nitrogen), N150 (150 kg N/ha through urea), GS (Green seeker-based urea application) and USG (urea super granules @150kg N/ha) in two contrasting tillage systems, i.e., CA-based zero tillage-ZT and conventional tillage-CT. The model accurately simulated maize cultivar's anthesis and physiological maturity, with observed value falling within 5% of the model's predictions range. LAI predictions by the model aligned well with measured values (RMSE 0.57 and nRMSE 10.33%), with a 14.6% prediction error at 60 days. The simulated grain yields generally matched with measured values (with prediction error ranging from 0 to 3%), except for plots without nitrogen application, where the model overestimated yields by 9-16%. The study also demonstrated the model's ability to accurately capture soil nitrate-N levels (RMSE 12.63 kg/ha and nRMSE 12.84%). The study concludes that the DSSAT-CERES-Maize model accurately assessed the impacts of tillage and nitrogen management practices on maize crop's growth, yield, and soil nitrogen dynamics. By providing reliable simulations during the growing season, this modelling approach can facilitate better planning and more efficient resource management. Future research should focus on expanding the model's capabilities and improving its predictions further.

Water budgeting in conservation agriculture-based sub-surface drip irrigation in tropical maize using HYDRUS-2D in South Asia.

In water scarce regions of South Asia, diversification of rice with maize is being advocated towards sustainability of cereal-based cropping systems. Adoption of innovative agronomic management practices, i.e., conservation agriculture (CA) and sub-surface drip irrigation (SSDI) are considered as key strategies for much needed interventions to address the challenges of water scarcity under projected climate change. Benefits from CA and SSDI concerning water economy are well-established, however, information about their complementarity and water budgeting in cereal-based systems are lacking. A field study was conducted with process-based model (HYDRUS-2D) to understand water transport, root water uptake and components of soil water balance in maize grown in rotation with wheat after five years of continuous adoption of conservation agriculture. In this study, altogether eight treatments comprising of 6 CA+ treatments (CA coupled with SSDI); permanent beds using sub-surface drip (PB-SSD) with (WR) and without (WOR) crop residue at different N rates, 0, 120 and 150 kg N ha-1 were compared with CA (PB using furrow irrigation-FI with crop residue-120 kg N ha-1) and conventional tillage practices (CT) (CT using FI without crop residue-120 kg N ha-1). Results showed that the model could simulate the daily changes in profile soil water content with reasonable accuracy in all the treatments. Simulated soil water balance indicated higher cumulative root water uptake (CRWU), lower cumulative evaporation (CE) and higher soil water retention in CA+ (PB-SSD+ crop residue at 150 and 120 kg N ha-1) than CA and CT plots. Hydrus-2D model efficiency > 0, RMSE between 0.009-0.026 and R2 value between 0.80-0.92 at P < 0.01 indicates that the model is performing efficiently. The mean evaporation from CA+ treatments was 10 and 36% less than CA and CT treatments, respectively. On average, CRWU under CA+ treatments were 14-48% higher than FI treatments. The mean cumulative deep drainage in CA+ plots was 80-100 mm less than CA and CT plots. In CA+ based plots significantly higher biomass production and radiation use efficiency were observed with reduced water use than CA and CT. Therefore, the study justifies the water-saving nature of CA+, while maintaining higher productivity and meeting the transpiration demand of crops and halting unnecessary evaporation and deep drainage losses.

Critical evaluation of functional aspects of evaporation barriers through environmental and economics lens for evaporation suppression - A review on milestones from improved technologies.

Climate change models predict an increase in rainfall variability, leading to floods and drought events, hence intensifying the need for reservoirs. However, up to 50% of reservoirs' capacity is lost by evaporation, affecting their function of ensuring water availability and stability. Over decades biological, chemical and physical barriers "covers" were developed for inhibiting evaporation. Such barrier's efficiency and applicability are still a matter of discussion, given their economic efficiency, environmental consequences, and operational difficulties are accounted for. In this review, we discussed the efficiency, applicability, and environmental suitability of these covers. Compared to the physical covers, the chemical and biological solutions tend to be less efficient. However, the use of physical covers is multidisciplinary, involving climate, material, and hydrological sciences, and are more efficient. Among the physical covers, the use of suspended covers and free-floating elements decreases evaporation to the tune of 85 and 80.0%, respectively. However, the economic efficiency of free-floating elements remains an open question since all studies overlooked their water footprint (water used in the manufacturing process of these covers), which was found to be very high. The use of these covers decreases heat storage, gas exchange rate, and light availability that could adversely influence dissolved oxygen, water quality, aquatic organisms, and the water ecosystem's function. These ecological consequences have not yet been investigated. The exception is the suspended covers, which have had determinate effects on dissolved oxygen and algae growth. Due to light weight, floating elements' operation is unstable and vulnerable to move due to wind effects. Therefore, such covers must be engineered to increase their stability. Free-floating elements could provide a visible and scalable solution to evaporation suppression when considering their economic visibility, environmental effects, and stability against wind and wave effects under the field conditions. However, these covers can be viable only when water availability is the limiting factor in crop production. We found that studies at reservoir scale are highly limited, therefore, investigations at reservoirs' scale emphasizing ecological aspects, cover stability and cost efficiency, are urgently needed.

Energy auditing and carbon footprint under long-term conservation agriculture-based intensive maize systems with diverse inorganic nitrogen management options.

A greater energy grant in diesel-fed machinery driven farming substantiate the higher GHGs emission along with improper input (fertilizer, pesticide and irrigation) use and intensive soil management. Practicing conservation tillage, residue retention and diversified crop rotations were advocated because of their multiple benefits. Hence we explored the energy requirement and carbon footprint of conservation agriculture (CA) based maize production systems. Coated N fertilizer [sulphur coated urea (SCU) and neem coated urea (NCU)] were compared with unfertilized and uncoated prilled urea (PU) in the scenario of with and without residue retention on permanent beds (PB) under diversified maize systems [MMuMb, maize-mustard-mungbean and MWMb, maize-wheat-mungbean] in search of a sustainable and energy efficient production system with lesser C-footprint. Results of the 4-year study showed that crops planted on permanent bed with crop residue (PB+R) registered 11.7% increase in system productivity compared to PB without residue (PB-R). N management through Neem coated urea (NCU) recorded 2.3 and 10.9% higher system productivity compared with non-coated prilled urea plot under PB-R and PB+R, respectively. MMuMb was marginally superior than MWMb system in terms of cropping sequence yield, profitability, and energy and carbon use efficiency. Crop residue retention in zero tilled PB increased cost of cultivation by 125 and 147 USD/ha in MMuMb and MWMb systems, respectively. The quantified carbon footprint value was higher in MWMb system. In CA-based practices, crop residues management contributed the highest energy input (61.5-68.4%) followed by fertilizer application (17-20%). Among N management practices, neem coated urea (NCU) significantly improved system productivity and profitability in all the residue applied plots compared to un-fertilized and prilled urea (PU) applied plots. Similarly, higher energy output was also observed in NCU treated plots. However, carbon footprint value was higher in PU (268-285 CO2-e kg/Mg) plots than NCU (259-264 CO2-e kg/Mg) treated plots. Thus, the study supports and recommends that the CA-based MMuMb system with efficient N management through NCU is an environmentally safe, clean and energy efficient one, hence can reduce carbon footprint, will ensure food security and will mitigate climate change.

Long-term impact of conservation agriculture and diversified maize rotations on carbon pools and stocks, mineral nitrogen fractions and nitrous oxide fluxes in inceptisol of India.

Given the increasing scarcity of production resources such as water, energy and labour coupled with growing climatic risks, maize-based production systems could be potential alternatives to intensive rice-wheat (RW) rotation in western Indo-Gangetic Plains (IGP). Conservation agriculture (CA) in maize systems has been widely promoted for minimizing soil degradation and ensuring sustainability under emerging climate change scenario. Such practices are also believed to provide mitigation co-benefits through reduced GHG emission and increased soil carbon sequestration. However, the combined effects of diversified crop rotations and CA-based management on GHG mitigation potential and other co-benefits are generally over looked and hence warrant greater attention. A field trial was conducted for 5-years to assess the changes in soil organic carbon fractions, mineral-N, N2O emission and global warming potential (GWP) of maize-based production systems under different tillage & crop establishment methods. Four diversified cropping systems i.e. maize-wheat-mungbean (MWMb), maize-chickpea-Sesbania (MCS), maize-mustard-mungbean (MMuMb) and maize-maize-Sesbania (MMS) were factorially combined with three tillage & crop establishment methods i.e. zero tilled permanent beds (PB), zero-tillage flat (ZT) and conventional tillage (CT) in a split-plot design. After 5-years of continued experimentation, we recorded that across the soil depths, SOC content, its pools and mineral-N fractions were greatly affected by tillage & crop establishment methods and cropping systems. ZT and PB increased SOC stock (0-30 cm depth) by 7.22-7.23 Mg C ha-1 whereas CT system increased it only by 0.88 Mg C ha-1as compared to initial value. Several researchers reported that SOC & mineral-N fraction contents in the top 30 cm soil depth are correlated with N2O-N emission. In our study, global warming potential (GWP) under CT system was higher by 18.1 and 17.4%, compared to CA-based ZT and PB, respectively. Among various maize systems, GWP of MMS were higher by 11.2, 6.7 and 6.6%, compared that of MWMb (1212 kg CO2-eq. ha-1), MCS (1274 kg CO2-eq. ha-1) and MMuMb (1275 kg CO2-eq. ha-1), respectively. The results of our study suggest that CA and diversified crop rotations should be promoted in north-western IGP and other similar agro-ecologies across the globe for ensuring food security, restoration of soil health and climate change mitigation, the key sustainable development goals (SDGs).