Matching N supply for yield maximization in salt-affected wheat agri-food systems: On-farm participatory assessment and validation

Driven by the UN-SDGs of achieving food security and agricultural sustainability, it remains more challenging in degraded ecosystems to simultaneously improve the crop performance without creating unintended favour for excessive fertilization and associated environmental consequences. We assessed the N-use pattern of 105 wheat-growers in sodicity affected Ghaghar Basin of Haryana, India, and then experimented upon to optimize and identify indicators of efficient N use in contrasting wheat cultivars for sustainable production. The survey results revealed that majority of farmers (88%) have increased their reliance on N nutrition (∼18 % extra N), and even extended their duration of N scheduling (12-15 days) for better plant adaptation and yield insurance in sodicity stressed wheat; albeit to a greater extent in moderately sodic soils applying 192 kg N ha^-1 in 62 days. The participatory trials validated the farmers' perception of using more than the recommended N in sodic lands. This could realize the transformative improvements in plant physiological [higher photosynthetic rate (Pn; 5 %) and transpiration rate (E; 9 %)] and yield [more tillers (ET; 3 %), grains spike^-1 (GS; 6 %) and healthier grains (TGW; 3 %)] traits culminating in ∼20 % higher yield at 200 kg N ha^-1 (N₂₀₀). However, further incremental N application had no apparent yield advantage or monetary benefits. At N₂₀₀, every additional kilogram of N captured by the crop beyond the recommended N improved grain yields by 36.1 kg ha^-1 in KRL 210 and 33.7 kg ha^-1 in HD 2967. Further, the varietal differences for N requirements, with 173 kg ha^-1 in KRL 210 and 188 kg ha^-1 in HD 2967, warrants the need of applying balanced fertilizer dose and advocate revision of existing N recommendations to cope up the sodicity induced agricultural vulnerability. Principal Component Analysis (PCA) and correlation matrix showed N uptake efficiency (N_UpE) and total N uptake (TNUP) as the highly weighted variables illustrating strong positive association with grain yield, and potentially deciding the fate of proper N utilization in sodicity stressed wheat. Key insights suggested that combining participatory research with farmers' knowledge and local perspective could be decisive in better integration of technologies, and serving to adapt the real-time soil sodicity stress and sustaining wheat yields with economized farm profits.

Halophytes as new model plant species for salt tolerance strategies

Soil salinity is becoming a growing issue nowadays, severely affecting the world's most productive agricultural landscapes. With intersecting and competitive challenges of shrinking agricultural lands and increasing demand for food, there is an emerging need to build resilience for adaptation to anticipated climate change and land degradation. This necessitates the deep decoding of a gene pool of crop plant wild relatives which can be accomplished through salt-tolerant species, such as halophytes, in order to reveal the underlying regulatory mechanisms. Halophytes are generally defined as plants able to survive and complete their life cycle in highly saline environments of at least 200-500 mM of salt solution. The primary criterion for identifying salt-tolerant grasses (STGs) includes the presence of salt glands on the leaf surface and the Na⁺ exclusion mechanism since the interaction and replacement of Na⁺ and K⁺ greatly determines the survivability of STGs in saline environments. During the last decades or so, various salt-tolerant grasses/halophytes have been explored for the mining of salt-tolerant genes and testing their efficacy to improve the limit of salt tolerance in crop plants. Still, the utility of halophytes is limited due to the non-availability of any model halophytic plant system as well as the lack of complete genomic information. To date, although Arabidopsis (Arabidopsis thaliana) and salt cress (Thellungiella halophila) are being used as model plants in most salt tolerance studies, these plants are short-lived and can tolerate salinity for a shorter duration only. Thus, identifying the unique genes for salt tolerance pathways in halophytes and their introgression in a related cereal genome for better tolerance to salinity is the need of the hour. Modern technologies including RNA sequencing and genome-wide mapping along with advanced bioinformatics programs have advanced the decoding of the whole genetic information of plants and the development of probable algorithms to correlate stress tolerance limit and yield potential. Hence, this article has been compiled to explore the naturally occurring halophytes as potential model plant species for abiotic stress tolerance and to further breed crop plants to enhance salt tolerance through genomic and molecular tools.

Deciphering trait associated morpho-physiological responses in pearlmillet hybrids and inbred lines under salt stress

Pearl millet is a staple food for more than 90 million people residing in highly vulnerable hot arid and semi-arid regions of Africa and Asia. These regions are more prone to detrimental effects of soil salinity on crop performance in terms of reduced biomass and crop yields. We investigated the physiological mechanisms of salt tolerance to irrigation induced salinity stress (EC_iw ~3, 6 & 9 dSm^-1) and their confounding effects on plant growth and yield in pearl millet inbred lines and hybrids. On average, nearly 30% reduction in above ground plant biomass was observed at EC_iw ~6 dSm^-1 which stretched to 56% at EC_iw ~9 dSm^-1 in comparison to best available water. With increasing salinity stress, the crop performance of test hybrids was better in comparison to inbred lines; exhibiting relatively higher stomatal conductance (gS; 16%), accumulated lower proline (Pro; -12%) and shoot Na⁺/K⁺(-31%), synthesized more protein (SP; 2%) and sugars (TSS; 32%) compensating in lower biomass (AGB; -22%) and grain yield (GY: -14%) reductions at highest salinity stress of EC_iw ~9 dSm^-1. Physiological traits modeling underpinning plant salt tolerance and adaptation mechanism illustrated the key role of 7 traits (AGB, Pro, SS, gS, SPAD, Pn, and SP) in hybrids and 8 traits (AGB, Pro, PH, Na⁺, K⁺, Na⁺/K⁺, SPAD, and gS) in inbred lines towards anticipated grain yield variations in salinity stressed pearl millet. Most importantly, the AGB alone, explained >91% of yield variation among evaluated hybrids and inbreed lines at EC_iw ~9 dSm^-1. Cumulatively, the better morpho-physiological adaptation and lesser yield reduction with increasing salinity stress in pearl millet hybrids (HHB 146, HHB 272, and HHB 234) and inbred lines (H77/833-2-202, ICMA 94555 and ICMA 843-22) substantially complemented in increased plant salt tolerance and yield stability over a broad range of salinity stress. The information generated herein will help address in deciphering the trait associated physiological alterations to irrigation induced salt stress, and developing potential hybrids in pearl millet using these parents with special characteristics.

The food-energy-water-carbon nexus of the rice-wheat production system in the western Indo-Gangetic Plain of India: An impact of irrigation system, conservational tillage and residue management

The conventional rice-wheat system in the western Indo-Gangetic plain of India is energy and water intensive with high carbon footprint. The transition towards resource-efficient eco-friendly production technologies with lower footprint is required for inclusive ecological sustenance. A five-year (2016-17 to 2020-21) field experiment was conducted in RWS with hypothesis that pressurized irrigation systems [drip (DRIP) and mini-sprinkler (MSIS)] in conservation tillage [reduced (RT)/zero (ZT)] and crop residue management [incorporation (RI)/mulch (RM)] might result in higher resource use efficiency with lesser carbon footprint compared to conventional system. Experiment consisted five treatments namely (1) puddled transplanted rice followed by conventionally tilled wheat (PTR/CTW), (2) DRIP irrigated reduced till direct seeded rice (RTDSR) followed by zero-till wheat with 100 % rice residue mulching (ZTW + RM) (DRIP-RTDSR/ZTW + RM), (3) surface irrigated RTDSR followed by ZTW + RM (SIS-RTDSR/ZTW + RM), (4) MSIS irrigated RTDSR followed by ZTW + RM (MSIS-RTDSR/ZTW + RM), and (5) MSIS irrigated RTDSR with 1/3rd wheat residue incorporation followed by ZTW + RM (MSIS-RTDSR + RI/ZTW + RM). The pressurized irrigation system in RWS established under conservational tillage and residue management (DRIP-RTDSR/ZTW + RM and MSIS-DSR + RI/ZTW + RM) produced at par system productivity compared to PTR/CTW. Substantial nitrogen (79-114 ka ha^-1) and irrigation water (536-680 mm) savings under pressurized irrigation systems resulted in 41-64 % higher partial factor productivity of nitrogen with 48-61 % lower water footprint. These systems had lower energy consumption attaining 15-21 % higher net energy, 44-61 % higher energy use efficiency, and 31-38 % lower specific energy. Efficient utilization of farm inputs caused lower greenhouse gas emission (39-44 %) and enhanced carbon sequestration (35-62 %) resulting 63-76 % lower carbon footprint over PTR/CTW. The information generated here might useful in developing policies for resource and climate-smart food production system aiming livelihood security and ecological sustainability in the region. Further, trials are needed for wider adaptability under different climate, soil and agronomic practices to develop site-specific climate smart practices.

Climate resilient integrated soil-crop management (CRISCM) for salt affected wheat agri-food production systems

Maximizing opportunities for climate resilient agriculture is vital for global food security, and ecological sustainability. To explore the improvement potential of mitigation and adaptation strategies in stabilizing wheat production and increasing farm income in sodicity-prone Ghaghar Basin of Haryana, India, participatory research trials on land reclamation (gypsum/pressmud) and crop management (varieties, nutrient management and weed control) practices were undertaken during 2016-2020. Results indicated that combining gypsum and pressmud together accelerated the reclamation process (soil pH: -3.3% and ESP: -22.1%) and improved plant adaptability (RWC: 10%; MI: -15%; Pn: 40%; gS: 36%; NaK_S: -38% and NaK_R: -42%), which in turn increased wheat yield by 20% compared to unamended control. With increasing sodicity stress, salt tolerant wheat variety KRL 210 exhibited better morpho-physiological adaptation, lesser yield reduction (0.8-1.1 t ha^-1) and attained 4.1% mean yield advantage compared to traditionally cultivated HD 2967. There were genotypic differences for N requirements in sodicity stressed wheat, with 173 kg ha^-1 in KRL 210 and 188 kg ha^-1 in HD 2967 as the economically optimum dose; further advocating for upward revision of current N recommendations beyond 150 kg N ha^-1. Balanced nutrition through foliage applied K compensated the sodicity hazards with lower proportion of Na⁺/K⁺ in leaf tissues (13%), and attained higher grain yield (4%) and incremental income (34 US$ ha^-1) compared to farmers' practice. Sequential use of herbicides provided affordable solution to check Phalaris minor infestation (84% WCE) and enhanced wheat productivity (5.7% higher) with incremental income of 48 US$ ha^-1 compared to farmers' sole dependency on post-emergence herbicides. Synergistic integration of gypsum and pressmud-mediated sodic land reclamation, usage of stress tolerant wheat variety, 15% higher N application, foliar K-nutrition and effective P. minor control substantiate appreciable reduction in soil sodicity, improved crop resilience, and ultimately translated into 5% and 26% higher yields over the recommended and local farm practices, respectively. The key insights of this study suggest a range of opportunities wherein inputs of CRISCM could potentially stabilize the wheat production, improve farm economy and reduce environmental risks beyond what is currently being achieved with existing farm practices.

Soil spatial variability characterization: Delineating index-based management zones in salt-affected agroecosystem of India

Farm level recommendation in salt-affected agricultural landscapes is practically difficult due to spatial variations in inherent soil salinity, diverse farming situations and associated land ownerships with small-scale production systems. This study presents spatial array analysis of 354 geo-referenced soil samples revealing widespread heterogeneity in soil sodicity and fertility status across salt-affected Ghaghar basin of Kaithal district in Haryana, India. Six principal components accounted for 73% of the total variability, and the most important contributors [electrical conductivity (EC_e), sodium adsorption ratio (SAR), DTPA extractable copper (Cu) and boron (B), soil organic carbon (OC) and available phosphorus (AP)] as minimum data set were used to develop the soil quality index (SQI). Geostatistical analysis revealed Circular (EC_e and AP), Exponential (SAR, OC and B) and Gaussian (Cu) as the best fit semivariogram ordinary kriging model with weak to moderate spatial dependence. Three soil management zones (SMZs) were delineated by grouping the entire area based on soil quality index (SQI). Fertilizer recommendations for rice-wheat cropping system in different SMZs were calculated using soil test crop response (STCR) equation to ensure balanced fertilization, resource saving and reducing environmental footprints. Gypsum requirement map was prepared for systematic allocation and distribution, and enabling farmers to precisely use the mineral gypsum in order to reclaim and reduce stresses led by sodic lands. The implications of this study showed zone-specific advocacy for gypsum application (as soil ameliorant) and balanced fertilization in sustainable restoration of sodic lands, improving nutrient use efficiency and stabilizing crop production in salt-affected regions of India and similar ecologies elsewhere.

In situ decomposition of crop residues using lignocellulolytic microbial consortia: a viable alternative to residue burning

Open field burning of crop residue causes severe air pollution and greenhouse gas emission contributing to global warming. In order to seek an alternative, the current study was initiated to explore the prospective of lignocellulolytic microbes to expedite in situ decomposition of crop residues. Field trials on farmers' field were conducted in the state of Haryana and Maharashtra, to target the burning of rice and wheat residue and sugarcane trash, respectively. A comparative study among crop residue removal (CRR), crop residue burning (CRB) and in situ decomposition of crop residues (IND) revealed that IND of rice and wheat residues took 30 days whereas IND of sugarcane trash took 45 days. The decomposition status was assessed by determining the initial and final lignin to cellulose ratio which increased significantly from 0.23 to 0.25, 0.21 to 0.23 and 0.24 to 0.27 for rice, wheat residues and sugarcane trash, respectively. No yield loss was noticed in IND for both rice-wheat system and sugarcane-based system; rather IND showed relatively better crop yield as well as soil health parameters than CRB and CRR. Furthermore, the environmental impact assessment of residue burning indicated a substantial loss of nutrients (28-31, 23-25 and 51-77 kg ha-1 of N+P2O5+K2O for rice, wheat and sugarcane residue) as well as the emission of pollutants to the atmosphere. However, more field trials, as well as refinement of the technology, are warranted to validate and establish the positive potential of in situ decomposition of crop residue to make it a successful solution against the crop residue burning.

Perceived Climate Variability and Compounding Stressors: Implications for Risks to Livelihoods of Smallholder Indian Farmers

Micro-scale perspectives are seldom included in planned climate change adaptations, yet farmers' perceptions can provide useful insights into livelihood impacts from interactions between climatic and other stressors. This research aims to understand how climate variability and other stressors are impacting the livelihoods of smallholder farmers in Azamgarh district, eastern Uttar Pradesh, India. Data from 84 smallholder farmers were collected using mixed qualitative and quantitative approaches, including interview and participatory methods, informed by multiple stressor and sustainable livelihood frameworks. Results revealed that farmers are increasingly facing problems caused by the reduced duration and number of rainy days, and erratic rainfall. Anomalies in seasonal cycles (longer summers, shorter winters) seem to have altered the local climate. Farmers reported that repeated drought impacts, even in years of moderate rainfall, are adversely affecting the rice crop, challenging the formal definition of drought. Climate variability, identified as the foremost stressor, often acts as a risk multiplier for ecological (e.g., soil sodicity), socio-economic (e.g., rising costs of cultivation) and political (e.g., mismatching policies and poor extension systems) stressors. In addition to climate stresses, resource-poor marginal groups in particular experienced higher risks resulting from changes in resource management regimes. This study provides an important cue to revisit the formal definitions of normal rainfall and drought, accommodating farmers' perceptions that evenly distributed rainfall, and not total rainfall is a key determinant of crop yields. Though India has developed adaptive measures for climate change and variability, integration of farmers' perceptions of climate and other stressors into such policies can improve the resilience of smallholder farmers, who have hitherto depended largely on autonomous adaptation strategies.

Municipal solid waste (MSW): Strategies to improve salt affected soil sustainability: A review

Salt-induced soil degradation is a serious threat to global agriculture which is responsible for diminished productivity of agro-ecosystems. Irrigation with poor quality water and indiscriminate use of chemical fertilizers to increase crop productivity creates salt accumulation in soil profile thereby reducing crop sustainability. High concentration of salts in soil inhibits plant growth due to low osmotic potential of the soil solution, ion toxicity and imbalance reduces nutrient uptake, crop yields. Low productivity of saline soils is not only due to salt toxicity or excess amounts of soluble salts but also lack of available mineral nutrients especially nitrogen, phosphorus, potassium and soil organic matter. Hence, sustainable management of salt-affected soils are paramount importance to meet the demands of food grain production for an ever-rising population in the world. Recently, municipal solid waste has gained importance as an organic amendment for restoring soil fertility and finally contributing to productivity of salt-affected soils. This paper compares extant waste generation, their properties and standards pertinent to municipal solid waste in different countries and explores the unique recent history in some countries that shows high environmental regard and rapid changes and also suggests policy experiencing from high environmental regard and rapid changes from other countries, so that policy makers can propose new or revise current municipal solid waste standards for salt affected soils. Municipal solid waste compost improves soil biological, physical and chemical properties because of high soil organic matter and lower concentration of pollutants. Therefore, the use of municipal solid waste in salt-affected soils could be an alternative to costly chemical amendments as well as reduce the reliance on chemical fertilizers for increasing productivity of salt-affected soil. The municipal solid wastes significantly improve crop yields. However, further long-term experimental investigations are needed to re-validate the application of municipal solid waste compost in improving physical, chemical and biological properties and to step up organic fertilization use in a wide range of both saline and sodic soils. In future, research should be directed to address these issues globally to minimise ecological disturbances and to set environmental standards, and evaluate the feasibility of the policies in different countries and their impact on socio-economic conditions of local people.

Survey of nitrogen use pattern in rice in the irrigated rice-wheat cropping system of Haryana, India

Seeing the sustainability of rice-wheat cropping system (RWCS) of the Indo-Gangetic Plain, adequate crop nutrition in general and nitrogen (N) in particular holds the key to sound crop management. The excessive application or insufficient management of N means an economic loss to the farmer and may lead to yield penalties and environmental problems. Improving N management in consonance with other nutrients is much important to break yield plateaus as breeding for high yielding is not happening in recent years. Findings from farm survey are used to evaluate the on-farm N management practices in rice crop of the study area. The crop management practices (especially time of sowing/transplanting and irrigation requirement) and resource base of the farmers decided the N use pattern of the farmers. The N(Physical optimum) and N(economic optimum) exceeding the recommended levels revealed the apparent need for the revalidation of the existing recommendations. Paddy yield increased significantly within different rice types. This study generated comprehensive data on N use pattern in rice in the study area.