Amritbir Riar

Chapter 4 – Nitrogen Use as a Component of Sustainable Crop Systems

The focus for efforts to expand food production in both developing and developed countries must be on raising crop yields on existing arable lands and improving production efficiencies. These outcomes can be achieved by using improved cultivars together with improved agronomic practices. In this chapter, we review the role of nitrogen (N) in relation to sustainable crop production and we outline strategies for improving the efficiency of N use. Current values of N use efficiencies are for most crops less than 50%, but there is considerable potential to improve this. Nitrogen use efficiency is restricted by limits associated mostly with uptake rather than utilization, and it is possible to improve N uptake by agronomic management. Agronomic management of N is affected by the availability/management of water; and strategies involving alteration of source, time, method, and rate of N fertilizer application are used to improve N use efficiency. For example, splitting or delaying the N application to meet the demand of the crop and/or to respond to water availability can be used as the tool to manage economic and environmental yield. However, caution is required when developing site-specific management approaches for targeting optimum N use, and the best practice will vary from situation to situation and cannot be prescriptive. Conservation agriculture is the foundation of best agronomic practices, and no-tillage, crop rotations, and management of N fertility by relating to crop demand will remain the foundation of a sustainable system.

Soil Biological Activity Contributing to Phosphorus Availability in Vertisols under Long-Term Organic and Conventional Agricultural Management

Mobilization of unavailable phosphorus (P) to plant available P is a prerequisite to sustain crop productivity. Although most of the agricultural soils have sufficient amounts of phosphorus, low availability of native soil P remains a key limiting factor to increasing crop productivity. Solubilization and mineralization of applied and native P to plant available form is mediated through a number of biological and biochemical processes that are strongly influenced by soil carbon/organic matter, besides other biotic and abiotic factors. Soils rich in organic matter are expected to have higher P availability potentially due to higher biological activity. In conventional agricultural systems mineral fertilizers are used to supply P for plant growth, whereas organic systems largely rely on inputs of organic origin. The soils under organic management are supposed to be biologically more active and thus possess a higher capability to mobilize native or applied P. In this study we compared biological activity in soil of a long-term farming systems comparison field trial in vertisols under a subtropical (semi-arid) environment. Soil samples were collected from plots under 7 years of organic and conventional management at five different time points in soybean (Glycine max) -wheat (Triticum aestivum) crop sequence including the crop growth stages of reproductive significance. Upon analysis of various soil biological properties such as dehydrogenase, β-glucosidase, acid and alkaline phosphatase activities, microbial respiration, substrate induced respiration, soil microbial biomass carbon, organically managed soils were found to be biologically more active particularly at R2 stage in soybean and panicle initiation stage in wheat. We also determined the synergies between these biological parameters by using the methodology of principle component analysis. At all sampling points, P availability in organic and conventional systems was comparable. Our findings clearly indicate that owing to higher biological activity, organic systems possess equal capabilities of supplying P for crop growth as are conventional systems with inputs of mineral P fertilizers.

A Diagnosis of Biophysical and Socio-Economic Factors Influencing Farmers’ Choice to Adopt Organic or Conventional Farming Systems for Cotton Production

Organic agriculture is one of the most widely known alternative production systems advocated for its benefits to soil, environment, health and economic well-being of farming communities. Rapid increase in the market demand for organic products presents a remarkable opportunity for expansion of organic agriculture. A thorough understanding of the context specific motivations of farmers for adoption of organic farming systems is important so that appropriate policy measures are put in place. With an aim of understanding the social and biophysical motivations of organic and conventional cotton farmers for following their respective farming practices, a detailed farm survey was conducted in Nimar valley of Madhya Pradesh state in central India. The study area was chosen for being an important region for cotton production, where established organic and conventional farms operate under comparable circumstances. We found considerable variation among organic and conventional farmers for their social and biophysical motivations. Organic farmers were motivated by the sustainability of cotton production and growing safer food without pesticides, whereas conventional farmers were sensitive about their reputation in community. Organic farmers with larger holdings were more concerned about closed nutrient cycles and reducing their dependence on external inputs, whereas medium and small holding organic farmers were clearly motivated by the premium price of organic cotton. Higher productivity was the only important motivation for conventional farmers with larger land holdings. We also found considerable yield gaps among different farms, both under conventional and organic management, that need to be addressed through extension and training. Our findings suggest that research and policy measures need to be directed toward strengthening of extension services, local capacity building, enhancing availability of suitable inputs and market access for organic farmers.

A Novel Framework for Identifying the Interactions between Biophysical and Social Components of an Agricultural System: A Guide for Improving Wheat Production in Haryana, NW India.

ABSTRACT Purpose: The purpose of this study is to develop a conceptual framework with related analysis methodologies that identifies the influence of social environment on an established cropping system. Design/methodology/approach: A stratified survey including 103 villages and 823 farmers was conducted in all districts of Haryana (India). Firstly, technical efficiency (TE) was modeled using biophysical data including grain yield, seeding rate, wheat varieties, tillage, sowing date, seed source, harvesting method and the application of fertilizer, herbicide and irrigation. The relationship between TE and social community factors such as farm size, farmer age, level of education and agricultural support programs was analyzed by regression tree. Findings: TE was lower with the farmers who only have education to a primary standard. Farmers with high TE scores were mostly between 35 and 40 years of age, and a higher TE association was common for farmers who use technical publications. Social individual factors such as farmers’ views on the future of farming were also analyzed across different TE levels. Practical implications: Farmers with lower TE are an obvious target for production improvement, particularly given the understanding that the overall production yield gap is small in Haryana. Theoretical implications: Our conceptual framework shows a quantitative way to establish the socio-ecological linkage, and to identify the opportunities for changes in management with extension services leading to productivity improvement. Originality/value: This paper provides a novel framework with detailed methodology to effectively identify the socio-economic factors that limit the biophysical production in an agricultural system.