Modeling Sunflower Productivity and Profitability in Relation to Adequate and Limited Sulphur Availability under Semiarid Irrigated Conditions

Inadequate and/or imbalanced fertilization has been identified as one of the critical bottlenecks holding oilseeds production and productivity. Sustainable production requires efficient use of inputs maintaining optimum yield and high quality product. The present study aims at defining the quantitative relationship between the fertilizer S applied and the sunflower yield obtained using a polynomial function. The analysis was done to allocate the S fertilizer for maximization of net profit over fertilizer cost depending on the availability of the fertilizer. The results indicated that the cost effective economically optimum dose of sulphur for sunflower cultivation was found to be 36.70？kg？S/ha under its full availability. The expected sunflower yield at this dose was worked out to be 2.619？t/ha. However, it is advisable to uniformly distribute the fertilizer to all over the cultivable area under its limited availability for exploiting the desired yield potential and maximum net monetary returns. 1. Introduction Sulphur (S) is considered the fourth most important essential element after N, P, and K owing to greater significance for plant growth, seed yield, oil and protein synthesis, and improved quality of produce having its role in enzymatic and metabolic processes [1–5]. In general, oilseeds have high demand of S owing to oil biosynthesis [6] and approximately 16？kg S (range 5–20) is required to produce one tonne of seed containing 91% dry matter [7]. The response of S fertilization to oilseeds crops ranged between 15 and 62？kg/kg？S applied depending on the inherent fertility status, prevailing weather condition, cropping system followed, and S source being used [8]. Therefore, soil S reserves and their optimal fertilization require immediate attention for sustaining the soil fertility and attainting higher crop productivity. No doubt the increased use of inputs induces an upward shift in production function to the extent that a technological change is embodied in them. But in the context of the law of diminishing marginal utility under unlimited availability of inputs, one may recommend optimum use of the resources; that is, marginal revenue equals marginal cost. Furthermore, the farmers do not use the recommended dose of nutrients even when they are convinced of the benefits of fertilizer application mainly because of their poor resource base, costlier fertilizers, and cultivation of oilseed crops under input-starved conditions leading to poor input/output ratio. Sunflower holds a great promise as an oilseed crop with chances of area expansion and