Economic Rate Analysis of Nitrogen Fertilization in Wheat

The response of wheat (Triticum aestivum L.) to macroelement fertilization was investigated on a large number of trials, with 195 short-stem varieties and 58 long-stem varieties. The results have shown that fertilization rates exceeding 195 lb N/acre do not result in higher yields. Economically optimum fertilizer rates were 158 lb N/acre for short-stem varieties and 139 lb N/acre for long-stem varieties. Analysis shows that the economic profit for a given yield curve is a function of the ratio of fertilizer cost to the price of product. This ratio cannot be higher than 9.75 for short-stem wheat varieties or higher than 14.5 for long-stem wheat varieties. Research QuestionFarmers supply enough fertilizer to meet the nutrient needs of their crops, but in most cases they have been following a higher fertilizer application rate for many years. In Greece, the wheat crop recovers close to 50% of the fertilizers used. The primary objective of this research was a systematic approach of wheat production with a more rational policy on N fertilization. Literature SummaryMany studies have been conducted in order to promote a better fertilization to secure higher yields of wheat grain production, and to alert people of the possible deterioration of water quality and natural resources. The most important fertilizer is N, and our attempts are focused on the effect of this nutrient in wheat grain production, leading to a maximum net return. Study DescriptionExperiments were conducted all over Greece for the last 10 consecutive years. Furthermore, the effect of N and its combination with P and K was studied. Wheat varieties: long stem and short stem Soil: Hilled and plano Weed control: Basagran, MCPA Treatments: Table 1 Applied QuestionsDid the production curve have a positive indication on the wheat grain production? In this research, all N fertilization levels led to an increased grain yield, following a diminishing return yield curve. This was clearer in the short-stem wheat varieties, than in long stem ones. In both cases, the maximum output was observed at the same fertilization rate (195 lb N/acre). Applying P in addition to any N rate had little effect on crop yield. Is the maximum economic return related to change of wheat grain and fertilizer prices? Starting from the ratio of wheat grain prices to the prices of fertilizers at 2.75, experimental data showed that long stem varieties are more sensitive to any increase of the above ratio, while short stem varieties have a double tolerance (Fig. 1). Presently, maximum net economic retum is achieved by applying ≅140 and ≅160 lb N/acre for long stem and short stem wheat varieties respectively. RecommendationWe recommend a fertilization level of ≅140 and 460 lb N/acre for long stem and short stem winter wheat varieties respectively. This will result in the highest net economic return. Fertilization rates beyond these levels should be avoided because of the decreasing net profit and the potential deterioration of water resources. Table 1Fertilization rates in wheat crop. Applied N, Ib N/acreGroups of wheat varieties0,81, 134, and 161Short stem0,54, 81, and 108Long stemFig. 1Maxium net economic return.