Within-field variation of actual and maximum winter wheat yield in relation to crop management

Context: The potential magnitude of agronomic yield gain through management is rarely explored at the field scale. Increasing yield through greater use of inputs without considering local potential yield may pose environmental and economic risks. Study objectives: i) examine yield gain through increased management intensity, including irrigation, and how it varies within and between fields, ii) evaluate the environmental and economic risks of uniform N-rates within fields. Methods: Field experiments were performed at three sites, with varying yield potential, in each of 12 fields with winter wheat (Triticum aestivum L.) in Sweden over three years. Irrigated and rainfed maximum yield under non-limiting cropping inputs (Yim and Ym), actual yield under conventional management (Ya), and yield gains (Yim-Ym and Ym-Ya) were determined. Results: More frequent pest control was most effective to increase yields, followed by higher fertilizer rates. However, within-field yield variation, relative to the lowest yield recorded in the field, was, on average, similar for Ya and Ym but reduced by irrigation (Yim). Thus, water limitation was the main reason for within-field yield variations, possibly related to soil texture. Conclusions: Actual and maximum yields vary between and within fields. This variation cannot be entirely compensated for by intensified management. Therefore uniform yield levels within fields should not be strived for, instead site-specific optimal levels should be the goal. Implications: The within-field variation in yield needs to be considered as N rates based on site-specific yield levels within fields were found to be more profitable than uniform N rates.