Crop yields and N losses tradeoffs in a garlic–wheat rotation in southern Spain

•CropSyst model was parameterized and verified for a garlic crop in southern Spain.•150 kgN/ha was found as the minimum garlic fertilization for a maximum, sustainable yield.•The potential of wheat in using the residual N after garlic was demonstrated.•The best trade-off for minimum N losses and maximum yields was determined.

The CropSyst model was parameterized and verified for garlic with data from six field experiments carried out in southern Spain from 2008 to 2011. The model simulated well crop dry matter production, N uptake, and yield from field plots with different N fertilization treatments. A garlic–wheat rotation was then simulated for a 30-year period to evaluate the role of wheat after garlic as a catch crop that utilizes and reduces the loss of residual soil N left at the time of garlic harvest. The scenarios studied were the combination of seven rates of mineral N fertilization in garlic (0, 50, 100, 150, 200, 250 and 300 kgN/ha) and three rates in wheat (30, 70 and 110 kgN/ha). Fertilization rates of 150 kgN/ha in garlic and 70 kgN/ha in wheat were found to provide the best tradeoff between N loss reductions (N leaching and N gas emissions) while attaining near-maximum yields. Increasing fertilization to 200 and 110 kgN/ha for garlic and wheat, respectively, rates not atypical in the region, had a minimum effect on yields but increased average N losses over the rotation by 19 kgN/ha/2-year (29%). Further reductions of N losses by decreasing N fertilization below the best tradeoff point are possible at the expense of crop yield.