Variable Rate Nitrogen Management Integrating Soil and Crop Properties.

Improving nitrogen use efficiency is key to improve crop productivity while reducing nitrogen loadings in the environment. Variable rate nitrogen management is an efficient way of improving the management of nitrogen in crop fields. Traditional way to manage nitrogen is a uniform rate over the whole surface. Several variable rate management strategies were investigated using remote sensing to monitor crop status or using management zones to account for soil productivity potential. Both soil and crop provide important information to accomplish variable rate nitrogen management. Our hypothesis is that combining both soil and crop information in the decision process enables higher nitrogen use efficiency than using only crop or only soil information. Our objectives were to measure the improvement in nitrogen use efficiency, the reduction in nutrient loadings and the improvement in productivity across four different strategies: traditional uniform approach, variable rate by management zone, variable rate by remote sensing and variable rate based on remote sensing within management zones. Our results demonstrate that combining both soil and crop information for variable rate nitrogen management resulted in the highest nitrogen use efficiency while maintaining productivity. It is thus believed that using N rate decision algorithm based on remote sensing values and modulated according to management zones is the best strategy to increase nitrogen use efficiency.