OPERATIONAL OPTIMIZATION OF ORGANIC FERTILIZER APPLICATION IN GREENHOUSE CROPS

Abstract

Organic fertilizers are the only fertilizers used in organic greenhouse horticulture. The nitrogen (N) in these fertilizers must be mineralized before it can be taken up by the crop. This makes it a challenge to minimize N losses while ensuring that adequate N is available to the crop at all times. The objective of our work was to develop an operational method to determine optimal fertilizer strategy (timing of applications, kind and amount of fertilizer for each application). We developed the model LinFert, in which mineralization and loss of N are linearly related to the amounts of fertilizer applied, and which can thus be optimized using linear programming. Cumulative mineralization and loss of N simulated with LinFert matched closely the equivalent numbers simulated by a detailed process-based model describing water movement as well as transport, uptake, mineralization and denitrification of nitrogen. We conclude that optimization runs with LinFert will be helpful to farmers when current fertilizer strategies are fine-tuned, and when in the future fertilizer strategies are needed that put greater emphasis on reducing nitrogen loss