Yield Response of Cauliflower to Different ‘Just-in-Time' Fertilization Treatments in An Online-Monitored Approach.

Today more than ever, increased crop production depends on judicious use of resources. In addition, issues such as climate change, climatic variability and environmental sequestration have become important issues. The objective of this study is to provide user-friendly ways for farmers to control the amount of nitrogen fertilizer in a very precise matter, in order to avoid overuse of fertilizer, which is not only harmful to the environment, but also a mayor production cost factor. This however should be realized without suffering from production or quality losses. An experimental site was set up, allowing real time follow-up of all fertilization and irrigation inputs and outputs. Drainage water per plot is being retained (impenetrable foil at depth of 90 cm) so that the volume can measured and sampled regularly for nitrogen content, as are the soil and the plants. Four different nitrogen application rates and 4 different treatments of fertilization resulted in a 4 by 4 completely randomized factorial design, replicated in two blocks. A broadcasting of calcium ammonium nitrate (CAN), a band fertilization with ammonium sulphate nitrate, a band fertilization of ammonium sulphate nitrate with a nitrification inhibitor and 2-weekly fertigation with CAN were the different administered fertilization schemes. Nitrogen target values were set at 50,100,150,200 kg N/ha at planting and 100,150,200,250 kg N/ha 5 weeks after planting. The corrective nitrogen application was done by subtracting the measured mineral nitrogen still present in the root zone from these target values). The values were chosen as such that the third highest dose coincides with the recommended value of the KNS-system (Kulturbegleitenden Nmin Sollwerte), a generally accepted reference. In this way luxury nitrogen availability as well as restricted availability was present in the experiment. Destructive growth analysis of plant biomass, both leaves and curd, was carried out on fortnight basis. At harvest time, about 83 days after planting, plants were sampled, commercially (i.e. with leaf crown) and non-commercially (i.e. the whole plant). Both the curd and leaves were analyzed for fresh weight, dry weight and nitrogen content. No significant differences, in commercial quality of cauliflower, were found when the different fertilization methods were compared. However, a significant difference was found between the nitrogen-doses applied. The third and fourth dose had a significant higher output in fresh weight, dry weight and quality. Growth curves for the different treatments were calculated and analyzed.