Strategic system to control N balance for sustainable non-polluted vegetable production

Nitrogen fertilization is usually regarded as the main factor to control nutrient supply in order to produce non-polluted vegetable. It is very significant to build up an advisory N recommendation system, with simple parameter input, friendly interface and multi-function, as a useful tool in the maintenance of sustainable vegetable production. A new strategic N recommendation system was developed to balance N fertilization through the empirical model prediction in crop N uptake, N loss, N release from soil organic pool and crop residue, and determination of soil N_min safety margin, soil N_min residue at preplanting. Three structural layers were selected in the design of advisory system program to be easy to acquire data through ADO (ActiveX Data Objects) and ODBC (Open Database Connectivity). A friendly human-machine interaction interface was built using Visual Basic 6.0, one of advanced program language. The system program was extended in the vegetable production in the open-field of Beijing suburb. From the results of several field experiments with different vegetable varieties, it was showed that in most cases there was no yield reduction from the recommended treatments in comparison with conventional fertilizer practice. However about 30%～60% of nitrogen fertilizer was saved in the recommended treatment using the developed program. It means that using the balancing fertilization strategy, it can not only reduce the fertilizer waste, but also maintain the sustainable vegetable production.