Effects Of Applied Granular Fertilizer On Growth And N Utilization Of Vegetables

Large-size granular fertilizer (LSGF, diameter size>2cm), using chemical fertilizers of ammonium-form nitrogen, phosphorus and potassium, and some additives as raw materials, was developed using conventional granulation technique. Effects of LSGF and modified application technique on N release and vegetable production of open-field cabbage, open-field cauliflower and greenhouse fennel were investigated in the vegetable fields in Beijing region, in comparison with conventional fertilization treatment with recommended N rate by local extension service center. Root development, rhizospheric changes and nitrate leaching was also evaluated in the treatment of LSGF application compared with those of conventional fertilization treatment. The main results showed that: In the field conditions, over 90% NH4+-N of granular fertilizer had been released into soil within one week after LSGF was applied. However, relative high NH4+-N content near to root zone was still retained between 2 and 5 weeks after LSGF was applied. In open-field autumn cabbage experiment, the peak of soil Nmin content near to root zone came out at 21st day after LSGF was applied, in accordance with the period of maximum nutrition demand of cabbage.In the vegetable field of Beijing region, with moderate-high soil fertility and organic manure application more or less one-third of applied chemical N could be saved in the treatment of LSGF application, compared with local recommended N applied rate in the conventional treatment with broadcast application method. However, no significant yield and N uptake reduction was found in open-field cabbage and greenhouse fennel.Application of LSGF with some organic carbon in the vegetable field (Nmin residue N was 76 kg.hm-2) significantly improved the growth of open-field spring cabbage, in comparison with the other types of LSGF, without any addition of organic carbon.Intensive root system was formed around the point of applied LSGF based on the root length density increased obviously in the place. Rhizosphere environment was also improved after ammonium-nitrogen was applied through LSGF and the soil pH decreased by 0.2-0.4 units. As a consequence this kind of acidification could also increase some nutrient availability in effective root zone.The results in open-field spring cabbage experiment showed that nitrate content in 0-30cm soil was significantly lower than conventional fertilization when N was applied as LSGF due to low N input. In deeper soil layers, LSGF application significantly decreased nitrate accumulation compared with conventional fertilization treatment. N use efficiency significantly increased in the treatment of LSGF application. Under the condition of this experiment, nitrate accumulation was significantly influenced by soil N min residue at preplanting and this influence was not investigated between different irrigation amounts.