Effect of special controlled release fertilizer application on nitrogen and potassium uptakes of tomato and their residue in soil with drip irrigation in the greenhouse

An experiment was conducted in a plastic greenhouse in a Beijing suburb to evaluate the effects on tomato yield, fruit quality, nitrogen and potassium uptakes and soil residual NO3--N and K with three controlled-release special fertilizers and traditional fertilizers. Six treatments were conducted in this study: no fertilizer N treatment (CK), manure fertilizer (MN), traditional fertilization (TN), controlled-release special fertilizerⅠ(CN1), special fertilizerⅡ(CN2) and special fertilizer Ⅲ(CN3). The results showed that fruit yields were 79.1-87.2 t/ha and there were no significant differences among all treatments，however, the fertilizer application time and labor input were saved. Nitrogen supplying was sufficient in the fruit expending stage with a single application of controlled-release fertilizers, which resulted in synchronization with the crop nitrogen uptake and in an increasing trend in fruit N and K concentration. A sigmoid nitrogen supply was found from the use of controlled-release nitrogen fertilizers, however, only 23.2 to 36.0 percent of the controlled-release potassium fertilizers was released and there was little effect of environmental temperature on the release of coated potassium fertilizers. The soil mineral nitrogen supply was consistent with the sigmoid release pattern of the controlled-release nitrogen fertilizers, which is better for high yield and high efficiency cropping production. Soil nitrate was concentrated in the top layer(0-20cm) and the sub-top layer(20-40cm)，where nitrate accounted for 87.1% of the total nitrate in 0 to 100cm soil layer. NO3--N accumulation for CN1 and CN2 treatments in 0-60cm soil layers was 37 to 55 percent less than the TN treatment at harvest, resulting in less nitrate leaching down to the deeper soil layer. Exchangeable K content in the top soil layer was increased in all treatments with potassium fertilizers. There were no significant differences in potassium contents in 20-100cm soil among all treatments, and no movements of potassium down to deep layers were also observed. In conclusion, the use of controlled-release special fertilizerⅠand fertilizerⅡcan provide reasonable nutrient supplyings without any topdressing, whereby both nitrate leaching loss and farmers labor input were reduced without yield losses.