Effect of N, P, K fertilization on young citrus tree growth, fruit yield and quality in area of red soil

A pot experiment in greenhouse was conducted to study on influence of N, P and K fertilization on young citrus tree growth and fruit yield and quality during 1999 to 2001.The results showed that the OPT treatment(Balanced fertilization, the rate g/(kg·a): N 0.15、P 0.05、K 0.15、Ca 0.23、Mg 0.0326、B 0.0006、Zn 0.004、Mo 0.0016、Cu 0.0005) increased leaf number and leaf weight and great affected on citrus tree shoot growth. The shoot growth without N, P and K treatments was only 14.5%, 74.5% and 91.6% compared with OPT treatments, respectively. Fertilization also influenced on citrus flowering and fruiting. The numbers of flower without N, P and K treatments were only 28.9%, 89.8% and 91.9% of OPT treatment, the fruiting rate were only 24.3%, 83.3% and 93.0% of OPT treatments and the yield of fruits decreased by 22.2%, 16.8% and 21.2%, respectively. The trial also found that some quality parameters especially orange appearance and commercial quality was affected by N, P and K fertilization. For N, P and K fertilizers, N had the greatest influence on citrus tree growth, and K showed the little response on nutritional growth stage. However, N and K had more influence on orange yield and quality than that of P. Three years study indicated that N, P, and K fertilization significantly promoted citrus growth in young stage and improved both fruit yield and quality as well.