Effects of N application with dripping irrigation on N absorption and utilization of apple

The characteristics of absorption, distribution and utilization of 15N-Urea with different numbers of drip irrigation emitters applied to eight year-old Kiazshi/Malus prunifolia (Willd.) Borkh were studied.The results show that the Ndff% values in plant organs are significantly different at fruit maturity with different numbers of emitters, the Ndff% values with DF2 are significantly higher than those of DF1 and CK. The Ndff% values of fruits in all the three samples ( or in 3 different treatments) are the maxima, 3.84%, 3.14% and 3.16%, respectively, while the fruit Ndff% values at the shoot growing and fruit swelling stage DF2 are lower than those of DF1 and CK. At the fruit maturity stage, the highest distribution (of 15N-Urea) is in reproductive organs and then in vegetative organs and storage organs, and there are not significant differences between the treatments. The utilization of DF2 15N utilization is 38.95%, and is significantly higher than those of DF1 (27.68%) and CK (23.69%). As the growth of the plants, the nitrate contents in the 0-20cm and 20-40cm soil layers show the same bimodal peaks which appear at the shoot growing and fruit swelling stages, and those of the 60-80cm, 80-100cm soil layers also show similar, mild trends. The soil nitrate contents in 40-60cm soil layers are significantly different, and the soil nitrate contents of DF2 are significantly higher than those of DF1 and CK.