[Effects of controlled-release nitrogen fertilizer and bag-controlled release fertilizer on utilization of N-urea in 'Orin' apple and its accumulation in soil].

Taking a six-year old 'Orin' apple tree plantation ('Orin'/SH6/ Malus micromalus Makino) as test material, the effects of common urea treatment (CU), bag-controlled release ferti-lizers treatment (BCRF) and controlled-release nitrogen fertilizer treatment (CRNF) on N-urea absorption, utilization, loss and accumulation dynamics of nitrogen content in 0-80 cm soil layer were investigated by N labeled tracer method. The results showed that compared with CU treatment, both CRNF and BCRF treatments increased the inorganic nitrogen content in soil at the late stage of apple growth, the leaf SPAD value, leaf nitrogen content, net photosynthetic rate and N derived from fertilizer (Ndff value) of different organs at fruit maturity stage, with CRNF showing stronger effects than BCRF. The amount of N residue in 0-40 cm soil layer showed a decreasing trend in different phenological stages. The amount of N residue was the highest in CRNF, followed by BCRF, and the lowest in CU, among which CRNF declined gently with N residue mainly concentrated in the 0-40 cm soil layer. N residue in 40-80 cm soil layer showed an increasing trend in different phenological stages, which was the highest in CU, followed by BCRF, and the lowest in CRNF, and that of CRNF increased gently. The N fertilizer utilization rate of CRNF was 32.6% at fruit maturity stage, which was 1.11 and 1.56 times as high as that of BCRF and CU, whereas its N loss rate was 21.6%, being obviously lower than BCRF (35.6%) and CU (59.6%). CRNF significantly improved fruit yield and quality and increased economic benefits.