Mineral N Accumulation And The Impact Factors In Apple Orchards Of Weibei Areas In Shaanxi Province

From November 2004 to February 2005 in Shaanxi main apple producing areas. Selected 10 years around, 9-12 Fuji orchards, 0-120cm layers of soil, each orchards selected 15 different points randomly, for every 20cm layer, the same layers mixed as a sample, a total of 87 orchards, 522 soil samples. Registered the fertilization,irrigation and sod culture. Tested the contents of NH4+-N and NO3--N in laboratory. The affect of different factors on NO3--N accumulation of the orchard soil was also studied at the same time. The results were as following:1. The content of ammonium nitrogen were 4.67±1.37 mg·kg-1 and don't change much in 0 -120 cm soil depth profiles of orchards in different apple producing regions, The average accumulation of ammonium nitrogen were 76.47±13.30 kg·hm-2 in 87 apple orchards .The content of nitrate nitrogen were 22.86±24.98 mg·kg-1, the amount of NO3--N had the tendency of becoming large with the depth of the soil layer, accumulating peak was mostly on 40-60 cm soil layer. The accumulation of mineral N was different in different apple orchard's profiles. The most accumulation was 940.80 kg·hm-2 and the latest accumulation was 211.10 kg·hm-2. Over 600 kg·hm-2 accumulation of mineral N were 40.24% on 0-120 cm soil depth.2. Much nitrogen will result in more nitrate accumulation than less nitrogen and organic fertilizer in 0-120 cm orchard soil layer .The accumulation peak of nitrate nitrogen was coming with the depth of the soil layer. But in orchard using organic fertilizer , the difference of each soil depth profile was very little ,the accumulation was 64.04±18.00 kg·hm-2 .3. The accumulation of nitrate nitrogen had the tendency of becoming small with the depth of the soil layer; the smallest amount was 74.70 kg·hm-2 on 60-80 cm, and then became large in irrigated orchard. In unirrigated orchard the accumulation of nitrate nitrogen became large firstly, and then became small with the depth of the soil layer, the largest amount was about 160 kg·hm-2 in 40-80 cm.4. The accumulation of nitrate nitrogen in high-density orchards was more than that in small density and good light distribution orchards. The accumulation peak became in 40-60 cm of the soil layer in both orchards, the amount was 215.02 kg·hm-2 and 149.10 kg·hm-2...