黄土高原沟壑区不同年限苹果园土壤碳氮磷变化特征

管理措施是影响土壤质量演变的重要因素.分析和讨论了5、10、15年苹果园耕层(0―20 cm)和0―200 cm土壤有机碳、全氮、全磷、有效磷和硝态氮含量及其影响因素。结果表明，5年、10年和15年的塬面苹果园表层土壤有机碳依次为7.5、6.7和6.7 g/kg；全氮依次为0.94、0.85和0.83 g/kg；但土壤全磷和速效磷含量随着种植年限而增加，与5年苹果园相比，塬面10年苹果园土壤全磷、速效磷含量分别提高了11%、60%，并且磷素的变异性随年限而增加。坡地10年、15年和20年苹果园土壤有机碳依次为6.3、6.2 和6.5 g/kg，全氮依次为0.76、0.76 和0.81 g/kg；与10年苹果园相比，15年苹果园土壤全磷、速效磷含量分别提高了20%、28%。土壤剖面0―80 cm内不同土地利用方式土壤碳、氮、磷含量随土层加深而降低，80 cm以下不同利用条件苹果园土壤碳、磷含量差异不大，氮素含量在土壤100 cm下随苹果园种植年限增加而增加。

Changes of orchard soil carbon, nitrogen and phosphorus in gully region of Loess Plateau

Management practice is an important factor for soil quality changes. Changes in SOC (soil organic C),TSN (total soil nitrogen),Total P, Olsen P and NO₃^--N were investigated in topsoil 0-20 cm and 0-200 cm of 5-year, 10-year, and 15-year orchard of Wangdonggou watershed in Gully Region of Loess Plateau. SOC and TSN content of topsoil in orchard changed little with planting year; however, total P and Olsen P contents significantly increased. For the orchard in the tableland, SOC is 7.5, 6.7, and 6.7 g/kg in 5-year, 10-year, and 15-year orchard, respectively, TSN is 0.94, 0.85, and 0.83 g/kg, respectively. For 15-year orchard in the tableland, total P and Olsen P increased by 11% and 60%, respectively, compared with 5-year orchard. For the orchard in the slopeland, SOC is 6.3, 6.2, and 6.5 g/kg in 10-year, 15-year, and 20-year orchard, respectively, TSN is 0.76, 0.76, and 0.81 g/kg, respectively. For 15-year orchard in the tableland, total P and Olsen P increased by 20% and 28%, respectively, compared with 10-year orchard. SOC, TSN, total P, and Olsen P in the 0-80cm soil profile decreased with depth, but SOC or total P or Olsen P content below 80cm were not significantly different. In addition, nitrate accumulation in 0-100 and 150-300cm increased significantly with planting year.