农林业系统沙兰杨-小麦、玉米群落类型氮、磷、钾营养元素循环的研究

农林业系统沙兰杨-小麦、玉米群落类型N、P、K营养元素循环研究结果表明:在整个群落中,元素N和P发生损亏,K基本平衡。在植物组分库和枯落物库中,元素N、P、K均发生累积;在土壤库中,元素N、P和K均发生亏损。土壤表层(0—20cm)N的含量是限制农作物正常生长发育的主要环境因子。土壤库中有效N和速效P的含量是限制沙兰杨正常生长发育的主要环境因子。群落的年输入输出量大,枯落物少,营养元素在各组分间的循环量大等是该群落类型营养元素循环的重要特性。

CYCLES OF NITROGEN, PHOSPHORUS AND KALIUM AS THE NUTRIENT ELEMENTS IN AN AGRO-FORESTRY ECOSYSTEM OF THE POPU-LUS/EURAMERICANA-TRITICUM SATIVUM -ZEA MAYS COMMUNITY-TYPE

A study on the cycles of nitrogen, phosphorus and kalium as the nutrient elements was carried out in an agro-forestry ecosystem of the Populuu/Euramericana-Triticum sativum-Zea mays community-type, It was found that in these cycles, in terms of the whole community,N and P have a deficit and K is kept basically balanced,Each of N,P and K is accumulated in both the plant stock and the litter stock, while having a deficit in the soil stock. N, P and K have the accumulations of 317.436, 70.917 and 235.758 kg/hm2, respectively in the plant stock, the annual uptakes of 310.444, 68.329 and 229.80lkg/hm2a,respectively,and the annual amounts of 24.35 3.79and33.96kg/hm2a,respectively,in litter.N,P and K which are stored in the depth of 0 to 80cm of soil have the amounts of 285.56,347.38 and 489.48 g/m2, respectively, of which 36.81, 26.54 and 62.87g/m2,respectively,are available to the plants. Thus,N,P and K have the annual return rates of 5.02, 3.1 and 10.5%, respectively, the absorption coefficients of 0.11, 0.02 and 0.0047,respectively,the utilization coefficients of 0.98, 0.76 and 0.98, respectively, and the cycle coefficients of 0.078,0.055 and 0.15, respectively.