氮锌复合作用对单播和混播牧草氮素来源的影响

在亚热带中山草地黄棕壤上研究了氮锌复合作用对单播和混播牧草氮素来源的影响 ,结果表明 :施氮降低了白三叶前期固氮百分数 ,但低水平施氮显著提高了白三叶后期固氮百分数。在各种施氮水平下 ,施锌 6mg kg之处理 %Ndfa最高。施氮显著降低了氮转移的数量 ,低量施锌促进了氮转移 ;施氮促进了牧草对肥料氮的吸收 ,所有施氮水平下 ,单播黑麦草 %Ndff以施锌 6～ 2 0mg kg较高。在施氮 3 0～ 90mg kg,混播黑麦草和混播白三叶 %Ndff以施锌 6～ 2 0mg kg较低 ;单播和混播黑麦草 %Ndfs随施氮水平增加显著下降 ,施锌对单播黑麦草的 %Ndfs影响不明显。在所有施氮水平下 ,施锌 6～ 2 0mg kg减少了混播白三叶和混播黑麦草对土壤氮的吸收

INFLUENCE OF THE COMPOUND EFFECT BETWEEN NITROGEN AND ZINC ON THE RESOURCE OF NITROGEN OF HERBAGE IN MIXED AND PURE CULTURE

Under pot culture, the influence of compound effect between nitrogen and zinc on the resource of nitrogen of ryegrass in mono culture and ryegrass/clover in mixture were studied on yellow brown earth which collected from sub tropic mountain sward of southern China. The result showed as follows:(1) The percentage of nitrogen derived from atmosphere (%Ndfa) was decreased by nitrogen application in early growth stage and suitable amount of nitrogen application increased it in later growth stage. The %Ndfa of white clover in mixture was the highest with 6 mg/kg zinc application in all nitrogen levels. The transfer of fixed nitrogen by white clover to ryegrass was decreased by nitrogen application and increased by low amount of zinc application. (2) The percentage of nitrogen derived from fertilizer(%Ndff) was significantly increased by nitrogen application, of which the treatments with 6～20 mg/kg zinc application was higher than other zinc application treatments on ryegrass in monoculture, and the treatments with 6～20 mg/kg zinc application on white clover/ryegrass in mixture was lower than other zinc treatments at the range from 30 to 90mg/kg nitrogen application. (3) The percentage of nitrogen derived from soil(%Ndfs) of ryegrass both in pure and in mixture was significantly decreased as the increase of the levels of nitrogen application, of which ryegrass in mono culture was not obviously influenced by zinc application, and ryegrass/clover in mixture was decreased by 6～20 mg/kg zinc application under all nitrogen levels.