云南湿热地区优良牧草距瓣豆的磷钾营养

采用单因子随机区组设计，在湿热地区赤红壤上开展优良热带豆科牧草—距瓣豆的磷、钾营养需求的试验。结果表明，施用磷、钾肥单位面积距瓣豆的干物质产量、氮磷钾总吸收量和粗蛋白产量明显提高；施磷可使距瓣豆的磷含量增加，氮含量相对稳定，钾含量逐渐下降；而且年均干物质产量和粗蛋白产量分别与施磷量存在的一元二次曲线方程的拟合程度较好（Yp＝1289+50.5X-0.55X2, r=0.9519**；Ycp＝254+12.2X1-0.14X12，r＝0.9398**）。施钾使距瓣豆的氮、磷含量趋于相对稳定，钾含量有所提高；年均干物质产量和粗蛋白产量分别与施钾量亦存在的一元二次曲线方程的拟合程度较好（Yk＝1259+19.2X-0.087X2，r=0.8546**；Ycp＝248+4.3X1-0.0204X12，r=0.8055**）。结果还表明，距瓣豆定植的第三年，必须按照磷钾比例1∶0.5～1.2施入磷、钾肥，以满足距瓣豆生长的营养需求和维持距瓣豆的高产稳产。

Study on nutrient requirements of phosphorus and potassium of a legumina (Centrosema pubescens) grown in Humid Subtropical Areas of Yunnan

Experiments of applying phosphorus (P) and potassium (K) using randomized complete block designs with six treatments and four replications were carried out to investigate the nutrient requirements of a tropical legume-- Centrosema pubescens grown on the latosolic red earth in humid subtropical areas of Yunnan province. Thus, the objective was to obtain successful establishment and sustainable high yield of excellent tropical legumes, resolve the shortage issue of high quality forage and increase the output of stock raised in the areas. The results showed that dry matter(DM) yield, the total uptake of nitrogen, phosphorus, potassium and yield of crude protein of Centrosema pubescens per hectare significantly increased with P and K fertilizer application, especially a significant increase of yield was obtained through K fertilizer application. There was a significant positive relationship between P application rate and DM yield (Y_p＝1289+50.5X-0.55X², r=0.9519^**) and yield of crude protein of Centrosema pubescens (Y_cp＝254+12.2X₁-0.14X₁²，r＝0.9398^**), phosphorus fertilizer application can increase P content and decrease K content with the growth of Centrosema pubescens. Meanwhile, there was a significant non-linear positive relationship between K rate and DM yield (Y_k＝1259+19.2X-0.087X², r=0.8546^**) and yield of crude protein of Centrosema pubescens.(Y_cp＝248+4.3X₁-0.0204X₁², r=0.8055^**), and K fertilizer application can increase K content of Centrosema pubescens. Based on analyses of plant and soil samples, it is concluded that P and K fertilizers should be applied at a ratio of 1:0.5-1.2 after Centrosema pubescens plant was established in the third year to maintain and stabilize high DM yield and quality of Centrosema pubescens.