果园生草对幼龄龙眼园土壤肥力和树体生长的影响

Effects of Sown Grass Mulch on Soil Fertility and Tree Growth of Young Longan Orchard

果园生草提高了土壤肥力，土壤中速效Ｎ和速效Ｋ比生草前分别提高了１８９．３％－２１７．１％和１２．８％－５９．１％，速效Ｐ由痕迹提高到１４．０×１０－６－２６．１×１０－６；全Ｎ和缓效Ｋ分别提高了１７．４％－２７．５％和３９．９％－１５７．１％，ｐＨ值和有机质也比生草前有所提高；全Ｐ和全Ｋ比生草前有所下降，可能与生草收割多翻埋少有关．生草还促进了龙眼树的生长，干周和冠幅的增长率分别由清耕对照的８８．４７％和６４８．５０％增加到１２０．１７％－１４５．５９％和７９０．８４％－８９６．６８％．在３种生草处理中，豆科格拉姆柱花草和格拉姆柱花草与禾本科宽叶雀稗混播处理，对提高土壤肥力和促进龙眼树生长效果较为明显。

Sown grass mulch in the young longan orchard improved soil fertility, such as, rapidly available nitrogen and potassium increased by 189.3%-217.1% and 12.8%-59.1%, respectively; rapidly available phosphorus increased from trace to 14.0×10 -6 -26.1×10 -6 ; total nitrogen and slowly available potassium were enhanced by 17.4%-27.5% and 39.9- 157.1% , respectively; and pH value and organic matter also rose to some extent. However, the total phosphorus and potassium in soil decreased after sown grass mulch, and it might be relevant to the more harvest and less turning. In addition, sown grass mulch also promoted growth of longan trees, the trunk perimeters and crown diameters increased from 88.[KG-4]47% and 648.50% in contrast to 120.17% -145.59% and 790.84%-896.68%, respectively. Among the treatments of 3 kinds of grass, the treatment of Stylosanthes guyanensis or the mixed sowing with Paspalum wettsteinii improved soil fertility significantly and promoted tree growth evidently, and the treatment of P. wettsteinii got the highest yielding of fresh grass.