Effects of covering white clover with different thickness in apple orchard on furrow soil fertility

In order to understand the effect of covering white clover on soil fertility in the apple orchard, the fresh white clover was covered in the furrow between apple trees rows. The thickness of white clover was 5 cm, 10 cm, 15 cm and 20 cm, respectively. The uncovered furrow was taken as the control. The soil fertility of the furrow was determined when white clover was decomposed for six months. The results showed that compared with the control, the fertility of 0-20 cm soil of the treatments, including the organic matter content, total and available N, P and K, all increased. Furthermore, fertility of 0-10 cm soil increased much more than that of 10-20 cm. When the thickness of cover white clover was less than 15 cm, the soil fertility went up as the thickness increased. However, when it reached 20 cm, the content of organic matter, total N and P, available P and K was lower than that of treatment with 15 cm. Conclusively, covering white clover can improve the fertility of apple orchard. And the positive effect is relative to thickness of covering white clover and soil depth. Covering 15 cm white clover has the best effect on soil fertility in six months.