Effects of weeding and fertilization on soil available nutrients under mixed forest of Dalbergia odorifera and Santalum album

Objective  To explore the responses of soil available nutrients to different tending measures and seasonal changes of the nutrient contents, select the tending measures that could effectively improve soil nutrient status of woodland, and provide references for tending system establishment of mixed plantation of Dalbergia odorifera and Santalum album.

Method  The surface soil of the mixed plantation of D. odorifera and S. album was studied. The experiment setted four treatments, including control (CK), weeding, fertilization, weeding+fertilization. Each treatment was repeated four times. Changes of soil available nutrient contents and pH values were measured quarterly.

Result  Weeding and fertilization did not significantly change soil pH, but enhanced acid-base buffering performance of soil in some extent, and slowed the seasonal fluctuation of soil pH value. The soil available nutrient contents were significantly affected by season and tending measure changes. The contents of ammonium nitrogen and nitrate nitrogen in four treatments peaked in autumn and winter. Compared to CK, the annual ammonium nitrogen contents of soil in weeding, fertilization and weeding+fertilization treatments increased by 16.87%, 8.17% and 20.25% respectively. Soil nitrate nitrogen contents of weeding and weeding+fertilization treatments increased by 12.69% and 21.45% respectively compared with CK, while the content of fertilization treatment decreased by 1.81%. Soil available phosphorus contents of fertilization and weeding+fertilization treatments increased by 19.58% and 50.63% respectively, while the content of weeding treatment decreased by 2.53%. Soil available potassium contents of weeding, fertilization and weeding+fertilization treatments increased by 117.18%, 57.91% and 142.54% respectively.

Conclusion  The soil available nutrients have different responses to tending measures. Weeding and fertilization increases the content of one or more available nutrients in soil, while weeding+fertilization promotes overall increases of soil available nutrient contents under the forest. The weeding+fertilization treatment is an ideal tending measure for D. odorifera and S. album mixed plantation, and it is expected to promote the tree growth well.