Abstract:

There are many problems, such as poor site conditions, poor soil structure, poor water conservation, low fertility and low production capacity, in the newly cultivated red soil formed by reclamation of slope wasteland. Improving soil organic carbon is considered to be an important way for rapid anthropogenic mellowing of red soil. To understand the different improving effects of various types of organic materials on organic carbon and fertility of red soil, two kinds of newly cultivated soil, red clayey soil and red sandstone soil, were selected. The effects of 10 kinds of common organic materials on various forms of organic carbon, available nutrients and enzyme activities in the soil were studied by indoor culture method. The results showed that the stability sequence of organic carbon from different organic materials in the soil was as follows: weathered coal humic acid > 50% weathered coal humic acid + 50% pig manure/rice straw compost > peat > pig manure/rice straw compost > domestic waste compost > biogas residue > mushroom stick compost > pig manure > chicken manure > rice straw > Chinese milk vetch. The stability of organic carbon in clayey soil (red clayey soil) was higher than that in sandy soil (red sandstone soil). The application of weathered coal humic acid, and 50% weathered coal humic acid + 50% pig manure/rice straw compost had the most significant effect on improving soil humus. The organic carbon remained in the soil of the newly cultivated land was mainly mineral bound organic carbon, and the proportions of free organic carbon and coarse-granule organic carbon in the total organic carbon were relatively low. The application of various organic materials could significantly improve soil microbial activity, promote the formation of soil water stability aggregates, slightly improve soil CEC, but the effect was significantly different among different organic materials. The results of comprehensive evaluation showed that the best soil property improvement effects were obtained by applying weathered coal humic acid, 50% weathered coal humic acid + 50% pig manure/rice straw compost, and pig manure/rice straw compost, while the effects of mushroom stick compost, rice straw and Chinese milk vetch were relatively poor. It is suggested that the mixed application of organic materials with different properties should be considered in improving newly cultivated land of low hilly red soil.

Key words: newly cultivated land, organic material, organic carbon accumulation, organic carbon stability, fertilizing