水土保持措施对红壤缓坡地土壤活性有机碳及酶活性的影响

基于植物篱和稻草覆盖控制红壤坡耕地水土流失的长期定位试验,以花生常规等高种植为对照(CK),研究红壤缓坡地香根草篱(H)、稻草覆盖(M)、稻草覆盖+香根草篱(HM)3种水保措施下旱、雨季土壤活性有机碳含量及土壤酶活性变化特征,探讨不同水保措施对土壤活性有机碳含量及土壤酶活性的影响。结果表明∶(1)稻草覆盖、香根草篱处理均能显著提高土壤微生物生物量碳含量(p0.05),其中稻草覆盖和香根草篱相结合效果最佳,且在旱季提升效果优于雨季;而稻草覆盖是提高土壤可溶性有机碳含量的主要影响因素;(2)稻草覆盖和稻草覆盖+香根草篱2种水土保持措施均能显著提高雨季土壤酶活性(p0.05),其中稻草覆盖起决定作用;各水土保持措施对旱季土壤酶活性的影响较小。(3)相关性分析表明,土壤β-葡(萄)糖苷酶和纤维素酶活性与土壤活性有机碳含量呈现良好的相关性(p0.05),对于评价红壤缓坡地水土保持措施土壤环境质量功能、指导实际生产等方面具有重要意义。

Effects of Soil and Water Conservation Measures on Soil Labile Organic Carbon and Soil Enzyme Activity in Gentle Slope Land of Red Soil

Red soil slopelands are one of the main land sources for agricultural production in South China,making the region an important agricultural zone of the country producing a huge variety of agricultural and forest products,thanks to its rich soil and hydrothermal resources and great biological production potential. However,owing to unreasonable development and its natural geographical environment,soil erosion in this area is getting more and more serious. The red soil region of South China amounts to a total of 2.03 million km2,of which more than 60 million km2 suffers a varying degree of soil erosion,putting the region next to the Loess Plateau in extensiveness and severity of soil and water loss in China. Hence soil erosion has become a major restraint hindering development of the agriculture production and improvement of the ecological environment and people′s living quality of the region improvement. A number of biological water and soil conservation measures,like growing hedgerows,mulching the fields with straw,are now being applied extensively both inside and outside the country. They were found to be able to reduce soil erosion by more than 85%,increase the content of organic matter by 9%~13%,and improve soil aggregate structure and water-stable aggregates in number and quality,thus enhncing erosion resistance of the soil significantly. Soil labile organic carbon(LOC)refers to the labile fraction of soil organic metter. It is readily available,easily decomposed and mineralized by soil microbesy to move and to be oxidized and mineralized, and directly available to plants and soil microorganisms. Although LOC accounts for a limited proportion in the soil total carbon,size and turnover of the fraction is very important to content,circulation and utilization of soil available nutrients. As soil enzymes are involved in decomposition and transformation of soil labile organic carbon and major regulators of soil biological processes,their activity is a good indicator of soil′s capability of nutrient transformation. Most studies in the past used to focus on effects of various soil and water conservation measures on soil erosion,non-point source pollution,soil organic carbon and inorganic nutrients,with little attention given to effects of these measures on soil labile organic carbon,soil enzyme activities and their relationships. Based on the soil and water conservation field experiments that started in 2009 and was designed to have three treatments,Treatment H(Hedgerows of Vetiver Grass),Treatment M(Mulching with rice straw), and Treatment HM(hedgerows of Vetiver Grass + mulching with rice straw),investigations were carried out of effects of the water and soil conservation measures on soil labile organic content and soil enzyme activity in a gentle slopeland of red soil grown with peanut and analyses done of relationships of soil enzyme activities with soil labile organic carbon,in an attempt to provide some theoretical basis for choosing reasonable water and soil conservation measures for peanut-growing gentle slopeland of red soil from the angle of soil micro-ecology. Results show that 1)all the treatments,H,M and HM,increased soil microbial biomass carbon content significantly(p<0.05),with Treatment HM in particular. And the effects were more significant in the dry season than in the wet season,and the mulched rice straw was the main factor improving soil soluble organic carbon content. 2)although both Treatments M and HM improved soil enzyme activity significantly in the rainy season(p<0.05),mulched rice straw was the decisive factor,and the soil and water conservation measures,including Treatment H,did not have much impact on soil enzyme activity in the dry season;and 3)soil β-glucosidase and cellulose were well related to content of soil labile organic carbon(p<0.05), which has a great implication to evaluation of the functions of the soil and water conservation measures in protecting soil environmental quality and guidance of practical production in gentle slopelands of red soil.