秸秆及其生物质炭还田提升旱地红壤地力的差异与机理研究

Upland red soil is marked by the primary barriers of “acidic, barren, harden, corrosive, etc.” during the process of soil-forming. At the same time, the rapid development of soil nutrient management mode of “replacing the organic fertilizer with chemical fertilizer” gives rise to the secondary barriers of the upland red soil “decline of soil fertility, acidification, attenuation of soil biodiversity, etc.”, which restrict the utilization and sustainable development of upland red soil resources severely. So “improving the soil fertility and removing the barriers” is the top priority of treating upland red soil by increasing the fertility and stabilizing crop yields. The practice of developed agricultural countries in the world proved that returning of stalk resource to fields is the most fundamental strategic technical measure of maintaining and improving soil fertility despite its unclear mechanism. In this project, a long-term trial of sweet potato and winter fallow in upland red soil is to be carried out, involving two kinds of organic materials, that is, sweet potato vines, and their biochars to be returned into the field. The soil physical and chemical properties (including soil moisture, temperature, pH, soil bulk density, etc.), the changes of soil nutrients and their components (including soil organic matter, N, P, K, etc.), soil microbial activity and community structure and crop yield are to be monitored and analysed with an aim to exploring the short-term and long-term effects of hoisting the upland red soil fertility through the returning of crop stalks and stalk biochars into field so as to reveal the mechanisms of increasing soil fertility of the returning of crop stalks and their biochars, and provide preliminary practical and theoretical guidance for the implementation of the circular agriculture in upland red soils.

旱地红壤地力低下，严重制约了江西红壤区农业的可持续发展。如何提高旱地红壤地力，实现高产稳产，是旱地红壤资源可持续利用的首要问题。实践表明，秸秆及生物质炭还田均能提高土壤肥力、增加农作物产量，是保持和提高土壤肥力最根本的战略性技术措施之一。但秸秆及生物质炭所含有机碳组成与活性不同，其对地力提升效果可能存在较大差异，提升地力的机理还不清楚，亟待试验加以探讨。本项目以田间定位试验为基础，结合室内控制试验，来探究不同秸秆及生物质炭施用水平下，旱地红壤土壤物理性质(土壤水分、土壤温度、土壤容重及孔隙率等)、土壤养分(土壤有机质、N、P、K等)、土壤微生物活性、微生物群落结构与多样性、红薯产量等的变化，分析秸秆及其生物质炭还田提升旱地红壤地力的差异，探讨影响旱地红壤地力提升的主导因子，揭示秸秆及其生物质炭提升旱地红壤地力的内在机制，为旱地红壤区农作物秸秆综合利用及循环农业的实施提供理论及实践指导。

旱地红壤是江西重要的农业生产资源，丰富的水热资源使得该区农业生产和经济发展潜力巨大。但由于旱地红壤地力低下，严重制约了江西红壤区农业的可持续发展。提高旱地红壤肥力，改善土壤生态系统环境，是旱地红壤资源可持续利用的首要问题。基于此，本项目选择旱地作物的红薯藤及由其制备的生物质炭为研究材料，设置7个处理：① CK：常规管理；② S1：施用红薯藤 (3000 kg/hm2)；③ S2：施用红薯藤 (4500 kg/hm2)；④ S3：施用红薯藤 (6000 kg/hm2)；⑤ BC1：施用红薯藤生物质炭 (1000 kg/hm2)；⑥ BC2：施用红薯藤生物质炭 (1500 kg/hm2)；⑦ BC3：施用红薯藤生物质炭 (2000 kg/hm2)，研究红薯藤及其生物质炭对旱地红壤理化性质、微生物活性、微生物群落结构及红薯产量的影响，探讨影响旱地红壤质量的主导因子，为旱地红壤肥力的提升提供科学依据，为旱地红壤区农作物秸秆综合利用及循环农业的实施提供理论及实践指导。.研究结果表明：（1）红薯藤及其生物质炭的施用均能降低土壤容重，提高土壤有机碳、全磷、水解氮含量，但对有效磷含量无显著影响。（2）红薯藤及其生物质炭的施用均能提高土壤呼吸强度、微生物量碳含量，在一定程度上提高了土壤FDA水解酶、脱氢酶、过氧化氢酶和蔗糖酶活性，红薯藤及其低剂量生物质炭的施用均能提高土壤脲酶活性。（3）红薯藤及其生物质炭的施用在一定程度上提高了土壤微生物总PLFAs含量及各菌群PLFAs含量，其中红薯藤及其生物质炭对土壤微生物总PLFAs含量、革兰氏阴性菌PLFAs含量增幅最大是在块根形成初期，其中处理S2、BC2对各菌群PLFAs含量的提高最显著。较多施用（处理S3、BC3）会降低土壤微生物总PLFAs含量及各菌群PLFAs含量。（4）红薯藤及其生物质炭的施用均能提高旱地红壤红薯产量。.综上所述，适量施用红薯藤及其生物质炭能够有效改善土壤理化性质、土壤微生物活性及微生物群落结构，提高红薯产量。施用生物质炭对旱地红壤质量的提升效果要优于施用红薯藤。施用红薯藤及其生物质炭对改良土壤微生物环境、减少土壤养分流失、提高土壤肥力等方面具有一定的可行性。