【作者】 韦武思；

【导师】 王定勇；

【作者基本信息】 西南大学 ， 环境科学， 2010， 硕士

【摘要】 随着人口不断增长、工农业日益发展以及城镇化加快,世界各国土地退化严重,土地沙化速度加快,土地日趋贫瘠,土地质量日趋下降,导致土地生产力严重衰退,耕地不断减少。我国是世界上受沙化危害最严重的国家之一,沙化面积大、分布广,加剧生态环境恶化,已严重影响我国工农业和社会经济的发展,威胁民族生存与发展空间,造成了严重经济损失；虽然近年来世界各国加大对退化土地的治理改良力度,并取得一定成效,但土地退化依然严重。因此,加强沙化土地治理,改良沙化土壤,防止土地退化,保护土地环境,形势迫在眉睫。近年来,各种土壤改良剂相继问世,并为改良沙化土壤取得很好成效。但土壤改良剂大多属于化学产品,成本较高,而且极易产生化学二次污染。为进一步研究退化土壤改良对策,并充分利用可再生资源、尽可能减少二次污染,本研究将不同作物秸秆预处理产物与膨润土、PAM配施成秸秆改良材料,通过土培试验,探讨三者协同作用对沙质土壤结构(团粒结构和容重)和水分特征(饱和含水量、田间持水量和饱和导水率)的改良与调控效应,揭示其改良与调控作用机理,并得出以下主要结论：1、秸秆改良材料能有效改良沙质土壤团粒结构。随改良材料用量(或PAM含量)的增大和土培时间的增长,土壤大粒级颗粒含量呈增大趋势,小粒级含量则呈减小趋势,但单位改良材料用量对提高土壤大粒级含量的效果随改良材料用量增加而下降。施用用量越大或PAM含量越高(小于2%时),土样1-5mm粒级(最具土肥价值的土壤结构体)含量呈明显增加趋势；而PAM含量太大(为3%时),土样1-5mm粒级含量反而减小；随土培时间的增长,土样1-5mm粒级含量先增大后减小,土培60d时土样1-5mm粒级含量最大。当秸秆改良材料用量为10g、PAM含量为2%(处理10.2)土培60d时土样1-5mm粒级含量最大,土壤结构改良效果最佳。3种秸秆改良材料中,麦秆改良材料对土样1-5mm粒级的改良效果最佳,玉米秆改良材料次之。2、秸秆改良材料能有效降低沙质土壤容重。添加秸秆改良材料后,土壤容重比对照明显减小；施用用量越大或施用PAM含量越高(小于2%时),土样容重呈明显减小趋势；PAM含量太大(为3%时),土壤容重反而变大。随土培时间的增长,土样容重先减小后增加,土培60d时容重最小。当秸秆改良材料用量为10g、PAM含量为2%(处理10.2)土培60d时土样容重最小,土壤结构改良效果最佳。3种秸秆改良材料中,麦秆改良材料对土样容重的改良效果最佳,玉米秆改良材料次之。3、秸秆改良材料能有效改良沙质土壤持水性能(饱和含水量、田间持水量和饱和导水率)。添加秸秆改良材料后,土壤持水性能比对照明显增大；施用用量越大或施用PAM含量越高(小于2%时),土样持水性能呈明显增大趋势；而PAM含量太大(为3%时),土壤持水性能反而减小。持水性能随土培时间的增大先增大后减小,土培60d时达到最大值,而对照土样持水性能随土培时间增大呈略减趋势(饱和导水率呈略增趋势),但减幅(增幅)很不明显。当秸秆改良材料用量为10g、PAM含量为2%(处理10.2)土培60d时土样持水性能最大,改良效果最佳。3种秸秆改良材料中,麦秆改良材料对土样持水性能的改良效果最佳,玉米秆改良材料次之。4、施加秸秆改良材料后,沙质土壤持水性能(饱和含水量、田间持水量和饱和导水率)的变化规律与其1-5mm粒级含量的变化规律基本一致,与容重的变化规律呈相反关系,可见,改良土壤结构(团粒结构、容重)是秸秆改良材料改良土壤水分特征(饱和含水量、田间持水量和饱和导水率)的基础,土壤结构转好,则土壤水分特征随之得以改善。更多还原

【Abstract】 With the growing population, increasing industrial, agricultural development and urbanization accelerated, the land is severely degenerated around the world, the desertification of land speeds up, the land becomes barren, and the land quality is deteriorating day by day. All leads to the severe decline of land productivity and the decrease in cultivated land. China is one of the countries that suffered the most serious damage by desertification in the world. In our country, desertification area is large and the distribution is wide. This aggravates the deterioration of ecological environment, affects our development of industrial and social economy, and threatens the national survival and development space, causing the serious loss of economy. Countries all over the world strengthen the efforts to governance and improve the deterioration soil, and achieved certain results in recent years, but the land degeneration is still serious. As a result, it’s important to strengthen the management of desertification land, improve the desertification soil, prevent the degeneration of land and protect the land environment.In recent years, a variety of soil modifiers have been come out, and achieved certain results in the modification of desertification soil. However, most of the soil modifiers belong to chemical product. They’re cost and produce secondary pollution easily. In order to study further about the improvement measures of degeneration soil, make full use of renewable resources, and minimize secondary pollution, this paper tries to use straw pretreatment product, bentonite and PAM in the pot experiment, explore the synergy effect of the three on the improvement and control effect of the sandy soil structure (aggregates and bulk density) and water characteristics (saturated water content, field moisture capacity, and saturated hydraulic conductivity), and reveal the mechanism of improvement and control. The major conclusions are as follows:1. Straw modified materials can improve sandy soil aggregate structure. With the improvement of modified material dosage(PAM content) and the increase of soil culture time, the content of large grain-sized particle tends to increase, the content of small grain-sized particle tends to decrease. But with the modified material dosage increases, per unit of modified material dosage to improve the content of large grain-sized particle tends to decrease. With higher dosage or higher PAM content(less than 2%), 1-5mm grain size in the soil samples (the most valuable soil fertility of soil structure) level increases significantly. But when the PAM content is too high (for 3%), the content of 1-5mm grain size decreases. With the growth of soil culture time, the content of 1-5mm grain size first increases and then decreases. When the soil culture time is 60 days, the content of 1-5mm grain size is the largest. When the dosage of the modified material is 10 gram, PAM content is 2% (treatment of 10.2), and the soil culture time is 60 days, the content of 1-5mm grain size is the largest, and the improvement of soil structure is the best. Of the three modified materials, wheat straw is the best to improve the content of 1-5mm grain size, followed by maize straw.2. Straw modified materials can reduce the bulk density of the sandy soil. Added straw modified material, bulk density decreases significantly compared with the contrast. With higher dosage or higher PAM content(less than 2%), bulk density shows a decreasing trend. But when the PAM content is too high (for 3%), bulk density becomes larger. With the growth of soil culture time, bulk density first decreases and then increases. When the soil culture time is 60 days, bulk density is the smallest. When the dosage of the modified material is 10 gram, PAM content is 2% (treatment of 10.2), and the soil culture time is 60 days, bulk density is the smallest, and the improvement of soil structure is the best. Of the three modified materials, wheat straw is the best to improve the bulk density, followed by maize straw.3. Straw modified materials can improve the water holding capacity (saturated water content, field moisture capacity, and saturated hydraulic conductivity) of sandy soil. Added straw modified material, water holding capacity increases significantly compared with the contrast. With higher dosage or higher PAM content(less than 2%), water holding capacity shows an increasing trend. Howerve, water holding capacity of sandy soil decreases when the PAM content is too high (for 3%). With the growth of soil culture time, bulk density first increases and then decreases. When the soil culture time is 60 days, water holding capacity is the largest. Whereas in the contrast sample, with the growth of soil culture time, bulk density decreases slightly (saturated water content shows a slightly increasing trend), but the reduction (increase) is not very significantly. When the dosage of the modified material is 10 gram, PAM content is 2%(treatment of 10.2), and the soil culture time is 60 days, water holding capacity is the best. Of the three modified materials, wheat straw is the best to improve the water holding capacity, followed by maize straw.4. Added straw modified material, water holding capacity (saturated water content, field moisture capacity, and saturated hydraulic conductivity) of sandy soil changes almost the same as the variation content of 1-5mm grain size, and opposite to the variation of bulk density. It’s easy to see that soil structure (aggregates and bulk density) is the base of water characteristics (saturated water content, field moisture capacity, and saturated hydraulic conductivity). Soil structure improves, and the water characteristics also improve.更多还原