Effect Of Straw Modified Material On Structure And Water Characteristics Of Sandy Soil

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.