掺混菜籽油渣减少土壤入渗改善持水特性

针对目前植物油渣较少应用于农业生产的现状,为探明植物油渣对土壤水分运动和土壤持水特性的影响,采用室内一维土柱入渗试验,以耕作层土壤为研究对象,定量掺混植物油渣,对比研究3种不同掺混深度(14、24和34 cm)条件下的土壤水分入渗特性,并对掺混油渣土壤的持水能力进行分析。结果表明:1)Philip和Kostiakov入渗模型均可用于描述掺混油渣条件的土壤水分入渗特性及参数拟合(R~20.99);2)与纯土相比,掺混植物油渣可有效减小累积入渗量和入渗速率,根层掺混油渣(34 cm土层)最大可分别减少累积入渗量和入渗速率约11.0%和41.7%;3)入渗结束时基于土壤剖面水分分布特征,土壤掺混植物油渣有利于提高土壤饱和含水率和根层土壤含水率,与纯土相比分别提高约14.3%和11.3%,有效增强了土壤持水能力;4)土壤掺混植物油渣可增加黏粒和粉粒、降低砂粒含量。该研究可为农田生产中植物油渣推广奠定理论基础,同时为植物油渣的田间土壤改良及应用提供参考。

Rapeseed dreg additive reducing soil infiltration and improving water retention

Plant dreg is a type of organic matter and a byproduct of vegetable oil extraction. Plant dreg as a fertilizer can be added to soils and it may also improve soil physical properties. An experiment based on the indoor vertical one-dimensional infiltration soil column was conducted to investigate the impact of rapeseed dreg additive on soil-water infiltration, movement, re-distribution and water retention. The soil in the experiment was collected from the 30-cm depth in a cultivated field in the district of Yangling in Shaanxi Province on the Loess Plateau of China (34°17′28″ N, 108°04′30″ E). The particle size of selected soil was measured by Mastersizer-2000 (made in Malvern Instrument Co. Ltd., Britain), and the soil was sandy loam with a particle size distribution of 3.75% for 0-0.002 mm, 21.73% for 0.002-0.02 mm and 74.52% for 0.02-2 mm. Samples were air dried, sieved through a 2 mm mesh, and compacted into plexiglass soil columns with a height and inner-diameter of 40 and 15 cm, respectively. The total soil depth in the column was 34 cm and soil bulk density was 1.45 g/cm3. The rapeseed dreg was air dried, pulverized, and uniformly mixed with soil samples. The plant dreg accounted for 2% of soil weight. The depth of mixed layer was set at 14, 24, and 34 cm. Pure soil samples without additives were used as a control (CK) treatment. A Mariotte bottle was used to provide a free water supply with about 1.5 cm in depth on the surface. The experiment started when the Mariotte bottle opened. The filter paper was laid at the soil surface to make the water head stable. The characteristics of soil water infiltration, distribution and water holding capacity were comparatively analyzed. The results showed that both Philip and Kostiakov models could well describe the relationship between cumulative infiltration and infiltration duration (R2>0.99). Compared with the CK, the soils mixed with plant dreg helped to decrease cumulative infiltration and infiltration rate, both of which decreased as the depth of mixed layer increased. The cumulative infiltration for the soils mixed with 14, 24, and 34 cm was 3.9%, 7.8%, and 11.0% lower than the CK, respectively. The infiltration rate for the soils mixed with 14, 24, and 34 cm was 25.0%, 33.3%, and 41.7% lower than the CK, respectively. From the final water distribution in soil profiles, the soils mixed with plant dreg helped to increase saturated soil moisture and soil water content in soil layers, which were increased by 14.3% and 11.3%, respectively, compared with the CK. This indicated that plant dreg additive could increase soil water retention and water storage in root zone. Plant dreg could increase clay and silt contents from 3.75% to 9.97% and from 21.73% to 55.15%, respectively, and reduce sand content from 74.52% to 34.88%, and the experimental soil changed to silt loam. This indicated that the ratio of medium and small particle-size increased, and the ratio of large particle-size decreased, demonstrating that plant dreg had the potential in improving desertification soils. From the above, mixing plant dreg powder with soils is of significant practical meaning for cultivated soils because of the enhancement of water retention and water storage. This study may provide valuable information for the promotion of plant dreg to cropland and the application and popularity of plant dreg in soil improvement and water-saving agriculture.