耕作方式对东北黑土坡耕地土壤物理性状及根系垂直分布的影响

为了明确耕作方式对东北薄层黑土坡耕地土壤物理性状以及玉米根系垂直分布的影响,该研究以东北薄层黑土坡耕地土壤为研究对象,设置免耕和翻耕2种耕作方式,研究耕作方式对不同坡位土壤水稳性团聚体粒径分布与稳定性、土壤容重、土壤孔隙度、土壤贯入阻力以及玉米根系在垂直方向主要分布深度的影响,并进一步探究各指标间的相互关系。结果表明,与免耕相比,翻耕处理通过增加土壤1～2 mm粒级水稳性团聚体含量,降低0～20 cm土层土壤容重,改善0～20cm土层土壤孔隙度,降低10～20cm土层土壤贯入阻力,增加玉米根系在垂直方向主要分布深度;但同时翻耕处理条件下5mm粒级土壤团聚体含量平均减少59.1%,平均重量直径平均降低31.9%。翻耕处理下,坡位对土壤孔隙度、5 mm粒级水稳性团聚体含量以及平均重量直径的影响都呈现坡中位与坡下位优于坡上位。研究结果表明,对于东北薄层黑土坡耕地,在坡中位和坡下位采用翻耕有利于降低土壤紧实度,促进玉米根系下扎;在坡上位可采用免耕改善土壤结构及其稳定性。该研究可为促进黑土可持续发展提供理论依据与参考。

Soil physical properties and vertical distribution of root systems affected by tillage methods in black soil slope farmlands in Northeast China

Slope farmland is the main type of farmland in the black soil region of northeastern China, accounting for about 60% in total. Currently, long-term high intensity utilization and irrational farming have led to the deterioration of soil physical properties, particularly on the gentle and long slope. However, it is still unclear on the effect of different tillage on the soil physical properties of slope positions. In this study, a 4-year field experiment was conducted at the Xiangyang experimental base of Northeast Agricultural University, in order to clarify the impact of farming modes on the vertical distribution of maize roots, and the soil physical properties in the slope farmland of thin black soil in Northeast of China. Two farming treatments were set as no-tillage (NT) and conventional tillage (CT). The slopes were divided longitudinally into three positions from high to low according to the altitude: upper, middle, and lower layer. Each treatment was repeated three times. The particle size distribution of soil water-stable aggregates was obtained at different slope positions. The indicators were measured, including the stability of water-stable aggregates, soil bulk density, soil porosity, soil penetration resistance, and the distribution of vertical depth in root systems. The results showed that: 1) Compared with NT, the CT significantly increased the soil porosity of 0-20 cm soil layer, and the main distribution depth of maize roots, the vertical direction (P<0.05), while significantly reduced the soil layer of 0-20 cm soil bulk density, and soil penetration resistance of 10-20 cm soil layer (P<0.05). 2) Compared with NT, the CT significantly reduced the content of water-stable aggregates larger than 5 mm (P<0.05), with an average reduction of 59.1%, and the average weight diameter of soil water-stable aggregates led to the deterioration of soil structure, but increased the content of water-stable aggregates of 1~2 mm. 3) In the CT treatment, the middle and lower slope were better than the upper slope, according to the evaluation on the influence of slope position on the soil porosity, the content of water-stable aggregates larger than 5 mm, and the average weight diameter. The NT effectively increased the content of water-stable aggregates stability larger than 5 mm in the upper slope soil, and the structural stability in the upper slope soil, thereby to improve the physical properties of the soil. 4) Correlation and regression analysis showed that the plowing can contribute to increase the content of 1-2 mm water-stable aggregates, soil porosity, and the vertical distribution depth of roots, while reduce the soil penetration resistance, the grain size greater than 5 mm the water-stable aggregate content, and the stability of soil structures. The results of the study demonstrated that the plowing can effectively improve the soil compaction and the rooting systems, while lead to the deterioration of soil structure on the slope. Therefore, it is recommended to take conservation measures of water and soil on the upper slope, in order to reduce the soil erosion of slope farmland in the thin black soil area of the Northeast China.