东北地区不同耕作方式农田土壤风蚀特征

为探究不同耕作方式农田土壤风蚀特征,揭示风蚀对表层土壤理化性质及养分含量的影响,以东北地区典型农田土壤(黑土和风沙土)为研究对象,通过野外集沙仪定点监测与室内理化分析等方法,对不同耕作方式(垄作、免耕)和不同地表覆盖措施(无覆盖、留茬、覆盖)下的土壤风蚀特征展开研究。结果表明:(1)风沙土的输沙量显著高于黑土,在0—100cm高度范围内风沙土的输沙量平均为黑土的168倍。随高度的上升输沙量急剧减少,其中0—10cm输沙量最大,占总输沙量的50%以上,40cm以上则无明显风蚀物;(2)不同耕作方式下,免耕农田土壤风蚀输沙量较垄作样地减少了66.0%~94.1%;而相同耕作措施下,不同地表覆盖的输沙量表现为无覆盖>留茬>覆盖,与无覆盖相比,留茬及秸秆覆盖下的输沙量可以减少90.3%~99.4%;(3)受风蚀影响,表层土壤颗粒、有机质及养分流失严重,其中风蚀物的砂粒含量是表层土壤的1.06~1.42倍,且10—20cm风蚀物中有机质、全氮和全磷含量均比表层土壤高;(4)通过修正风蚀方程(RWEQ)估算得出,垄作无覆盖(RTNF)风蚀模数高达181.7~86582.9t/(km^2·a),风蚀剧烈,而免耕覆盖(NTF)的风蚀模数仅为9.89t/(km^2·a),为微度风蚀。研究显示垄作及无覆盖方式下农田土壤风蚀程度剧烈,加剧了表层土壤颗粒和养分流失的风险,而免耕和地表覆盖能有效缓解风蚀危害。

Effects of Tillage Methods on Wind Erosion in Farmland of Northeastern China

Wind erosion is a serious problem in agricultural regions of Northeastern China,where a north continental monsoon climate is prevalent and land is prepared for seeding using conventional cultivation ways such as ridge tillage or no tillage method. Affected by wind erosion, many studies reported the effect of tillage methods and coverage types on soil wind erosion,and pointed out that soil fine particles and nutrients (i.e., nitrogen and phosphorus) of top soil lose seriously by wind erosion, which have negative impacts on agricultural production and environment. Generally, wind erosion was affected by wind speed,soil water content,soil texture,and even the land cover types (like standing residues and flat residues) after harvest during wind season. Moreover, conservation tillage like no tillage or residue cover, could reduce soil wind erosion effectively on farmland. However, differences between black soil and aeolian sandy soil with different tillage and cover methods, especially in soil particles distribution and nutrient contents of wind erosion sediments, were unknown. Field experiments were conducted with ridge tillage and no tillage on farmland of three typical cover methods (no residue cover, remain standing residues and flat residues) on black soil and aeolian sandy soil in Northeastern China from April to June in 2016 and 2017. The soil particle distribution, organic matter, total nitrogen and phosphorus of wind erosion sediments were measured. Our results showed that the amount of wind erosion significantly decreased with increasing height; it was the highest at 0-10 cm and accounted for more than 50%, while it was closed to zero above 40 cm. The sediments from black soil were significantly lower than that from sandy soil. Furthermore, the amount of wind erosion of aeolian sandy soil was 168 folds than that in black soil at 0-100 cm in the same farming methods. In terms of tillage methods, the amount of sediments of no tillage were reduced by 66.0% to 94.1% as compared with ridge tillage, which indicated that no tillage could greatly decrease wind erosion. Apart from tillage types, flat residues can also reduce wind erosion obviously. Compared with no flat residues, the amount of sediment was reduced more than 90.3% by remain standing residues and flat residues during the spring. Affected by the wind erosion, the organic matter content of sediments was increased by 73.3%~85.8%, and even the soil particle distribution and nutrients of sediments lose seriously. The results of model analysis with RWEQ were verified by the results of our experiments, and the wind erosion modulus of RTNF (ridge tillage with no flat residues) was 181.7 to 86 582.9 t/(km²·a),however it was only 9.89 t/(km²·a) in NTF treatment (no tillage with flat residues). Our experiments indicated that remained stubble and residue cover management were effective ways to prevent soil wind erosion, while the ridge tillage and no residues can result in severe erosion and nutrients. It is, therefore, essential to pay high attention to the ridge tillage and no cover cultivate methods and adjust tillage and cover methods in Northeastern China.