秸秆还田下耕作深度对土壤机械组成和土壤密度影响

为探明耕作深度对秸秆还田下土壤机械组成和土壤密度的影响,进行了小麦秸秆还田玉米大田试验,设置了20 cm、25 cm、30 cm三个耕作深度,测定了玉米生育期的土壤机械组成、土壤密度和玉米收获时的根系量和产量。结果表明:三个耕作深度下,以犁底层为界,砂粒、粉粒和黏粒的含量在犁底层之上和之下变化显著,砂粒随着土层深度加大而减小,粉粒和黏粒则相反,但播前和收获时耕作深度对三个粒级在剖面的分布规律没有明显的影响。三个耕作深度的土壤密度在玉米不同生育时期的变化趋势相似,方差分析表明玉米生育时期对同一土层深度的土壤密度有影响,但规律不明显。耕作深度对玉米产量和根系量的影响相同,以耕作深度25 cm的根系量和产量为最大,耕作深度与耕层平均土壤密度呈显著负相关。

Influence of tilling depth under straw-returning condition on soil tillage machinery composition and soil density

In order to ascertain the influence of tilling depth under straw-returning condition on soil tillage machinery composition and soil density，the experiment of returning wheat straw to maize field is carried out，for which three tilling depths，i． e． 20 cm， 25 cm and 30 cm，are set，and then the soil tillage machinery composition and soil density during the growth of maize as well as the amount of root system and yield of maize during harvest are measured． The result shows that by taking the plow pan as the boundary，the contents of sand particle，silt particle and clay particle above and below the plow pan under the three tilling depth conditions are significantly changed; for which the content of sand particle is decreased along with the increase of the soil-layer depth，while the silt particle and clay particle are just on the contrary，but no any obvious influences are there from the tilling depth before sowing and during harvest on the distributions of the three particle gradations at the soil profile． The changing trends of the soil bulk densities at the three tilling depths during different growth periods of maize are similar，while the relevant variance analysis shows that the maize growth period has an influence on the density of the soil at the same soil-layer depth，but the law is not so significant． The influences on both the maize yield and amount of root system from tilling depth are the same with the maximum amount of root system and maize yield at the tilling depth of 25 cm，while a significant negative correlation is there between the tilling depth and the mean soil density of tilling layer．