Effect of tillage depth on soil physical properties and yield of winter wheat-summer maize

Abstract: Given the common problem of plow pan which affects the growth of crops in Huang-Huai-Hai Plain (HHHP), agronomists are calling for a management practice to ameliorate plow pan. Little information is currently available on the effects of breaking the plow pan partially or thoroughly on the soil water content, penetration resistance and crop growth in HHHP. In order to better understand the effect of plow pan on soil water retention and crop yield, 4 treatments were conducted including the original plow pan (RT15), breaking the plow pan by 1/3 of thickness (DL20), breaking the plow pan by 2/3 of thickness (DL25) and breaking the plow pan thoroughly (DL40) in the HHHP, aiming to explore the effect of different thickness of plow pan on soil water characteristics, the dynamics of penetration resistance and crop yield. The result showed that breaking the plow pan could reduce the bulk density and penetration resistance for 10-30 cm soil layer significantly, with a trend of DL40 < DL25 < DL20 < RT15. Breaking plow pan could increase water infiltration after irrigation or rainfall, and the average soil water content of 20-70 cm soil layer increased by 5.3%-23.6% and 7.7%-15.8% compared with RT15 treatment at seedling stage of summer maize and winter wheat separately. Because of uneven seasonal distribution of precipitation in HHHP, breaking the plow pan was beneficial for winter wheat to make full use of soil water in the deep soil layers, and could reduce the ineffective dissipation of soil water by promoting the water storage during summer maize season. The water consumption of DL20, DL25 and DL40 treatment increased by 4.9%, 10.2% and 11.6% separately compared with RT15 during winter wheat season, however, the water consumption of DL20, DL25 and DL40 treatment decreased by 5.8%, 7.6% and 10.5% respectively compared with RT15 during summer maize season. Because of the influence of temperature, soil water content, tillage practice and crop growth, the dynamic changes of penetration resistance under different topsoil structures were different from each other. The dynamic changes of penetration resistance of 0-15 and 15-30 cm during winter wheat season were similar with that of 0-15 and 15-30 cm during summer maize season. However, the penetration resistances of 30-45 cm under different treatments at the late growth stage of winter wheat and summer maize were different from each other. The penetration resistance of 30-45 cm under different treatments at the late growth stage of winter wheat was manifested as DL40 > DL25 > DL20 > RT15, while that of summer maize was DL40 < DL25 < DL20 < RT15. Compared with traditional topsoil structure, breaking plow pan could improve water use efficiency, and eventually promoted crop yield. However, the highest yields of winter wheat and summer maize were found at DL25, and the crop yield of the treatment with plow pan broken thoroughly (DL40) was relatively lower. Considering the yield of winter wheat and summer maize under DL40 treatment decreased by 4.2% and 2.4% respectively compared to DL25, the relatively better way to transform the plow pan without consuming much energy was DL25 which not only possessed permeable performance, but also could promote the crop yield.