Suitable Tillage Depth Promotes Maize Yields by Changing Soil Physical and Chemical Properties in A 3-Year Experiment in the North China Plain

Rotary tillage is a common farming method because of its ease of operation and low cost in the North China Plain. However, the rotary tillage depth is generally no more than 20 cm, and successive years of rotary tillage harden the root soil layers, which reduces maize’s ability to take root into the deep layer and decreases maize yields. The impact of the different rotary tillage depths and different plow pan thicknesses on maize yields was unclear and needs further study. In this study, a 3-year experiment was conducted, and three rotary tillage depths were designed: 20 cm tillage depth (D20), 25 cm tillage depth (D25), and 30 cm tillage depth (D30). The effects of different rotary tillage depths on soil’s physical and chemical properties, water use efficiency, photosynthetic rate, and maize yields were investigated. The results showed that soil bulk density significantly decreased and field capacity significantly increased in 10–30 cm soil layers by increasing the rotary tillage depths; soil water consumption, photosynthetic rate, and maize yields of D25 significantly increased in comparison to those of D20 and D30; soil bulk density, plow pan thickness, total nitrogen, total phosphorus, and total potassium had an obvious negative correlation with tillage depth and field capacity; the Denitrification–Decomposition (DNDC) model predicted maize yields well; structural equation models (SEM) revealed that rotary tillage depths and soil water consumption played an important role on maize yields; and D25 could increase maize yields by improving maize water use efficiency and photosynthetic rate. The tillage depth of 25 cm is a suitable rotary tillage depth for the increase in maize yields in the North China Plain