Tillage method suitable for farmlands with different maize yield levels in Hetao Plain, Inner Mongolia

Objectives Shallow rotary tillage is common way in the Hetao Plain, Inner Mongolia. The long term use of the tillage method has led to shallow top soil layer, hard plough pan and deteriorative water capacity. Plowing and subsoiling were attempted in this paper as alternative tillage in the area, so as to provide reference for the choice of suitable tillage methods for the sustainable use of farmland.

Methods The tested fields located in the Yellow River coast of Bayannaoer, Inner Mongolia, where the maize production relies on irrigation heavily. The fields with maize yield of low (LY, <7500 kg/hm²), middle (MY, 7500−12000 kg/hm²) and high level (HY, >12000 kg/hm²) were chosen, and rotary tillage (RT, 10−15 cm deep), plowing (F, 20−30 cm deep) and subsoiling tillage (S, 30−35 cm) were used in each yield level fields, forming a total of 9 treatments. Soil samples were collected in depth of 0−20, 20−35 and 35−50 cm in each plot. The soil bulk density, soil solid liquid gas, contents of water, total nitrogen, available P, readily available K and organic matter were measured, and the maize yields were investigated. The effects of subsoiling and plowing on soil quality and maize yield were compared with rotary tillage, and the yield increase potential using the two tillage methods were calculated.

Results Compared with rotary tillage, both the subsoiling and plowing tillage improved soil physical and chemical characteristics and the yields of maize under different yield level farmland, and the effects were in order of subsoiling >plowing > shallow rotation. With the subsoiling and the plowing, soil moisture content was increased by 7.25%−32.11% and 5.36%−21.91%, soil bulk density was decreased by 5.23%−8.61% and 0.69%−4.91%, the R value of solid/liquid/gaseous phases of soil was decreased by 12.24%−89.97% and 7.30%−57.74%, total nitrogen content of soil was increased by 17.88%−55.60% and 9.81%−22.25%, available phosphorus contents were increased by 21.23%−41.26% and 10.84%−22.04%, readily available potassium contents were increased by 36.85%−71.99% and 6.01%−50.99%, and organic matter contents were increased by 28.85%−54.14% and 14.63%−36.38%. The yield increase potential of maize were 22.75%, 16.96%, 16.55% by using plowing tillage and were 29.56%, 25.37%, 16.13% by using subsoiling tillage in the farmlands with low, middle and high yield levels.

Conclusions In Hetao Plain, Inner Mongolia, replacing shallow rotary tillage with subsoiling and plowing tillage will be able to improve the physical and chemical properties of farmlands, and further increase maize yield significantly, the effect of subsoiling is better than that of plowing. The subsoiling performs well in low and medium yield level of farmlands, and both subsoiling and plowing perform well in high yield farmland.