Effects of short-term plowing and organic amendments on soil physical properties and maize yield in dark brown soil in Northeast China

Abstract: Constructing a suitable plough layer is one of the important technical methods to solve the problem of "shallowing, thinning and hardening" of the plough layer in dry farmland, especially for soils with high soil clay content. In this study, a field experiment including different tillage layer construction models was set up in Aihui experiment garden, Heihe. Effects of different soil tillage depth (15 cm and 35 cm) and organic matter (maize straw and cattle manure) amendments on soil physical properties, maize yield and its yield components were investigated. Eight field treatments were established with four replicates and random block design, including shallow tillage (0-15 cm) without or with maize straw return (T15 and T15+S), deep plowing (0-35 cm) without or with straw return (T35 and T35+S), deep plowing (0-35 cm) with cattle manure (T35+OM) and cattle manure plus maize straw (T35+S+OM), no tillage with maize straw mulching (NT+SM1) or ridged-mulching (NT+SM2) on the surface. The returning rate of maize straw and cattle manure were 10 000 kg/hm2 and 30 000 kg/hm2, respectively. Results obtained from 2019 and 2020 showed that soil physical properties were largely influenced after one-year different soil plowing and organic amendments practices. Compared with T15, T35+S, T35+OM and T35+S+OM significantly decreased soil bulk density, increased total porosity, saturated water capacity, water holding capacity, content of >0.25 mm water-stable aggregates, as well as optimized the soil three phase ratio (P<0.05). T15+S obviously improved soil physical properties in 0～15 cm soil layer, while T35+S, T35+OM and T35+S+OM significantly improved soil physical properties in 15-35 cm sublayer. The maize yield, harvest index and yield components were also influenced by soil plowing and organic amendments practices, and seemed to differed with annual precipitation. Compared with T15, in the year of normal precipitation (2019), the maize yield in T35+S, T35+OM and T35+S+OM treatments was not significantly different (P>0.05). While in 2020 with surplus precipitation, the maize yield in T15+S and T35+S+OM and significantly increased by 27.6%-37.0%, harvest index increased by 22.75%-28.57% (P<0.05). Averaged crop yield in no-tilled soils decreased (P<0.05). Soil tillage and organic amendments significantly increased ear length and number of kernels per row, decreased bare top length, consequently caused increases in maize yield. In conclusion, deep plowing plus organic amendment into soil is a feasible agricultural management for improving soil physical properties, optimizing soil three phase ratio, and increasing maize yield. This technique is applicable in the construction of reasonable plough layer of dryland in dark brown soil in northern China.