Effects of agricultural measures on soil profile physical properties of winter wheat field in Weibei highland, China

Objectives This study aimed to compare the effects of long-term different fertilization and mulching methods on physical properties in 0–40 cm soil layer of winter wheat field in arid farming area of Loess Plateau, to provide the guideline for maintaining good soil physical properties and seeking for suitable and sustainable development agricultural measures of the Weibei Highland.

Methods A 15-years' winter wheat field experiment, started in 2002 and located in Weibei Highland, was used in this study. Six treatments were setup, NP (N 150 kg/hm² + P 75 kg/hm²), NPK (NP + K 30 kg/hm²), NPB (NP + biochar14.0 t/hm²), NPFFT (NP + film mulching during summer fallow period), NPFGT (NP + film mulching during growth period) and NPFWT (NP + whole year film mulching). After winter wheat harvested in 2017, samples were collected in 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm soil profiles, and the soil moisture, bulk density, saturated hydraulic conductivity (SHC) and water-stable aggregate contents were determined.

Results Compared with NP treatment, NPK treatment decreased the 0–20 cm soil bulk density, increased the 0–20 cm soil total porosity and the > 2 mm size water-stable aggregate content in 0–40 cm profiles. The > 2 mm size water-stable aggregate content in 0–10 cm layer increased by 1.3 times (P < 0.05). NPB treatment decreased the soil bulk density, increased the soil total porosity, but decreased the SHC significantly by 27.9% in 0–20 cm layer. Both water content and > 2 mm size water-stable aggregate contents increased in the profile, and the > 2 mm size water-stable aggregate contents in the surface layer increased by 1.0 times significantly. NPFFT reduced the water content in the profile, but increased the soil bulk density and decreased the soil total porosity of tillage layer at harvest time. NPFGT reduced the water content of the profile, increased the soil bulk density but reduced the soil total porosity of tillage layer, meanwhile reduced the SHC of the profile, among which especially in the surface layer it was reduced by 60.2% significantly. NPFWT increased soil bulk density but decreased the total soil porosity of tillage layer, decreased the SHC in surface layer, but increased it in 10–40 cm layers by an average of 57.5%, meanwhile the water content, > 2 mm size water-stable aggregates content, MWD and GMD of profile were all increased. Affected by the local traditional tillage depth, the effects of different fertilization and mulch measures on soil bulk density, saturated hydraulic conductivity and porosity were mainly concentrated in 0–20 cm soil layer, while little effect had in the 20–40 cm soil layer.

Conclusions Based on the combination of N and P fertilizations, the application of potash, biochar and film mulching around whole year could effectively improve soil physical properties. From the perspective of economic input and degree of improvement in soil physical properties, the addition of potash and whole year film mulching were effective measures to maintain the good physical properties of soil profile in Weibei Highland.