Effects of rotational tillage on soil physiochemical propertiesand spring maize yield in Weibei Highlands

A study was conducted to investigate the effects of different rotational tillage patterns on soil physiochemical properties and spring maize yield. The study consisted of a continuous experiment of spring maize in six rotational tillage treatments conducted in the Weibei Highlands of Heyang County, Shaanxi Province from 2008 to 2010. The tillage treatments included NT/ST/NT (3-year rotational no-tillage, sub-soiling and no-tillage system), ST/CT/ST (3-year rotational sub-soiling, conventional tillage and sub-soiling rotated system), CT/NT/CT (3-year rotational conventional tillage, no-tillage and conventional tillage system), NT/NT/NT (3-year continuous no-tillage system), ST/ST/ST (3-year continuous sub-soiling system) and CT/CT/CT (3-year continuous conventional tillage system). Among other parameters, soil bulk density, soil nutrient and spring maize yield under different rotational tillage treatments were measured and analyzed. Compared with CT/CT/CT, conservation tillage significantly (P < 0.05) decreased soil bulk density but also enhanced soil total porosity and field capacity. Compared with CT/CT/CT, NT/ST/NT decreased soil bulk density by 11.43% in the 0~20 cm soil layer and 9.79% in the 20~40 cm soil layer. Soil porosity increased by 11.05% and 9.87% respectively in the 0~20 cm and 20~40 cm soil layers under NT/ST/NT treatment. NT/ST/NT had significant effects on soil organic matter and total nitrogen contents in the 0~20 cm soil layer (P< 0. 05). Under NT/ST/NT treatment, average soil organic matter content in the 0~60 cm soil layer was the highest (10.36 g·kg^-1) for all the treatments. The average total soil nitrogen content under NT/ST/NT treatment increased by 10.65% and 4.31% respectively compared with initial value and CT/CT/CT treatment. Total N and alkali-hydrolyzable-N contents in the 0~20 cm soil layer and available P and K contents in the 20~40 cm soil layer were more significantly affected by different tillage treatments compared with other indexes. Rotational conversation tillage treatments showed significantly higher soil fertility-enhancing effect compared with the conventional tillage. Spring maize yield under NT/ST/NT, ST/CT/ST, CT/NT/CT, NT/NT/NT and ST/ST/ST increased by 22.42%, 16.33%, 3.77%, 9.91% and 14.18% (P < 0.05), respectively, compared with CT/CT/CT. The rate of increase of spring maize yield under NT/ST/NT treatment was the highest among all the treatments.