Rotation with Soybean Improved Weed Control and Foxtail Millet Yield

Abstract

Foxtail millet is an important characteristic grain crop in northern China. However, weeds compete seriously with foxtail millet and have long been a biological factor that has plagued foxtail millet production. Rotation requires determining the species and sequence of crops, and reasonable rotation has many benefits for agriculture, including reducing the damage by weeds. In order to clarify the combination effects of foxtail millet–soybean rotation sequence and herbicide on weed control and crop yield, fixed-position experiments were designed in three growing seasons. Foxtail millet and soybean were planted following the sequence below in successive years (FFF, foxtail millet–wheat–foxtail millet–wheat–foxtail millet; SFF: soybean–wheat–foxtail millet–wheat–foxtail millet; SSF, soybean–wheat–soybean–wheat–foxtail millet; SSS, soybean–wheat–soybean–wheat–soybean), and weed density, biodiversity, weed seedbank, and crop yield were examined and analyzed. The results showed that the average weed density of SFF and SSF was reduced by 61.7% and 66.3% compared with FFF in the three years and by 16.5% and 26.6% compared with SSS, separately. Foxtail millet–soybean rotation (SFF and SSF) increased the species richness and the Margalef species richness index of the weed community and reduced the Simpson index compared with the continuous foxtail millet and the continuous soybean cropping (FFF and SSS). The weed seedbank of SFF and SSF was 45.7% and 55.8% smaller than that of FFF and increased by 92.7% and 56.7% compared with SSS, respectively. The weed density in the FFF treatment was significantly correlated with the 0–5 cm grass seedbank size, while there was no significant correlation in the other three treatments. Benefiting from the lower weed damage intensity, the yield of foxtail millet in SFF and SSF increased by 54.05% and 221.81% compared with FFF, respectively. The research results revealed that both SFF and SSF can effectively reduce the damage of weeds and help improve biodiversity. SSF has a higher weed control effect and higher foxtail millet yield than SFF. This study contributes to the understanding of crop–weed interactions in foxtail millet–soybean rotation and can be applied to areas with similar environments.