Effects of mechanical-chemical synergistic weeding on weed control in maize field

Abstract: Weed control has been the agricultural component of pest control, in order to reduce the presence of weeds on a farm. Weeds generally compete with the crops for the nutrients and water, leading to a parasitic environment for the pests and diseases, thus directly detrimental to the crop yield and quality. Herbicide application and mechanical weeding are two current means of weed control in China. However, the mechanical weeding cannot completely break the agglomeration of weed roots in the soil, whereas, the herbicides cannot evenly and fully be deposited on weeds, due to the limitations of the field environment and machine operation capacity. It is a high demand for the higher performance of weed control with less environmental pollution, according to the current national standard of "chemicals reduction and efficiency enhancement" and "weed control environment-friendly". One individual improvement in weeding machinery or chemicals cannot balance the harsh requirement of weed control in modern agriculture. Taking the maize field as the research object, the mechanical-chemical synergistic weeding strategy was proposed to determine the efficacy of weeding control during the growth period. A synergistic weeding experiment was also carried out using two mechanical weeding approaches (inter- and intra-row weeding), three chemical reduction ratios (25%, 50%, and 75%), and two chemical applications (full width and only rows). Some parameters were measured, including the conventional weeding index, such as the control efficacy, and the growth indexes of maize at the silking and mature period. The results showed that the improved mechanical weeding significantly reduced the soil compactness of the weeding area by more than 64.4% than before, indicating the loose soil in the maize field. The control efficiency of the weed plant was 83.4% under the inter-row weeding machinery after two-week treatment, which was better than that under the intra-row weeding machinery (46.7%). The weed status in the silking period of maize showed that the efficacy of the inter-row weeding with the herbicide reduction was better than that of the intra-row weeding with herbicide reduction, while, the weeding efficacy of mechanical-chemical synergistic treatment was better than that of single mechanical weeding. The leaf area and dry matter weight of maize under the mechanical-chemical synergistic weeding treatment were greater than those under the single mechanical or chemical weeding treatment. It infers that the mechanical-chemical synergistic treatment was conducive to the accumulation of plant nutrients for the better promotion of crop growth. Furthermore, the average yields of intra-row mechanical-chemical synergistic weeding treatment were 55.9% and 5.1% higher than those of single mechanical and chemical ones, respectively, while, those of inter-row one were only 29.0% and 20.4% higher. The best yield of maize was achieved under the synergistic treatment of mechanical weeding and herbicide application reduction of 25%, where the 1 000 grain weight and yield were higher than the rest. In the inter-row mechanical weeding, the 1 000 grain weight and yield were the highest under the full-width application of 75% herbicide amount and mechanical-chemical synergistic treatment. In the intra-row mechanical weeding, the grain number per ear, 1000 grain weight and yield were the highest under only the row application of 75% herbicide amount and mechanical-chemical synergistic treatment. Therefore, the mechanical weeding synergized with the chemical reduction strategy can be widely expected to reduce the number of chemical herbicides without the loss of weeding efficacy for the high yield of maize. This finding can provide a new approach for herbicide reduction and weed control in an environmentally friendly way in the maize field.