Increased planting density combined with one-pass shallow rotary drill sowing optimized seedling quality and population structure, thereby improving grain yield and economic return of rice-stubble wheat

Le résumé fourni par la source

In recent years, the development and application of large-scale integrated seeders capable of one-pass shallow rotary tillage and drill sowing have greatly improved the sowing quality of rice-stubble wheat. However, the appropriate pre-sowing tillage practice and corresponding planting density under this context remain unclear. In this two-year field experiment, we used such integrated seeders to conduct one-pass shallow rotary drill sowing across all treatments, while varying the pre-sowing tillage methods and planting densities. The responses of sowing quality, yield formation, and economic return were then evaluated. The results showed that direct sowing under no pre-sowing tillage (NTS) resulted in higher seed exposure rate and surface straw coverage, averaging 21.97 and 63.02%, respectively. Compared with NTS, ploughing followed by rotary tillage before sowing (PTS) and rotary tillage before sowing (RTS) significantly improved sowing quality by increasing sowing depth (29.54–68.40%) and reducing seed exposure rate (37.56–78.88%) and surface straw coverage (30.58–38.04%), with no significant difference between PTS and RTS in the latter. Seedlings under NTS showed better individual growth than those under PTS and RTS, with higher seedling vigor and more tillers per plant. However, NTS had an insufficient population at the mid-to-late growth stages compared with PTS and RTS under low planting density, as reflected by lower leaf area index, dry matter accumulation, and productive spike number, which was associated with its lower productive tiller rate. At high planting density, the population size of NTS was effectively compensated, resulting in significantly higher yield than that at low density, whereas excessive population size under PTS and RTS led to yield reduction. Quadratic fitting showed that the fitted optimum planting densities for PTS, RTS, and NTS were 289.0×10 4 , 294.8×10 4 , and 343.8×10 4 plants ha −1 , respectively. Under one-pass shallow rotary drill sowing, all three tillage practices could achieve high yield levels (>6,500 kg ha −1 ) when planting density was optimized. Although NTS required greater seed input to attain the target planting density, its reduced machinery and labor costs resulted in the highest net return in both seasons. Collectively, NTS combined with one-pass shallow rotary drill sowing under optimized high planting density constitutes a high-yield and high-efficiency strategy for wheat production in rice-stubble fields using large-scale integrated seeders.

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