Relationship between dry matter accumulation and maize yield in Southwest China

To explore the differences in dry matter accumulation and yield of maize varieties having different nitrogen-use efficiencies in Southwest China, a field experiment was conducted in Yongchuan, Chongqing, and Deyang, Sichuan, from 2019 to 2020. Two varieties, the nitrogen-efficient Zhenghong 311 (ZH 311) and the nitrogen-inefficient Xianyu 508 (XY 508), were tested across four nitrogen levels (0–360 kg ha⁻¹). The results showed that compared to XY 508, ZH 311 exhibited a significantly higher accumulation of dry matter at various stages and periods, particularly in the roots during the R6 stage, and in the stem sheaths and leaves throughout all stages. Furthermore, the number of kernel rows, number of kernels per row, number of kernels per ear, and grain yield were significantly higher for ZH 311 than XY 508, whereas the 100-grain weight was significantly lower for ZH 311 than XY 508. The yield difference between the two varieties was the largest when the nitrogen application rate was 240 kg ha⁻¹. The yield performance of ZH 311 was always better than that of XY 508, and less nitrogen was needed to obtain the best yield. The accumulation of maize dry matter had a highly significant effect on the number of kernel rows, kernels per row, and kernels per ear, and grain yield. The direct effect of the number of kernels per ear on grain yield was very low. However, it affected grain yield through the number of kernel rows and kernels per row. The dry matter accumulation of V6−V12 and R3−R6 contributed the most to grain yield, while in vegetative organs, the effect of leaf dry matter accumulation and yield was the greatest. This investigation will provide insights into factors affecting variations in maize yield under low nitrogen conditions and offer guidance for N-fertilizer management strategies.