Characteristics of dry matter accumulation and yield formation of dense planting maize in different row spacings

Spatial layout is crucial to determine the dense planting potential of maize. However, the influence of row spacing allocation on maize yield and its components with different planting densities is unclear. This uncertainty leads to a lack of a theoretical basis of the utilization of the dense planting potential of maize by optimizing the allocation of row spacing. From 2017 to 2018, with the same bandwidth, this study investigated how three row spacing allocation treatments-ratios of wide to narrow rows spacing of 7:3 (L1:56 cm:24 cm), 6:4 (L2:48 cm:32 cm), and 5:5 (L3:40 cm:40 cm)-affected maize yield and its components under five planting densities (D1:82 500 plants·hm^-2; D2:90 000 plants·hm^-2; D3:97 500 plants·hm^-2; D4:105 000 plants·hm^-2; and D5:112 500 plants·hm^-2). Row spacing allocation, density, and their interactions significantly affected grain yield. Compared to L3 row spacing allocation, L1 increased significantly grain yield by 5.2%-10.5%. Compared to D1 density, D2 and D3 increased grain yield by 6.1%-12.0% and 6.5%-15.0%, respectively (P < 0.05). Compared with L3D1 treatment, L1D3 and L2D3 increased grain yield by 8.3%-34.2% and 4.8%-27.5%, respectively (P < 0.05). Compared with L2D3, the regulatory effect of L1D3 was more prominent. The findings indicated that wide-narrow rows spacing allocation could enhance the tolerance of maize plants in higher planting density and increase the dense planting potential of maize. Wide-narrow rows spacing allocation combined with dense planting were beneficial to increase biomass. L1 row spacing allocation significantly increased biomass by 3.0%-6.6% (P < 0.05) compared to L3 treatment. Compared to D1 density, D3 significantly increased biomass by 3.4%-8.0% (P < 0.05). Compared with L3D1 treatment, L1D3 significantly increased biomass by 5.2%-15.0% (P < 0.05). There were three possible reasons for wide-narrow rows spacing allocation increased dense planting potential of maize. Firstly, dry matter accumulation rate of maize was significantly increased from the large bell mouth stage to the filling stage, as evidenced by the 32.9%-42.0% increase of dry matter accumulation rate with L1 row spacing allocation compared to L3 row spacing allocation, the 9.2%-23.9% increase of dry matter accumulation rate with D3 density compared to D1 density, and by the 29.1%-34.3% increase of dry matter accumulation rate with the treatment of L1D3 compared to L3D1. Secondly, there was an increased transformation of photosynthetic product to ear. Compared with the traditional density D1, D3 density increased harvest index by 6.4% in 2017, compared with L3D1, L1D3 increased harvest index by 16.2% in 2017, and there was no significant difference in 2018. Thirdly, a significantly effective ear and kernel number was observed, with a 16.0%-20.2% increase of ear number with D3 density compared to D1 density, 16.9%-25.9% increase of ear number with L1D3 compared to L3D1, 3.0%-4.4%; and 3.9%-7.0% increase of kernel number with L1 row spacing allocation compared to L2 and L3 row spacing allocation, respectively. The wide-narrow rows spacing allocaton of 56 cm:24 cm combined with planting density of 97 500 plants·hm^-2 is an ideal planting mode for high yield and high dense planting potential in the Oasis Irrigation District.