Synergistic Effects of Wide-Narrow Row and Density Enhancement on the Photosynthetic Characteristics and Resource Utilization of Maize in Oasis Irrigation Areas

To address the scientific challenges of limited yield potential, inefficient resource use efficiency, and constrained economic benefits in equidistant maize planting in the Northwest oasis irrigation zones of China, this study investigated the effects of wide–narrow row planting patterns on maize density tolerance and yield potential.

This experiment began in 2017 and the data were collected from 2019 to 2021, using a split-plot design. The main plot treatments comprised three line spacing configurations characterized by alternating wide-narrow line spacing: L1 (7:3 ratio, 56 cm wide line spacing: 24 cm narrow line spacing), L2 (6:4 ratio, 48 cm wide line spacing: 32 cm narrow line spacing), and L3 (5:5 ratio: 40 cm wide line spacing, 40 cm narrow line spacing). The split-plot treatments were four maize planting densities: D1 (8.25×10⁴ plants/hm², local conventional planting density), D2 (9.00×10⁴ plants/hm², increased density by 9.1%), D3 (9.75×10⁴ plants/hm², increased density by 18.2%), and D4 (10.50×10⁴ plants/hm², increased density by 27.3%). The effects of these spacing arrangements under increasing planting density on maize photosynthetic characteristics, yield, resource utilization, soil nitrogen content, and economic benefits were investigated.

Both wide-narrow line spacing planting and increased maize planting density enhanced photosynthetic characteristics, yield, and resource utilization efficiency of maize in the Hexi Oasis Irrigation District. Compared with wide-narrow line spacing ratio of 5:5 treatment, wide-narrow line spacing ratio of 7:3 treatment increased maize average leaf area index, light interception score at the big flare stage, grain yield, light use efficiency, water use efficiency, and nitrogen use efficiency by 9.7%, 7.1%, 8.8%, 8.2%, 12.7%, and 14.1%, respectively. Increased density by 9.1% and 18.2% treatments increased maize average leaf area index by 11.4% and 15.7%, light interception score at the big flare stage by 7.4% and 10.1%, grain yield by 9.6% and 11.3%, light use efficiency by 4.0% and 6.1%, and water use efficiency by 10.2% and 20.5% than that with local traditional planting density, respectively. Wide-narrow line spacing ratio of 7:3 with an 18.2% density increase demonstrated significant potential for comprehensive improvement. Compared with wide-narrow line spacing ratio of 5:5 and traditional planting density, wide-narrow line spacing ratio of 7:3 and increased density by 18.2% increased average leaf area index by 28.4%, enhanced light interception score at big flare and grain filling stages by 22.0% and 17.1%, respectively, and raised grain yield, biomass, and harvest index by 22.2%, 13.1%, and 8.0%, respectively. Wide-narrow line spacing ratio of 7:3 and increased density by 18.2% also improved average leaf area index, water use efficiency, and nitrogen use efficiency by 13.5%, 39.6%, and 24.0%, respectively, while reducing soil total nitrogen, ammonium nitrogen, and nitrate nitrogen contents by 11.2%, 18.0%, and 16.8% compared with wide-narrow line spacing ratio of 5:5 and traditional planting density, respectively. Additionally, wide-narrow line spacing ratio of 7:3 and increased density by 18.2% treatment increased net profit and the ratio of benefit and cost by 50.1% and 23.3%, compared with wide-narrow line spacing ratio of 5:5 and traditional planting density, respectively.

The wide-narrow line spacing ratio cropping pattern of 7:3 enhanced the comprehensive effects of densely planted maize by improving photosynthetic characteristics, resource use efficiency, and soil nitrogen supply.