Optimum combination of planting density and fertilization mode for high yield, quality and nitrogen utilization of spring-sown fresh waxy maize

Objectives Coordinated plant density and fertilization mode is one of the primary conditions for high yield, quality, and fertilization efficiency in crop production. We studied the effects of different plant density and fertilization combinations on spring-sown fresh waxy maize production in Jiangsu Province.

Methods A field experiment with split design was conducted in Nantong, Jiangsu Province in 2021 and 2022, the test maize cultivar was “Suyunuo 11”, a spring-sown waxy maize hybrid. The main plots were five plant densities, including 4.5×10⁴ (D1), 5.25×10⁴ (D2), 6.0×10⁴ (D3), 6.75×10⁴ (D4), and 7.5×10⁴ plant/hm² (D5); and the subplots were three fertilization modes under the same total N rate 225 kg/hm², including: basal applying compound fertilizer N 75 kg/hm² and topdressing urea N 150 kg/hm² at six-leaf stage (CF); basal applying all the slow-release compound fertilizer (SF-b); topdressing all the slow release compound fertilizer at six-leaf stage (SF-t); and a no N fertilizer control was arranged under each density. The plant biomass and N contents were investigated at silking and milking stage, and the fresh ear and grain yields, and the grain quality indices were measured at milking stage.

Results Under the same fertilization mode, D2, D3, D4, D5 increased the fresh ear yield by 4.14%, 7.68%, 11.68%, and 7.17%, increased grain yield by 6.09%, 7.48%, 12.19%, and 7.08% on average, compared to D1. D4 was recorded significantly higher fresh ear and grain yield, dry matter and N accumulation at pre- and post-silking stage than the other densities, thus achieved the largest partial productivity and recovery efficiency of nitrogen fertilizer. The grain starch, soluble sugar and protein contents decreased with the increase of plant density to different extent, and not affecteded by fertilization modes. Under the same plant density, SF-t was recorded significantly higher fresh ear and grain yields than CK and SF-b, but lower translocation of dry matter and N accumulation from pre-silking to post-silking stage; SF-b was recorded similar or higher fresh ear and grain yields, and dry matter and N translocation rate to CF mode. Among all the total 20 combinations, D4 combined with SF-t showed the highest yield and N use efficiencies.

Conclusions In comparison to applying all nitrogen fertilizer as basal fertilizer and basal applying compound fertilizer and topdressing urea at six-leaf stage, topdressing all the nitrogen fertilizer in once at 6-leaf stage of maize, using slow-release compound fertilizer, could significantly increase the dry matter and nitrogen accumulation at post-silking stage, which is more effective for yield formation. Comprehensively, plant density 6.75×10⁴ plant/hm² combined with one topdressing of N 225 kg/hm² using slow-release fertilizer at six-leaf stage could be taken as the optimal cultivation measure for spring-sown fresh waxy maize production in Jiangsu.