Optimization of agronomic management mode for high-yield continuous spring maize cropping system

Objectives Planting density, fertilization and soil tillage are the three key measurements in maize production. Their combination effect was studied in spring maize in order to set up a high-yield and high efficiency cultivation management measure for continues cropping of maize.

Methods A maize cultivar, XY335, was used as tested material in a field experiment. Four agronomic management modes were tested: agronomic management including 50000 plants/hm², one basal application of all the NPK fertilizers, stubble rotary tillage (CK), plant density 60000 plants/hm², N 195–P₂O₅ 75– K₂O 82.5 kg/hm², nitrogen was applied in basal of 78 and topdressing of 117 kg/hm², basal applied manure 15000 kg/hm² and micronutrients 60 kg/hm², stubble rotary tillage (Opt-1), plant density 70000 plant/hm², N 300–P₂O₅ 120–K₂O 120 kg/hm², N was applied 120, 120, 60 kg/hm² in basal, jointing and skilling, respectively, both P and K were applied 96 and 24 kg/hm² in basal and jointing stage, 15000 kg/hm² of manure and 150 kg/hm² of micronutrients were basal applied, soil deep loosing at jointing at stage (Opt-2), plant density 70000 plant/hm², N 225–P₂O₅ 90–K₂O 90 kg/hm², N was applied at 90, 90, 45 kg/hm² in basal, jointing and skilling, respectively, both P and K were applied at 72 and 18 kg/hm² in basal and jointing stage, 15000 kg/hm² of manure and 150 kg/hm² of micronutrients were basal applied, soil deep loosing at jointing at stage (Opt-3). Maize grain yields, N uptake, 0–60 cm soil physical properties and dynamic changes of roots were analyzed.

Results The increase of grain yield was mainly caused by increased ear number, and the yields of Opt-1, Opt-2 and Opt-3 were 12.1%, 15.3%, and 13.9% higher than that of CK on average, respectively. Compared to Opt-3, the nitrogen fertilizer rate of Opt-2 was increased by 33.3%, nitrogen uptake was increased only 6.9%, and was mainly distributed in stem. Deep loosing of soil at jointing stage increased the gas phases in soil, which was good for the deep development of roots. Especially in milk stage, solid phases was reduced by 8.8% and 7.4% and soil permeability was increased in the arable layer of 0–40 cm in Opt-2 and Opt-3. The root length, root weight and root surface area of Opt-1, Opt-2, Opt-3 were higher than those of CK. In the early growth period, the total root weights of CK and Opt-1 were higher those of Opt-2 and Opt-3. In 30–40 cm of soil layer, compared with CK, the root length and root surface area of Opt-2 and Opt-3 were increased by 36.6%, 44.6% and 34.9%, 37.1%. Compared with CK, the soil nitrogen residue of Opt-1, Opt-2 and Opt-3 was decreased by 45.7%, 31.0%, 23.2%, respectively. Relatively larger root volumes in deep soil stimulated the absorption of NO₃^–, which was usually leached into the deep soil layer at the later growth stage of maize, promoted the N use efficiencies.

Conclusions Increasing plant density, optimization of nitrogen fertilization and deep loosening significantly improved soil structure, reduced soil bulk density, which was good for the root development in the later growth stage. The yield and nitrogen uptake of Opt-3 were 13.9% and 9.5% higher than those of conventional agronomic mode (CK). Opt-3 is thought to be the optimized agronomic management mode for high yield and nutrient efficient maize production in the tested area.