Optimal plant density and potassium application rate for spring maize under drip-fertigation in Northeast China

Objectives Appropriate plant density and fertilizer application rate are important factors to achieve high yield and fertilizer efficiency of crop production. We studied the suitable combination of plant density and potash application rate for the spring maize production in Northeast China under semiarid climate area.

Methods A field experiment was conducted from 2018 to 2019 in Qian'an County, Jilin Province, with maize cultivar ‘Fumin 985’ as tested material. A complete block design was used, including plant densities of 60000 plants/hm² (D1), 75000 plants/hm² (D2) and 90000 plants/hm² (D3), and potassium application rates of K₂O 0, 60, 90, 120 and 150 kg/hm² (recorded as K0, K1, K2, K3 and K4, respectively). The accumulation, distribution and translocation of NPK, yield, benefit and K utilization efficiency of maize were investigated.

Results Under the same K₂O application rate, the highest maize yield and benefit were recorded in D2 treatment. Compared to D1 and D3, D2 increased the average maize yield by 8.1% and 5.3%, and increased the benefit by 10.3% and 9.4%. Regardless of plant densities, the maize yield increased with the increase of K₂O rate; however, the yield and benefit increase were similar under D1 when K₂O was ≥90 kg/hm², and under D2 and D3 when K₂O was ≥120 kg/hm². The K recovery efficiency, agronomic efficiency and partial factor productivity decreased with increasing K₂O application rate, but they remained higher in D2 than in D1 and D3 in the same K rate. The planting density and K₂O rate had significant interaction on the accumulation of N, P and K before and after silking stage. D2K3 increased the accumulation and transfer of N, P and K to the grains before silking stage, and increased the assimilation of N, P and K and their contribution rates to grains after silking stage. The correlation analysis showed that the accumulation of N, P and K before and after silking stage and the grain yield were highly significantly correlated (r=0.636–0.971), and the correlation coefficients after silking stage were higher than those before silking stage.

Conclusions Planting density and K fertilizer interactions significantly affected maize yield, nutrient uptake, translocation and K-use-efficiency under drip irrigation with integration of water and fertilizer in the semi-arid region of Northeast China. The best combination was planting density of 75000 plants/hm² and K₂O rate of 120 kg/hm² under fertigation.