Maize yield responses to potassium fertilizer and regional differences in Jilin Province

Objectives In this study, maize yield responses to potassium (K) fertilizer in Jilin Province and the regional difference at the scale of ecological zones and counties were estimated, based on the big data of field experiments in Soil Testing and Formula Fertilization Project, aiming efficiently to provide references for high and stable yields and high use efficiency of K fertilizer in local maize production.

Methods The data were collected from the treatments N₂P₂K₂ (+K) and N₂P₂K₀ (–K) in maize “3414” field experiments carried out in Jilin Province during 2005–2013. The yield response, agronomic efficiency (AE) and fertilizer contribution rate (FCR) of K fertilizer and their regional differences were estimated at ecological zones and county levels. The relationships between maize yield brought by K application, FCRs and the basic yields were established to determine the effects of K fertilizer on maize yield and the regional difference.

Results In the –K treatment, maize yields ranged from 3.29–14.5 t/hm² and averaged 8.44 t/hm² in eastern humid mountainous area (EHMA), ranged from 3.77–15.3 t/hm² and averaged 9.45 t/hm² in central sub-humid plain area (CSPA), and ranged from 3.89–12.84 t/hm² and averaged 8.11 t/hm² in western semi-arid plain area (WSPA). The K fertilization significantly increased maize yield across the ecological zones, with averaged yield increases of 1.31 t/hm² (18.1%) in EHMA, 1.06 t/hm² (12.2%) in CSPA and 1.30 t/hm² (17.4%) in WSPA, respectively. Under current optimal K fertilizer management practices, the averaged AE of K fertilizer was 19.7 kg/kg in EHMA, 14.6 kg/kg in CSPA, and 20.2 kg/kg in WSPA. The values for FCR of K fertilizer were 13.9%, 10.2% and 13.3% in the three ecological zones, respectively. Statistical analysis results indicated that maize yield response were equal among different ecological zones, but yield increase rate was significantly higher in EHMA than that in CSPA. Both the highest AE and FCR of K fertilizer were observed in EHMA. A significant positive and linear correlation was observed in maize yields between +K and –K treatments in each ecological zone, the model equation was y = 0.769 x + 3261 (R² = 0.616^**) for EHMA, y = 0.883 x + 2158(R² = 0.757^**) for CSPA and y = 0.873 x + 2328(R² = 0.637^**) for WSPA. Meanwhile, a significant negative and logarithmic correlation was observed between FCRs of K fertilizer and maize yields in –K treatment, these model equations were y = –28.4 ln(x) + 270.1(R² = 0.348^**), y = –15.9 ln(x) + 156.1(R² = 0.172^**) and y = –16.3 ln(x) + 160.6(R² = 0.123^**), respectively. Compared with the other ecological zones, with the increasing of soil K supply capacity, EHMA showed larger increase in maize yield in +K treatment and greater decrease in FCR of K fertilizer.

Conclusions The maize K fertilizer management in Jilin Province should be optimized based on regional soil K content, natural climatic conditions and crop responses to K fertilizer. At the present stage, more K fertilizer should be applied in EHMA to enhance soil K supply capacity and ensure high and stable grain yield.