GIS-based NPK recommendation and fertilizer formulae for wheat production in different regions of Henan Province

Objectives Henan Province is one of the most important wheat-producing areas in China. Developing a wheat production formula based on rational fertilization could help clarify the appropriate application rate of nitrogen (N), phosphorus (P) and potassium (K) in different regions of Henan Province, as well as establish a fertilization formula map.

Methods Henan Province was geologically divided into five regions: east-northern plain region (EP), central hilly region (CH), western mountain region (WM), southern basin region (SB), and rice-wheat rotation region (RW). Based on 2829 wheat field experiments and 837100 groups of soil nutrient data, we analyzed farmer's wheat yield, targeting yield and 100-grain P requirement. The N recommendation rate was calculated according to the yield economic response to the N fertilizer rate. The relative yields of 80%, 85%, 90% and 95% were taken to establish the abundance-deficiency indexes of soil available P and K. The recommended P fertilizer rate was calculated under a balanced P budget, and K fertilizer rate based on yield response in soils with different K levels. Using ArcGIS software, the NPK recommended application rates were superimposed and converted into fertilization formulas with a total NPK content of 45%. Further, wheat fertilization formulas and formula maps of different regions in Henan Province were drawn.

Results The target wheat yields were 8671 kg/hm² in EP, 5950 kg/hm² in RW, 7780 kg/hm² in SB, 7590 kg/hm² in CH, and 7400 kg/hm² in WM. The calculated optimal N rate was 178 kg/hm² in SB, 170 kg/hm² in EP, 160 kg/hm² in RW, 150 kg/hm² in CH and WM. According to the <80%, 80%–85%, 85%–90%, 90%–95% and >95% of the target yield, the adjusted critical values for the five grades of soil available P were <10 mg/kg, 10–15 mg/kg, 15–24 mg/kg, 24–37 mg/kg and >37 mg/kg, and those for the five grades of soil readily available K were <80 mg/kg, 80–105 mg/kg, 105–140 mg/kg, 140–180 mg/kg and >180 mg/kg, respectively. The recommended P fertilizer (P₂O₅) rates were 63 kg/hm², 75 kg/hm², 81 kg/hm², 95 kg/hm², and 105 kg/hm² in turn, and the recommended K fertilizer (K₂O) rates were 43 kg/hm², 48 kg/hm², 58 kg/hm², 64 kg/hm², and 73 kg/hm², respectively. Based on the NPK recommendation, we worked out 8 formulae for basal plus topdressing and 9 formulae for one-off fertilization. The formula for basal plus topdressing fertilization were 15–19–11, 16–17–12 and 17–16–12, and those for one-off fertilization were 24–12–9 and 25–12–8 in the fertilizer map.

Conclusions The wheat yield and soil available nutrient contents varied greatly among the ecological regions of Henan. The N fertilizer recommendation was based on N requirement of target wheat yields; P and K recommendation considered both target yield requirement and soil nutrient content. We worked out 8 fertilizer formulae for basal plus topdressing fertilization and 9 formulae for one-off fertilization around Henan Province.