ObjectivesLow nutrient use efficiency is mianly caused by irrational fertilization.Present fertilizer recommendation technologies based on soil test or plant diagnose are difficult to be used for smallholder farms due to constraints such as access, cost and timeliness in multiple cropping systems. A fertilizer recommendation method, Nutrient Expert for Hybrid Maize (NE), is established in base of yield response and agronomic efficiency.

MethodsIn this paper, 193 on-farm experiments were conducted in 2010-2014 to validate and optimize the effects of Nutrient Expert for Hybrid Maize from agronomic, economic and environmental aspects on spring maize in the Northeast China. Five treatments were designed in the maize field experiments, including (1) farmers' practices (FP), (2) nitrogen, phosphorous and potassium fertilizer input calculated using NE, (3-5) eliminating nitrogen, phosphorous or potassium input in the NE treatment, which were used for the calculation of nutrient use efficiencies. The grain yield, fertilizer cost, net profit, nitrogen (N), phosphorus (P) and potassium (K) use efficiency and N loss were investigated at harvest.

ResultsN and P fertilizer input in NE treatment were significantly decreased by 43.5 and 23.6 kg/hm² than in FP, about 21.0% and 27% of decrease (P < 0.001), while K fertilizer input was increased by 8.3 kg/hm² (P=0.001). The grain yields in all the experimental sites were in average 0.6 kg/hm² higher in NE than in FP, with the increase rate of 5.2% (P < 0.001), the averaged gross return was increased by 1466 yuan/hm² (P < 0.001), of which, 1192 yuan/hm² was from grain increases, accounting for 81.3%. As compared to FP, NE increased agronomic efficiency (AE), recovery efficiency (RE) and partial factor productivity (PFP) of applied to N by 5.8 kg/kg (+53.8%)、11.0% (+47.8%) and 16.8 kg/kg (+29.6%), increased AE, RE and PFP of applied to P by 12.3 kg/kg (+125.9%)、13.5% (+87.5%) and 44.0 kg/kg (+29.6%), increased AE and RE of applied to K by 4.0 kg/kg (+30.2%) and 13.7% (+36.1%), but decreased PFPK by 22.4 kg/kg. Given to three-year total calculated N balance, N fertilizer application in NE was lower than in FP, decreased by 102.8 kg/hm², but N uptake in the above-ground in NE was above 38.7 kg/hm² than in FP, the high N fertilizer input also led to N accumulation in the soil, the results indicated that the residual N at harvest in 2014 with NE significantly less than with FP, decreased by 63.0 kg/hm². Furthermore, totaled 78.5 kg/hm² of apparent N loss was reduced by using NE than with FP across three-year. However, the yield in NE attained 12.3 t/hm², increased by 0.9 t/hm² compared with FP.

ConclusionsIn summary, using Nutrient Expert for Hybrid Maize (NE) for fertilizer recommomdation not only increased grain yield, profit and nutrient use efficiency, but also reduced apparent N loss. The Nutrient Expert for Hybrid Maize, which based on yield response and agronomic efficiency, has proved to be a science-based, reliable and feasible method and can be used to make fertilizer recommendation for spring maize in the Northeast China.