Long-term comprehensive effects of recommended fertilization based on nutrient expert system of maize in Northeast China

A long-term site-specific experiment of fertilizer recommendation from 2012 to 2020 was conducted to evaluate the comprehensive effects of nutrient expert decision support system on yield, benefit, fertilizer use efficiency, and soil nutrient of spring maize in northeast China. Five treatments included no-fertilizer (CK) as the control, currently traditional farmers’ practices (FP), fertilizer recommended using a nutrient expert system (NE), slow/controlled-release nitrogen fertilizer using the same rate as NE treatment (NER), and conventional fertilizer recommendation using soil testing (ST). The current study also investigated the long-term changes of maize yield, benefit, fertilizer use efficiency, the contents of inorganic N, available P, and available K in the soil, as well as the balance of nutrient input/output during the nine-year period. The results showed that the maximum, minimum, or mean values of fertilizer inputs in NE, NER, and ST treatments were all significantly lower than that of FP treatment (P<0.05), respectively. In different nutrients, NE, NER and ST treatments significantly reduced the amounts of nitrogen (N) and phosphorus (P) fertilizers application (P<0.05), but significantly increased the amount of potassium (K) fertilizer application (P<0.05), compared with that of FP treatment, respectively. As compared to FP treatment, NE, NER and ST treatments significantly improved maize yield and net income. In which, NE treatment achieved the highest value, with the average increment by11.0% and14.3%, respectively. In all the treatments, NE treatment achieved the highest stability, and followed by ST and NER treatment.The recovery efficiency, agronomic efficiency, and partial factor productivity in the NE, NER, and ST treatments were significantly higher than those in FP treatment, where increased by 29.0%-40.1%, 31.3%-44.3%, and 22.0%-31.7%, respectively. Specifically, the highest value was observed in NE treatment, followed by NER and ST treatments. Compared with FP treatment, NE, NER and ST treatments significantly improved the inorganic N content in 0-30 cm soil layer (P<0.05), but significantly reduced inorganic N content in >30-90 cm soil layer (P<0.05) and available P content in 0-30 cm soil layer (P<0.05). But the soil available K content wasn’t significantly different (P>0.05) among different fertilization treatments. The contents of soil inorganic N, available P, and available K in NE treatment were close to the initial testing values before planting. The nutrient input/output balance was obtained during the nine-year period, where the N and P balances were surplus under all fertilization treatments, whereas, the K balance was deficient. But the surplus of N, P, and the deficiency of K in NE treatment attained the lowest values, followed by NER and ST treatments. In conclusion, compared with farmers’ practices and the conventional fertilizer recommendation system, the NE fertilization recommendation system fully met the nutrient requirements of maize, with optimal fertilization rate, time, and ratio. Consequently, the NE fertilization recommendation system has the potential to improve maize yield, benefits, and fertilizer use efficiency, thereby maintaining the soil nutrient stability under the reduction of fertilizer application amount, compared with farmers’ practices. However, the simplified fertilization of slow/controlled-release nitrogen fertilizer in the NE fertilization recommendation system also obtained higher benefits, but reduced labor cost. Therefore, the NE system is an appropriate fertilizer recommendation for maize in northeast China.