The study of intelligent fertilizer recommendation method for wheat based on yield response and agronomic efficiency

Objectives Aiming to optimize fertilizer application rate and improve fertilizer use efficiency with a simple and easy-to-operate recommendation system, we constructed Nutrient Expert (NE) system suitable for the north of China and the Yangtze Valley, respectively, and verified their feasibility by large amount of field experiments.

Methods The wheat yield and nutrient uptake database was setup using multi-year and -site wheat field experiments from International Plant Nutrient Institute (IPNI) China Program, our research group and the published literatures. QUEFTS model was used to calculate the nutrient uptake, yield response, agronomic efficiency and relative yield in the north of China and the Yangtze Valley, respectively, to establish the interrelationships among them, and construct a fertilizer application model and develop NE system for wheat. Totally 467 field experiments were conducted in eleven provinces in the main wheat producing areas of China from 2011 to 2020 to calibrate and improve the system. Each experiment included six treatments: fertilizer recommendation based on Nutrient Expert system (NE), farmers’ practices (FP), conventional recommendation based on soil testing (ST), and N omission, P omission and K omission based on the NE treatment. Wheat yield, economic benefit, nutrient use efficiency and fertilizer agronomic efficiency were investigated.

Results 1) The calculation results by QUEFTS model showed that the aboveground N, P and K requirements to produce 1 ton of wheat grain were 25.6, 4.6 and 20.1 kg in the north region, and 20.6, 3.9 and 16.1 kg in Yangtze Valley, respectively; the average yield responses to N, P and K fertilizer were 1.69, 0.85 and 0.69 t/hm² in the north region, and 2.60, 0.99 and 0.72 t/hm² in the Yangtze Valley; the average agronomic efficiency of N, P and K fertilizer were 8.7, 8.9 and 7.0 kg/kg in the north region, and 12.6, 12.2 and 8.4 kg/kg in the Yangtze Valley. The average relative yield of N, P and K fertilizer were 0.76, 0.88 and 0.90 kg/kg in the north region, and 0.59, 0.83 and 0.87 kg/kg in the Yangtze Valley. 2) The results of field validation showed that NE treatment applied 37.4% and 26.1% less N and P fertilizer and 39.2% more K fertilizer than FP treatment, and 18.2% and 14.1% less N and P fertilizer than ST treatment and the same amount of K fertilizer with ST. Compared with FP, NE treatment increased yield and net profit by 0.22 t/hm² and 998 yuan/hm²; compared with ST, NE treatment produced the same yield but extra 260 yuan/hm² of net profit. Compared with FP and ST treatments, NE increased N recovery efficiency by 12.9 and 4.6 percentage points, and the agronomic efficiency of N fertilizer by 4.0 and 1.5 kg/kg; increased P recovery efficiency by 5.7 and 1.1 percentage points, and the agronomic efficiency of P fertilizer increased by 2.9 and 0.6 kg/kg; increased K recovery efficiency by 2.0 percentage points than FP treatment and exhibited similar K recovery efficiency to the ST treatment.

Conclusions The north of China requires more N and K, and similar P for one ton of wheat production, compared to the Yangtze Valley. The yield response to N and the agronomic efficiency of N fertilizers in the Yangtze valley are higher than in the north region, and both regions have similar yield response to P and K and the agronomic efficiencies of P and K fertilizers. The multi-year and -site field experiments verified the easy-to-operate and simplification of the constructed Nutrient Expert for Wheat system specified for the north region and the Yangtze Valley.