Using QUEFTS to calculate the parameters needed for fertilizer recommendation of sunflower

Objectives The yield and nutrient application data were collected in this research, aiming to construct fertilizer recommendation method and provide guide for scientific fertilization of sunflower.

Methods The data were from the published results of 483 field experiments since 2002, covering Northeast, North and Northwest of China. The characteristic parameters such as yield response, agronomy efficiency and nutrient recovery were calculated. The nutrient uptake of N, P and K in sunflower was estimated by QUEFTS method.

Results Across the main production area, the average yields of sunflower seeds and straws were 3334.9 kg/hm² and 7222.7 kg/hm²; the average N, P₂O₅ and K₂O contents in sunflower seeds and straws were 25.0, 4.7, 8.5 g/kg and 8.4, 1.2, 32.8 g/kg; the average N, P and K uptake of aerial part were 145.7, 55.1 and 318.5 kg/hm²; the average harvest indexes of N, P and K were 0.59, 0.66 and 0.11 kg/kg; the internal efficiency (IE) of N, P₂O₅ and K₂O application were 23.8, 63.8 and 11.3 kg/kg, and the N, P₂O₅ and K₂O required for producing sunflower seeds were 43.2, 16.4 and 94.9 kg/t. According to the QUEFTS model, the nutrient amounts required for producing 1000 kg of aerial part were N 40.8, P₂O₅15.8 and K₂O 78.1 kg when the target yield was 60%–70% of the potential yields, with the N, P₂O₅ and K₂O ratio of 2.58∶1.00∶4.93. Yield response of N, P and K fertilizer is 621.9, 467.0 and 361.3 kg/hm², and the relative yield under deficient applying of either N, P or K was 0.82 (n = 1071), 0.87 (n = 914) and 0.90 (n =1108). There was a significant negative linear correlation between yield response and relative yield, and the coefficient of determination (R²) was 0.712* for N (n = 1071), 0.693* for P (n = 914) and 0.763* for K fertilizer (n = 1108). The agronomy efficiencies showed significantly exponential correlation with yield responses, with R² of 0.634* for N (n = 1061), 0.697* for P₂O₅ (n = 905) and 0.702* for K₂O (n = 1092). The regression formulas of agronomy efficiency (AE) and yield responses (YR) were AE_N = 0.0152YR_N^0.8796, AE_P = 0.0269YR_P^0.8797, AE_K = 0.0229YR_K^0.9009.

Conclusions The nutrient uptake and utilization parameters of sunflower are estimated using QUEFTS model. The single nutrient requirement can be estimated by the relation between single nutrient yield increase and its rlative yield, as well as its agronomy efficiency. Nitrogen fertilizer could be directly recommended according to its yield response and nitrogen agronomy efficiency. For the recommendation of P and K, except for the nutrient requirement, yield response and agronomy efficiencies of them, the residual effect of last season and amount from straw returning to field are also need taken into consideration.