Study on optimal fertilization for wide-width uniform sowing flax of irrigated land along Yellow River of central Gansu

Field experiment was conducted to investigate the optimal fertilization for flax under wide-width uniform sowing (WUS) in irrigation land along Yellow River of central Gansu.The results showed that, the fertilization treatment increased the fruit number per plant by increasing the branch number per plant and thus increased the yield per plant.The combination of N, P and K fertilizers significantly increased the yield of WUS flax.With the increased rate of nitrogen, phosphorus and potassium from 75.0 kg · hm^-2, 37.5 kg · hm^-2 and 22.5 kg · hm^-2 to 225.0 kg · hm^-2, 112.5 kg · hm^-2 and 67.5 kg · hm^-2, the N, P, K fertilizer use efficiency decreased from 35.3% to 15.8%, 26.6% to 11.1% and 21.4% to 9.5%, respectively; while the N, P, K fertilizer agronomic use efficiency decreased from 9.4 kg · kg^-1 to 4.1 kg · kg^-1, 21.3 kg · kg^-1 to 9.0 kg · kg^-1 and 7.9 kg · kg^-1 to 3.6 kg · kg^-1, respectively.As for the fertilization treatment of N 150+P₂O₅ 75+K₂O 45 kg · hm^-2, the use efficiency of N, P, K fertilizer was 28.3%, 17.0% and 16.5%, while the agronomic use efficiency of N, P, K fertilizer was 7.5 kg · kg^-1, 13.5 kg · kg^-1 and 5.9 kg · kg^-1, respectively.The relative yield in N, P and K deficiency plots was 62.0%, 66.2% and 91.1%, respectively; the compliance of N, P and K fertilizer was 38.0%, 33.8% and 8.9%, respectively, indicating that this area was deficient of nitrogen and phosphorus but rich in potassium.Phosphorus and nitrogen nutrient are the most important factors limiting the production of WUS flax.In irrigated area along Yellow River of central Gansu, the N, P and K optimal fertilizing rate of WUS flax is N 158.8, P₂O₅ 85.0 and K₂O 44.4 kg · hm^-2, respectively; the ratio of N∶ P₂O₅∶ K₂O is 1∶ 0.54∶ 0.28.