I frowned summarily, and froze up Recommendation II: BB fertilizer + release + Efficiency Balanced fertilization, on the one hand is based on soil test data, crop varieties, target production of fertilizer and other factors to determine the total amount of crop nutrients in the ratio of aggregate demand with the balance of the quarter; the other hand, fertilizer nutrient release time, release and crop dynamic balance of nutrient requirements at different growth stages; Solve the N-release nitrogen supply and crop demand dynamic equilibrium problem, and can not ignore the P, K and trace elemen