[Effects of different slow/controlled release fertilizers on yield, quality of fresh maize and ammonia emissions]

A field experiment with five treatments, control (CK, no fertilizer), conventional fertilization (U), double-effect inhibitor synergistic urea (DU), coated urea (CU) and slow/controlled release urea mixture (CDU), was conducted to investigate the effects of conventional fertilization (240 kg N·hm^-2) and one-off application of different slow/controlled release fertilizers (180 kg N·hm^-2) on the yield and quality of fresh maize, soil inorganic nitrogen (N), and ammonia (NH₃) emissions. The results showed that the total amount of ammonia volatilization was the highest in treatment of conventional fertilization (U), with N topdressing being an important source of NH₃ emission. Compared with U treatment, the NH₃ volatilization in the DU, CU, and CDU treatments was reduced by 78%-81%. At harvest stage, the soil layer of 80-100 cm in the U treatment had the highest nitrate concentration (51.6 mg·kg^-1), resulting in a high risk of N leaching. In contrast, the nitrate concentrations in the same soil layer in the slow/controlled release fertilizer treatments were much lower, reducing the risk of leaching. In comparison with U, three slow/controlled release fertilizer treatments with 25% lower N application did not decrease yield but increased seed Vc, soluble sugar and protein contents. The agronomic efficiency and economic benefit of DU treatment were the highest among three slow/controlled release fertilizers treatments. In conclusion, the application of new type of slow/controlled release fertilizer could improve the yield and quality of fresh maize, and significantly reduce the risk of ammonia loss and N leaching. Considering the higher cost of the polymer coated urea, the double-effect inhibitor urea has lower cost and is more convenient to make. It is therefore a better choice to fresh maize planting.