Negligible ammonia volatilization loss with one-time root-zone targeted application of common nitrogen, phosphorus, and potassium fertilizers in transplanted rice cultivation

The minimization of nitrogen (N) loss and enhancement of efficient N use are of great importance in agricultural crop production. Here we propose a method of one-time root-zone targeted fertilization (ORZTF), to reduce ammonia volatilization (AV) loss and increase N use efficiency. ORZTF is updated from one-time root-zone fertilization (ORZF), in which common N fertilizer is one-time applied in crop root-zone, and phosphate (P) and potassium (K) are surface broadcasted. In ORZTF, common N, P and K are together placed at certain sites in the root-zone. Three rice field trials with the methods of conventional surface broadcasting (CSB), ORZF, and ORZTF, and a soil incubation experiment with CSB and ORZTF, were conducted. In 2018, the treatments comprised CSB with no N (N0), with the local N rate (CSB, 195 kg N hm−2 and 150 kg N hm−2 for two sites, respectively), with higher N (HCSB, 225 kg N hm−2 and 195 kg N hm−2, respectively), ORZF (195 kg N hm−2 and 150 kg N hm−2, respectively), and ORZTF (195 kg N hm−2 and 150 kg N hm−2, respectively). In 2019, the treatments were: N0, CSB, ORZF, ORZTF with urea (ORZTF-U), with ammonium chloride (ORZTF-Cl), and with ammonium sulfate (ORZTF-S) at 180 kg N hm−2. In the incubation experiment, there're three treatments: N0, CSB, and ORZTF. The rates of P and K were the same in all experiments. Compared with CSB, ORZTF and ORZF significantly increased the yield, N uptake, N recovery efficiency, and N partial factor productivity of rice with the same N input. After 4.5 months of incubation, 78.5–92.7% of fertilizer N was reserved in the soils with ORZTF, about two-fold that with CSB. In all field and incubation experiments, AV loss was negligible when N was one-time root-zone applied alone or together with PK, close to that in N0 treatment. Compared with ORZF, ORZTF seemed to be a more promising method in rice fertilization, having the similar effect on N uptake increase and N loss reduction, but more convenience. Although the benefits of targeting fertilization were not significantly observed in the current work, with the idea of 'fertilizing the roots but not the soil', the method of ORZTF with common N, P and K fertilizers should be beneficial for cleaner and more efficient agricultural crop production in China.