Improving nitrogen management for zero-tillage rice in China

Zero-tillage has become increasingly attractive in rice production in China. This study was conducted to determine the feasibility of two possible improved N management practices with fewer N applications in zero-tillage rice: (1) two split applications of urea at 75 kg N ha−1 at mid-tillering and 45 kg N ha−1 at panicle initiation (U120-2), and (2) a single application of cross-linked polyacrylamide-coated urea (a slow-release fertilizer) at mid-tillering at a rate of 150 kg N ha−1 (PCU150-1). Three field experiments were conducted to compare grain yield and N-use efficiency among several N treatments: a zero-N control (CK), U120-2, PCU150-1, a single application of urea at mid-tillering at a rate of 150 kg N ha−1 (U150-1), and a commonly recommended N management practice for conventional tillage rice (three split applications of urea with 75 kg N ha−1 as basal, 30 kg N ha−1 at mid-tillering, and 45 kg N ha−1 at panicle initiation) (U150-3). Treatments with N application (U120-2, PCU150-1, U150-1, and U150-3) produced 1.08-3.16 t ha−1 higher grain yields than CK. Grain yields under both U120-2 and PCU150-1 were comparable to that in U150-3. Recovery efficiency of N (REN), agronomic N-use efficiency (AEN) and partial factor productivity of applied N (PFPN) were increased under U120-2 and were similar under PCU150-1 to those under U150-3. U150-1 showed lower grain yield, REN, AEN, and PFPN than U150-3. These results suggest that U150-3 can be replaced with U120-2 to achieve both an increase in N-use efficiency and a reduction in number of N applications and or by PCU150-1 to achieve a maximum reduction in number of N applications in zero-tillage rice production in China.