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 75kgNha⁻¹ at mid-tillering and 45kgNha⁻¹ at panicle initiation (U_120–2), and (2) a single application of cross-linked polyacrylamide-coated urea (a slow-release fertilizer) at mid-tillering at a rate of 150kgNha⁻¹ (PCU_150–1). Three field experiments were conducted to compare grain yield and N-use efficiency among several N treatments: a zero-N control (CK), U_120–2, PCU_150–1, a single application of urea at mid-tillering at a rate of 150kgNha⁻¹ (U_150–1), and a commonly recommended N management practice for conventional tillage rice (three split applications of urea with 75kgNha⁻¹ as basal, 30kgNha⁻¹ at mid-tillering, and 45kgNha⁻¹ at panicle initiation) (U_150–3). Treatments with N application (U_120–2, PCU_150–1, U_150–1, and U_150–3) produced 1.08–3.16tha⁻¹ higher grain yields than CK. Grain yields under both U_120–2 and PCU_150–1 were comparable to that in U_150–3. Recovery efficiency of N (RE_N), agronomic N-use efficiency (AE_N) and partial factor productivity of applied N (PFP_N) were increased under U_120–2 and were similar under PCU_150–1 to those under U_150–3. U_150–1 showed lower grain yield, RE_N, AE_N, and PFP_N than U_150–3. These results suggest that U_150–3 can be replaced with U_120–2 to achieve both an increase in N-use efficiency and a reduction in number of N applications and or by PCU_150–1 to achieve a maximum reduction in number of N applications in zero-tillage rice production in China.