Response of direct seeded rice to increasing rates of nitrogen, phosphorus, and potassium in two paddy rice soils

Juan Hirzel1*, Mario Paredes1, Viviana Becerra1, and Gabriel Donoso1
The rice (Oryza sativa L.) crop is very important worldwide for its contribution to human nutrition. Rice grain yield depends on several agronomic management factors that must also be adjusted to the cropping system such as permanent inundation (anaerobic conditions) or direct seeding (aerobic and anaerobic conditions) mainly in response to the application of nutrients such as N. In Chile, the cropping system with direct seeding has limited agronomic and scientific development. The objective was to determine the effect of increasing N (0, 40, 80, 120, and 160 kg ha-1), P (0, 30, 60, and 120 kg P2O5 ha-1), and K (0, 30, 60, and 120 kg K2O ha-1) rates on grain yield and N agronomic efficiency (NAE) (kg grain produced per kg N applied) in two paddy rice soils for two consecutive seasons. Grain yield had a positive response to increasing N rates in the two evaluated soils (grain yield increased from 6.7 to 8.9 Mg ha-1 in the Vertisol and from 7.4 to 11.0 Mg ha-1 in the Alfisol) and a low response to P rates in the Vertisol. The Alfisol showed no response to increasing P rates, and both soils had no response to K application. The N rates that obtained the highest rice grain yield were 120 and 160 kg ha-1 for Alfisol and Vertisol, respectively. The P rate that obtained the highest rice yield in the Vertisol was 30 kg ha-1 P2O5. In addition, NAE values associated to those N rates were 74 and 61, respectively. In conclusion, direct seeding in rice cropping had a response to high rates of applied N, low response to P, and no response to K.
Keywords: Direct seeding, fertilization, grain yield, Oryza sativa.
1Instituto de Investigaciones Agropecuarias, INIA Quilamapu, Av. Vicente Méndez 515, Chillán, Chile.
*Corresponding author (jhirzel@inia.cl).