Anaerobic Incubation Without Shaking Over a Prolonged Period as a Method to Determine Mineralizable Nitrogen in Rice Soils

ABSTRACT

Fertilization rates of nitrogen (N) in rice crop are based on crop needs and the capacity of the soil to supply it, which is determined by several methods. This study evaluated a method of anaerobic incubation without shaking for extended periods of time. Three rice soils of the Inceptisol, Alfisol, and Vertisol orders were fertilized with N rates of 0, 80, and 160 kg ha-1 and
incubated for 0, 7, 14, 21, and 28 d at 20 and 40ºC. The methodology also used short−term anaerobic incubation and constant shaking for 7 d at 40ºC. Field experiments were conducted with rice in the same soils with equal N rates; and extracted plant N was compared with mineralized N. Results indicated that the methodology without shaking is comparable to the constant shaking procedure for short-term incubations. However, incubations without shaking for longer periods of time had the highest relation to crop extracted N.

Keywords: paddy rice soils, nitrogen mineralization, anaerobic incubation method.