
%0 Journal Article
%A Angus, JF 
%A Ohnishi, M 
%A Horie, T 
%A Williams, RL 
%T A preliminary study to predict net nitrogen mineralisation in a flooded rice soil using anaerobic incubation
%J Australian Journal of Experimental Agriculture
%D 1994/11/01
%V 34
%N 7
%P 995-999
%K 
%R https://doi.org/10.1071/EA9940995
%U https://www.publish.csiro.au/paper/EA9940995 
%X Complementary field and laboratory studies were conducted to determine whether laboratory measurements of net nitrogen (N) mineralisation under anaerobic conditions could be used to predict field rates in a flooded soil and N uptake by a rice crop. The laboratory experiment consisted of measurements of ammonium accumulation at 10, 20, 30, and 40¦C for 7, 14, and 28 days of anaerobic incubation. There was no accumulation of ammonium at 10¦C, but increasing ammonification rate at temperatures of 20¦C was observed, except for a slower rate at 40¦C after 14 days. Two models were tested on the data: a zero-order reaction in which rate of mineralisation was a linear function of temperature; a first-order reaction in which net N mineralisation rate was a proportion of a depleting pool of labile organic N. In the second model, the rate was also linearly related to temperature. Both models fitted the laboratory data well (R2 = 0.94 and 0.97, respectively), but the second model accounted better for mineralisation at 40¦C for the 28-day incubation. These models were then run, using daily mean temperatures over a rice-growing season, to predict net mineralisation in the field. The predictions were compared with measured net N mineralisation in a flooded soil and N uptake by the crop measured throughout the season in the field from which the incubated soil was sampled. Net N mineralisation and crop uptake increased throughout the season, reaching maximum values of 115 and 111 kg N/ha at maturity. The zero-order and first-order models both predicted net N mineralisation accurately until the middle of the season, after which the zero-order model overestimated net N mineralisation but the first-order model predicted the reduction in the rate of net N mineralisation with reasonable accuracy. The close agreement between the laboratory incubations and field measurements of net mineralisation and crop N uptake suggest that incubation tests may provide useful information for including in a model to assist rice growers' decisions about N fertiliser. 
