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Photosynthetic aquatic biomass (PAB – algae and other floodwater flora) is a significant source of organic carbon (C) in rice-based cropping systems. A portion of PAB is capable of fixing nitrogen (N), and is hence also a source of N for crop nutrition. To account for this phenomenon in long term simulation studies of rice-based cropping systems, the APSIM modelling framework was modified to include new descriptions of biological and chemical processes responsible for loss and gain of C and N in rice floodwater. We used well-tested algorithms from CERES-Rice, together with new conceptualizations for algal dynamics, in modelling the contribution of PAB to maintenance of soil organic C and soil N-supplying capacity in ricebased cropping systems. We demonstrate how our new conceptualization of PAB growth, turnover, and soil incorporation in flooded rice systems facilitates successful simulation of long-term soil fertility trials, such as the IRRI Long Term Continuous Cropping Experiment (35+ years), from the perspectives of both soil organic carbon levels and yield maintenance. Previous models have been unable to account for the observed maintenance of soil organic C in these systems, primarily due to ignoring inputs from PAB as a source of C. The performance of long-term rice cropping system simulations, with and without inclusion of these inputs, is shown to be radically different. Details of our modifications to APSIM are presented, together with evidence that the model is now a useful tool to investigate sustainability issues associated with management change in rice-based cropping systems.

Item Type:	Refereed Article
Keywords:	APSIM, ORYZA2000, rice, cropping systems, biological nitrogen fixation, algae
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Agriculture, land and farm management
Research Field:	Agricultural systems analysis and modelling
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Grains and seeds
Objective Field:	Rice
UTAS Author:	Meinke, H (Professor Holger Meinke)
ID Code:	75146
Year Published:	2012
Web of Science® Times Cited:	49
Deposited By:	Agricultural Science
Deposited On:	2012-01-12
Last Modified:	2017-11-02
Downloads:	2 View Download Statistics