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Phosphorus nutrition of rice and temporary loss of soil-water saturation in lowland soils of Cambodia

Seng, V., Bell, R.W., Willett, I.R. and Nesbitt, H.J. (2000) Phosphorus nutrition of rice and temporary loss of soil-water saturation in lowland soils of Cambodia. In: Soils 2000 : making our science more useable : proceedings of conference Muresk Institute of Agriculture, 11 - 13 July, Northam, WA, Australia pp. 189-194.

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Abstract

In the rainfed lowlands, temporary loss of soil-water saturation during crop growth is a common factor limiting rice (Oryza sativa L.) yield but its effects on phosphorus (P) availability are poorly understood. Rice plants were transplanted into pots containing soils that were either continuously flooded, maintained at field capacity or flooded and then dried to field capacity for 3 weeks during the vegetative stage. A black clay soil (Kandic Plinthaquult) from south-east Cambodia were studied with or without amendment by rice straw and P fertilizer. Under continuously flooded conditions, the growth of rice was vigorous without straw addition and there was a strong response of rice growth to the addition of P fertilizer. The soil underwent reduction, which increased pH from 4.2 to 5.5 in the black clay. By contrast, a loss of soil-water saturation 3 weeks before panicle initiation (PI) markedly impaired the growth of rice. This was not through any effect of water stress, and the growth reductions were not as strong as with continued loss of soil-water saturation from transplanting to PI. Fluctuations in soil pH and Eh corresponded closely to changes in soil-water regimes. Growth reductions were attributed to decreased shoot P levels resulting from the decline in P availability during the loss of soil-water saturation. The addition of rice straw stimulated soil reduction and lessened changes in soil pH and Eh during the loss of soil-water saturation in both soils. Straw addition enhanced P uptake by the rice plants during loss of soil-water saturation, but its beneficial effects could not be attributed to the direct addition of P, N or K to the soils. Thus the application of rice straw may be effective in lessening the effects of temporary loss of soil-water saturation on rice growth in lowland rice soils by minimising the decline in P availability.

Publication Type: Conference Paper
Murdoch Affiliation: School of Environmental Science
Publisher: Australian Society of Soil Science Inc (WA Branch) and the Environmental Consultants Association (WA Inc.)
Copyright: © Australian Society of Soil Science Inc (WA Branch)
URI: http://researchrepository.murdoch.edu.au/id/eprint/18847
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