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Residual effect of phosphorus fertilizer for rice in rainfed lowland soils of Cambodia

Pheav, S., White, P.F., Bell, R.W. and Kirk, G.J.D. (2000) Residual effect of phosphorus fertilizer for rice in rainfed 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. 184-188.

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Phosphorus (P) deficiency is widespread in Cambodian rice growing soils, and strong responses are generally obtained from P fertilizer application. Since P fertilizer use is expected to increase in Cambodian rice crops, the present study was conducted to examine the residual value of P fertilizer applied to rice. Phosphorus fertilizer at a rate of 16.5 kg P ha-1 was applied to a wet season rainfed rice crop on a sandy lowland soil (Plinthustalf) in 1997, and the response of rice to this P was quantified in four successive rice crops by reference to yield obtained from a fresh application of 16.5 kg P ha-1 in each succeeding crop. In crop one, P increased rice yield from 1.5 to 2.8 t. ha-1 , whereas in the crop two, grown with irrigation in the following dry season, the residual P and the freshly applied P, increased grain yield by 62 and 85 %, respectively. In crop three, the residual P from crop one barely increased growth, producing a yield of about 2.0 t.ha, whereas the residual P from crop two increased growth by 60%, and freshly applied P increased growth of 70%. In the fourth crop, grain yield responded only weakly or not at all to the residual P from that applied to crop one. These results suggest that P needs to be reapplied every two crops on sandy lowland soils of Cambodia provided grain yields similar to those obtained in the present study are maintained. The mechanisms underlying the decline in residual value of P, including P removal in harvested crop products and long-term reactions of P with soils under alternating waterlogged and dry conditions warrant further investigation. These data will be incorporated into a model of P cycling in the lowland rainfed rice ecosystems of Cambodia.

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)
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