Logo image
Back
Phosphate sorption-desorption behaviour and phosphorus release characteristics of three contrasting lowland rice soils of Cambodia
Journal article   Open access   Peer reviewed

Phosphate sorption-desorption behaviour and phosphorus release characteristics of three contrasting lowland rice soils of Cambodia

S. Pheav, R.W. Bell, P.F. White and G.J.D. Kirk
Cambodian Journal of Agriculture, Vol.6, pp.39-54
2002
pdf
lowland_rice_soils_of_Cambodia.pdfDownloadView
Published (Version of Record) Open Access

Abstract

Understanding the P sorption and release characteristics of different soils can help in determining fertiliser P requirements for the growth of rice (Oryza sativa L.). Glasshouse and laboratory experiments were undertaken to observe the long-term release characteristics of P from added fertiliser for the early growth of rice, and also to determine P sorption-desorption behaviour of three contrasting lowland soils from Cambodia: Prateah Lang (Plinthustalf), Koktrap (Plinthaquult) and Toul Samroung (Endoaqualf). In the pot experiment, rice was treated with four P rates (0, 5, 10 and 20 mg/kg soil) and grown over five successive cropping cycles, each of six to eight weeks. Phosphorus sorption desorption isotherms were constructed by equilibrating with 0, 10, 20 and 40 mg P/1 in 0.01 M CaCl2 solution at 25 oC. On the sandy Prateah Lang (PL) and clayey Toul Samroung (TS) soils, addition of 10 mg P/kg soil was adequate in the first crop for maximum tiller number, plant height, total dry matter, P concentration, and total P uptake. By contrast, about 20 mg P/kg was needed for the maximum growth and total P uptake on the clayey acid Koktrap (KT) soil. After two crops, plant growth progressively declined at all P levels, but the decrease in yields and total P uptake on the clayey TS and KT soils was slower than for plants grown on the sandy PL soil. Resin-P extractable was the smallest P fraction compared to other major soil-P (NaOH-Pi, NaOH-Po and Residual-P) pools in all soil groups, but recovery from the Resin-P pool was higher in the sandy PL soil than in the clayey TS and KT soils. The declining amounts recovered from all the extractable soil P fractions, especially major soil P (NaOH-Pi and Po and Residual-P) pools with succeeding rice crops grown on all the soils could be attributed to continued reactions of the added P fertiliser by soils in addition to plant P uptake during each plant-growing cycle. The clayey KT and TS soils sorbed five-fold more P than the sandy PL soil in oxidized conditions. Phosphorus desorption was initially greatest from the sandy PL soil: but with increasing numbers of soil extractions, the release of sorbed P declined faster than in the clayey KT and TS soils. The cumulative desorbed P was greater from the clayey KT and TS soil than from the sandy PL soil. The greater P sorbed by the clayey soils should ensure a longer duration of the residual P effect.

Details

Metrics

133 File views/ downloads
76 Record Views
Logo image