Sovuthy Pheav

Publications (2)4.53 Total impact

• Source

  Available from: Richard W. Bell

  Article: Phosphorus Mass Balances for Successive Crops of Fertilised Rainfed Rice on a Sandy Lowland Soil

  Sovuthy Pheav, R. W. Bell, P. F. White, G. J. D. Kirk
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  ABSTRACT: Raising and sustaining rice yields in the rainfed lowlands requires an understanding of nutrient inputs and outputs. On sandy lowland rice soils, managing phosphorus (P) supply is a key factor in achieving increased yields and sustainable production. Phosphorus inputs, rice yields, and crop P uptake were used to quantify P requirements of rice: together with results on soil P fractions, P balance sheets were constructed over five consecutive cropping seasons on a sandy Plinthustalf near Phnom Penh, Cambodia. Grain yields ranged from 665 to 1557kgha−1 with no added P. Average yields increased significantly with P fertiliser application over five consecutive crops by 117, 139 and 140% when the phosphate fertiliser was applied at 8.25, 16.5 and 33kgPha−1, respectively. Without added P fertiliser, a net loss of 1.2kgPha−1 per crop was estimated with straw return and 2.0kgPha−1 per crop with straw removed from the field, whereas, with added P fertiliser, there was a net P gain in the soil of 5.6 or 9.5kgha−1 per crop when straw was removed and returned to the soil, respectively. After one crop, the addition of P fertiliser significantly (P < 0.01) increased recovery in all soil P fractions. Across five successive crops, repeated application of 16.5 and 33kgPha−1 rates resulted in progressive P accumulation in the soil, especially a labile NaOH–Po pool, but had no effect on yields and P uptake of rice. By contrast, 8.25kgPha−1 per rice crop was generally adequate for grain yields of 2.5–3.0tha−1 and to maintain soil P pools.
  Nutrient Cycling in Agroecosystems 04/2012; 73(2):277-292. · 1.79 Impact Factor
• Article: Phosphorus cycling in rainfed lowland rice ecosystems on sandy soils

  Sovuthy Pheav, R. W. Bell, G. J. D. Kirk, P. F. White
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  ABSTRACT: Phosphorus cycling in rainfed lowland rice ecosystems is poorly understood. Soil drying and grazing of rice straw during the long dry season, the growth of volunteer pastures during the early wet season, and intermittent loss of soil-water saturation while the rice crop is growing are important distinguishing characteristics of the rainfed lowlands in relation to P cycling. We studied P cycling in an acid sandy rainfed lowland soil that covers about 30% of the rice growing area of Cambodia. Soils with similar properties in comparable rainfed sub- ecosystems occur in Laos and northeast Thailand. We developed a general schema of P pools and fluxes in the crop and soil for rice-based cropping systems in the rainfed lowlands of Cambodia. The schema was derived from a number of field experiments carried out over five consecutive cropping seasons to quantify the residual value of P fertiliser, P mass balances, soil P fractions, the effect on subsequent rice crops of crop residues and volunteer pastures incorporated into the soils, and the dynamics of P turnover in the soil. With a single rice crop yielding 2.5–3 t ha−1, application of 8–10kg P ha−1 maintained yields and a small positive P balance in the soil. However, the soil P balance was sensitive to the proportion of rice straw returned to the soil. Volunteer pastures growing during the early wet season accumulated significant amounts of P, and increased their P uptake when soils were previously fertilised with P. These pastures recycled 3–10kg P ha−1 for the succeeding rice crops. While inorganic soil P pools extractable with ion exchange resins and 0.1 M NaOH appeared to be the main source of P absorbed by rice, microbial and organically-bound P pools responded dynamically to variation in soil water regimes of the main wet, dry and early wet seasons. The schema needs to be developed further to incorporate site-specific conditions and management factors that directly or indirectly affect P cycling, especially loss of soil-water saturation during the rice cropping cycle. The paper discusses the application of results for acid sandy soils to other significant rice soils in the rainfed lowlands of southeast Asia.
  Plant and Soil 01/2005; 269(1):89-98. · 2.73 Impact Factor