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Phosphorus turnover between rice crops in the rainfed lowlands from residual P fertiliser, rice straw and volunteer pastures

Pheav, S., Bell, R.W., White, P.F. and Kirk, G.J.D. (2004) Phosphorus turnover between rice crops in the rainfed lowlands from residual P fertiliser, rice straw and volunteer pastures. In: 4th International Crop Science Congress, 26 September - 1 October, Brisbane, Australia

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Abstract

The fate of residual P fertiliser and P in crop residues in sandy rainfed lowland soils is poorly understood. Field experiments were undertaken to determine the effects of rice straw incorporation, and of residual fertiliser P on biomass of volunteer pastures and to quantify the fate of P recycled from them on subsequent rice growth. Returning rice straw with P fertilisation had additive effects on growth and yields of rice during the main wet season. Straw addition alone increased grain and straw yields on the nil-P and applied-P soils by about 10 and 5 %, respectively. Subsequently, in the early following wet season, the biomass of volunteer pastures responded significantly to the residual P and the straw incorporation. All soil P fractions significantly increased at 2 weeks after rice straw incorporation. The minor resin-P fraction fluctuated more over time compared to major soil P fractions (NaOH-Pi and NaOH-Po). Phosphate added with straw increased microbial biomass C but had only small effects on microbial biomass P. Microbial biomass P declined dramatically in the active growth stage of rice, suggesting strong competition for available P from crop uptake, whereas, microbial C increased progressively for up to 40 weeks after straw incorporation. In conclusion, the application of crop residues alone marginally increased rice productivity, soil P fractions and microbial biomass C and P, whilst greater increases were obtained with the combined application of P fertiliser with crop residues. There remains to be investigated the long-term impact of residual P fertiliser and organic inputs on crop yields, soil P forms and P turnover processes.

Publication Type: Conference Paper
Murdoch Affiliation: School of Environmental Science
URI: http://researchrepository.murdoch.edu.au/id/eprint/20446
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