Benefits of organic residues and chemical fertilizer to productivity of rain-fed lowland rice and to soil nutrient balances |
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Authors: | Bruce A Linquist Vongvilay Phengsouvanna Pheng Sengxue |
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Affiliation: | (1) Department of Plant Science, University of California, Davis, USA;(2) Provincial Agriculture and Forestry Office, Champassak, Lao PDR;(3) National Agriculture and Forestry Research Institute, Vientiane, Lao PDR |
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Abstract: | Low yields and high risk characterize many rain-fed lowland rice environments, including those in Laos. Drought and fluctuating
soil-water conditions (from aerobic to anaerobic states) can limit productivity and the efficient use of applied nutrients.
Although addition of organic matter may improve the efficiency of fertilizer use, on-farm residues, for example farmyard manure
(FYM), rice straw and rice hulls, are, currently, poorly utilized in these systems. Single and multi-year experiments were
designed to evaluate the effect of these residues on rice productivity and efficiency of fertilizer use at four sites. Rice
yield without fertilizer but with addition of residues ranged from 1.1 to 1.7 t ha−1 across sites and years. In response to fertilizer, yields increased on average by 1.4 t ha−1. For all sites and years there was a significant response of yield to organic residues applied without fertilizer, with responses
ranging from 0.2 to 1.4 t ha−1. In 58% of cases there was no residue×fertilizer interaction (benefits of residues when applied with fertilizer were additive).
In 38 and 4% of cases the interaction was negative (no response to residues if fertilizer was already applied) or positive
(synergistic), respectively. In the multi-year studies, the type of interaction varied between years, suggesting that seasonal
events, rather than soil type, determine the type of interaction. The greatest benefits of applying organic and chemical fertilizers
together were observed in years when soil-water conditions were unfavorable (fluctuating anaerobic–aerobic conditions). The
long-term effects of these different management strategies on soil nutrient balances suggest that N, P, and K balances were
maintained as a result of balanced commercial fertilizer management but that addition of residues further enhanced these balances.
All residues, when applied alone, resulted in positive soil Si balances; only with FYM were long-term N, P, and K balances
maintained or positive, however. For resource-poor farmers, applying on-farm residues can be a sustainable approach to increasing
productivity. |
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Keywords: | Fertility management Interactions Nitrogen Nutrient-use efficiency Organic Phosphorus Potassium Rain-fed lowland rice Residue Silica Synergistic benefits |
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