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Haefele S.M.,International Rice Research Institute | Sipaseuth N.,National Agricultural and Forestry Research Institute NAFRI | Phengsouvanna V.,National Agricultural and Forestry Research Institute NAFRI | Dounphady K.,National Agricultural and Forestry Research Institute NAFRI | Vongsouthi S.,National Agricultural and Forestry Research Institute NAFRI
Field Crops Research | Year: 2010

Soils used for cropping of rainfed lowland rice are frequently rather poor, and nutrient limitation is known to be a major constraint for grain yields. However, actual fertilizer use by most rainfed rice farmers is still very low even if input-responsive rice varieties are widely adopted. To address this contradiction, this study, conducted in central and southern Laos, intended to test existing fertilizer recommendations in farmers' fields and under their crop management, to evaluate the effect of topographic field position on fertilizer response, and to conduct an economic evaluation of fertilizer use based on farmers' input and output prices. Trials were conducted for two seasons in three different agroecological environments (rainfed rice in lower fields and in middle/upper fields, and irrigated rice in lower fields). Tested were five different fertilizer treatments in four farmers' fields per site and season. Commercial organic fertilizer increased yields but resulted in negative economic returns in almost all cases because of its unfavorable nutrient/price ratio. In lower fields, farmyard manure and inorganic fertilizer gave good yield responses and positive economic returns but the average value/cost ratios of 1.3-1.6 were at the lowest level required for widespread adoption of fertilizer use. Water limitation reduced attainable yields in middle/upper fields and in this environment good fertilizer response was observed only for farmyard manure and half the recommended rate of inorganic fertilizer. The actual benefit of fertilizer use depended strongly on the input/output price ratios at each site. Thus, site-specific fertilizer management options, including economic parameters, are required to make fertilizer use in rainfed lowland rice more profitable. The necessary information for such guidelines is available but needs to be prepared in the form of decision tools to help farmers choose the optimal nutrient management option for their agroecological and socioeconomic production environment. © 2010 Elsevier B.V. Source


Xangsayasane P.,National Agricultural and Forestry Research Institute NAFRI | Xangsayasane P.,Khon Kaen University | Fukai S.,University of Queensland | Mitchell J.H.,University of Queensland | And 4 more authors.
Field Crops Research | Year: 2014

Drought is a major problem for rainfed lowland rice in Laos as well as for other countries in the Mekong region, and different drought screening methods under managed environments have been used to develop varieties adapted to drought prone environments. This paper evaluates the appropriateness of on-research station screening methods conducted under intermittent and terminal drought conditions, using the yield results of 12 on-farm multi-location trials with 25 genotypes some of which had been selected for drought tolerance. In these multi-location trials drought stress was rather mild, even in the intermittent or terminal drought trials which tended to develop in the higher fields of the rainfed lowlands. The high position generally produced low yielding crops but no significant interaction between position and genotypes were found for grain yield of 25 genotypes grown at 4 pairs of high and low field positions. Genotypes that performed well under higher yielding conditions in the on-(research) station experiments also performed well in on-farm multi-location trials. Genotypes that were identified as drought tolerant using drought response index as a criterion in the on-station experiments generally performed well in the on-farm multi-location trials (r= 0.49**), particularly in high yielding environments, but not under low yielding environments where low soil fertility appeared to be a major limitation for high yield. Similarly, genotypes that were identified to have high potential yield in flooded conditions in the on-station experiments also performed well in on-farm multi-location trials (r= 0.43*). Drought tolerance determined on-station either intermittent or terminal drought was similarly effective and was at least as effective as potential yield determined on-station in predicting on-farm yield. On-farm multi-location trials in combination with on-station experiments identified several promising lines that were well adapted to rainfed lowland conditions. It is concluded that genotypes selected for high yield potential under favorable conditions and for high drought tolerance determined in the on-station experiments would result in the development of well adapted cultivars suitable for drought-prone rainfed lowlands, and that either intermittent or terminal drought conditions developed at a research station is suitable for this purpose. The intermittent drought condition had the added advantage that genotypes selected directly for high yield, performed well in farmer's fields in the rainfed lowlands. © 2014. Source

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