Upland Rice Response to Phosphorus Fertilization in Asia

Abstract

1998). Traditional upland rice is adapted to soil acidity (Garrity et al., 1990; Wade et al., 1988); moreover, im-Upland rice (Oryza sativa L.) yields on infertile, acid soils in the provement in upland rice adaptation to soil acidity can Asian uplands average only 1 Mg ha Ϫ1 . Phosphorus deficiency is considered a major soil constraint to increased yield, but little quantitative be brought about by breeding (Zeigler et al., 1995; Kirk information is available. We analyzed P responses of traditional rice et al., 1998). Given that upland rice is inherently tolerant on farm in Laos, Thailand, and the Philippines and improved varieties to soil acidity and that improved acid soil adaptation can in researcher-managed trials in the Philippines. Treatments in onbe incorporated into superior germplasm, nutrient defarm trials were a control and 50 kg P ha Ϫ1 Ϯ 100 and 50 kg ha Ϫ1 N ficiency, particularly P, becomes a major soil constraint and K, respectively. Treatments in researcher-managed trials were P to production in upland rice areas (Garrity et al., 1990; rates on an unlimed and limed Ultisol. Mehlich-1 extractable P cor- Kirk et al., 1998). Hedley et al. (1994) found that upland related with on-farm grain yield (r ϭ 0.47). Phosphorus fertilization rice varieties quickly became P deficient in a high P-fixing, increased average grain yield (1 Mg ha Ϫ1 ) by 20%, total biomass acid upland soil in the Philippines. Even in shifting culti-(4 Mg ha Ϫ1 ) by 27%, and P uptake (4.1 kg ha Ϫ1 ) by 53%. Yield vation systems where ash deposits and nutrients from increased 37% with P ϩ N ϩ K, but only 16% of the 2.4 Mg ha Ϫ1 biomass increase was grain. Improved rice in researcher-managed trials mineralized organic matter are considered sufficient for responded to P, with a larger proportion of biomass partitioned to reasonable rice yield in the initial years after clearing grain [i.e., higher harvest index (HI)]. Grain yield of 'UPLRi-5' infallows (Roder et al., 1995a), P deficiency was found to creased from 3.2 to 4.6 Mg ha Ϫ1 in limed soil while that of 'IR55423-01' be a major nutrient limitation to upland rice yield (Van increased from 3.4 to 4.0 Mg ha Ϫ1 in unlimed soil. Phosphorus fertiliza- Reuler and Janssen, 1989). Phosphorus fertilizer applition always increased the frequency of higher yields averaged across cation has been reported to increase upland rice yield in trials, soils, varieties, and growing conditions. Yield gain from onthe Cerrado region of Brazil (Fageria et al., 1982), West farm P fertilization of traditional rice was small because of low HI, Africa (Van Reuler and Janssen, 1996;Sahrawat et al., unlike in improved varieties, which had a HI. We infer that increasing 1995), and Southeast Asia (Schmidt et al., 1990). upland rice yield in Asia would require genotypes with higher HI inThe poor infrastructure and lack of markets in the addition to P fertilization. fragile environments of Asia often do not offer much economic incentive for farmers to use purchased fertilizers. When inputs are purchased, they...

Farmers' knowledge of soils in relation to cropping practices: A case study of farmers in upland rice based slash-and-burn systems of northern Laos

“…Similarly, Roder et al (1995a) also reported from one study that soil organic matter was associated with rice yield (r = 0.42), while in another study comparing high and low yielding areas in 55 fields, pH, total N, total C, extractable P and CEC were significantly higher in the high yielding areas. Unlike George et al (2001), extractable P measurements in this study were not correlated with rice yield, but there was a significant relationship with total P uptake.…”

“…Shortened fallow periods have rendered these systems unsustainable as soil quality (due to nutrient depletion and erosion) is declining, weed pressure and labor inputs are increasing, and yields are declining with the end results being lower returns on productivity and increased poverty (Asian Development Bank, 2001;Linquist et al, 2005;Saito, 2005). The major soil fertility constraints in the Lao uplands are low N and P supply (George et al, 2001;Roder, 2001;Saito et al, 2006a,b).…”

The role of tolerant genotypes and plant nutrients in reducing acid-soil infertility in upland rice ecosystem: an appraisal

“…These results are in accordance with those reported by George et al (2001) who analyzed P responses of traditional rice varieties on farms in Laos, Thailand and the Philippines and improved varieties in researcher-managed experiments in the Philippines. Phosphorus fertilization significantly increased the yield, total biomass and P uptake in improved rice varieties, while the yield gain from on-farm P fertilization of traditional rice varieties was small.…”

Crop performance, nitrogen and water use in flooded and aerobic rice

“…Drains of 0.4 m deep surrounded each field and plastic sheets were installed to 0.4 m depth in the bunds to separate the fields hydrologically. Flooded and aerobic fields were divided into one subplot receiving no fertilizer-N (0-N plot) and another subplot receiving 150 kg urea-N ha -1 (150-N plot) in three splits: 50 kg N ha )1 basal, 50 kg N ha (George et al, 2001). In the long-term experiment, several other cultivars were tested .…”