Nutrient Status of Cambo dian Soils, Rationalisation of Fertiliser Recommendations and the Challenges Ahead for Cambodian Soil Science

Blair, Graeme J.; Blair, Nelly

doi:10.12944/carj.2.1.02

Cited by 17 publications

(13 citation statements)

References 10 publications

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“…Interestingly, the yield response to K input combined with N input was also significant on the Toul Samroung soil, except at Battambang in 2016 ( Figure 2). Previous studies suggested a low requirement for supplemental K on the Toul Samroung soil, since the soil is already relatively rich in plant-available K (Table 1; Blair and Blair, 2014;Oberthur et al, 2000;White et al, 2000). It is likely that long-term intensive use of N and P fertilizers on this fertile soil leads to increased K uptake by plants, thereby gradually depleting the available K in many fields (Seng et al, 2001).…”

Section: Discussionmentioning

confidence: 95%

“…The low soil fertility results from weathering of soils with a low carbon content, as is typically seen in the Prateah Lang and Prey Khmer soil groups, which cover 25-30% and 10-12%, respectively, of the country's rice-growing area (White et al, 2000). Blair and Blair (2014) estimated that 87% of the country's soils have less than 10 g kg −1 of organic carbon content. Coarse-textured soils respond poorly to nutrient management owing to their low nutrient-holding capacity (Haefele et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Together with the development of national soil classification systems in Cambodia based on a database of country-wide soil tests (Oberthur et al, 2000), White et al (2000) proposed a user-friendly guideline for soil-specific nutrient management, which was subsequently adopted by a governmental agency, the Cambodian Agricultural Research and Development Institute (Seng et al, 2001). However, the overall fertilizer recommendations for each soil group provided poor net returns (gross economic return minus total production cost) due to low inputs of fertilizers that resulted in low yield (Blair and Blair, 2014). The total fertilizer consumption in Cambodia has increased from 7873 t N during the 2002-2005 period to 63,784 t during the 2012-2015 period, from 12,512 t P 2 O 5 in 2002-2005 to 17,112 t in 2012-2015, and from 1033 t K 2 O in 2002-2005 to 3926 t in 2012-2015 (FAOSTAT, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Importance of phosphorus and potassium in soil-specific nutrient management for wet-season rice in Cambodia

et al. 2019

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Rice is widely grown in rainfed lowlands during the wet season in the Mekong region. Limited nutrient availability is a common constraint on crop yield, and the optimal rate of fertilizer application depends on the soil type. The objective of our study was to evaluate rice productivity and the economic feasibility of various nutrient management regimes in Cambodia. We conducted field experiments on three soil types (Prey Khmer, Prateah Lang, and Toul Samroung, equivalent to Psamments, Plinthustalfs, and Endoaqualfs, respectively) in four provinces (Battambang, Kampong Thom, Pursat, and Siem Reap) during the 2016 and 2017 wet seasons to compare nine (2016) and seven (2017) N–P–K combinations. Grain yield ranged from 0.9 to 4.8 t ha−1 in 2016 and from 1.0 to 5.2 t ha−1 in 2017, depending on soil type and nutrient management. The Prey Khmer soil contained around 80% sand, and rice yield responded most weakly to nutrient management. The moderate fertilizer input in the current soil-specific recommendation was effective on this soil type. However, on more fertile soils with a higher clay content and a higher cation-exchange capacity (Toul Samroung and Prateah Lang), an additional 20 kg N ha−1 combined with adding 15 kg ha−1 of P2O5 or 20 kg ha−1 of K2O significantly increased yield and economic return. Although P and K use during Cambodia’s wet season is uncommon, our results demonstrate the importance of these nutrients in improving the country’s rice production.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Importance of phosphorus and potassium in soil-specific nutrient management for wet-season rice in Cambodia

et al. 2019

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“…A number of field studies have focused on the improvement of nutrient management of wet-season rice in Cambodia to close the nationwide yield gap, that is, increasing mean farm yield (3.3 t ha −1 ; MAFF, 2018) towards potential yield (Blair and Blair, 2014;Seng et al, 2001;Wade et al, 1999;White et al, 2000). Potential yield is the yield of a cultivar grown in environments to which it is adapted with non-limiting water and nutrient conditions (Evans and Fischer, 1999).…”

Section: Introductionmentioning

confidence: 99%

Potential yield and nutrient requirements of direct-seeded, dry-season rice in Cambodia

et al. 2019

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The area of dry-season rice (Oryza sativa L.) has rapidly increased in Cambodia owing to the large-scale development of irrigation infrastructure. But little is known of potential productivity and adaptive crop management. The objective of our study was to evaluate potential yield and nutrient requirements of dry-season rice in Cambodia, and the economic feasibility of soil-specific management recommended by the government. Field experiments were conducted on four soil types (Bakan, equivalent to Alfisol; Krakor, Inceptisol; Prateah Lang, Plinthustalfs; and Toul Samroung, Endoaqualfs) in four provinces (Battambang, Kampong Thom, Pursat, and Siem Reap) during the 2016 and 2017 dry seasons to compare 14 (2016) and 8 (2017) N-P-K combinations. Grain yield ranged from 1.0 to 5.5 t ha−1 in 2016 and from 1.3 to 6.7 t ha−1 in 2017. Potential yield from the experiments was 6–7 t ha−1 on Toul Samroung soil, 5–6 t ha−1 on Bakan soil, and 3–5 t ha−1 on Prateah Lang and Krakor soils. A rate of 140-60-60 kg ha−1 of N-P2O5-K2O was more than enough to achieve the best yields on any soil group. On the other hand, modest application rates in soil-specific management (44–78 kg ha−1 of N, 23–28 kg ha−1 of P2O5, 0–30 kg ha−1 of K2O) proved reasonable for resource-poor farmers in Cambodia, since the treatment always provided >75 % of the highest economic profit in high-input plots.

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“…The main production area is characterized by highly weathered sandy Fluvisols with low organic matter and N contents ( Seng et al, 2001), extremely low available P contents, and low‐activity material dominating the clay fraction ( White et al, 1997). Mineral fertilizer sources are often unaffordable to small‐scale producers ( Blair and Blair , 2014), the efficiency of recommended application rates is highly variable, and profitability is often low ( Seng et al, 2001), possibly the result of leaching losses of nutrients other than P. Only low amounts of farmyard manure (FYM) are generally applied due to the limited number of farm animals.…”

Section: Introductionmentioning

confidence: 99%

Effect of phosphorus management in rice–mungbean rotations on sandy soils of Cambodia

Ro¹,

Becker

Manske³

2016

J. Plant Nutr. Soil Sci.

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Nitrogen (N) and phosphorus (P) deficiencies are key constraints in rainfed lowland rice (Oryza sativa L.) production systems of Cambodia. Only small amounts of mineral N and P or of organic amendment are annually applied to a single crop of rainfed lowland rice by smallholder farmers. The integration of leguminous crops in the pre‐rice cropping niche can contribute to diversify the production, supply of C and N, and contribute to soil fertility improvement for the subsequent crop of rice. However, the performance of leguminous crops is restricted even more than that of rice by low available soil P. An alternative strategy involves the application of mineral P that is destined to the rice crop already to the legume. This P supply is likely to stimulate legume growth and biological N2 fixation, thus enhancing C and N inputs and recycling N and P upon legume residue incorporation. Rotation experiments were conducted in farmers' fields in 2013–2014 to assess the effects of P management on biomass accumulation and N2 fixation (δ15N) by mungbean (Vigna radiata L.) and possible carry‐over effects on rice in two contrasting representative soils (highly infertile and moderately fertile sandy Fluvisol). In the traditional system (no legume), unamended lowland rice (no N, + 10 kg P ha−1) yielded 2.8 and 4.0 t ha−1, which increased to 3.5 and 4.7 t ha−1 with the application of 25 kg ha−1 of urea‐N in the infertile and the moderately fertile soil, respectively. The integration of mungbean as a green manure contributed up to 9 kg of biologically fixed N (17% Nfda), increasing rice yields only moderately to 3.5–4.6 t ha−1. However, applying P to mungbean stimulated legume growth and enhanced the BNF contribution up to 21 kg N ha−1 (36% Nfda). Rice yields resulting from legume residue incorporation (“green manure use”–all residues returned and “grain legume use”–only stover returned) increased to 4.2 and 4.9 t ha−1 in the infertile and moderately fertile soil, respectively. The “forage legume use” (all above‐ground residues removed) provided no yield effect. In general, legume residue incorporation was more beneficial in the infertile than in the moderately fertile soil. We conclude that the inclusion of mungbean into the prevailing low‐input rainfed production systems of Cambodia can increase rice yield, provided that small amounts of P are applied to the legume. Differences in the attributes of the two major soil types in the region require a site‐specific targeting of the suggested legume and P management strategies, with largest benefits likely to accrue on infertile soils.

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Nutrient Status of Cambo dian Soils, Rationalisation of Fertiliser Recommendations and the Challenges Ahead for Cambodian Soil Science

Cited by 17 publications

References 10 publications

Importance of phosphorus and potassium in soil-specific nutrient management for wet-season rice in Cambodia

Importance of phosphorus and potassium in soil-specific nutrient management for wet-season rice in Cambodia

Potential yield and nutrient requirements of direct-seeded, dry-season rice in Cambodia

Effect of phosphorus management in rice–mungbean rotations on sandy soils of Cambodia

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