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Soil Mechanics 2018 Chapter 2: Review of Related Literature and Studies Related Studies In the paper, “Soil properties of major irrigated rice areas in the Philippines”, discussed the productivity of irrigated lowland rice (paddy) fields that is controlled by soil properties. Hence, this study was conducted to assess the soil pH, organic matter (OM) and available phosphorus (P) levels, and soil texture in the major lowland areas of the Philippines. It also determined the factors that control the levels or nature of soil properties. Thirty-two lowland soils were collected from the country's characterized paddy soils. Results showed that paddy soils had slightly acid to very strongly acid pH due to the removal of basic cations during crop uptake as these soils are continuously producing high rice yields. Most Laguna, Bicol, and Mindanao soils had high OM contents (>5.8%) due to high precipitation, shallow water table, and poor drainage characteristics of such soils. Most Central Luzon soils had low and medium OM contents (<3.8%) due to the region's low precipitation. Soil OM contents were also controlled by the amount of clay. The Villasis (Pangasinan), Sta. Rosa City b (Laguna), Polangui (Albay) and San Miguel (Iloilo) soils had the highest amounts of available P (>37 mg kg(-1)) because they had medium acid to neutral soil pH ranges that allow P availability. Meanwhile, most Central Luzon soils had low available P levels (<5.4 mg kg(-1)) due to their strongly acidic pH that cause P precipitation. Soils on floodplains and natural levees have high silt contents, while soils on backswamps have low sand and high clay contents. The study confirms that paddy soil properties are controlled by farm practice, precipitation level and landforms, and are related with each other. Incorporation of rice biomass, especially biochar, and organic fertilizers from outside sources is recommended for
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  • Spring '16
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