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The Composition of Mekong River Silt and Its Possible Role as a Source of Plant Nutrient in the Delta
|Title:||The Composition of Mekong River Silt and Its Possible Role as a Source of Plant Nutrient in the Delta|
|Authors:||Nishina, Melvin Sanji|
|Abstract:||It is alleged that the flood waters which annually inundate most of the Mekong Delta add nutrient-rich sediment to Delta soils. To test the validity of this allegation, the mineralogical and chemical composition of Mekong River sediment as well as soils of the Mekong Delta of Viet Nam was examined to establish the relationship between sediment deposition and soil fertility.|
River sediment was collected at regular intervals from October 1972 to May 1973 at Long Xuyen, Cantho, and My Tho in South Viet Nam, Soils were collected along transects running perpendicular to the river at locations near the sediment sampling sites.
Small but significant differences in mineral, chemical, and acid extractable nutrient content were measured between sediment and soil, The sediment samples were higher in mica, hematite, kaolinite, feldspar, and chlorite-montmorillonite and lower in quartz contents, The sediment samples were also higher in magnesium, phosphorus, potassium, calcium, and manganese and lower in aluminum contents. The readily extractable phosphorus, potassium, and calcium content were also higher in the sediment than in soil samples.
Based on these data, the quantity of phosphorus, potassium magnesium and calcium added to a soil each year by sediment was computed. A one millimeter· thick deposit of one g/cm3 bulk density was assumed. The readily soluble nutrient added to a one Hectare area as measured by mild acid extraction amounted to 1.0 kologram P, 3.2 kilogram K, 4 kilogram Mg, and 50 kologram Ca per hectare. It was concluded that even if these computed values were doubled, the sediment deposit could not significantly increase the fertility of Delta soils.
Careful examination of the soil data confirmed the above conclusion. Soil data was examined on the assumption that soils which occur near the river bank would receive a larger quantity of sediment and therefore would contain a higher soluble nutrient content than soils which occur some distance from the river. The soil data did not bear this out.
Soil texture and soil moisture release data also did not vary with distance from the river channel.
Based on mineralogical, chemical, and physical analyses of sediments and soils of the Delta, it was concluded that the annual deposition of sediment does not measurably increase the fertility of Mekong Delta soils.
|Appears in Collections:||
M.S. - Agronomy and Soil Science|
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