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Evaluation and Development of Lime-based Products to Reduce Phosphorus Loss from Agricultural Soils

出版	McGill University Libraries, 2020
URL	http://books.google.com.hk/books?id=OGsCzgEACAAJ&hl=&source=gbs_api

註釋"Phosphorus loss from agricultural fields is one of the main contributors to the rapid eutrophication of lakes and rivers. There exists an urgent need for cost-effective novel materials as soil amendments to mitigate phosphorus loss. Lime-based products, as high calcium-containing materials, could be promising soil amendments in retaining phosphorus in the soil. However, limited study has been conducted on lime as a phosphorus-immobilizing amendment in neutral and alkaline soils. Therefore, the main goal of this research was to evaluate the effectiveness of existing lime-based products on reducing phosphorus concentration in the leachate from common agricultural soils without interfering with crop growth as well as to develop a novel, cost-effective lime-based product to increase soil phosphorus adsorption capacity in the soil. This principle goal was achieved through 5 main objectives by both laboratory and lysimeter experiments as follows. Based on a laboratory study with repacked soil columns amended with various application doses of four different lime products, high calcium hydrated lime and lime kiln dust #2 were able to reduce phosphorus concentration in the leachate from clay loam soil columns to less than 0.03 mg L-1 at the lowest application dose of 1% by air-dried soil mass. In order to study the interactions between lime and phosphorus leaching in different soil types with alkaline pH, intact soil columns with three different soil textures of sandy loam, loam and clay loam were studied and compared to laboratory repacked columns. The results showed that hydrated lime applied to the top 5 cm of soil could significantly reduce soluble reactive concentrations in the leachates from sandy loam and loam soil columns in both intact and repacked columns, while soluble reactive phosphorus concentrations in the clay loam soil leachates did not show a significant change. Total dissolved phosphorus was reduced in limed loam and limed clay loam leachates in indoor intact and repacked columns. In order to study the effect of lime application on phosphorus leaching and soybean growth at field-scale under natural conditions, lysimeters packed with sandy soils of neutral pH were used. The results showed that lime could significantly reduce soluble reactive phosphorus in the leachate collected from lysimeters by 50% without having negative impacts on soybean growth. Soybean yield was increased by 10% with lime treatment. Adsorption studies were conducted on the four different soil types (sandy, sandy loam, loam, and clay loam) amended with high calcium hydrated lime and lime kiln dust. The results demonstrated that soils amended with both hydrated lime and lime kiln dust significantly increased the Freundlich adsorption coefficient by 3.2, 2.4, 2.0, and 1.6 times in loam, sandy, sandy loam, and clay loam soils, respectively. Although the hydrated lime showed higher potential to increase the maximum adsorption capacity in comparison to lime kiln dust, they both exhibited similar performance in lower phosphorus concentration ranges. Given the potential of lime kiln dust, and being inexpensive, this product was modified through an iron-coating procedure to further increase its adsorption capacity and to develop a neutral pH product. The novel iron-coated lime kiln dust had a pH of 7.65 and an increased surface area of 35 m2 g-1. Both image and chemical analysis confirmed the presence of iron loads on the lime kiln dust (16% of total mass). The clay loam amended with the iron-coated lime kiln dust had an increased phosphorus adsorption capacity by 30%, while the Langmuir phosphorus adsorption affinity was increased by 4 times compared to the non-amended clay loam soil. Given the simple development procedure, high efficiency, and low-cost final product, the iron-coated lime kiln dust could be a promising soil amendment to increase soil phosphorus adsorption to eventually mitigate rapid eutrophication of downstream water bodies"--