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Organic residues as liming materials and supplementary nutrient sources for acid soils
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|Title:||Organic residues as liming materials and supplementary nutrient sources for acid soils|
|Authors:||Licudine, Danilo Lucero|
|Keywords:||Liming of soils -- Tropics|
Soil amendments -- Tropics
|Abstract:||Soil acidity is a major constraint to successful crop production in many highly weathered tropical soils. While liming of temperate soils causes immediate and favorable changes, tropical soils often react differently. Where lime is expensive, difficult to obtain, or ineffective at economic rates, alternatives or supplemental practices to liming must be sought. Recent research has shown that additions of organic wastes and green manures to acid soils could reduce AI phytotoxicity and increase crop yields. The "liming effect" of four organic manures (Ieucaena and cowpea green manure, chicken manure, sewage sludge) was quantified and compared with lime (CaCO3) in a greenhouse experiment. Lime at four different rates (0, 1/2, 1, 2X exchangeable AI of the unamended soil) and organic manures (20 g kg-1 soil) were mixed with two acid soils (Kaneohe series, Humoxic Tropohumult; Paaloa series, Rhodic Kandiudult) and then incubated for 1,6, and 12 months under greenhouse conditions. Aluminum sensitive legumes (Sesbania cochinchinensis and Desmodium intortum) were planted as test crops. Results showed that animal manures were more effective than their green manure counterparts as liming materials. In terms of detoxifying AI, increasing soil solution pH, and increasing plant root and shoot dry matter yield, animal manures were comparable to the highest rate of lime application. The liming effect of the organic amendments persisted up to one year after soil incorporation. To evaluate the persistence (residual) of the liming effect of the organic manures, the same soils were allowed to incubate for another 6 months without any additional amendments and then replanted. Chemical analysis showed that soil acidity effectively decreased while the supply of basic cations increased in the organically amended soils resulting in improved plant height and total dry matter yield of plants. The mechanisms that were responsible for the residual liming effect of the organic amendments were a) their ability to increase and maintain soil pH b) AI-organic matter complexation c) and ameliorative effect of Ca ions on AI toxicity. A 24-week incubation and leaching study was also conducted to determine the rate of N mineralization and ease of release of Ca, Mg, and K from the organic manures as well as their ability to reduce P sorption. Nitrogen in the animal manures was mineralized faster than that in the green manures. The faster rate of N mineralization in the animal manures could have been due to their lower C:N ratio. On the other hand, the higher lignin and polyphenolic contents of the green manures could have slowed the mineralization of N. The cations were released steadily from the decomposing organic manures during the entire incubation period and followed approximately the order, K > Mg ≥Ca. Among the organic amendments, chicken manure was the most effective while leucaena green manure was least effective in reducing P sorption. Animal manures also increased soil P levels better than the green manures. In the last experiment, the effectiveness of surface-applied animal manures in ameliorating acidity and increasing Ca concentration in a Paaloa subsoil has been compared with lime (CaCO3) and gypsum (CaSO4.2H2O). The animal manures were more effective than lime and gypsum in increasing Ca and decreasing soil solution AI and AI saturation in the subsoil, particularly below the 15-cm depth. Organic anions were also produced during the decomposition of the animal manures as evidenced by an increase in the soluble C levels of the animal manure treated soils. The movement of Ca down to the subsoil may have been facilitated by the formation of Ca-organic anion chelates which could move easily down the soil profile.|
|Description:||Thesis (Ph. D.)--University of Hawaii at Manoa, 1995.|
Includes bibliographical references (leaves 167-170).
xx, 170 leaves, bound ill. 29 cm
|Rights:||All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.|
|Appears in Collections:||CTAHR Ph.D Dissertations|
Ph.D. - Agronomy and Soil Science
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