Improving Liquid Fertilizer Urea Efficiency Using Humic Acids Additives Extracted from Tropical Peat
Kasim, Susilawati (2009) Improving Liquid Fertilizer Urea Efficiency Using Humic Acids Additives Extracted from Tropical Peat. PhD thesis, Universiti Putra Malaysia.
One of the most important sources of organic matter is peat. Being organic in nature, peat are high in humic and fulvic acids. These substances can be reconstituted with N and K to produce ammonium and potassium-h u mates (organic fertilizer). This could be realized if they could be rapidly and cheaply isolated from peat soils. Factors which affect the humic and fulvic acids isolation from soils include extraction, fractionation, and purification periods. Thus, part of this study investigated whether a relationship could be separately established between extraction time, fractionation time, and the yield of humic acids ( HA) of tropical peat soil (hemists), as well as the relationship between both variables on the yield of HA of this soil. M odified standard procedures using 0 . 1 M KOH (analytical grade) were used to isolate humic acids from the soil. Results showed that, there was a quadratic relationship between extraction period and yield of HA. There was however no relationship between fractionation period and yield of HA. There was negative correlation between the yields of extraction and fractionation periods. This finding enables the isolation of HA of hemists in less than 10 h instead of existing average period of 2 to 7 days, therefore helping in facilitating the idea of producing for instance ammonium-humate or potassium-humate (N and K foliar organic fertilizers) from peat. The second part of the study was development of NH4'" -K-humate by reconstitution of humic and fulvic acids. The organic fertilizers developed via reconstitution were evaluated under laboratory conditions. E ffectiveness of organic fertilizer in enhancing N availability was the main concern of this study. This was d ue to high N loss by N fertilizer (e.g. urea) after surface application. Nine treatments namely urea (solid), urea (liquid), ammoniu m sulfate (solid), ammonium sulfate (liquid), humic acids + urea, fulvic acids + urea, humic and fulvic acids (acidified) + urea and humic, fulvic acids (unacidified) + urea a nd control (soil alone) were used in this study with the a i m of reducing N loss from urea application. A closed dynamic air flow system was used to esti mate N loss from soil. Usage of fulvic together with u rea decreased soil pH and as well as ammonia volatilization. However, the use of HA significantly reduced ammonia volatilization. This suggests the effectiveness of the organic based fertilizer formulated in controlling N loss and enhancing N availability. Besides being effective in controlling N loss, promotion of plant growth and development are other factors which should be considered in order to confirm the effectiveness of the formulated organic fertilizer. Hence, a pot experiment (third part of the study) was set u p with seven treatments excluding liquid ammonium sulfate. Results showed that, organic based N fertilizers enhanced N, P a nd K uptake. They also promoted N use efficiency particularly for the treatments with fulvic acids.
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