Towards Sustainable Use of Potassium in Pineapple Waste

Due to the 1997/98 haze problem in South-East Asia and the increasing need for sustainable food production and development, the usual management of crop residues (including pineapple wastes) through burning is prohibited. As a result, the need for alternative uses of pineapple wastes in pineapple production has been emphasized. This study investigated an environmentally friendly means of recycling pineapple leaves for agricultural use. Pineapple leaves were shredded and composted in a composting drum for 30 days. Part of the shredded leaves was ashed in a muffle furnace for 4 h. Humic acid (HA), K-fulvate, and K in HA and compost were analyzed using standard procedures. An ash to water ratio of 1:7 was used to extract 0.1 molar (M) KOH from the shredded leaves. The 0.1 M KOH contained 50% K and was able to extract 20% HA from the composted pineapple leaves. Percent K in the fulvate using 0.1 M KOH was 43. Besides serving as a foliar spray (supplement soil application K fertilizers), source of K for freshwater fish (e.g., tilapia), the HA produced can be used as a soil conditioner. Studies show that between 0.050–01 g of HA per kg soil retards runoff by 36% in sandy and sandy loam soils. The K-fulvate can be used as a fluid fertilizer. In addition, the pH of 2 of the K-fulvate suggests it could be used to dissolve phosphate rocks, particularly those in the arid regions where high soil pH does not facilitate the dissolution of these important rocks that serve as one of the sources of phosphorus fertilizer in agriculture

Temporal Variation of Ammonium in Sulfic Tropaquept Cultivated with Rice in Experimental Pots

Hypothetically, monitoring of soil solution NH4+-N dynamics may allow estimation of nitrogen (N) transformation rates such as the rates of nitrification, denitrification, mineralisation and immobilisation. Such observations can be used to evaluate and improve performance of N dynamics models for flooded rice systems. Therefore, the objective of this study was to evaluate temporal variation of ammonium dynamics in fertilised and flooded rice pots. Concentrations of NH4+-N were determined in soil solutions that were extracted by MacroRhizon samplers. MacroRhizon is a soil solution sampler with a pore size of 0.15 μm manufactured by Rhizosphere Research, the Netherlands. In comparison to typical soil sampling methods, some advantages of using MacroRhizon are repeated sampling at the same spot possible, easy to install and less disturbance to the soil due to the small diameter, and maximum pore size of 0.2 μm which requires no further filtering prior to chemical analysis. Results showed that under current agronomic and management practices, broadcast N application had no obvious and consistent influence on soil solution NH4+-N. Analysis of the results suggest that suitability of soil solutions extracted using the MacroRhizon samplers as alternatives for the labourious and destructive conventional soil samplings is subject to further investigation

Temporal Variation of Ammonium in Sulfic Tropaquept Cultivated with Rice in Experimental Pots

Hypothetically, monitoring of soil solution NH4+-N dynamics may allow estimation of nitrogen (N) transformation rates such as the rates of nitrification, denitrification, mineralisation and immobilisation. Such observations can be used to evaluate and improve performance of N dynamics models for flooded rice systems. Therefore, the objective of this study was to evaluate temporal variation of ammonium dynamics in fertilised and flooded rice pots. Concentrations of NH4+-N were determined in soil solutions that were extracted by MacroRhizon samplers. MacroRhizon is a soil solution sampler with a pore size of 0.15 μm manufactured by Rhizosphere Research, the Netherlands. In comparison to typical soil sampling methods, some advantages of using MacroRhizon are repeated sampling at the same spot possible, easy to install and less disturbance to the soil due to the small diameter, and maximum pore size of 0.2 μm which requires no further filtering prior to chemical analysis. Results showed that under current agronomic and management practices, broadcast N application had no obvious and consistent influence on soil solution NH4+-N. Analysis of the results suggest that suitability of soil solutions extracted using the MacroRhizon samplers as alternatives for the labourious and destructive conventional soil samplings is subject to further investigation