Problem statement: Ammonia volatilization is a major pathway for nitrogen loss from surface applied urea. While all top-dressed ammonia and ammonium based N fertilizers can volatilize, the potential loss is greatest with urea and fluids containing urea. As much as 20-50% of N applied to soils is lost through volatilization alone. Thus, the objective of this laboratory study was to reduce ammonia loss from urea via mixing with humic and fulvic acids isolated from coal. Approach: This study compared four different types of treatments which were urea without additives (T1), urea with humic acid-powdered form (T2), urea with fulvic acid-liquid form (T3) and urea with humic and fulvic acids-liquid form (T4). Comparisons were made based on ammonia loss, soil NH 4 and NO 3 − contents as well as exchangeable cations in the treated soils. Soil samples from typic paleudults (Bekenu series) were used. Humic substances were isolated using standard procedures. Daily ammonia loss from soil was measured using a modified closed-dynamic air flow system method. Results: All of the treatments with humic substances significantly reduced ammonia loss ranging between 13 and 25% compared to urea alone. The treatment with both humic and fulvic acids (T4) showed pronounced ammonia loss reduction. All treatments with humic substances significantly increased NH 4 + and NO 3 − content in soil samples compared to urea alone except for treatment having humic acid alone (T2). Treatments with fulvic acid (T3 and T4) also showed significant increase in exchangeable K + and Na + compared to urea alone. The increase in the formation of NH 4 + over NH 3 , soil exchangeable cations and temporary reduction of soil pH may had retarded urea hydrolysis in the immediate vicinity of the fertilizer. Conclusion: Surface applied urea fertilizer efficiency could be increased if applied together with humic and fulvic acids.
Okra (Abelmoschus esculentus) is an important vegetable crop grown with high demand and economic value. Thus, to improve the growth and development of okra, organic fertilizer can minimize inorganic fertilizer usage. The experiment was carried out in a greenhouse for 6 weeks to compare the growth rate of okra between a combination of organic waste fertilizers and NPK fertilizer and to determine the most suitable organic waste fertilizer combination with NPK fertilizer for the growth and development of okra. The experiment was laid out in a randomized complete block design (RCBD) with 4 replications consisting of 5 treatments, where T0: no fertilizer, T1: NPK 12:12:17:2 (20 g), T2: NPK 12:12:17:2 (10 g) + vermicompost (25 g), T3: NPK 12:12:17:2 (10 g) + biochar (25 g), T4: NPK 12:12:17:2 (10 g) + chicken manure (25 g), respectively. Parameters assessed were plant height, number of leaves, chlorophyll content, number of fruits, fresh and dry weight, and soil pH. Results indicated that the growth and development of okra were significantly the lowest in T0 and T1 while the highest in T4. Okra in T4 showed the best performance by achieving the highest value for all parameters assessed after 6 weeks of planting. It can be deduced that NPK 12:12:17:2 (10 g) + chicken manure (25 g) might be the most suitable fertilizer combination to promote the higher growth of okra while reducing the dependency on inorganic compound fertilizers.
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