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Improvement of fertilizer management for enhancing rice productivity in Cambodia
Dissertation Abstract:
The rice cultivation area in Cambodia has been expanded gradually because of improvement of irrigation system, increase cropping season, and farmers converted floating rice to recession rice. Total rice production area in 2018 was 3.21 million ha in which wet season 2.66 million hectares and dry season 0.5million hectares. The average yield is 3.298T/ha (MAFF, 2017). The yield both in wet and dry season still lower than the neighboring countries. The Royal Government of Cambodia still put target to improve productivity and boosting rice export to the international market. Improvement of fertilizer management for enhancing rice productivity and economic efficiency of farmers in Cambodia. To achieve this goal, the studies were conducted in wet season 2013-2014, and 2016 and 2017 in wet and dry season.
The first study aimed to check yield increase and economic efficiency by different fertilization rates and combination of N-P-K to provide evidence-based recommendation for the best fertilization rates to rice farmers in Southern of Cambodia, second study aims to evaluate the importance of phosphorus and potassium in soil-specific nutrient management for wet-season rice in Cambodia and the third study aims to evaluate potential yield and nutrient requirements of dry-season rice in Cambodia, and the economic feasibility of soil-specific management recommended.
Based on the result from the three studies, it would be able to draw conclusion that
adding 20-25 kg of ha-1 and 15 kg of P ha-1 or just add only 25 kg of K ha-1 to all type of soils would improve yield and economic return for wet season rice especially Prateah Lang and Toul Samrong soil type. Although P and K used during Cambodia's wet season is uncommon, our results demonstrated the importance of these nutrients in improving the country's rice. The Prey Khmer soil contained around 80% sand, and rice yield responded most weakly to nutrient management. The moderate fertilizer input in the current soil-specific recommendation was effective on this soil type. While the grain yield increased with the higher fertilizer rate, the optimum rate to maximize the income was achieved at a rather low fertilizer rate, and hence the fertilizer cost should be considered before determining the best fertilizer management strategy. However, the applications of fertilizers more than an optimal level would not be necessary to achieve the maximum profit but also cause serious environmental degradation resulting in lower crop yields (K.M Atikuman Rahman et al. 2018). In this regard, the application rates of fertilizers should be carefully examined by considering the soil types and cropping season and soil property. For dry season, the potential yield from the experiments was 6-7 t ha-1 on the Toul Samroung soil, 5-6 t ha-1 on the Bakan soil, and 3-5 t ha-1 on Prateah Lang and Krakor soils. A rate of 140-60-60 kg ha-1 of N-P2O5-K20 was more than enough to achieve the best yields on any soil group. On the other hand, modest application rates in the soil- specific management (44-78 kg ha-1 of N, 23-28 kg ha-1 of P2O5, and 0-30 kg ha-1 of K10) proved reasonable for resource-poor farmers in Cambodia, since the treatment always provided more than 75% of the highest economic profit in high-input plots.
In order to confirm our implication in these studies, on-farm validation trials in multiple
locations are needed in future research. The result from these studies will contribute to the improvement of rice production and rice-farmer income through sharing the new recommendation to the technical department and research institutes for consideration to update soil specific nutrient management for rice production in Cambodia. Training of Trainers should be organized for provincial department of agriculture forestry and fisheries and farmer training on nutrient management and field demonstration of new recommendation should be conducted widely in the country. Since these studies were conducted only two years and on few soil types in only four provinces, the result is hard to conclude in general for Cambodia. So, similar studies in other sites of different soil types, seasons to cover the entire rice growing areas of Cambodia are needed. Furthermore, timing and fertilizer application methods, and effects of fertilizer application on pests and diseases should also be considered. Soil testing for the national data base should be conducted and soil specific nutrient management should be conducted every 10 years to maintain higher yields and better profitability for farmers in Cambodia.