Current practices in rice production leave a huge amount of wet straw on the field, which cannot be used as feed or for food production. Compost production is one way of effectively utilizing rice straw. Spent rice straw from mushroom production is also used as compost but this has low nutrient value and is poorly decomposed when using it as a soil improver. This wet, low-quality straw, as well as byproducts from mushroom and cattle feed production, could be used to produce better-quality compost to return nutrients back to the field. Mechanization in mixing the materials, i.e., a compost turner, is necessary to have good aeration, increase the decomposition process, and reduce labor cost. This chapter provides an overview of composting technology and current practices of rice-straw composting. Updated information on this topic, resulting under the current BMZ-funded IRRI rice-straw management project (2016)(2017)(2018)(2019), which has been implemented in Vietnam and the Philippines, is also included here, particularly in the sections on vermin-composting and mechanized composting.
A flatbed dryer with a reversible airflow was introduced in the Philippines through a collaborative project between Nong Lam University of Vietnam and the Philippine Rice Research Institute (PhilRice). In this design, airflow is reversed at some point during the drying period to achieve uniform drying without mixing the grain.
An 8-ton capacity dryer was constructed at PhilRice Central Experiment Station in Nueva Ecija to evaluate its performance and adaptability under Philippine conditions. Appropriate and locally available materials were used in the construction of the pilot unit. Nine (9) additional dryers were then constructed at PhilRice stations (Nueva Ecija, Isabela, Negros, Agusan, Central Mindanao University, and Midsayap) that served as pilot units for technology promotion in their respective areas of coverage. Performance of the dryer was evaluated in terms of the following parameters: (1) drying; (2) quality of dried grains; and (3) economic analysis of using the dryer. The performance evaluation was conducted in three drying batches of newly harvested rice seeds.
Paddy dried with the reversible airflow flatbed dryer at full load capacity has a uniform moisture content with one percent (1%) moisture gradient at different layers of the grain mass along the depth and across the drying bin. The drying rate was 1% moisture reduction per hour.
The drying cost of using the reversible dryer is PhP0.74 per kg which is lower than the prevailing mechanical drying cost of PhP1.13 per kg. It has a payback period of 2.5 years and break-even point of 53.0 batches/year. To date, eight (8) privately-owned units have already been constructed and fully operational in the provinces of Nueva Ecija, Quirino, and Bukidnon, with PhilRice receiving inquiries from interested individuals here and abroad regarding the technology.
Rice straw is a rice by-product, which is currently mostly wasted in Vietnam, in particular in the Mekong delta. At present, the cost of straw gathering is increasing because of the increased use of combine harvesters. High labor cost and lack of labor makes manual collection unfeasible. Farmers therefore often just burn it, which causes pollution, increased greenhouse gas emissions and loss of opportunities to value add. An economic and environmental evaluation and technical field testing of a straw baler with 4 ha/day capacity was therefore conducted in Long An province. During the field testing data on the gathering capacity, fuel consumption, labor requirement and other cost items were collected. The test results showed that the baling cost is US$19.0 per ton of rice straw, the pay-back period of 2.1 years and the internal rate of return of 38%. In addition to the baling cost, the transportation cost varies from US$24 for a distance of 100 km to US$32 for 150 km. The benefits of the machine are not only economical but also include the reduction of field burning.
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