In this study, three paddy harvesting systems, manual harvesting of paddy (MHP), reaper harvesting of paddy (RHP), and combine harvesting of paddy (CHP), were evaluated considering field capacities, field efficiencies, time and fuel consumption, mechanization indices, greenhouse gas emissions, straw availability, and direct and indirect costs. Field experiments were conducted in the North Central Province of Sri Lanka. The effective field capacity, field efficiency and fuel consumption of the combine harvester were 0.34 hah⁻¹, 60.8%, and 34.1 Lha⁻¹, respectively, and those of the paddy reaper were 0.185 hah⁻¹, 58.2%, and 3.8 Lha⁻¹, respectively. The total time consumed by MHP, RHP, and CHP were 76.05 hha⁻¹, 39.76 hha⁻¹, and 2.94 hha⁻¹, respectively. The highest energy utilization was recorded by the CHP, at 1851.09 MJha⁻¹, while MHP recorded the lowest at 643.20 MJha⁻¹. The direct cost of the MHP was 1.50 and 1.52 times higher than those of the CHP and RHP, respectively. MHP recorded the lowest greenhouse gas emissions (32.94 kgCO₂eqha⁻¹), while CHP recorded the highest (176.29 kgCO₂eqha⁻¹). The RHP exhibited an intermediate level in all aspects. Although the CHP has higher field performance and direct costs, it has higher GHG emissions and indirect costs. Therefore, an optimum level of mechanization should be introduced for the long-term sustainability of both the environment and farming.

Crop water production function models (WPFMs) are required methods to study the relationships between yield and water consumption under regulated deficit irrigation (RDI). In this study, a pot experiment was established to study the effect of water deficit during both individual growth stages and across two consecutive growth stages of rice on yield, water consumption, and water use efficiency (WUE) in 2017 and 2018. Light, medium, and severe water deficits were set as 80~90%, 70~80%, and 60~70% of saturated soil moisture content, respectively. The accuracies of five WPFMs were tested based on the experimental results. The results showed that yields and WUE of a light water deficit were higher than those of medium and severe water deficits at each growth stage. The yields and WUE of light drought stress treatments in the flowering and milky stages were higher than the saturated soil moisture control by 4~7.4% and 5.3~20.6%, respectively. Water consumption decreased with increasing water deficit across two consecutive growth stages. The Minhas model had the highest simulation accuracy of the five WPFMs, with relatively lower AE, RMSE, C_v, CRM, and higher R², which were 0.0002, 0.0634, 6.9965, 0.0002, and 0.9951 in 2017 and 0.0110, 0.0760, 8.9882, 0.0131, and 0.9923 in 2018, respectively. The sensitivity indices for the Minhas model more accurately reflected the sensitivity of rice yield to water deficit at different growth stages in 2017 and 2018, compared with the Jensen model, Stewart model, Blank model, and Singh model. Rice yield was most sensitive to water deficit at the jointing and booting stage. The results indicate that the Minhas model is the most suitable WPFM for guiding rice irrigation practices in cold and black soil regions of China.

Appropriate technology for the conversion of solar radiation to thermal energy is vital for food dehydration. Solar drying considered an advancement of sun-drying is an efficient solar energy system. A reliable and low-cost multi-crop solar drying technique is required for small scale farmers in Sri Lanka. Therefore, the objective of this study was to develop a solar heater assisted multi-crop dryer for small scale farmers. The main components of solar dryer are flat plate solar collector, drying chamber, solar panel with air DC heater, turbo ventilator, exhaust fans, and temperature control system. The performance of the fabricated solar assisted multi-crop dryer with DC air heater was evaluated for drying rate and drying efficiency of three agro-products; bitter gourd (Momordica charantia), jackfruit (Artocarpus heterophyllus) and mushroom (Pleurotus ostreatus). The drying rates were 0.151 kgh-1 for bitter gourd, 0.145 kgh-1 for jackfruit, and 0.154 kgh-1 for mushroom. The efficiency of solar collector was 25.84%. The drying efficiencies for bitter gourd, jackfruit, and mushroom were 12.85%, 12.35%, and 13.15%, respectively. Further, favorable colour could be achieved by the modified solar assisted multi crop dryer. Therefore, the solar assisted multi-crop dryer designed in the present experiment is an effective method of converting solar radiation to thermal energy and could be recommended for small scale farmers in Sri Lanka for drying agro products. Further improvements are required to increase solar thermal efficiency.

Rice (Oryza sativa L.) is the staple food crop in Sri Lanka occupying 34% of the total cultivated area. Seed paddy production is one of the major economic activities in the paddy sector, which is fully mechanized only at the large-scale level. Unavailability of an affordable mechanical solution is a big barrier for entering small and medium scale producers in to the seed paddy industry. Therefore, the aim of this study was to introduce an efficient and affordable electrical motor driven small or medium scale paddy cleaning machine for seed paddy production. The main components of the machine are paddy sieving unit, blowing unit and stone separator. According to the variety of paddy, the sieve size of the sieving unit can be changed. The performance of the machine was evaluated using paddy samples with purposely added light and heavy impurities such as straw particles and different sized stones. The suitable speeds for the better operation of sieve, separator and blower were 90, 200 and 960 rpm, respectively. The separation percentages of the large, light, and same size impurities were 96%, 74%, and 86%, respectively. The effective capacity of the machine was 252 kgh-1 with 79% mechanical efficiency. Based on the overall satisfactory performance, the newly built paddy cleaning machine can be recommended to small and medium scale paddy farmers in Sri Lanka. The machine can be further developed with a magnetic separator for removing iron particles.

In this study, three paddy harvesting systems; manual harvesting of paddy (MHP), reaper harvesting of paddy (RHP), and combine harvesting of paddy (CHP) were evaluated considering field capacities, field efficiencies, time and fuel consumption, mechanization indices, greenhouse gas emissions, straw availability, and direct and indirect costs. Field experiments were conducted in North central province of Sri Lanka. The effective field capacity, field efficiency and fuel consumption of the combine harvester were 0.34 hah-1, 60.8%, and 34.1 Lha-1, respectively, and those of the paddy reaper were 0.185 hah-1, 58.2%, and 3.8 Lha-1, respectively. The total time consumed by MHP, RHP, and CHP were 76.05 hha-1, 39.76 hha-1, and 2.94 hha-1, respectively. The highest energy utilization was recorded by the CHP, at 1851.09 MJha-1, while MHP recorded the lowest at 643.20 MJha-1. The direct cost of the MHP was 1.50 and 1.52 times higher than those of the CHP and RHP, respectively. MHP recorded the lowest greenhouse gas emissions (32.94 kgCO2eqha-1), while CHP recorded the highest (176.29 kgCO2eqha-1). The RHP exhibited an intermediate level in all aspects. Although the CHP has higher field performance and direct costs, it brings higher GHG emissions and indirect costs. Therefore, an optimum level of mechanization should be introduced for the long-term sustainability of both the environment and farming.