Water absorption characteristics of two newly-released maize hybrids, Obatanpa and Mamaba, during soaking were measured at four temperatures of 30, 40, 50 and 60ºC. The absorption kinetics followed the Fick's law of diffusion during the first hours of soaking. The values determined for water diffusion coefficients varied from 7.31 x 10 -12 to 9.33 x 10 -12 m 2 /s and from 6.30 x 10 -12 to 8.25 x 10 -12 m 2 /s for Obatanpa and Mamaba respectively. An Arrhenius-type equation was used to relate the diffusion coefficient of Obatanpa and Mamaba to temperature, and the energy of activation for Obatanpa and Mamaba was estimated. The values determined were 6.54 kJ/mol and 6.82 kJ/mol for Obatanpa and Mamaba respectively.

Abstract. Performance of a Sifang mini rice combine, originally developed in China, was evaluated under local farmer field conditions in Benin. Results from field evaluation show that the combine worked satisfactorily on less dense rice fields with minimal weeds at grain moisture contents between 19.1% and 20.1% w.b. on soils with moisture content from 23% to 33% d.b. while causing no significant changes to soil physical properties. With harvesting speed ranging from 0.8 to 4.5 km/h, the harvester had a field capacity of 0.10 to 0.39 ha/h and consumed fuel of up to 11 L/ha while having track slip of 6% to 9%. Harvesting using 2- and 1-L gear offered the best efficiency for IR841 and Nerica L20 rice varieties, respectively. As harvesting speed increased, harvesting efficiency decreased and crop throughput increased irrespective of rice variety. The combine produced low mechanical grain damage with total grain loss ranging from 1.43% to 4.43% and 1.85% to 5.6% for the IR841 and Nerica L20 rice varieties, respectively. At an investment cost of US$5000 and hiring at US$10 per h, owning the mini combine harvester becomes profitable after 342 h of machine use; equivalent to approximately 133 ha of paddy field harvested at a harvesting capacity of 0.39 ha/h. Further testing of the combine under a wide range of crop and soil conditions across different agro-ecological zones and economic comparison with manual harvesting is recommended. This would offer smallholder farmers diverse options of rice harvesting mechanization to facilitate future adoption of improved technologies. Keywords: Crop throughput, Field capacity, Field efficiency, Grain loss, Mini rice combine, Sifang.

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Coupled partial differential equations were developed to investigate which collector lengths are appropriate for drying and adsorbent regeneration under prevailing Ghanaian weather. Unlike approaches based on empirical data, the numerical model is more flexible. Effects of operational and design variables on outlet temperature and performance were systematically studied. Collector length and air speed affect performance indicators. Operational overall heat loss coefficient, an important characteristic of the collector, is not constant but varies during the day. With plausible physical parameters, the model describes the experimental data well. Collector lengths of 1.5 and 4.5 m suited drying and regeneration, respectively.

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Storage, handling, processing, and other postharvest operations of agricultural products require information about their physical properties for the design of related machinery. This study was carried out to evaluate the effect of drying on some physical properties of "asontem" cowpea variety within the moisture content range of 19.00% wb and 9.58% wb using standard techniques. Four levels of moisture content were used namely, 19.00%, 15.13%, 11.50%, and 9.58% wb. The average length, width, and thickness decreased with decreasing moisture content from 8.16 to 7.11 mm, 6.36 to 6.28 mm and 4.77 to 4.61 mm respectively. The geometric mean diameter, surface area, and volume decreased nonlinearly with decreasing moisture content from 6.27 to 5.89 mm, 123.88 to 109.46 mm 2 , and 130.23 to 108.02 mm 3 , respectively. 1000 grain mass decreased non-linearly from 132.85 to 120.92 g and true density increased non-linearly with decreasing moisture content from 1063.80 to 1185.92 kg/m 3 . The filling angle of repose decreased non-linearly from 29.34 to 27.92• , while the coefficient of static friction also decreased non-linearly from 0.36 to 0.29, 0.35 to 0.28, and 0.31 to 0.21 for plywood, mild steel, and rubber, respectively.

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Performance of a Yanmar DB 1000 mechanised paddy thresher was comparatively assessed against manual threshing by impact method using a locally-made wooden box for Amankwatia and AGRA rice varieties under farmer's field conditions at Nobewam in the Ashanti Region of Ghana. The mechanised thresher was evaluated at various threshing drum speeds (550 rpm, 600 rpm and 650 rpm) and feeding rates (200 kgh -1 , 400 kgh -1 and 600 kgh -1 ). Results showed that threshing was satisfactory at grain moisture content between 16.9% w.b. and 18.0% w.b. for both rice varieties. Threshing efficiency increased from 94.6% to 95.8% with no significant difference observed whereas cleaning efficiency decreased significantly from 84.2% to 81.6% with increasing feed rate irrespective of rice variety. Again, threshing efficiency increased with increasing drum rotational speed, irrespective of feed rate and rice variety. Percentage broken grain and grain loss both increased with increasing peripheral drum speed and paddy feed rate irrespective of rice variety. Average fuel consumption, physical energy requirement and threshing capacity increased significantly with increasing drum speed and feed rate. Crop moisture content and shattering ability influenced the threshing efficiency, threshing capacity, grain loss, broken grain, fuel and physical energy requirement at threshing. AGRA rice variety generally performed better than Amankwatia under both mechanical and manually threshing methods. Mechanised threshing was significantly better at reducing grain loss and physical energy demand whilst yielding over 200% higher threshing capacity than manual threshing by impact using the wooden box. Mechanised threshing was financially rewarding, yielding over 500% higher profit margin than the manual threshing option. Further research on optimum crop moisture content for improved threshing of different rice varieties is suggested.