THRESHING INJURY AND MATHEMATICAL MODELING OF STORAGE DETERIORATION IN FIELD BEAN SEED (PHASEOLUS VULGARIS L.)

Studies were conducted at the International Center for Tropical Agriculture (CIAT) in Columbia on the production and storage of field bean (Phaseolus vulgaris L.) seed by small farmers. Two studies are reported, one on threshing injury and the other concerning the deterioration of bean seed during storage.;Field beans (cv. Calima) were adjusted to 8.0, 12.1, 16.1, 19.9 and 24.0% seed moisture and stored in hermetically sealed bags under a range (-15 to 60C) of temperatures and sampled for rolled towel germination during a two year period. Data were analysed using Ellis and Roberts' (1981) 'New improved viability equation': v = Ki - p/10('(Ke-CwLogM)-ChT-CqT2)) where v = probit germination, p = storage period, M = % seed moisture, T = storage temperature, by incorporating the angular transformation in a nonlinear regression model. R('2) on the basis of germination angle was 0.83. Parameter estimates were: Ki = 6.68, Ke = 9.08, Cw = 5.20, Ch = 0.0057, Cq = 0.00079. Evidence is presented that probit analysis should be conducted only on the portion of the seed poplation which is initially germinable unless the initial germination is higher than approximately 97%.;Eight cultivars of field bean at two ranges of seed moisture, 8-10% and 11-15%, were threshed by hand shelling, flail threshing inside sacks, open flail threshing on concrete and soil surfaces, and two mechanical systems; an Almaco small plot thresher and an Allesdrescher K thresher. Sack threshing recovered the most seed while open flail methods recovered 91-96% of the sack yield and mechanical methods 81-84%. The Almaco and Allesdrescher machines cracked 17 and 27% of the testas while the sack, concrete and soil flail methods cracked 6, 2 and 1% of the testas respectively. Under representative field conditions, mechanically threshed samples averaged 69-70% emergence while flail and hand shelled treatments averaged 77-79%. Though not different in susceptibility to threshing injury, hand-shelled white seeded lines averaged 63% emergence in the field under favorable conditions versus 89% for colored lines.