Cone threshing of chaffy grass seeds to improve handling characteristics

Abstract

Cone threshing was used to remove awns, sterile florets and some surface hairs from the normal chaffy dispersal units of Andropogon gayanus, Bothriochloa insculpta and B. pertusa. This facilitated subsequent cleaning to increase analytical purity with little or no reduction in germination, even after storage for up to 20 months. Small scale commercial use of cone threshing to process 450 kg of B. insculpta seed was also monitored with similar results, although germination tests showed some evidence of more rapid deterioration in processed samples after storage for 25 months. About 50-60% of caryopses were removed from Chloris gayana seed by the same method, with little or no apparent reduction in germination when stored for up to 18 months. It was concluded that provided a seed lot does not contain an excessive amount of other seeds and is pre-cleaned to remove straw before cone threshing, subsequent cleaning could be largely restricted to aspiration. This sequence produces less bulky, higher quality seed that flows more readily. As a result, purity testing is faster and easier, storage and transport costs are reduced, and seed can be distributed more uniformly during sowing.