J.M. HOPKINSON and B.H. ENGLISH
Queensland Department of Primary industries, Research Station, Walkamin, Qld. 4872
Header harvest efficiency was monitored in seven seed crops of Panicum maximum cv. Gatton and six of Brachiaria decumbens cv. Basilisk grown on the Atherton Tableland, Queensland, between 1976 and 1979.
On average, direct heading recovered a little over half the pure seed of Gatton panic standing in the crop, gathering and separation losses each being about 25%. The operation did not selectively recover mature seed, and the characteristics of standing and harvested pure seed were alike. Gathering losses in signal grass were estimated at about 66% of the total pool of seed, which included detached seed caught in the mat of leaf. Separation losses amount to 16%. Separation was selective for mature seed, and the pure seed discharged over the straw walkers was predominantly immature.
Gathering losses in both species arose largely from seed being over-ridden by the cutter bar, the depth of cut being governed by the need to avoid intake of excess leaf and stem. Separation losses were due predominantly to inefficient threshing, the greater loss of Gatton panic by this route being tentatively attributed to its small seed size relative to that of the cereal grains for which threshing systems are designed.