The effect on annual dry matter yield of using a hand-controlled mower or a plot harvester for cutting herbage on small-plot trials

A sward of S24 perennial ryegrass was sampled at 4-weekly intervals over two seasons with either a Haldrup 1500 plot harvester or a hand-controlled mower fitted with a fixed reciprocating cutter bar. Plot dimensions were adjusted to the width of the machines'cutter bars (1.5 m and 1.0 m respectively) so that there were no discard areas to require removal. Plots were cut either once, or twice in opposite directions. After cutting, residual stubble heights and the proportion of ground surface covered by leaf laminae were recorded.
Mean annual dry matter (DM) yields recorded in ten harvests made each year showed no overall significant difference between the machines. However, previous practice had been to sample plots with one pass of the hand-controlled mower and to trim the sampled area while removing the usual discard strips. The comparison of annual DM yields from one cut taken with the Haldrup or from two cuts taken with the mower, but with the yield at the second cut excluded, showed a mean advantage of 1.55 t DM ha⁻¹ a⁻¹ for the Haldrup technique or a 14.6% increase over previous practice.
Cutting twice significantly ( P <0.001) reduced herbage production by a mean of 0.85 t DM ha⁻¹ a⁻¹, mean residual stubble height by 9.8 mm and the proportion of ground covered by leaf laminae by 9.8%. Provided that judgment is exercised when planning treatments and layout of trials, it is concluded that the Haldrup 1500 plot harvester is a valuable labour-saving tool. However, DM yields from trials cut frequently with this machine are likely to exceed those from similar trials cut with a hand-controlled mower, following the usual G.R.I. Staff (1961) technique.