THE INFLUENCE OF WEIGHT OF RYEGRASS PER UNIT AREA AND TREATMENT AT AND AFTER MOWING ON RATE OF DRYING

The rates of drying of perennial ryegrass, subjected to different trea tments at mowing and after mowing, were assessed in the field by weigh t change of grass fresh weight in wire-mesh trays over 3.5 d (76 h). I n a 5 x 3 x 3 factorial experimental design, the effects of five weigh ts of grass per unit area [1.5, 3, 6, 12 and 24 kg fresh material (FM) m(-2)], three treatments at mowing (no treatment, mower-conditioned, flail-treated) and three treatments after mowing (no treatment, invert ed, mixed) were examined. The experiment was replicated twice on 16 oc casions in 1992 at the Agricultural Research Institute of Northern Ire land. This gave a total of thirty-two replicates per treatment. The tr ays were weighed at 2-h intervals from 09.00 to 17.00 h each day. Data sets were restricted to rain-free days and also to the first day afte r mowing (day 1). On day 1, grass weight per unit area was a major fac tor dictating drying; reducing the grass weight per unit area of uncon ditioned grass from 6 to 3 kg FM m(-2) increased grass drying rate by 47%. There was no significant (P>0.05) benefit over the untreated gras s on day 1 from mixing or turning mower-conditioned or the uncondition ed grass. Mixing of the flail-treated grass improved drying rate signi ficantly (P>0.001) over the control. Over the whole 76-h period, the r elative benefit from either mower conditioning or flail treatment over no treatment was dependent upon both grass weight per unit area and i nitial dry-matter (DM) concentration. At higher initial DM concentrati ons (> 150 g kg(-1)) and lower grass weights (<6 kg FM m(-2)) both mow er conditioning using a nylon brush type conditioner and intensive con ditioning by flail treatment gave substantial increases in drying over no treatment. Moisture regain of grass exposed to overnight dew was s mall. Rain had a much greater effect than dew on subsequent moisture r egain. Unconditioned grass at 12 kg m(-2) retained 82% less water foll owing rainfall than unconditioned grass at 3 kg m(-2).