ALBERT

Notes: Two small-plot experiments were carried out to assess the influence on herbage dry matter (DM) production, chemical composition and soil fertility status of applying undiluted silage effluent at a range of application rates and intervals after a silage cut. In the first experiment, in 1990, silage effluent was applied at 25, 50, 100, 150 and 200 m3 ha−1 1, 8, 15 and 22 d after a silage cut in August. In the second experiment, in 1991, silage effluent was applied at 7, 14, 21, 28, 35, 42, 49, 75, 100, 125 and 150 m3 ha−1 1, 4, 8, 15, 22 and 29 d after silage cuts were taken from different sites in May, July and August. An untreated control and an Inorganic fertilizer treatment were incorporated in both experiments. The immediate effects of the treatments on herbage yield, chemical composition and soil nutrient status were assessed 6–8 weeks after the initial application; residual effects on herbage and soil fertility were measured at a subsequent harvest. Compared with the untreated control, herbage yield increases were obtained with increasing rates of effluent application. Although there was evidence that higher yields could be obtained from earlier applications, up to 50 m3 ha−1 of effluent could be applied up to 15 d after taking a silage cut with little damage to the sward. Delaying the timing of application, and increasing the application rate, increased the proportion of the sward which was damaged; this reached a maximum of 0·84 when the highest application rates were applied 29 d after a silage cut. The increase in the proportion of dead herbage in the sward, associated with increasing rate of effluent application, reduced the quality of the herbage harvested in Experiment I. In Experiment 2 the N, P and, in particular, the K content of the herbage increased with increasing rate of effluent application, whereas the effect on Mg content was variable with contents generally being less than 2·0 g kg−1 DM. Apparent recovery of nutrients applied in the effluent was both low and variable ranging from 0·58 to −0·03 for N, 0·10 to −0·005 for P, 0·34 to −0·02 for K and 0·21 to −0·002 for Mg over both experiments. Effluent had little effect on soil pH, whereas P and, in particular, K contents increased with increasing rate of effluent application. There was evidence that effluent had a beneficial effect on both herbage yield and chemical composition at the residual cut, the extent depending upon rate and time of effluent application.

Notes: Results from a series of five small-scale plot experiments which simulated different strategies for lowering ammonia volatilization following slurry application to grassland are reported. Strategies studied were band spreading, shallow-channel application, spike injection, rate of surface application and dilution. Volatilization was measured over the first 4 h following application with ventilated enclosures. Band spread slurry resulted in 0·4 of the volatilization that occurred from surface application of the same rate of slurry. The benefit of band spreading was shown to arise from higher application rates in the bands when compared with the same quantity of slurry spread over the surface. When surface-spread slurry was applied to the same depth of slurry as in bands, the volatilization per unit volume of slurry was the same. Shallow-channel application was more effective than band spreading and lowered volatilization per unit volume of slurry to 〈0·1 of that from surface-spread slurry. Spike injection was equally effective as shallow-channel application but, owing to perceived difficulties in machine design, construction and operation, was deemed impractical. Shallow-channel application has potential, though further work is required to optimize centre-to-centre spacing of the channels. As the application rate of surface-applied raw slurry increased, ammonia volatilization per unit volume of slurry applied decreased. Application at 50 m3 ha−1 resulted in 0·4 of the specific volatilization per unit volume of slurry that occurred at 6·3 m3 ha−1. Within the dilution treatments, the amount of water added to the slurry was linearly and inversely related to volatilization. At a dilution of 0·9-1·2:1 water: slurry the specific volatilization per unit volume of slurry was 0·5 of that from undiluted slurry.

Notes: The rates of drying of herbage, cut from perennial ryegrass (Lolium perenne L.) – dominant swards and subjected to different treatments, were investigated under field conditions by changes in weight of herbage in wire mesh trays in 1995 and 1996. A series of replicated factorial experiments studied the effects, in different combinations, of intensity of conditioning achieved by passing the cut herbage through a laboratory-scale macerator zero (0C), once (1C), three (3C) or six (6C) times; weight of herbage per unit area equivalent to 450, 675 and 900 g dry matter (DM) m−2. In one experiment, pressing the herbage to form a mat was incorporated into the experimental design. A further experiment investigated the effect of varying the proportion of conditioned herbage in the herbage mass from 0·00, 0·25, 0·50, 0·75 and 1·00 on drying rate. On each occasion the trays plus herbage were weighed at hourly intervals over an ≈6-h period and the DM content of the herbage estimated from the change in weight. On all occasions, conditioning and weight of herbage per unit area significantly (P 〈 0·001) influenced herbage drying rate. Lowering the weight per unit area of both unconditioned and conditioned herbage increased the rate of moisture loss. Unconditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was on average 1·5–1·8 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Similarly, conditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was 1·8–2·3 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Increasing the level of conditioning produced a non-linear response in rate of moisture loss, consequently 3 passes through the macerator produced 〉0·95 of the total moisture loss that was produced by 6 passes through the macerator. Increasing the proportion of conditioned herbage in the herbage mass increased rate of moisture loss and consequently final DM content (P 〈 0·001) although there was little effect from increasing the proportion of conditioned herbage above 0·75. The effects of conditioning and weight of herbage per unit area treatments on total nitrogen , water-soluble carbohydrate and acid-detergent fibre concentration of the herbage were small.

Notes: The rates of drying of perennial ryegrass, subjected to different treatments at mowing and after mowing, were assessed in the field by weight change of grass fresh weight in wire-mesh trays over 3·5 d (76 h). In a 5 × 3 × 3 factorial experimental design, the effects of five weights 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, inverted, mixed) were examined. The experiment was replicated twice on 16 occasions in 1992 at the Agricultural Research Institute of Northern Ireland. This gave a total of thirty-two replicates per treatment. The trays 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 after mowing (day 1). On day 1, grass weight per unit area was a major factor dictating drying; reducing the grass weight per unit area of unconditioned 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 grass on day 1 from mixing or turning mower-conditioned or the unconditioned grass. Mixing of the flail-treated grass improved drying rate significantly (P 〉 0·001) over the control. Over the whole 76-h period, the relative benefit from either mower conditioning or flail treatment over no treatment was dependent upon both grass weight per unit area and initial dry-matter (DM) concentration. At higher initial DM concentrations (〉150 g kg−1) and lower grass weights (〈6 kg FM m−2) both mower conditioning using a nylon brush type conditioner and intensive conditioning by flail treatment gave substantial increases in drying over no treatment. Moisture regain of grass exposed to overnight dew was small. Rain had a much greater effect than dew on subsequent moisture regain. Unconditioned grass at 12 kg m−2 retained 82% less water following rainfall than unconditioned grass at 3 kg m−2.

Notes: The effects of forage matting on rate of grass drying and silage fermentation, digestibility, and intake were examined using perennial ryegrass swards. Treatments compared were: forage mats, where grass was processed through a laboratory scale macerator prior to matting and wilting to 228 g dry matter (DM) kg−1 (FM treatment); unconditioned grass which was direct ensiled at 163 g DM kg−1 (DE treatment); unconditioned grass which was wilted for the same period as FM to 213 g DM kg−1 (UC treatment); unconditioned grass which was wilted to 234 g DM kg−1 (UC25, treatment). All forages were dried on black plastic sheeting. For each treatment a total of approximately 80 kg grass DM was ensiled in seven 290 I plastic bins for 136 d prior to feeding to wether sheep. A further total of 14 kg grass DM from each treatment was ensiled in twenty-one plastic pipes (152 mm diameter, 762 mm long) to give a total of 84 pipes. Rate of silage fermentation was determined by destructively sampling pipes following 1, 2, 4, 6, 13, 20 and 50 d of ensilage. Over the mean wilting period of 6·9 h, grass from the FM treatment dried significantly faster (P 〈 0·001) and required less solar energy per unit of moisture loss than unconditioned grass. The rate of grass drying was highly correlated with solar radiation. The FM treatment did not influence the rate or extent of silage fermentation. The intakes and digestibilities of FM, UC and UC25 were not significantly (P 〈 0·05) different from each other but were higher than for the DE treatment (P 〈 0·05 for digestibility and NS for intake). In Northern Ireland it is unlikely that there will be sufficient solar radiation to allow forage mats to be made, wilted to a level to prevent effluent production and harvested within one working day. Further work is required to optimize mat-making technology for more rapid drying and to determine the effect of adverse weather on nutrient losses from mats.

Notes: The rates of drying of cut perennial ryegrass (Lolium perenne L.) herbage over short periods of time were measured in four experiments in a controlled environment room. Standard weights of 33·7 g grass dry matter (DM) were placed in half the area of wire-mesh trays (0·5 m long × 0·3 m wide × 0·07 m high with 11-mm-square mesh) which, so as to simulate conditions in a swath, were supported on wooden frames within dark plastic boxes 25 mm above 35-mm-thick wet sponges. The trays of grass in the controlled environment room were weighed hourly for 7 h, drying rate being assessed by the change in grass fresh weight. Light was supplied from 400-W mercury vapour lamps, while an air conditioning unit within the controlled environment room allowed control of vapour pressure deficit (VPD). Only one particular VPD could be created on any one day and resource limitations restricted the study to one replicate per day. The first experiment correlated drying rates under the mercury vapour lamps with drying rates in the open air under sunshine over 3 d. This work showed that a distance of 200 mm between the tray and lamps equated to 1081 W m–2, 400 mm to 432 W m–2 and 600 mm to 281 W m–2. Experiment 2, conducted with previously frozen grass, was a 4 × 4 factorial design with light intensity and VPD as factors. The third experiment (Experiment 3) compared the drying rate of freshly cut grass with grass that had previously been frozen in a 2 × 2 × 2 factorial design with the two grasses, two light intensities and two wind speeds as factors. The final experiment (Experiment 4) was a 3 × 2 × 2 factorial design with light intensity, VPD and wind speed as factors. A wind of approximately 3 m s–1 was simulated using a 22-mm, 30 W fan set in a fixed position 600 mm from each tray plus grass. Fresh grass was cut each morning of the experiment. There were six replicates of each treatment. The effect of the three radiation intensities on grass DM concentration in Experiment 2 was highly significant (P 〈 0·001). VPD had less effect (P 〈 0·05). Results from Experiment 3 showed that previously frozen material dried much more rapidly than fresh grass and as a result would not simulate actual grass drying in the field. Consequently in Experiment 2 fresh grass was used as opposed to previously frozen material. In Experiment 4, light intensity had the greatest influence on grass drying followed by VPD and wind speed. However, the influence of wind speed was variable. A wind speed of ≈3 m s–1 increased the rate of water loss from grass with a low initial DM concentration (〈160 g kg–1) receiving low levels of solar radiation (281 W m–2), while at higher initial DM concentrations (〉210 g kg–1) and higher solar radiation levels (432 W m–2) the effect of wind was to slow grass drying. The results from Experiments 2 and 4 also indicated that high levels of either wind (3 m s–1) or VPD (〉6 mbars), when associated with low levels of solar radiation, resulted in large increases in grass DM concentration. However, these extreme weather conditions are unlikely to occur in practice.