COMPARISONS OF SHEEP AND GRAIN PRODUCTION FROM SYSTEMS OF PASTURE AND OATS A. AXELSEN,* F. H. W. MORLEY* and M. CROUCH* Summary Sheep and grain production were compared between whole-farm systems of improved pasture and of pasture plus one-third grazing oats, at two stocking rates, over three years. When ewes were grazing oats they gained more weight than ewes grazing pasture during the corresponding period, but only in one year did this result in higher weight gain for the whole year. In the same year, wool weight per head was higher at the low stocking rate. There was no indication that stocking rates could be higher on the oats than on the pasture system. The grain yield at harvest was insufficient to cover the costs of the enterprise if fertiliser nitrogen were used. I. INTRODUCTION Winter pastures grazed by pregnant ewes in the Tablelands of N.S.W. are often supplemented by fodder crops such as oats, but evidence in support of this practice is generally inconclusive. Wheeler (1963, 1965) reported higher herbage yields from winter crops of oats than from improved pasture, but did not get increased production from pregnant ewes. Crofts (1966) found substantial liveweight advantages with oats sown in March with fertilizer nitrogen at high seeding rates, but replication was not possible and grain yields were not presented. A valid assessment of fodder cropping must be based on comparisons among whole-farms, or on parts of whole-farm systems, which are sufficiently independent of interactions with other parts (Morley and Spedding 1968). This paper reports comparisons of sheep and grain production over three years at Canberra, A.C.T. between whole-farm system of improved pasture, and of two thirds pasture and one third oats for grazing and grain. II. METHODS AND MATERIALS In 1965, 1966 and 1967, oats were sown with the eight pastures evaluated by Axelsen and Morley (1968). The pastures consisted of one annual brome (Bromus mollis) and seven perennial grasses (Phalaris tuberosa, Phalaris hybrid, a local ecotype and a cv. Tasmania No. 1 of Lolium perenne, Currie and Brignoles cv. of Dactylis glomerata, and Festuca arundinacea), and each pasture included sown and volunteer legumes (Trifolium repens and subterraneum) and volunteer annual grasses (Hordeum Zeporinum and Bromus spp.). There were 16 plots of 0.4 ha and 16 plots of 0.32 ha. Each year, the same one third area of half the plots was cultivated and sown using methods suggested by Crofts (1966) as shown in Table 1. In 1965, sulphate of ammonia was applied at the same rate as to the *C.S.I.R.O., Division of Plant Industry, Canberra, ACT. r 422
TABLE 1 Oats sowing and grazing, and sheep schedule oats to small caged areas of the pasture to determine the effect of N on pasture growth. On each plot, six Border Leicester x Merino ewes (born in 1962), lambing in August-September, gave stocking rates of 15 and 18.75 ewes per ha. In 1966, lamb mortality had been high owing to an outbreak of vibriosis, with 40 per cent of all ewes affected, so weaners only were stocked at seven per plot from October 4 to December 2. All plots were divided into three equal areas and grazed in rotation as follows: in 1965, a two-paddock rotation on both systems while the oats were closed, and a three-paddock rotation for the remainder of the year; similarly in 1966, but the three-paddock rotation commenced three weeks earlier on the pasture than on the oats system; and in 1967, the pasture system was grazed on a three-paddock rotation throughout the year. Oats grazing times are shown in Table 1. Requirements for supplementary feed (using wheat grain) were similar on both systems in July and August 1965, and in August 1967; for three weeks from May 6, 1966 it was required for the oats system only where ewes received a total of 12 kg S.E. per head. Animals were fed a maintenance ration, only to prevent ewe deaths associated with severe loss of weight during pregnancy. Animals were weighed monthly, and wool weighed at shearing in November. The annual rainfalls from 1965 to 1967 inclusive were 450, 782, and 441 mm respectively. In 1965, rainfall to the end of June was only 70 mm, resulting in very little winter growth and no oats was available for grazing until after lambing. The crop was also grazed into late spring to get as much benefit as possible from grazing and no grain was available for harvest. In 1966, good early grazing was obtained and a satisfactory crop harvested. In 1967, rainfall to the end of June was 175 mm allowing some early grazing before lambing, but grain yields were low. Pasture and crop growth were measured by cutting quadrats to ground level before and after grazing. Grain was harvested with an auto-header. III. RESULTS (a) Animal Production Results in Table 2 show performance of sheep on the oats system less performance on the pasture system. Ewe weight gain before oats grazing began was 423
TABLE 2
greater (P < 0.001) on the pasture system in 1966 and 1967 at both stocking rates. However, while grazing oats, ewes gained more (P < 0.001) than did ewes on the pasture system, although only in one year (1966) did this lead to a gain for the whole year. Ewe wool weight was greater on the oats than the pasture system only in 1966 (P < O.OOl), and only at the low stocking rate. Lamb gain per day was greater on the oats system in 1966 (P < 0.05) and on the pasture system in 1967 (P < O.OS), but weaner gain was no different in 1966 when lambs did not graze oats. Ewe and lamb mortality were not effected by treatment; average ewe mortality over the three years was 11 per cent and 13 per cent for pasture and oats systems respectively, while average lamb mortality was 27 per cent and -21 per cent. - (b) Herbage Production Dry matter yields of pasture and oats are presented in Table 3. In 1965, pasture production increased with the addition of N (P < 0.05) and was greater than oats production at the low stocking rate (P < 0.001). In 1966, there was no difference between pasture and oats production at the first grazing in May but, by the August grazing, oats production had increased greatly over pasture production (I? < 0.001) and this difference was maintained to harvest at the low stocking rate. In the dry year of 1967, there was no difference in herbage production by the time of the first grazing in July.. (c) Grain Production Grain yields for 1966 and 1967 are presented in Table 4. Grain yields were extremely variable, presumably because of varying levels of defoliation and previous histories of plots. TABLE 3 J 425
(d) Pasture Spmecies Pasture species differences in ewe weight gain, ewe wool per head and lamb gain per day were similar to those from 1962 to 1966 shown by Axelsen and Morley (1968). However, the different pasture species, when associated with oats, did not give any consistent differences in yields of oats for grazing or for grain. IV. DISCUSSION (a) Animal and Herbage Production Ewe weight gains while grazing oats were much greater than those on pasture s during the corresponding period, even when there appeared to be little difference in total herbage dry matter available. Although higher herbage yields with crops have been reported by Crofts (1966), the benefits of winter forage cropping were dubious in the dry years of 1965 and 1967. In 1965, sowing was not until late April, but there was so little rain to the end of June that growth would have been no better with an earlier sowing. In 1966, oats conferred significant benefits. Thus the inclusion of oats in the system conferred the greatest benefit in the year in which it was least required. Differences in herbage production due to grazing pressure in previous periods (stocking rates) are so large that they emphasise the probable importance of increased stocking rates on the uncropped portion of the farm, which are necessitated by exclosure of portion for cropping - in this experiment for an average of 250 days. In 1966, the one third areas cropped with oats were stocked at the equivalent of 7.1 and 9.6 ewes/ha, while the associated two thirds of pasture areas had to carry 18.5 and 23.0 ewes/ha. It may well be that one third of the area for cropping is too high a proportion and the common farm practice of using a much smaller area of crop to finish stock for sale, or prevent pregnancy toxaemia, could give useful benefits. (b) Grain Production and Economic Assessment Evaluation of oats for grazing requires comparisons among at least three systems. These are (Morley 1968, p. 102): i. Grazing pastures without fodder oats, ii. Grazing with portion of the area devoted to fodder oats (or wheat or barley), iii. Grazing combined with grain production from a portion of the farm which is not grazed during the growing season, including the period of fallow, ripening, and harvesting. The results obtained in the three years of this experiment do not indicate marginal profits necessary to justify the outlay of some $40.0O/ha (Crofts 1966) on the cropped area of the farm (system ii.) unless the major costs of the enterprise are covered by grain production. This requires a minimum production of 1438 kg/ha (32 bushels/at at 50c/bushel), which was not obtained, even at the low 426
stocking rate in 1966 in this experiment, although extra value for wool could reduce this figure. Lower levels of fertilizer nitrogen may give satisfactory results and enable costs to be reduced. To compare systems ii. and iii. above, the effects of grazing on grain yields must be evaluated. Mengersen (1967) reported breeding of dual purpose oat varieties whose grain yields were little effected by grazing. Dan (1968) showed that clipping reduced grain yield, but suggested that it may be more economic in some years to graze the crop and suffer the consequent reduction in yield. In dry years, grazing may cost little in grain yield as production is already low. However, in 1968, Dann and Axelsen (unpublished data) measured reductions in grain yields from 2372 kg/ha without grazing to 2080 kg/ha with a June grazing, and to 1442 kg/ha with June plus August grazings, showing that one early grazing may cost little in grain yield but later grazings can reduce yield considerably. The grain loss of 638 kg/ha caused by later grazing (valued at $18.OO/ha) and the additional land use, seed, and fertilizer costs of the fodder crop over the grain crop (valued at $18.00/ha) would give total marginal costs of $36.00/ha of crop. If the crop occupied one third of the total area, total marginal costs of a fodder crop over a grain crop would be $12.00/ha over the whole farm. To cover this cost, 2.4 extra ewes/ha (giving marginal gains of $5.00 per ewe) would have to be carried without any loss in production per head over the whol*e year. However, there is little indication from these results that carrying capacity could be increased. Indeed, the benefits obtained were more pronounced at the low than at the high stocking rate. Obviously, one experiment such as this cannot answer all aspects of fodder cropping, including various combinations of management and production techniques. Nevertheless the crucial questions seem to be the costs of fertilizer N and especially the effects of grazing on yield of grain. These are being examined in further experiments. V. ACKNOWLEDGMENTS We wish to thank L. Coulton and P. Larkham for assistance and P. Dann for assistance and constructive criticism of the experiment. VI. REFERENCES AXELSEN, A., and MORLEY, F. H. W. (1968). Proc. Aust. Soc. Anim. Prod. 7: 92. CROFTS, F. C. (1966). Univ. of Sydney, School of Agric., Report No. 7. DANN, I?. R. (1968). Aust. J. exp. Agric. Anim. Husb. 8: 731. MENGERSEN, F. (1967). Agric. Gaz. N.S.W. 78: 633. MORLEY, F. H, W. (1968). In Pasture Improvement in Australia. (Ed. B. W ILSON.) (K. G. Murray: Sydney.) MORLEY, F. H. W., and SPEDDING, C. R. W.( 1968). Herb. Abstr. 38: 279. W HEELER, J. L. (1963). Aust. J. exp. Agric. Husbd. 3: 62. WHEELER, J. L. ( 1965). Proc. 9th int. Grassld. Congr. Brazil: 975.