Grass Dry Matter Yield Research Articles

Herbage Production: Conventional Mixtures vs. Alternating Strips of Grass and Legume

AbstractSoil N influences the agronomic characteristics of grass‐legume herbage. A conventional grass‐legume stand was compared for productivity, quality, and botanical composition, at two locations for three production years, to three stands comprised of alternating, broadcast‐seeded strips (40‐, 60‐, or 80‐cm width) of pure grass and pure legume. Stands were of smooth bromegrass (Bromus inermis Leyss.) and alfalfa (Medicago sativa L.), and were grown under three N fertilizer treatments: N0 = no N; NGL = 150 kg ha−1 N applied uniformly to grass and legume; and NG = 150 kg ha−1 N but with the distribution of N restricted to plot areas seeded to grass. Grass dry matter (DM) yield declined as strip width increased with N0 (1.80‐0.92 t ha−1) and NGL (3.67−2.56 t ha−1), but was unaffected by strip width with NG (3.60 t ha−1). Herbage DM digestibility was 698, 699, and 708 g kg−1 for the 40‐, 60‐, and 80‐cm strip‐culture stands, respectively, and 690 g kg−1 for the conventional mixture. Legume concentration in harvested herbage (DM basis) ranged from 726 to 798, 489 to 524, and 411 to 426 g kg−1 for the strip‐culture stands with N0, NGL, and NG, respectively; it was 658 and 375 g kg−1 for the conventional mixture with N0 and NGL, respectively. Strip‐culture stands have potential for manipulating grass/legume ratios of herbage, and may provide a way to supply optimal N fertilizer to grass plants in grass‐legume associations, without relinquishing the N‐fixing contribution of the legume.

Effect of plant density and spatial arrangement on the yield of Leucaena leucocephala cv. Peru in subcoastal south-eastern Queensland

Leucaena (Leucaena leucocephala cv. Peru) was sown at 5 plant densities with 2 spatial arrangements at Brian Pastures Pasture Research Station, Gayndah, to determine the effects of these factors on leucaena and inter-row grass dry matter yield. During the 2 year establishment phase, yields of edible leucaena (leaves, pods, flowers and stems to a diameter of 5 mm) averaged 4400 and 2440 kg/ha respectively. Yields in subsequent years stabilised to an overall mean of 1360 kg/ha, with the amount of edible leucaena increasing with increasing leucaena plant density from 640 to 2260 kg/ha at 6000 and 62 500 leucaena plants/ha respectively. Edible leucaena yield for the mean of the 5 plant densities was increased by 38% when row spacing was doubled. Yields of both total and senesced leucaena were directly related to the annual rainfall. At the end of each growing season in May, edible leucaena yield remained stable between rainfall extremes of 492 and 878 mm while the amount of senesced leucaena litter increased. Edible leucaena yield was directly related to leucaena plant density (R2= 0.86). Annual total leucaena yield (edible leucaena yield plus leucaena litter) was best related to the plant parameters leucaena plant volume (R2 = 0.92), leucaena stem numbers (R2 = 0.90) and leucaena stem diameter (R2 = 0.90). Number of green panic (Panicum maximum var, trichoglume) shoots showed a marked increase at the 3 higher leucaena densities (mean of 28 shoots/m2) compared with the 2 lower leucaena densities (mean of 7 shoots/m2). Total soil nitrogen also increased at the 3 higher leucaena densities (mean of 0.186%) relative to the 2 lower leucaena densities (mean of 0.170%). Inter-row grass and grass litter yields both declined from 4640 and 4010 kg/ha to 31 10 and 2420 kg/ha respectively with increasing leucaena density. Maximum yields of edible leucaena were obtained when leucaena was grown at a density of 62 500 plants per ha in rows 0.8 m apart.

Effects of pesticides and fertilizer on invertebrate populations of grass and wheat plots in Kent in relation to productivity and yield

AbstractAt a site in Kent, perennial ryegrass (Lolium perenne) variety S24 and Italian ryegrass (L. multiflorum) variety RVP, wheat varieties Armada and Norman, and the original mixed grass ley were grown in small plots during 1982–84. Two toxic pesticides (phorate and aldicarb) were applied to half the total number of plots three times each year to eliminate soil invertebrate populations. Fertilizer was also applied to most plots. The yields of the crops, grown with and without pesticide, and the effects of the fertilizer were compared. Grass herbage yield was measured on three occasions during the summers of 1983 and 1984. Wheat grain yields were also determined in 1983.During the first year significant differences were not apparent in grass dry matter yield between pesticide‐treated and non‐treated plots, but significant differences were found in the second year. The perennial ryegrass was more susceptible to pest damage than the Italian ryegrass or the grass ley. Grass yields varied between cuts and in relation to variety and pesticide treatment, yields tending to be greater in untreated plots. Fertilizer treatment greatly increased grass dry matter yields, particularly with the Italian ryegrass. The effects of pesticide treatment on both wheat varieties varied although some yield enhancement was evident.Invertebrate animal populations in pesticide and fertilizer‐treated plots were also assessed in autumn 1982, spring and autumn 1983 and spring 1984. In contrast to pesticide treatment, fertilizer treatment had little effect on soil invertebrate populations. Nematode populations were reduced at each sampling occasion by the pesticide treatment. Slug populations were initially unaffected but were subsequently reduced. Leatherjackets, by far the most abundant pest in both grass and wheat plots, were markedly affected by pesticides on all sampling occasions. Generally, fewer soil‐dwelling dipterous larvae were recovered in spring than in autumn. Stem‐boring dipterous larvae were virtually absent.

Dry matter production by a subtropical grass (Makarikari grass) grown in association with a temperate annual legume (barrel medic) and nitrogen fertilizer in southern Queensland

The effects of a temperate annual legume, barrel medic (Medicago truncatula) cv. Cyprus, and five levels of fertilizer nitrogen (N), from 0 to 400 kg/ha.year, on the dry matter (DM) production and N economy of Makarikari grass (Panicum coloratum var. makarikariense) cv. Pollock, were investigated in a cutting experiment between 1973 and 1979. Each year, N fertilizer on grass alone increased both DM production and N uptake, up to N application rates of 200 and 400 kg/ha.year respectively. The mean annual effect of medic was to increase DM production and N uptake of associated grass each year by 90 and 130% respectively, and of the grass-medic system by 230 and 530%, respectively, for fertilizer rates between 0 and 100 kg N/ha.year. The increased DM production of associated grass occurred in summer and autumn; grass DM production was suppressed in spring, probably by competition with the medic. A trend for the DM yield of grass grown without medic to decline with time was most evident in the treatment without N fertilizer; in the comparable grass-medic pasture, grass DM production was as great in the sixth year as in the first. Medic DM yield varied with winter season rainfall. When the study concluded, the amount of N in the soil (0-10 cm depth) was higher after grassmedic than grass alone, except at the highest level of N fertilizer application. It was estimated that medic had fixed about 71 kg N/ha.year.

Subsidence of low moor peat soils in the western Netherlands

Three experimental fields were laid out to study the effects of deeper drainage on the processes of subsidence. It was found that 6 years after ditchwater levels had been lowered, surfaces had subsided 6–10 cm. Of this subsidence, 65% could be ascribed to shrinkage and oxidation of organic matter in the layer above the groundwater level and 35% to compression of the layer below groundwater level. Compression accounted for 1–4 cm of subsidence after 6 years. Because the deep peat is affected only very slightly by deeper drainage, it may be assumed that compression of it caused little or no subsidence over the past 1000 years in areas with high groundwater levels. By comparing the bulk density of organic matter in the layers above and below groundwater level, it was found that about 0.30 m, or approximately 15% of the total subsidence of 2 m in the past 1000 years, could be ascribed to shrinkage of the upper layer. This leaves 85% to be ascribed to the oxidation of organic matter. If it is assumed that higher contents in mineral elements in the upper layer result from oxidation of organic matter, the rate of oxidation can be calculated by comparing the bulk density of mineral elements in the layers above and below groundwater level. In this way oxidation of 1.75 m was estimated which would explain surface subsidence of about 1.75 mm per year. This theory is supported by the fact that organic soils supply more nitrogen to the crop than mineral soils. At deeper drainage of organic soils this additional N-supply increases considerably. The additional N-supply is calculated from the N-content of the dry matter yield of grass of the experimental fields. The loss of organic matter can be calculated from the additional N-supply, taking the N-supply of mineral soils as a reference level. According to this calculation, the annual losses of organic matter per hectare are 4 tons in shallowly drained and 12 tons in more deeply drained (0.5 m more) peat soils. With a bulk density of organic matter of the toplayer of 0.2 g cm −3, the rate of loss of organic matter is 2 mm per year at shallow drainage and it increases to 6 mm per year after 0.5 m deeper drainage. These rates of 2 and 6 mm per year are in good agreement with the soil losses above groundwater level measured by means of disks placed at various depths in the profile, some years after drawdown of the ditchwater levels. In this manner a plausible explanation can be given for the surface subsidence of the low moor peat soils in the western Netherlands.

Effect of mechanical defoliation on botanical composition and yield of a Townsville stylo-sabi grass sward

A sabi grass (Urochloa mosambicensis)-Townsville stylo (Stylosanthes humilis) sward on cleared land at Katherine, Northern Territory, was mechanically defoliated for three seasons. The wet season defoliation treatments were no defoliation, late light, early heavy, and regular heavy. The sward's defoliation responses were measured in terms of dry matter production, quality, and botanical composition. In the non-defoliated treatment, sabi grass was highly competitive and this grass dominance was not reduced by any of the mechanical defoliation treatments studied. The legume dry matter proportion declined consistently from an initial all-treatment mean of 66 per cent to 9 per cent in the third season. Annual grasses failed to colonize the sward. Sabi grass dry matter yield was unaffected by defoliation in the first season, although plant vigour was reduced resulting in yield reduction in subsequent years. Townsville stylo and total dry matter were reduced by heavy wet season defoliation. Legume weighted mean phosphorus concentration was increased by heavy defoliation, but sabi grass mean phosphorus concentration, although higher than for Townsville stylo, was variable and seasonally dependent. Weighted mean nitrogen concentration was generally higher with heavy defoliation for both Townsville stylo and sabi grass, although the legume nitrogen concentration was approximately twice that of sabi grass.

Wet season grazing of Townsville stylo pasture at Katherine, N.T

At Katherine, N.T., stocking rates of 1.33, 1.00, and 0.67 Shorthorn steers an acre for a period of 18 weeks in the wet season beginning January were imposed on established pastures sown to Townsville sty10 (Stylosanthes humilis) alone but subsequently invaded to varying degrees by annual grasses. The experiment was repeated over three years. There were no significant differences in mean liveweight gain per head over three years ; hence liveweight gain per acre at the heaviest stocking rate was approximately twice that at the lightest rate. The mean dry matter yield of grass increased significantly with decreasing stocking rate, but there were no significant differences between stocking rates in Townsville stylo dry matter yield, nitrogen yield, or phosphorus yield. Correlation coefficients were calculated using data from individual paddocks and years. There was a highly significant positive correlation between liveweight gain per head and pasture nitrogen yield, and between liveweight gain per head and pasture phosphorus yield.

The Plant-growth Stimulating Properties of Ethylene-bis-nitrourethane and Related Compounds

Ethylene-bis-nitrourethane (EBNU), NN'-dinitroethylene urea, and ethylene dinitramine were found to increase the growth of some broad-leaved plants (peas, broad beans, and tomatoes), grasses and cereals. Other plants were un affected, and furthermore experiments with peas showed pronounced differences between the responses of several varieties of one species. Treatment of dicotyle dons increased the growth of the stem by promotion of internode extension pos sibly based on enhanced cell growth. Leaf areas and dry weights were less affected. The leaf length of cereals was increased, and small improvements in the dry matter yield of grass were obtained in field experiments. Stimulated plants re mained relatively normal in appearance, and in some cases the effect of a single treatment with EBNU persisted throughout the entire vegetative development. In some respects the effects of EBNU resembled those of gibberellic acid, but important differences were found when the two chemicals were applied to a number of pea varieties, and when internode growth-rates were measured. EBNU and related chemicals stimulated the later stages of internode growth, high rates pro longing the period over which the internodes extended. It is suggested that they may antagonize processes leading to the cessation of cell growth. Pot and field trials suggest that the activity of EBNU is not sufficiently great to make it useful in agricultural practice. It is also known to be dermatitic, and its relatives are explosive.

Studies on lucerne and lucerne-grass leys VI. Further studies on the effect of systems of grazing management on the persistence of a lucerne-cocksfoot ley

1. Two experiments are described in which the effects of grazing a lucerne/cocksfoot ley at various intervals throughout the season were examined, together with the effects of a June hay cut and an autumn rest period. The results are discussed.2. In the year of treatment: (a) The wet year 1954 favoured the grass fraction and the dry year 1955 favoured the lucerne fraction but, in general, the proportion of lucerne in the sward decreased as frequency of defoliation increased. (b) The largest yields of lucerne dry matter were obtained from treatments that included a June hay cut and the largest yields of grass dry matter came from those treatments that included an autumn rest period, (c) Within the chosen programmes of defoliation, there was a tendency for greater yield of dry matter from those treatments defoliated four times when compared with one cut three times, but yields from treatments defoliated more frequently tended to be smaller, with a marked reduction from seven grazings.3. In subsequent years: (a) Treatments in the wet year had a greater effect on subsequent lucerne vigour than treatments in the dry year, (b) Yields of lucerne dry matter from three hay cuts in the first residual year were reduced by all the grazing treatments, the greatest difference occurring at the first cut. Lucerne yield decreased with increasing frequency of treatment defoliation. There was a tendency for the autumn rest period to increase lucerne yield and for the June hay cut to reduce it. (c) Total grass dry matter yield was greatly increased by grazing treatments, the majority of this difference occurring at the first cut, and it also increased with increasing frequency of treatment defoliation. (d) The proportion of cocksfoot in the grass fraction of the sward was reduced by treatments that included defoliation during the period September–October, and it was further reduced by treatments that included a June hay cut. (e) In the second year following treatment the effect of grazing on the grass fraction had disappeared but reductions in lucerne vigour from too frequent defoliation were still evident, though reduced.4. Grazing a lucerne/cocksfoot ley reduced the subsequent vigour of the lucerne more than would have been expected from cutting it a similar number of times. This reduction is attributed to increased competition from the grass arising from its response to nutrients in the excreta of the grazing animals. In a wet year four grazings caused a permanent reduction in lucerne vigour and more frequent grazing almost eliminated the lucerne, but in a dry year four grazings caused only a temporary reduction in lucerne vigour and had no lasting effect.5. The interval between defoliation and the subsequent onset of flowering in the lucerne was very much less in the hot dry year than in the cooler wet year. There appeared to be a relationship between the onset of flowering and the ability of the lucerne to recover from defoliation.