Spear Grass Research Articles

Polysaccharides of tropical pasture herbage. II. A xylan from the leaf of spear grass (Heteropogon contortus)

Alkaline extraction of spear grass holocellulose gave a xylan which was purified by fractional precipitation as a copper complex. Acid hydrolysis yielded L-arabinose, D-xylose, and an aldobiouronic acid consisting of D-xylose and 4-O-methyl-D-glucuronic acid. Hydrolysis of the methylated xylan gave 2,3,5-tri-O-methyl-L- arabinose, 2,3,4-tri-, 2,3-di-, and 2-O-methyl-D-xylose, and 3-O-methyl-2-O-(2,3,4-tri-O-methyl-D-glucopyranosyluronic acid)-D-xylose. The conditions for isolation of the methylated sugars for gas chromatography were investigated with particular reference to difficulties arising from volatility of the tri-O-methyl pentoses. The xylan is composed of chains of 1,4-linked �-D-xylopyranose residues to which are attached single units of L-arabinofuranose at position 3 and 4-O-methyl-D-glucuronic acid at position 2 of the basal residues.

The effect of dicalcium phosphate supplements on the intake and digestibility of Townsville lucerne and spear grass by sheep

Sheep were fed either Townsville lucerne (Stylosanthes humilis) or spear grass (Heteropogon contortus) with and without dicalcium phosphate for an 11-week period. Voluntary intake, dry matter digestibility and liveweight changes of the animals were measured. Sheep fed Townsville lucerne gained body weight whereas those fed spear grass lost weight. Added dicalcium phosphate (4.5 g/day) increased dry matter intake and liveweight gain of the sheep fed Townsville lucerne, but not the digestion coefficient. Sheep consuming spear grass did not respond in any way to the supplement. All sheep fed spear grass received urea daily (2.9g N/day) as a nitrogen supplement. The difference between the two groups in response to dicalcium phosphate is discussed in terms of the chemical composition of the two feeds.

Effects of sodium sulpate and gluten supplements on the intake and digestibility of a mixture of spear grass and Townsville lucerne hay by sheep

Voluntary intake and dry matter digestibility of a mixture of 80 per cent spear grass hay and 20 per cent Townsville lucerne hay by sheep, in 'metabolism cages, supplemented with sodium sulphate, gluten, or sodium sulphate and gluten, were measured during a six-week experimental period. Apparent retentions of nitrogen, sodium, potassium, calcium, and phosphorus were also determined. All sheep receiving supplements gained weight whereas sheep on the basal ration lost weight. After four weeks supplementation, sheep receiving gluten alone or gluten + sodium sulphate consumed 64 per cent more feed than the control sheep, whose intake gradually declined over the experimental period. Sheep fed sodium sulphate alone consumed 48 per cent more feed than the control group. Dry matter digestibility of feed was increased by 5 to 7 percentage units when sheep were supplemented with either sodium sulphate or gluten.

Soil temperatures and seed burial in relation to the performance of Heteropogon contortus and Themeda australis in burnt native woodland pastures in Eastern Queensland

The factors underlying the increasing dominance of Heteropogon contortus (bunch or black spear grass) as a result of regularly burning native pastures in eastern Queensland have been investigated. In the subtropical environment of this experiment the removal of ground cover by burning or other means significantly increased the average maximum temperature of the surface soil. Burning favoured the germination of buried H. contortus seed at a time when ambient temperatures were too low for this to occur in unburnt situations. In late seasons and in the seasonally dry tropics insufficient soil moisture would tend to limit growth and germination until ambient temperatures are high, in which case the burning effect would be less pronounced. The efficient seed burial mechanism of H. contortus places it at an establishment advantage over other commonly associated species such as blue grasses (Bothriochloa, Dichanthium) and others whose seeds remain largely in the surface litter. Fire destroys much of this litter, the microhabitat for seed germination at ground level, and some of the weaker perennial plants. The implications of these results in relation to the increased dominance of either H. contortus or Themeda australis (kangaroo grass) are discussed.

Breed and nutritional effects of the composition of faeces, urine, and plasma from Hereford and Brahman X Hereford steers fed on high and low quality diets

A comparison is presented of the composition of the faeces, urine, and plasma when Hereford and Brahman x Hereford steers were fed two different quality diets at three levels of intake. On a high quality diet (lucerne hay), the Brahman x Hereford steers produced significantly less faecal dry matter, total nitrogen, and non-dialysable nitrogen than the Hereford steers, but there were no significant differences between the breeds or between animals within a breed in total urinary nitrogen or any of its major constituents. On a low quality diet (blue grass–spear grass hay) the two breeds were not significantly different in faecal dry matter, total nitrogen, or non-dialysable nitrogen. The Brahman x Hereford steers excreted more total nitrogen, urea, and creatinine in their urine, part of which could be attributed to a higher liveweight; and they had significantly lower nitrogen balances. In animals of the same breed, water intake and urine volume were negatively correlated with plasma urea and nitrogen balance and positively correlated with urinary total nitrogen, creatinine, and uric acid.

Phenological variation in Heteropogon contortus and its relation to climate

Heteropogon contortus Beauv. ex Roem. & Schult. (spear grass or tanglehead) exhibits conisiderable: morphological and phenoiogicai variation. Wniie the morphological variation is apparently unrelated to geographic distribution, the phenological variation appears to be closely associated with differences in climate. Flowering is largely governed by day length, but the seasonal pattern of rainfall distribution has selected only those day lengths which promote flowering within the rainfall season. In the tropical region of north-eastern Australia flowering occurs in late summer and short days, since the wet season prevails over the second half of the summer. When northern material is grown in uniform grass gardens south of this tropical region, late maturity still prevails; hence this behavioural pattern is genetically fixed. In the subtropics, on the other hand, adequate rain may fall over the entire potential growing season or any part of it. In the garden great variation of phenology marks the southern material. Furthermore, sampling within local populations may also show great variation from early maturity through to late. It is suggested that in Australia H. contortus is naturally a species of the semi-arid tropics. It has spread into the subtropics through its ability to match the extended but more uncertain rainfall season by producing types of differing day length response. This variation is fixed by the predominantly apomictic mode of reproduction, while the perenniality of the plants ensures survival over periods of unsuitable climate. A long-term equilibrium is therefore established between the flowering behaviour of the population and its climate. A knowledge of the patterns of behaviour within and between populations is likely to be Important for increased pastoral efficiency, firstly, in preventing natural populations from deteriorating towards earlier maturity, and secondly, in lengthening the productive season of pasture growth.

Control of seed setting in Stipa falcata

Stipa falcata Hughes (slender spear grass) causes substantial losses to the sheep industrt through injury to young sheep, and damage to skins. The present methods of control, avoidance and mitigation, are ineffective. A t Deniliquin, N.S.W., a substantial reduction in the number of inflorescences and in the amount of mature seed can be achieved by mowing during the seven to ten days between elevation of the flowering tillers, and flowering. The seeding of Danthonia caespitosa Gaudich. was not affected by mowing at this time. A dragging method was ineffective in controlling Stipa seed-set. Mowing is expensive, and cheaper methods are needed.

Siratro — a tropical pasture legume bred from Phaseolus atropurpureus

A new perennial tropical pasture legume, that has been named Siratro, has been bred from a cross between two Mexican strains of the wild species Phaseolus atropurpureus DC. It is a composite of three high yielding selections which are transgressive segregates from the cross with a marked intensification of the stoloniferous character. The breeding method wed was to select superior recombinants in the F2 population and then subject plots of the F3 and F4 families from them to a system of heavy intermittent grazing with cattle. This mass-selected those plants able to spread and produce seed under high grazing pressure. Siratro has inherited the high resistance of the parents to root-knot nematode and the virus disease legume little leaf. These resistances are necessary in pasture legumes grown in northern Australia. Under grazing, Siratro not only outyields the parents but also all other introduced strains of P. atropurpureus available. The marked stoloniferous habit of the selections in Siratro gives greater persistence and density and high yielding ability. This in turn results in the selections maintaining the Rhodes grass sown with them. The composite nature of Siratro should give it sufficient variability for its adaptation to the spear grass zone Queensland and other coastal and sub-coastal areas of northern Australia.

Increased beef production from Townsville lucerne (Stylosanthes sundaica Taub.) in the spear grass pastures of central coastal Queensland

The performance of Townsville lucerne (Stylosanthes sundaica Taub.) as a legume for inclusion in native pastures dominated by spear grass (Heteropogon contortus (L.) Beauu. ex R. & S.) has been studied near Gladstone, in central coastal Queensland. A pasture mixture of Townsviille lucerne and spear grass, given 10.5 cwt 73 superphosphate, 1.5 cwt potassium chloride, and 5 oz sodium molybdate an acre, over a six-year period: produced five times as much Live-weight gain per acre as untreated native pasture. This increase was a combination of higher carving capacity and greater live-weight gain per head. In addition stock. were marketed at from one to two years earlier than normal. Pot and small replicated field experiments showed that Townsville lucerne responded significantly only to superphosphate and did not require potassium or various trace elements including molybdenum on these soils.

Bunch spear grass dominance in burnt pastures in South-Eastern Queensland

The results are reported of a study of the effect of annual burning, in the absence of grazing, on the botanical composition of a native pasture in south-eastern Queensland. The main effect of burning was to give dominance of Heteropogon contortus (L.) Beauv. ex R. & S. This appeared to be due to three main causes: established plants were resistant to fire; fire favoured the germination of seed; and fire reduced the basal ground cover of other species. The effects on other species and on the proportion of bare ground are reported. The significance of the results in relation to the present distribution of H. contortus-dominant pastures is discussed.

Characteristics of a bunch spear grass (Heteropogon contortus (L). BEAUV.) pasture grazed by cattle in subtropical Queensland.

A study of a native pasture of bunch spear grass (HHeteropogon contortus (L.) Beauv.) grazed by beef cattle in subtropical Queensland is reported. The yield and botanical and chemical composition under continuous grazing were recorded over 4 years. Spear grass contributed up to 90 per cent. of the yield of dry matter which ranged from 1 to 2 tons/acre. Approximately 60 per cent. of the total yield was produced between January and April, and there was almost complete absence of growth in the cooler months even when rain occurred. The nutritive value of the forage was low for much of the year, with the crude protein content falling to 2-3 per cent. in the winter. The degree of consumption of forage by stock was low, particularly in the winter, and it was apparent that under the existing form of management the stock had little effect on the pasture. It is concluded that there is little prospect of increasing beef production per acre by grazing management of the native pasture, and that, as the major drawbacks to production stein from the pasture species rather than the climate in which they grow, the logical approach is to replace them by sown grasses and legumes. This involves studies of introduced species and, as many of the soils are of low fertility, attention to plant nutrient deficiencies. Work along these lines is now in progress.

American Agricultural Grasses 1

HOWEVER complicated the systematic synonymy of the Gramineæ may be, the popular nomenclature of the grasses is probably in an even more unsatisfactory state. In the former case the name of the author appended to the scientific name of the plant is usually sufficient to dispel any ambiguity as to what particular plant is meant, even though that plant may have received half a dozen systematic names from as many different botanists. In the case of the trivial name, however, even this means of identification is lacking, and it is no un common circumstance to find the same name applied to several different grasses, each one of which may, more over, have one or two additional names. To those who are studying the grasses in their agricultural aspect this confusion is very perplexing, particularly as both the English and the American agricultural journals usually refer to a grass by its trivial name. The difficulties which surround this subject are well exemplified in the volume before us. For example, in American agricultural publications the term “salt-grass” is frequently met with, and we searched this volume in the hope of finding out the species so denominated. But instead of one we find no less than four distinct species, in as many genera, called “salt-grass,” namely, Vilfa depauperata, Sporobolus aroides, Brizopyrum spicatum (Distichlis maritima) and Spartina juncea. To an English agriculturist foxtail means Alopecurus pratensis only, whereas in America the name is also given to A. geniculatus, Hordeum murinum, H. jubatum, and Setaria setosa. Rye-grass in England is Lolium perenne; in America the term is applied in addition to four species of Elymus. Blue grass is the name given to four distinct species of Poa, varying considerably in their agricultural value, and one of these, P. pratensis, often spoken of as Kentucky blue-grass, is also called “June grass” “spear grass” and “red top,” the last name being equally applied to Agrostis vulgaris. Bunch grass is more vague in its application, for it embraces at least six species in five genera, while in Canada the same name is given to two other grasses, Elymus condensatus and Kœleria cristata, the former of which is known in the United States as “giant rye grass.” The term “goose grass,” which in England is restricted to the rubiaceous hedgerow weed Galium Aparine, is, in America, applied to Poa annua, which is also called annual spear grass, and to Panicum Texanum, further known as Texas millet. The grass Holcus lanatus, which to all English farmers is known as Yorkshire fog, is variously termed velvet grass, velvet mesquite, satin grass, and meadow soft grass, this last term being also current in England.