Desert Grass Research Articles

Effects of prolonged exposure of Oryzopsis hymenoides to SO2

Oryzopsis hymenoides, a desert grass, was exposed to low concentrationsof SO2 ranging from 0.03 to 1.00 ppm for six week fumigation periods. Deleterious effects were noted only at atmospheric SO2 concentrations of 0.13 ppm and above. These effects included necrotic lesions and reduced net primary productivity. At concentrations below 0.13 ppm, the SO2 appeared to have a beneficial effect on productivity. The deleterious effects noted at the higher concentrations have ecological implications if pollutant sources are located in desert environments.

The effect of level of water intake on some aspects of digestion and nitrogen metabolism of the ‘desert sheep’ of the Sudan

SUMMARYFive successive trials were conducted using eight adult rams (Sudan desert sheep) to study the effect of restriction of water intake on some aspects of digestion and nitrogen metabolism. The feeds used in this study were berseem hay (Medicago sativa), lubia hay (Dolichos lablab), maize hay (Zea mais), a concentrate mixture, and dry desert grasses (hummra) (a mixture ofDactyloctenium aegyptium, Schoenefeldia gracilis, Eragrostis pilosa, Aristida funiculataandAristidaspp.).Restriction of water did not affect the digestibility coefficients of organic matter, crude protein and crude fibre significantly. The digestibility coefficient of ether extract was significantly reduced whereas that of nitrogen-free extract was slightly higher when water was restricted.The concentrations of ammonia and volatile fatty acids in the rumen and of urea in the blood were recorded before and 3 h after feeding. Increases in rumen ammonia and blood urea nitrogen concentration were reduced by water restriction except when hummra was fed.Restriction of water intake also slightly increased thein vitrorate of fermentation of rumen contents which is taken as a measure of microbial activity in the rumen, and the retention of nitrogen. These results are interpreted as indications of more efficient nitrogen utilization under conditions of water restriction.There were no significant effects of the treatments on changes in the concentration of volatile fatty acids.The significance of these findings in relation to the management of desert sheep in the arid parts of the Sudan is discussed with special reference to the effect of the level of dry-matter intake on nitrogen balance.

Further studies on the prediction of the nutritive value of protein for ruminants

SummarySix successive trials with three adult rams (Sudan desert sheep) were conducted with the main object of finding a suitable index for the prediction of the nutritive value of protein in non-legumes for ruminants.The mean change in the concentration of ruminal ammonia, blood urea and ruminal V. F. A. 3 h after feeding legumes was considerably greater than after feeding the nonleguminous hays. Among the legumes berseem hay gave the least change in the concentration of ruminal ammonia, blood urea and V. E. A. The leguminous hays produced more gas underin vitroconditions than the non-legumes. Berseem hay produced the greatest volume of gas. Butterfly pea hay and lubia hay gave more or less similar results. Among the non-legumes the desert grasses gave the lowest values.Of all the feeds studied maize hay gave the highest nitrogen retention, followed by berseem hay. Despite this superiority of maize hay, the overall mean nitrogen retention of legumes was much greater than that of the non-legumes. Among the non-legumes dry desert grasses displayed a negative nitrogen balance.Regression equations based on the present data indicated that nitrogen retention only of leguminous hays could be always predicted from changes in blood urea concentrations. The present results also showed that the nitrogen retention of non-legumes and to a lesser extent that of all feeds taken together (i. e. legumes and non-legumes) can be assessed by using volume of gas producedin vitro(i. e. rate ofin vitrofermentation).

Germination Responses of Three Desert Grasses to Moisture Stress and Light

Lehmann lovegrass appeared very susceptible to physiological drought while Arizona cottontop and plains bristlegrass were not appreciably affected until osmotic tensions exceeded 12 atm. Lehmann lovegrass was the fastest and plains bristlegrass was the slowest to germinate. This study indicated that the adaptability and responsiveness of Lehmann lovegrass is due to its ability to germinate rapidly whereas the other two species require more time of moisture availability. Lehmann lovegrass and Arizona cottontop appeared adversely affected by constant darkness which suggests that they require a shallow planting while plains bristlegrass seemed to have the opposite response, which suggests that it requires a deeper planting

The use of ruminal ammonia and blood urea as an index of the nutritive value of protein in some food-stuffs

1. Nine successive trials with three adult desert rams were carried out, with the aim of using ruminal ammonia or blood urea concentration as an index of the nutritive value of the proteins in the various types of forage grown in irrigated parts of the northern Sudan.The change in the ruminal ammonia and blood urea concentration were considerably higher 3 h after feeding on leguminous forages than on the non-legumes. Among legumes, lubia and lubia hay produced the highest concentrations of both rumen ammonia and blood urea. Feeding the rams on berseem hay reduced the concentrations of ruminal ammonia and blood urea to levels below those given by feeding on fresh berseem.3. Most of the nitrogen excretion from leguminous forages was in the form of urinary nitrogen whereas for grasses faecal nitrogen made up the bulk of the nitrogen excreted. Berseem hay gave the highest nitrogen retention, followed by the butterfly pea and fresh berseem. Lubia and lubia hay gave the lowest nitrogen retention. The desert grasses produced a negative nitrogen balance when offered to the desert rams.

AEROVISUAL GEOBOTANICAL OBSERVATIONS IN DESERTS AND SEMIARID REGIONS

The techniques of aerogeologic observations and the coordination of such observations with ground studies are described. Some broad distinctions of plant associations are described, notably those including various species of sagebrush (Artemisia), beachgrass (Calamagrostis), Tamarix and various desert grasses. Certain species are best mapped when seasonal color changes occur. The violet bloom of the halophyte Statice suffruticosa, for instance, makes it possible to distinguish saline areas on the Ustyurt Plateau. Aerovisual observation gives the supervisor a chance to check the mapping accuracy of subordinates. — A. Eustus