African Journals Online
African Journal of Range & Forage Science

VOLUME 19 (3) (2002)
Abstracts 

African Journal of Range & Forage Science 2002, 19: 131–136
Printed in South Africa — All rights reserved

Tree canopies facilitate invasion of communal savanna rangelands by Lantana camara

JG Rodger¹ and WC Twine²*

¹ School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag X3, Wits 2050, South Africa.

² Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand c/o Wits Rural Facility, Private Bag X420, Acornhoek 1360, South Africa

* Corresponding author, e-mail: [email protected]

Received 20 May 2002, 4 October 2002

This study investigated pattern in the distribution of the alien invasive shrub, Lantana camara L., in communal versus conservation land-use in a lowveld savanna. Pattern was investigated relative to land-use type, and sub- or inter-canopy micro-sites. Lantana was significantly more prevalent on communal lands than in the conservation area, and in sub-canopy micro-sites than inter-canopy micro-sites. The communal lands had significantly lower herbaceous biomass than the conservation area, and Lantana prevalence was inversely related to herbaceous biomass. Higher prevalence of Lantana in communal areas was probably due to more intense disturbance of the herbaceous layer in this land-use type, although this was not conclusively demonstrated. The difference in the prevalence of Lantana between sub-canopy and inter-canopy micro-sites is most likely explained by either seed dispersal patterns imposed by avian dispersal agents and/or micro-site variation. An assessment of population size class structure of Lantana in the communal lands suggested that the population is stable and rapidly recruiting.

Keywords: alien invasive, degradation, land-use, micro-site

African Journal of Range & Forage Science 2002, 19: 137–145
Printed in South Africa — All rights reserved

Fire and the dynamics of a semi-arid grassland: influence on soil characteristics

HA Snyman

Department of Animal, Wildlife and Grassland Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

e-mail: [email protected]

Received 15 April 2002, accepted 9 October 2002

The short-term impact of fire burning with the wind (head fire) and against the wind (back fire) on soil characteristics (soil-water content, soil compaction, soil temperature, organic matter, pH, exchangeable Ca, Mg, K, Na and extractable P) were determined in a semi-arid grassland. This study was conducted over two growing seasons (2000/01 and 2001/02) after only one burning treatment in August 2000. The back fire moved approximately 7.5 times slower than the head fire, leading to the greatest change in hydrological characteristics. The decline in plant cover due to the fire resulted in a considerable increase in soil compaction, soil temperature and a decrease in organic material in turn leading to a lowered soil-water content. Much of the influence of these variables had not been completely reduced two growing seasons after the fire. Burning reduced the soil-water content (0mm to 300mm soil depth) after one month and one year by 13.4% and 31% respectively. Temporary wilting for all grass species occurred more rapidly with burning. During March of the first year, the greatest soil temperature difference (50mm depth) occurred between burnt and unburnt grassland, with the highest soil temperatures recorded in January. The highest temperature on the surface of the soil for each year after burning also occurred during January. Over the first growing season burning significantly reduced organic carbon (C) and total nitrogen (N) content and extractable phosphate, but increased the pH and concentration of exchangeable Ca, Mg, Na and K in the soil, over the first 0–50mm layer. There were no differences in the soil properties of head and back fires, except for organic material that was further lowered by the back fire. With depth, organic matter and K decreased significantly and Ca increased between surface (0mm to 50mm) and lower (50mm to 100mm) layers due to burning. Thus, an unplanned event can increase the intensity and frequency of seasonal droughts in the ecologically sensitive semi-arid grassland areas leading to increase risk management in the short-term.

Keywords: back and head fires, organic matter content, soil compaction, soil-water content, soil temperature, soil properties, temporary wilting

African Journal of Range & Forage Science 2002, 19: 147–155
Printed in South Africa — All rights reserved

Mineral element status of soils, native pastures and cattle blood serum in the mid-altitude of western Ethiopia

Lemma Gizachew¹, Adane Hirpha¹, Fikadu Jalata¹ and GN Smit²*

¹ Animal Feeds and Nutrition Division, Bako Research Centre, PO Box 74, Bako-Shoa, Ethiopia

² Department of Animal, Wildlife and Grassland Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

* Corresponding author, e-mail: [email protected]

Received 5 February 2002, accepted 4 October 2002

Despite the crucial role of mineral elements in animal production and health, their status in soil, native pasture and animal body tissues or fluids in the mid-altitude of Ethiopia has had little study. To determine the concentration of mineral elements in soil, native pasture and blood serum of Horro cattle (local zebu), samples were collected from four sites situated within a 30km radius of Bako Research Centre (BRC) at the end of the rainy season and during the following dry season. Mean mineral element concentrations in soil and native pasture in the bottomlands tended to exceed levels in the uplands for almost all investigated elements. Soil Ca, Mg, K, Fe, Mn and Cu concentrations were within the optimum range for active plant growth, but the levels of available Zn and P were below the critical limit. At the upland sites the effect of season on native pasture mineral element concentration was significant only for P (P<0.05) and K (P<0.01). Upland native pasture Zn concentrations in both wet and dry seasons and Cu and P in the dry season were below cattle requirements, but the remainding mineral elements were above or within the recommended range. Except for P, season affected serum mineral element concentrations significantly (P<0.01). There was no significant (P>0.05) difference between male and female cattle for any serum mineral measured. A season x gender interaction was significant (P<0.05) only for serum P. Dry season serum Zn and Mg concentrations in female cattle and dry season serum Cu concentration in both sexes fell below the critical value. The correlation coefficient between soil and native pasture was r = 0.81 for Ca (P<0.05) and r = 87 for Mg (P<0.05). A negative relationship was obtained between wet season soil Mg and serum Mg in male cattle (r = -0.96; P<0.05).  A high negative correlation (r = -0.99; P<0.01) was also obtained between native pasture Mg and serum Mg from male cattle in the wet season. Based on the information obtained from soil, native pasture and serum assays, low levels of Zn, P, Cu and Mg in soil and native pasture could potentially limit livestock production in the study area.

Keywords: animal nutrition, communal grazing, Horro cattle, seasonal changes, minerals

African Journal of Range & Forage Science 2002, 19: 157–160
Printed in South Africa — All rights reserved

Dry matter yield and quality of five annual subtropical fodder crops at different irrigation levels

D Marais*, NFG Rethman and JG Annandale

Department of Plant Production and Soil Science, University of Pretoria, Pretoria 0001, South Africa

* Corresponding author, e-mail: [email protected]

Received 7 February 2002, accepted 20 September 2002

Maize, soybean, cowpeas, fodder sorghum and pearl millet were cultivated in a small plot trial under a rain shelter. The crops were subjected to four irrigation levels. The yields of fodder sorghum and pearl millet were better under severely water stressed conditions (W1) in comparison to that of maize. However, maize yields under control conditions (W4), were the highest. Soybean produced higher yields than cowpeas. Cowpeas were more digestible than soybeans and also had a higher crude protein content than the other four crops. Fodder sorghum and pearl millet have comparable digestibilities and crude protein contents. Maize has a high digestibility but is very poor in crude protein content. It is thus advisable to combine maize with a legume. Whether soybean or cowpeas should be considered would depend on the need of bulk or protein. Under dryland conditions (W1) fodder sorghum and pearl millet would be better choices than maize.

Keywords: Zea mays, Glycine max, Sorghum x Sudangrass, Pennisetum glaucum, Vigna unguiculata

African Journal of Range & Forage Science 2002, 19: 161–166
Printed in South Africa — All rights reserved

Grass composition and rangeland condition of the major grazing areas in the mid Rift Valley, Ethiopia

Amsalu Sisay^1,2 and RMT Baars²*

¹ Adami Tulu Research Centre, Ziway, Ethiopia

² Alemaya University, Dire Dawa, Ethiopia

* Corresponding author, e-mail: [email protected]

Received 25 February 2002, accepted 8 October 2002

A range inventory and condition study was conducted in three altitude zones: lowland (1 500–1 700m), medium altitude (1 700–2 000m), and highland (2 000–2 500m). Each altitude zone was stratified into four or five important grazing areas. One area represented lightly grazed government ranches or parks which were used as benchmarks, another area represented the seasonal grazing areas with an intermediate grazing pressure and the remaining were the heavily grazed roadsides, lakeshores and other communal grazing lands. The range condition assessment was based on the composition of the herbaceous layer, basal cover, litter cover, relative number of seedlings, age distribution of grasses, soil erosion and soil compaction. Dry matter was sampled in the mid-wet season to assess the relationship between available dry matter and range condition. A total of 36 grass species, 3 legume species, 2 sedge species, 15 other herbs and 31 species of trees were identified. The palatable Cenchrus ciliaris was dominant in the benchmarks and seasonally grazed areas of the lowland while Hyparrhenia spp. dominated in the same areas of the medium altitude. Cynodon dactylon, and the non-palatable Eleusine floccifolia and Pennisetum schimperi were dominant on heavily grazed areas of the lowland, medium altitude and highland, respectively. The total score for range condition of the benchmarks (34 out of 50 points), was significantly higher than that of the seasonally grazed areas (26), the heavily grazed communal grazing areas (19), roadsides (16) and lakeshores (17) (P<0.05). The highlands showed a higher score for benchmarks and seasonally grazed areas only. There was a significant linear relationship between available dry matter of grasses and range condition (excluding unpalatable pioneer grasses, r² = 0.56, P<0.01). Seasonally grazed areas were identified as key sites for pasture improvement since these are privately owned and managed. Pasture improvement will reduce the grazing pressure on the heavily grazed roadsides, lakeshores and other communally grazed areas.

Keywords: basal cover, above-ground available phytomass, herbaceous species, soil erosion

African Journal of Range & Forage Science 2002, 19: 167–173
Printed in South Africa — All rights reserved

The influence of nitrogen and defoliation on the nitrogen content of Lolium multiflorum cv. Midmar

JF Theron¹*, WLJ van Rensburg² and HA Snyman²

¹ Department of Agriculture, Private Bag X01, Glen 9360, South Africa

² Department of Animal, Wildlife and Grassland Sciences, University of the Free State, Box 339, Bloemfontein 9300, South Africa

* Corresponding author, e-mail: [email protected]

Received 15 March 2001, accepted 3 September 2001

The response of the nitrogen content in ryegrass (Lolium multiflorum cv. Midmar) to a variation in applied nitrogen (0kg N ha^-1, 150kg N ha^-1, 300kg N ha^-1 and 450kg N ha^-1) and defoliation intervals (every 2, 4, 6 and 8 weeks, as well as twice a season) was determined. In a field trial, the four nitrogen levels were combined with the five defoliation intervals. The quality of the dry matter (DM) was determined by Near Infrared Spectroscopy (NIRS). Total nitrogen, non-protein nitrogen and true protein were significantly (P£0.01) influenced by nitrogen level, defoliation interval and the interaction between these two factors. The total nitrogen content varied from 0.68% to 3.38%, the true protein from 0.57% to 2.74% and the non-protein nitrogen from 0.11% to 0.65%. Nitrogen assimilated in the aboveground material ranged from 9.8kg N ha^-1 to 423.0kg N ha^-1. Linear relationships (P£0.01) between total nitrogen, true protein and non-protein nitrogen (NPN) respectively were found.

Keywords: NPN, nitrogen content, ryegrass, true protein

African Journal of Range & Forage Science 2002, 19:  175–176
Printed in South Africa — All rights reserved

Short Communication

Estimation of grazing by herbivores from analysis of dung

LV Mabinya¹*, JM Brand¹, JG Raats² and WSW Trollope²

¹ Department of Biochemistry & Microbiology, University of Fort Hare, Alice 5700, Eastern Cape, South Africa

² Department of Livestock and Pasture Science, University of Fort Hare, Alice 5700, Eastern Cape, South Africa

* Corresponding author, e-mail: [email protected]

Received 7 February 2002, accepted 2 September 2002

Two phenolic acids, p-coumaric and ferulic acid, can be liberated from grass material by mild alkaline hydrolysis and resolved by thin layer chromatography (TLC). The two acids can also be recovered from the dung of various herbivores and their presence can be used as evidence of grazing by animals such as cattle, hippopotamus and warthogs. The reduced presence of these compounds in the dung of goats supports the fact that goats both graze and browse. Analysis of the dung of typical browsers such as kudu, black rhinoceros and giraffe suggests that kudu and black rhinoceros may occasionally graze when grass is available. p-Coumaric and ferulic acid are not readily detectable by this method in extracts of the major tree species browsed by goats in the area studied. The yield of these two compounds in the dung of goats gives a reasonable estimate of the extent to which goats are known to graze in this area. The simplicity and uniqueness of this approach in obtaining a rough estimate of the extent of grazing by browsing animals is particularly attractive as it is more practical than field observations and invasive techniques studying gut contents.

Keywords: black rhinoceros, cattle, goats, hippopotamus, p-coumaric acid, ferulic acid