NUTRITIONAL PROBLEMS OF LIVESTOCK PRODUCTION FROM SEMI-ARID GRASSLANDS IN THE TROPICS*

Herbage of very low quality forms the main diet of ruminants on the semi-arid grasslands in the tropics for several months of the year. The grasses available have a high content of dry matter and crude fibre, a low digestibility and a very low crudeprotein content. Ruminants are unable to eat enough herbage to supply the nutrients required for their body functions and it is this inadequacy which is the major factor limiting animal production from semi-arid grasslands in the tropics.     

BEEF PRODUCTION FROM PASTURE LEYS IN UGANDA*

The potential for producing beef in savanna grassland areas is discussed in relation to the results obtained from grazing trials on sown pastures at Serere Research Station, Uganda. Liveweight gains from small East African Zebu stock are used to illustrate the progress that has been made in the selection of improved pasture species and mixtures grown at various levels of fertilizer application. The utilization of herbage from selected pastures is shown to vary under different grazing management systems, grazing pressure having the greatest effect upon animal production. The need for further investigations and the integration of existing research findings into farming practice is stressed.     

INCORPORATED VERSUS SUBSURFACE VERNOLATE FOR WEED CONTROL TN PEANUTS*

Summary. Under dry field conditions, vernolate (S-propyl dipropylthiocarbamate) incorporated by conventional methods controlled less yellow nutsedge (Cyperusesculentus L.) and injuied peanuts (Arachis hypogaea L., groundnuts) more than when injected in lines under the soil or subsurface-applied through sweep applicators. In glasshouse studies, vernolate eliminated production of new nutsedge tubers if it was applied below the soil surface either 1 in. above or 1 in. below the parent tuber. Method of placement was less critical in determining control of most annual weeds. When averaged over two soil types and 2 years, peanuts yielded 14% more after subsurface applications than after incorporated treatments of vernolate. In comparison with the optimum subsurface placement, the yield from incorporation was significantly lower in three of four field studies, the reduced yields probably resulting from a combination of herbicide injury and poor weed control. Factors affecting the distribution of vernolate vapours (such as method of placement, soil type and amount of rainfall after treatment) apparently determine the differential toxicity of this herbicide. Neither market quality nor germination of peanut seed was adversely affected by vernolate treatment.     

SOME SELECTIVE EFFECTS OPERATING ON WHITE- AND RED-CLOVER IN SWARDS

Populations of white- and red-clover were examined after they had been grown for several years in grass/clover swards. The method of sowing, nitrogen application, management and season affected the ratio of very similar clover cultivars differing specifically in the leaf mark when sown in the same mixture. The companion grass also infiuenced the proportion of legume cultivars in the sward. In addition, the mean date of emergence of a single cultivar of broad-red clover was affected by management.