THE USE OF MOUNDS OF THE TERMITE MACROTERMES FALCIGER (GERSTÄCKER) AS A SOIL AMENDMENT

Twelve termite mounds and adjacent Ah and Ap horizons were sampled at three sites near Salisbury, Rhodesia. The mass of termite mounds occupied by M. falciger at one site was estimated at 620 t/ha, and contained the following amounts of nutrients expressed as percentages of the amounts in mounds and Ap horizon combined: extractable Ca 95%, mineral N 81% extractable K 69%, and available P 69%. Pot experiments using perennial ryegrass gave higher dry matter yields from termite mounds than from the Ap and Ah horizons. Crop production could therefore be increased by mixing termite mounds with the soil.     

ADSORPTION OF THE HERBICIDE 2,4-D ON GOETHITE

Adsorption, of the herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) on an iron oxide, goethite, was studied in aqueous suspensions as a function of solution pH, ionic strength of the medium, and initial 2,4-D concentration. The 2,4-D anion was reversibly adsorbed on positively charged goethite surfaces, maximum adsorption being observed near the pK_a of 2,4-D (2.73) and at low ionic strength. Within certain levels of adsorption (5–22 mg 2,4-D adsorbed/g goethite) the complex became hydrophobic and floated to the liquid surface. This flotation effect disappeared on further adsorption. It is suggested that adsorbed 2,4-D anions are orientated with their hydro-phobic aromatic ends directed towards the solution, the carboxyl groups being weakly bound to positive sites on the oxide surface. At high levels of adsorption, some of the anions are orientated in the opposite direction by π–π interaction, with the first adsorbed layer and the surface reverts to its hydrophilic nature.     

Effect of the pre-emergence bioherbicide Phomopsis convolvulus on seedling and established plant growth of Convolvulus arvensis

The effects of the fungal pathogen Phomopsis convolvulus Ormeno on seedling and established plant performance of Convolvulus arvensis L. were compared under both controlled and field conditions. Under a controlled environment, a granular barley formulation of the fungal inoculum that had been applied on to the soil surface of pots containing pre-germinated C. arvensis seeds resulted in above-ground biomass reductions of up to 87%. However, application of the fungus to established plants that had been cut to ground level produced biomass reductions (43%) that were nearly half of those obtained for seedlings. In a parallel field experiment conducted over two growing seasons, application of P. convolvulus resulted in dramatic above-ground biomass reductions for both seedlings and established plants. In one trial, biomass reductions of up to 100% and 98%, respectively, were obtained. C. arvensis coverage within field plots was closely correlated with above-ground biomass. Findings in this study indicated that P. convolvulus may provide effective control of C. arvensis when applied pre-emergence.     

A comparison of continuous grazing systems for milk production

In two experiments conducted with Ayrshire dairy cows in 1974 and 1975 on swards of S23 perennial ryegrass, four systems of continuous grazing were investigated. The leys received 345 and 370 kg ha^-1 fertilizer nitrogen in 1974 and 1975 respectively and were stocked at the rate of five cows per ha. In 1974, a comparison was made between two systems which either integrated silage making with, or separated it from, the continuous grazing. The provision of a silage aftermath in late July increased milk yield after that time, but had no significant effect on milk yield over the 19-week experimental period. In 1975, a comparison between weekly and monthly applications of fertilizer N showed no significant differences between milk yields in a 20-week period. The feeding of supplementary concentrates from late July onwards significantly increased milk yield. The treatments in both years had only small and mainly non-significant effects on milk composition. On average, excluding the concentrate treatment, the annual output of milk was 10,800 kg ha^-1 using spring-calved cows.     

Silage and milk production: a comparison between four rates of groundnut cake supplementation of silage of high digestibility

Grass silage made in late May from S24 perennial ryegrass was offered to twelve Ayrshire cows in a 16-week feeding experiment. The silage had a DM content of 25.3%, a pH of 3.91, and contained 16.8% CP and 68.4% digestible organic matter in the DM. The silage was fed ad libitum and was the sole feed in the control treatment. In the other three treatments the silage was supplemented with a cube offered at rates of 0.8, 1.4 and 2.0 kg per 10 kg milk. The cube contained 82.2% groundnut, plus molasses and minerals, and had 37.9% CP in the DM. The daily intake of silage DM was 11.4 kg per cow on average over the four treatments which did not differ significantly. The mean daily milk yields were 14.8 kg per cow in the control treatment, and 16.5, 18.2 and 18.4 kg in the 0.8, 1.4 and 2.0 kg supplement treatments respectively. The SNF, CP and lactose contents of the milk were Wghest on the 1.4 kg supplement treatment. It is concluded that with a high digestibility silage, there is little evidence to support the feeding of more than 1.4 kg of high-protein cubes per 10 kg milk in the declining phase of lactation.     

Silage and milk production: a comparison between additives for silage of high digestibility

Three grass silages made in early June from S23 perennial ryegrass were compared in a 16-week feeding experiment with twelve Ayrshire cows. The silages were made from uniform herbage which received either formic acid (‘Add-F’) at the rate of 201 t^?1, or a formalin-sulphuric acid mixture (‘Syiade’) at rates of 2.0 and 4.4 1 t^?1. The silages were offered ad libitum either alone or supplemented with a cube containing 38% CP in the DM at the rate of 1.4 kg per 10 kg milk. The daily intakes of silage DM were not significantly different on the three silage treatments, and averaged 10.7, 11.0 and 11.0 kg per cow on the formic acid and the 2.0 and 44 1 t^?1 formalin-acid treatments respectively. The mean daily yields of milk were 15.1, 13.3 and 13.7 kg per cow in the unsupplemented treatments, and 18.2, 18.1 and 18.0 kg per cow in the supplemented treatments on the formic acid and the 2.0 and 44 1 t^?1 formalin-acid treatments respectively. On the basis of total animal production expressed in terms of metabolizable energy requirements, it was concluded that the differences between the three silages were small.     

Oestrogen-induced alopecia in a bitch

An 8-year-old, spayed female Labrador Retriever, which had been treated with oestrogens for urinary incontinence, developed non-pruritic, bilaterally-symmetrical alopecia and skin hyperpigmentation, with enlargement of mammary glands and vulva. Skin biopsy changes were consistent with an endocrine alopecia, hypothyroidism and hyperadrenocorticism were excluded by hormonal tests. Oestrogen-induced alopecia was suspected and hormonal treatment withdrawn. Two months later, hair regrowth was almost complete and genital changes were lessened.