Vicia faba cv. Minden was precision planted at densities of 12–100 plants/m2 in 1977 and 30–60 plants/m2 in 1978 with and without seed-bed applications of aldicarb (10 kg/ha).

Nitrogenase activity per plant decreased significantly with increased plant density but this was compensated for on an area basis by increased numbers of plants. When expressed on the basis of area, nitrogenase activity was higher with closely, than with widely spaced plants both early and late in the season. Irrespective of planting density nitrogenase activity reached a peak during vegetative growth of the plant and a second peak during rapid pod and seed development. In 1977 the second peak was interrupted by very dry soil conditions but later activity increased following rain.

Aldicarb consistently increased nitrogenase activity at all harvests after Sitona damage to the nodules was evident. Over this period plots treated with aldicarb had twice the nitrogenase activity of untreated plots in 1977 and 55% more in 1978.

Silage, dried-grass wafers and dried-grass pellets all prepared from a single crop of perennial ryegrass were given ad libitum as sole diets to six rumen-fistulated wether sheep.

Feed intake, intake of digestible nutrients and the concentration of volatile fatty acids (VTA) in the rumen were lowest with silage, highest with pellets and intermediate with wafers. Conversely, digestibility, eating and ruminating time per kg D.M. consumed, rumen pH, the rate of D.M. and cellulose digestion in the rumen and the mean retention time of digesta in the alimentary tract were highest for silage, intermediate for wafers and lowest for pellets. The pattern of rumen fermentation differed significantly between silage and the dried-grass treatments. The rumen fluid contained higher proportions of acetic, iso-butyric, n-valeric and iso-valeric acids, but lower proportions of propionic and n-butyric acids with silage than with dried grass. Differences in rumen. VFA between the two forms of dried grass were small. Nitrogen retention was lowest for the silage treatment and this was associated with a high concentration of ammonia in the rumen.

Low nitrogen status with silage could have limited voluntary intake, whereas the difference in intake between the wafer and pellet treatments probably arose from differences in the retention time of digesta in the alimentary tract.

Grass silage (21.0 % D.M.) was given ad libitum to sheep together with supplements of rolled barley, dried-grass pellets or dried-grass wafers at 12 and 25 g organic matter (OM)/kg0·75.

Intake of silage was greater with supplement at 12 g/kg0·75 but total intake of OM and digestible organic matter (DOM) increased with increasing supplement. Intake of OM was higher with the pellet supplement than with other supplements. Intake of DOM, however, did not differ between the pellet and barley treatments, but was lower with wafers.

Concentrations of ammonia and total volatile fatty acids and the molar proportions of butyric and higher volatile fatty acids were higher when silage was supplemented with barley than with dried grass. Mean rumen retention times of silage and of supplement were highest in the barley-supplemented treatments. Dried-grass wafers were retained longer than dried-grass pellets. Supplement treatments did not differ significantly for eating and ruminating times, rumen fluid volume and pH, digestion rate in the rumen and nitrogen retention.

At the low supplement rate silage consumption may have been controlled by factors associated directly with the silage, whereas at the high rate intake was limited either by physical factors or by the potential energy demand of the animals.

In previous studies of the reactions of groundnut varieties to infection with Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton, the existence of disease resistance has been demonstrated. However, these investigations have not resulted in the production of high yielding, disease resistant, varieties and it has been suggested that disease resistance is physiologically linked to low seed yield. In the present study, two aspects of the host–pathogen interaction were investigated: these were varietal response to chemical disease control, and the effect of plant sterility on host and pathogen development. It was found that a general score of resistance to leaf spot did not always relate to the varietal response to disease control and reasons for this were proposed. The prevention of pod production did not affect pathogen development, but vegetative growth of the treated plants was increased. It was concluded that host and pathogen development could be confounded during the assessment of disease resistance. In future varietal screening trials, the use of single branch comparisons should prevent this confusion.

An experiment was carried out to study the effects of underfeeding during late pregnancy and early lactation on the structure and chemistry of liver and muscle of dairy cows. Two groups of cattle were fed at 60 and 40% of estimated requirements for maintenance and pregnancy or lactation for 13 weeks before and 13 weeks after calving, and one group was fed at maintenance level only for the same period. A control group was fed at 100% of estimated requirements for the same period. All groups were subsequently fed at the control level for a further 24 weeks.

Underfeeding resulted in significant changes in muscle and liver of dairy cows. In particular, there was a decrease in liver cell volume in the underfed groups and a persistence of post-parturient fat in the moderately underfed cows. Muscle fibre diameter was reduced and there was a loss of fast twitch oxidative glycolytic fibres in the underfed cows.

The magnitude of response to fertilizer-N and fertilizer-P decreased with increasing amounts of total soil-N and available soil-P, respectively. Attempts have been made to group the soils into N- and P-fertility classes based on the magnitude of response to applied fertilizers on soils of different fertility with respect to these two nutrient elements.

The neutron method of estimating soil moisture content in the field has the advantage that once access tubes are installed no further disturbance to the site is necessary and readings can be taken repeatedly throughout the soil profile at a fraction of the time necessary for the gravitational method. However, measurement of moisture content in the surface layer of soil, the top 10 cm, has proved difficult since the source and detector must be at a depth less than the sphere of influence allowing some neutrons to escape to the atmosphere. This air-soil interface effect can lead to an underestimation of moisture content which is greatest in wet soil (Van Bavel, Hood & Underwood, 1954).

In anaerobic glyoolysis lactic dehydrogenase (LDH) is the terminative enzyme in the sequence of reactions that promote the breakdown of sugars to lactate. The LDH activity of cattle semen and seminal plasma together with its relationship with various characteristics of semen have been reported (Stallcup & Hayden, 1960; Roussel & Stallcup, 1965). Such work in respect of buffalo semen is not available, although there are some reports on LDH activity of spermatozoa and seminal plasma (Singh & Sadhu, 1972; Chauhan & Srivastava, 1973). The present investigation was undertaken to determine the LDH activity of buffalo whole semen as well as of seminal plasma and to find correlations with some physical characteristics of semen.