In Bedouin goats maintained outdoors during the summer, fed lucerne hay and watered once daily, drinking was followed by a 35% increase in rumen fluid volume, with a concomitant drop in osmolality from 300 to 150 m-osmol/kg. When water was provided to these goats only once every 4 days, a three-fold increase in the rumen fluid volume was recorded and osmolality dropped from 360 to 80 m-osmol/kg.

Feeding, which was depressed during the hot hours of the day, resumed in the afternoon and was followed by an expansion of rumen fluid volume. This expansion occurred irrespective of drinking and was sustained throughout the night. On the 1st day of water denial it amounted to 40% of the noontime rumen fluid volume and was less pronounced during the rest of the water deprivation period. An evening increase in the concentrations of volatile fatty acids, along with a compatible increase in the osmolality and a drop in the pH, also followed the afternoon resumption of feeding.

In goats maintained on wheat straw, drinking as well as feeding time affected the physico-chemical conditions in the rumen to a lesser degree than in goats maintained on lucerne hay.

Phosphate adsorption on Narrabri medium clay loam soil followed a four-region Langmuir isotherm equation, i.e. the plot showed four distinct linear portions. These four regions corresponded closely to saturation with respect to hydroxyapatite, β-tricalcium phosphate, octacalcium phosphate and dicalcium phosphate dihydrate, shown by a calcium phosphate solubility diagram. The differential isosteric heat of adsorption, AH, of P adsorption on soil between 4 and 22 °C, plotted against phosphate sorbed, revealed discontinuities corresponding to the breaks in slope found on the Langmuir plot.

Depth accumulation of exchangeable Na+ was measured in Ca-saturated sandy loam soil columns (length 50 cm; diameter 5 cm) after percolating 500, 1000, 1500 and 2000 ml of 013 M Na+, as NaCl, NaHCO3, Na2SO4 and Na2CO3 solutions. The values of exchangeable sodium percentage (ESP) increased gradually with the increase in the volumes of the solution percolated. Two conceptual layer models, based on whether solutions were added to the topmost soil layer in one lot (M-I) or in splits equal to the saturation deficit (M-II), were used to predict the depth distribution of ESP of soil. The chemical processes considered in the models were the formation of ion pairs and the exchange equilibria of Na+ and Ca2+. The predicted values of ESP were considerably higher for model M-II than model M-I. The consideration of ion-pair formation and the accompanying anion had only negligible effect on the predicted ESP. The model M-II over-predicted the experimental ESP throughout the soil columns, whereas the model M-I under-predicted it for the upper layer(s) and over-predicted for the lower layers. On the basis of average ESP of the whole columns, the less realistic model M-I predicted experimental results better than model M-II. This was attributed to the presence of mobile and immobile zones for the flowing solutions.

The effect on live-weight gain from dosing cattle with rumen bacteria capable of degrading 3-hydroxy-4(l H)-pyridone (DHP) was measured on cattle grazing leucaena and native grass pastures in south-east Queensland. Dosing increased the growth rate of cattle grazing only leucaena pasture: from 0·52 kg/head per day when not dosed, to 1·03 kg/head per day when dosed, in the period 6·19 weeks after treatment. Dosing did not affect the growth rate of cattle either grazing leucaena with native pasture, or grazing only native pasture. The introduced bacteria spread naturally to untreated cattle after 19 weeks post-dosing.

The response to dosing occurred when untreated cattle grazing only leucaena pasture had high urinary concentrations of DHP (maximum 0·28%) and low concentrations of serum thyroxine (< 30 nmol/1). The results show that DHP-induced depressions in growth rate may occur in this environment when cattle graze mainly on leucaena-based pasture. Dosing with DHP-degrading bacteria will overcome this problem.

Following a winter with low temperatures during a period with no snow cover, lucerne (alfalfa; Medicago sativa L.) plants were dug from the field and various root and crown lesions were identified and rated according to severity. The plants were then put into pots of soil and grown for 6 weeks to determine if they would live or die. The relationship between lesions present at the time of digging and survival was then studied to see if the lesions could be used to predict survival. Injuries to several characteristics were found to be associated with plant death: bud vigour, leaf vigour, resistance of root bark to peeling, resistance of root to squeezing, root interior colour and, depending on site, the presence of fungi on the root surface. A model combining injury ratings for three characteristics (bud vigour, root colour, and root resistance to peeling) was developed and survival probabilities based on this model are presented. Use of this model will allow for an early evaluation of low-temperature injury without having to wait for aerial growth to occur.

Between weeks 3 and 16 of lactation 191 British Friesians received a basal ration ad libitum of either grass silage (GS), grass and maize silage (GS/MS) blended in a ratio of 1:2 or grass silage and 4% NaOH-treated barley straw (GS/TS) blended in a 4:1 ratio. The grass silage, which was not well preserved, had an estimated metabolizable energy (ME) content of 9–9 MJ/kg D.M., while corresponding values for the GS/MS and GS/TS mixtures were 106 and 9–5 MJ/kg D.M., respectively. A conventional concentrate (CC) based on barley and soyabean meal was fed at three levels (9, 6 and 3 kg fresh weight/day). Although the 9 kg level was only used in conjunction with GS, the two lower levels were fed with all three forage types. Concentrate composition was also varied at the 6 and 3 kg levels by replacing, in each case, 2 kg CC with a special concentrate (SC) which, in addition to barley, wheat and soyabean meal contained, on an air-dry basis, 25 % fishmeal and 25 % protected fat in the form of Megalac

In many areas of the world grazing cattle lose weight for part of the year because the dry standing pasture on offer is of poor quality and animals are unable to eat enough to meet their maintenance energy requirements. In countries where growth promoting anabolic agents are used, a perod of liveweight loss may coincide with the functional life of an implanted agent. There is evidence to suggest that diethylstilboestrol, a xenobiotic with oestrogenic activity, may increase maintenance energy requirements (Rumsey, Tyrrell & Moe, 1980). This has the effect of increasing the rate of live-weight loss under restricted submaintenance feeding conditions (Oltjen et al. 1973). One of the most common anabolic agents currently in use is the naturally occurring oestrogen, oestradiol-17β. However, its effects on energy requirements of animals either gaining or losing weight are unknown.

Water soluble P fertilizers have been reported to be best for potato (Mattingly, 1963; Sharma, Grewal & Sud, 1976). However, they are irretrievably fixed in the acid soils because of their high P fixation capacity. Placement of P fertilizers is, therefore, necessary for their efficient use. Furrow placement of P fertilizers reduces their contact with soil and enhances P availability to the plants. Placement of P in spots, rather than in furrows, will further reduce the contact between the soil and the fertilizers and may improve its efficiency over furrow placement. The present investigation was undertaken to study the relative efficiency of these two methods of P application for potato in the spring season.

Organic manures, despite their low nutrient analysis, play a significant role in meeting fertilizer needs of crops. When manures are applied in conjunction with fertilizers, yields are generally higher than with equivalent fertilizers alone. An increase in the yield optima leads to uncertainties in working out fertilizer economy in quantitative terms. In order to overcome this, a concept of fixed yield is described in this paper.

Zinc deficiency has been one of the major micronutrient disorders of flooded rice. Several researchers have reported that Zn deficiency could be corrected by the application of various Zn fertilizers to soil (Mikkelsen & Brandon, 1975), to seedling root (Yoshida et al. 1970; Katyal & Ponnamperuma, 1975) or to plants as foliar spray. Also there has been much speculation about the most suitable form of Zn fertilizer for correcting Zn deficiency of flooded rice. A glasshouse study was conducted to compare the effectiveness of various Zn fertilizers for rice grown under flooded conditions.

Fertilizer work in the savannah soils of northern Nigeria has been largely confined to the two most limiting nutrients N and P. The gradual shift towards continuous intensive cultivation coupled with the introduction of improved crop varieties and better crop management has necessitated the consideration of other elements, such as magnesium. The widespread use of K fertilizer in the absence of Mg fertilization may have an adverse effect on Mg availability in view of the well-known ionic antagonisms between Mg and K in plant nutrition (Jacob, 1958; Welter & Werner, 1963). Plants require greater amounts of Mg than normal to prevent deficiency under conditions of high soil K (Ulrich & Ohki, 1956; Kabu & Toop, 1970). Therefore soils hitherto considered to be adequately supplied with Mg may well be suffering from induced Mg deficiency under the present fertilizer programme which involves only K as the major cation. Tobacco is an important cash crop generally rated as a high Mg demanding crop (Adams & Pearson, 1967). The growth characteristics of the crop (enormous leaf development and rapidity of plant growth) make it an excellent crop to study. The abnormality in growth of tobacco, now known as sand drown, was first observed on tobacco grown on sandy soils, especially during periods of excessive rainfall. The abnormality was later found to be due to Mg deficiency.