The influence of rest interval and grazing duration on herbage production of dryland lucerne (Medicago sativa L., cv. Hunter River) pastures was studied in a 6-year experiment on a black earth in subtropical southern Queensland. Rest intervals (R) of from 32 to 60 days were combined with grazing durations (G) of 4, 8 or 16 days, or with mowing (M), in the following treatments: (1) R32-4, (2) R32-G16, (3) R44-G4, (4) R44-G16, (5) R56-4, (6) R40-G8, (7) R36-M, (8) R48-M and (9) R60-M. Grazing was with sheep at a rate equivalent to 20/ha on a year-round basis. Amounts of dry matter of lucerne and of volunteer species on offer were measured prior to grazing or mowing, and some measurements of the residue remaining after grazing were made. Chemical composition of representative lucerne samples was also determined.

Mean total amount of lucerne on offer declined from 10·8 to 7·2 t/ha/year between the first 2 years and the last 2 years, whereas total amount of volunteer species, principally grasses, increased from 3·0 to 18·2 t/ha/year over the same period. This difference was partly due to lower utilization of volunteer species. The decrease in amount of lucerne was due to loss of plants, and treatment effects arose through differences in the degree to which amounts from individual surviving plants increased to compensate for stand thinning. Concentrations of mineral elements in lucerne were always above critical levels for plant and animal growth.

Treatment R40-G8 maintained the largest amounts of lucerne on offer to the end of the experiment, with treatments R32-G4 and R32-G16 then having least. Large amounts of grass were associated with 4-day grazing, and to a lesser extent with short rest periods. The results confirm the need for a minimum rest period between grazings in a subtropical environment and also show the need for grazing to control excessive grass growth as well as lucerne if lucerne productivity is to be ensured. Some requirements which would lead to more successful management of lucerne in the subtropics are discussed.

During 1973–8 six field experiments examined the effect of 0, 41, 82, 124, 166 and 207 kg N/ha with and without irrigation on the growth, yield and quality of sugar beet. The culture of the crops was planned to produce a large yield in order to determine the optimal nitrogen application for the above-average crops which many growers are now seeking to produce. Ammonium nitrate was used as the nitrogen source, broadcast in one dose before sowing as was recommended practice in the early 1970s. The growth of the crop was monitored from the seedling stage to harvest in December, as was nitrogen uptake by the crop, and water removal from the soil using a neutron probe.

In 3 years when the weather was dry after drilling, the fertilizer significantly depressed the number of plants which established but plant weights showed that some nitrogen fertilizer was needed early for rapid seedling growth. Changes in the method of applying fertilizer for sugar beet are therefore suggested and are being tested. Soil analyses in the plough layer during establishment (May–June) indicated an optimum concentration of mineral nitrogen of about 40 mg N/kg soil at this stage.

Nitrogen fertilizer was very important for a high yield; throughout the growth of the crop it greatly increased total dry-matter yield and at final harvest this was reflected in sugar yield. Considering the six years together, sugar yield was linearly related to both dry-matter yield and total nitrogen uptake. However, within a year, increasing nitrogen uptake above 200 kg N/ha with nitrogen fertilizer did not increase sugar yield; maximum yields of sugar each year were normally obtained with 125 kg N/ha fertilizer or less, and irrigation had little effect on the optimum amount. Explanations for the lack of responsiveness of sugar beet to greater applications of nitrogen fertilizer are being sought in further more detailed analyses of the crop and its environment.

A pot experiment was made to study the effect of green manuring and iron application on the pE, pH, Fe concentration and iron equilibria in a calcareous and a noncalcareous soil. Green manuring drastically decreased the pE and pH and increased the Fe concentration of the equilibrium soil solution to a greater extent than submergence alone. Addition of Fe decreased pE, pH and increased Fe concentration both with and without green manuring. In calcareous soil pE and pH were high and Fe concentration was low compared with non-calcareous soil. In the absence of green manure and added iron, although there were wide variations in pE, pH and Fe concentration, Fe(OH)3-Fe2+; Fe3(OH)8-Fe2 + and Fe(OH)3-Fe3(OH)8 systems were controlling the solubility of Fe after 1 week of submergence in both the soils. But on green manuring all the above systems in calcareous soil and only Fe(OH)3-Fe3(OH)8 system in non-calcareous soil were operating at 1 week of submergence and continued afterwards. Addition of iron, with and without green manure, failed to bring an appreciable effect on these systems in calcareous and as well as in non-calcareous soil.

The soils of on area around Llangadog (mid-Wales) have been systematically sampled on a grid basis at 0–8 cm and 30–35 cm depths.

A P-sorption index was determined for these samples as were Fe and Al extractable by both 0·1 M K-pyrophosphate solution and 0·2 M-NH4-oxalate solution at pH 3. The reactivities of the soils with 1 M-NaF solution at pH 6·8 and pH 8 were also measured.

The results were stratified in terms of parent material, soil classification at subgroup level and soil series, and correlation coefficients calculated between the P-sorption index and the other variables (singly and in combination).

Only pyrophosphate-extractable Fe, i.e. ‘organically bound’, correlated reasonably well with the P-sorption index. However, the correlation was such that tolerably good estimates of P-sorption in an agronomic context could be made from pyrophosphate-extractable Fe values only for previously uncultivated brown podzolic soils (Manod series).

Fluoride reactivities at both pH values were poor predictors of P-sorption in these soils. Fluoride reactivity at pH 6·8 and oxalate-extractable Al, which have both been proposed as indices of the amounts of ‘poorly-ordered’ Al compounds in soils, failed to group these soils in similar ways. Doubt exists therefore as to whether these variables are measures of the same (or similar) property in these soils.

Five selections of Stylosanthes guianensis var. guianensis with a short-day flowering response were grown at three sites at altitudes of 10, 280 and 1000 m on the island of Bali, Indonesia at latitude ca. 8° 30′ S. Mean site temperature was ca. 6 °C lower at the highest site whilst mean short-wave radiation was lowest at the intermediate site.

Date of 50% floral initiation (FI) varied from 1 February to 21 June, when daylength (sunrise to sunset plus half civil twilight) decreased from 12·85 to 12·00 h. FI was independent of site for cv. Graham and cv. Cook, but at 1000 m it was 14 and 77 days earlier for cv. Endeavour and cv. Schofield respectively relative to the 280 m site. Little flowering of cv. Schofield occurred at 10 m, and it is suggested that cool temperatures promoted an increase in the critical photoperiod for this cultivar, or that warm temperatures inhibited flowering. FI was delayed at 1000 m in CPI 34906.

The duration of the phase from FI to flower appearance (FA) varied from 29 to 75 days according to selection and to site, and was negatively related to mean temperature, radiation, and maximum temperature for cv. Graham, cv. Cook, and CPI 34906 (but not for cv. Endeavour). Number of nodes at FA in this determinate species generally reflected growing conditions in the pre-flowering phase and was positively associated with age at FA in plants of particular varieties.

Seed production of five selections of Stylosanthes guianensis var. guianensis was studied in Bali, Indonesia (latitude 8° 30′ S) with a series of harvests at three sites of increasing altitude and rainfall: (1) Sesetan, 10 m, (2) Kuwum, 280 m and (3) Pekarangan, 1000 m. Seed yield of cv. Graham, CPI 34906, cv. Cook and cv. Endeavour was maximal at Sesetan with yields of 109, 39, 38 and 166 g/m2 respectively, whilst cv. Schofield, which flowered little at low altitude, produced 12 g/m2 at Pekarangan. Optimum time of harvest varied from 26 April for cv. Graham at Sesetan to 1 November for cv. Schofield at Pekarangan. Yield stability over sites was greatest in cv. Graham, in which increased number of florets per spike at high altitude partially compensated for negative altitudinal effects on spike density. Disease reduced yields of cv. Cook and cv. Endeavour at Kuwum and Pekarangan and the incidence of rainfall at advanced stages of crop development reduced spike density and seed maturation.

It is suggested that the high seed yields attained at the low altitude, low latitude Sesetan site were attained via (1) vigorous vegetative growth and a longer duration of floral induction resulting in high bud site density, (2) high bud site fertility, (3) high seed set (ca. 70–80%), (4) high seed weight and (5) little or no disease or insect damage. The greater synchrony of flowering at higher latitude sites may be less critical for high levels of seed production than the greater length of crop development available at low latitudes.

Fat thickness measurements, taken over the M. longissimus between the 6th and 13th ribs by the automatic-recording probes, SFK Meat-Fat probe (MF), Hennessy and Chong Fat Depth Indicator (FDI) and Ulster probe (UP), and a simple ruler probe (RP), were compared with one another and a visual fat score (VSC) in terms of the precision with which carcass lean and subcutaneous fat percentages were predicted. The comparisons were made in four separate trials with RP and VSC common to all of them. A total of 182 carcasses were involved; 130 of these were probed both hot and cold. Comparisons were made among carcasses of the same weight.

VSC was the best single predictor in most circumstances. Fat thickness measurements taken on the cold carcass provided a more precise prediction than those taken on the hot carcass. There was an interaction between the relative precision of the MF and RP probes and the condition of the carcass: the former generally gave the more precise prediction on cold carcasses and the latter on hot carcasses. Measurements taken by FDI tended to be better predictors than those taken by RP on both hot and cold carcasses. The use of two fat thickness measurements gave an improvement in precision over the best individual fat thickness measurements. There was also an improvement in precision in most circumstances when a fat thickness measurement was used in addition to VSC.

There was little indication that specific fat measurements were particularly precise predictors when taken by specific probes, and no fat measurement was consistently the best predictor. A measurement taken 7·5 cm from the dorsal mid line at the 6th rib occurred most commonly in pairs of measurements giving the most precise prediction.

Hormonal anabolic compounds are used in certain countries to improve the efficiency of meat production from ruminant animals. The combination of trenbolone acetate (TBA) and oestradiol-17β (OE2) has been shown to be particularly effective in stimulating growth in cattle (e.g. Galbraith & Topps, 1981). These improvements in growth have been associated with increases in nitrogen retention and changes in protein metabolism within the animal. The present study therefore investigated the effect of implantation with TBA + OE2 on the growth and metabolic response of growing steers to alterations in protein nutrition.

Public concern continues to be expressed about the quality of water discharged from agricultural lands. High concentrations of nitrate nitrogen are often blamed on modern agricultural practice in general and to land drainage in particular (Royal Commission on Environmental Pollution, 1979, para. 4.38). However, undrained land also discharges water by flow within the soil and across the soil surface and it may discharge significant quantities of solutes.