An experiment was conducted during the rabi seasons of 1980–1 and 1981–2 to study the effect of exchangeable sodium percentage (ESP) of 87, 62, 44, 34 and 27 on growth, yield and chemical composition of toria (Brassica campestris var. Toria), raya (Brassica juncea L.) rapeseed (Brassica campestris var. Brown Sarson) and taramira (Eruca saliva). Number of branches per plant, number of siliquae per plant and seed yield of these crops were highest at 27 ESP. Increasing ESP decreased N, P, K, Ca, Mg, Fe, Zn, Cu and Mn concentrations and decreased that of Na in seed and stover. These crops can be grown successfully up to about 44 ESP without significant reduction in yield. Raya and rapeseed produced higher yields than the other oilseed crops on sodic soil.

Soil samples taken in the autumn after ploughing ryegrass, clover, and ryegrass/clover leys were used to measure the mineral-N (ammonium-N + nitrate-N) in the fresh soil (mineral-Nfresh), the increase in mineral-N on incubating the fresh soils (Δmineral-Nfresh), and the increase in mineral-N on incubating the re-wetted air-dry soils (Δmineral -Nair-dry). Mineral-Nfresh and Δ mineral-Nair-dry were measured on further soil samples taken the following spring. Values of Δmineral-Nair-dry, not only correlated best with grain yields and N uptakes by wheat without fertilizer-N, but also with yield responses and fertilizer-N recovered from fertilizer-N applied to the winter wheat.

Treatment of the ley altered measurements on samples taken in the autumn but not those taken the following spring.

Soil samples taken in the autumn 1960 from under three-year grass leys were used to measure mineral-Nfresh, Δ mineral-Nfresh and Δ mineral-Nair-dry Spring wheat was grown in 1961 followed by spring barley in 1962. Further soil samples were taken in spring 1962 after cultivations were complete and before the barley was sown or fertilizers applied.

A mineral-Nair-dry was the best measurement to use on soils from under grass leys. Values depended on grass species, and were increased by N applied to the ley. Differences had largely disappeared 18 months later. A mineral-Nalr.dry was positively correlated with grain yields of spring wheat grown both with and without fertilizer-N, and with the yield response or the nitrogen recovered from, a dressing of 56 lb N/acre.

With fertilizer-N yields of winter wheat after the mixed leys tended to the same maximum value independently ofmineralizable-N in the soil. After grass leys maximum yields of spring wheat given fertilizer-N increased with increasing mineralizable-N in the soil.

Effects of diseases on growth and yield of linseed (cv. Antares) were assessed by controlling diseases with fungicide treatments in field experiments at Rothamsted from 1988 to 1990. Fungicide seed treatments decreased the incidence of Alternaria lesions on cotyledons and stem bases of emerging seedlings in 1989 but decreased emergence in 1990. The incidenceof leaf browning, associated with Alternaria spp. and Botrytis cinerea, was less in 1989 and 1990 than in 1988 when the period, in July, between flowering and harvest was wet, but the incidence of powdery mildew was greater in 1989 and 1990 than in 1988. Fungicide spraysdecreased leaf browning in 1988 and powdery mildew in 1990. In 1988 there were more capsules per plant and the crop was taller than in either 1990 or 1989, when July and August were hot withperiods of dry weather. The incidence of plants with dark brown stems, associated with Verticillhun dahliae, was greater in 1989 and 1990 than in 1988, but was not greatly affected byfungicide treatments. The incidence of Alternaria linicola on sepals, capsule cases and seed from capsules sampled before harvest was decreased by fungicide treatments. Other fungi isolated from these tissues included A. alternata, A. infectoria, B. cinerea, Fusarium spp. and V. dahliae. Yields of grain and oil were increased by fungicide treatments in all three years, but the yield increases were greatest in 1988 when fungicide treatments also increased 1000-grain weight. The incidence of fungi on the harvested seed was not greatly affected by fungicide treatments.

Wheat production in Australia relies heavily on superphosphate to maintain maximum grain yields. The current rock-phosphate supplies for superphosphate manufacture are derived from Nauru and Christmas Island in the Pacific Ocean; these supplies are anticipated to last only for the next 10–20 years. The supplies of ‘A’ grade ore (apatite) which can be used directly for superphosphate production are greatly overshadowed by large amounts of lower grade rock phosphate which is high in total phosphate but low in apatite. This material is termed ‘C’ grade rock and, to date, it has found little use in Australian agriculture.

1. A brief description is given of an experiment in which some of the factors influencing the role of clover in grass—clover swards fertilized with nitrogen at different rates were studied.

2. Reference is made to a previous paper detailing the experimental methods and reporting the results pertaining to the effects of the grass varieties included in the seeds mixture on the yields of mixed herbage and of clover. The effects of the clover varieties on these yields are discussed in the present paper.

1. The consolidation in a light soil produced by sheep folding has been investigated.

2. The soil affected extended to a depth of 10 cm., the maximum compression occurring at a depth of 3–4 cm.

3. The consolidation produced was not totally destroyed by ploughing and was still apparent 5 weeks later when the seed was drilled.

In the introduction the crying need for research into animal nutrition under tropical conditions is emphasised. In Trinidad the stock are normally fed on mixed natural herbage grazed or cut from waste areas or from cultivated perennial grass crops. This system of rationing is a common one in many insular tropical climates.

The experiment was designed to test the effect of stage of cutting on the yield and composition of Elephant Grass (Pennisetum purpureum), a perennial fodder grass widely cultivated in Trinidad to-day. Three times of cutting were chosen, namely series A—cut every four weeks, series B— cut every eight weeks, and series C— cut every twelve weeks.

Two gene markers were observed among cowpea breeding lines in Ibadan, Nigeria. One is the swollen stem base which is due to a larger quantity of phloem parenchyma in the bottom part of the stem below the first primary leaf than in the normal stem. It is inherited as a simple dominant trait and the symbol Sw is suggested. The other is the hastate-leaf which is expressed as extremely narrow trifoliate compared with the normal. It is inherited as a simple dominant trait and the symbol Ha is suggested. Dominance may not be complete in both cases as variable expressions of the marker genes were observed in F2. The effects of the marker genes on yield and other characters are currently being investigated.

Field experiments were conducted at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, for four seasons to evaluate the effect of harvest interval on yield, quality and viability of indeterminate cowpea (Vigna unguiculata (L.) Walp.) seeds. Decreasing harvest frequency from every week to every 4 weeks reduced seed yield, quality and viability. Rate of yield losses was highest at close spacing and intermediate at wide spacing during the first rainy season, and lowest at wide spacing with supplementary irrigation during second rainy season. Time of harvest study conducted with six cultivars indicated that these yield losses were attributable to reduced seed weight and increased pod losses after mature pods were exposed to weathering for more than 1 week. The reduction in seed quality and viability was associated with a high degree of fungal and bacterial infection in the seed. Varietal differences in resistance to weathering were noted among the cultivars tested. TVu 2616 P-O1D, that has thick, leathery pods and smooth, tan seed coat was the most resistant to weathering.

The mechanical and eleetromyographic activity of the pyloric antrum and duodenum of sheep has been studied both under resting conditions and while infusing various solutions to alter the chemical composition of the chyme.

Bursts of spike-type electrical activity, synchronized with the depolarization phase of slower potential variations, accompanied duodenal contractions. Both mechanical distension and chemical stimulation of the proximal duodenum influenced the electrical activity and led to changes in the frequency, duration and amplitude of contractions.

1. A study of the length of the rachilla in barley shows that it is a varietal character, although strongly affected by environmental factors.

2. Rachilla length as a varietal character is affected by the density of the ear and the type of hairs or bristles borne on the rachilla.

3. In six-row barleys the length of the rachilla of the lateral spikelet is greater than that of the corresponding median spikelet.

4. In the absence of any of the complicating factors mentioned above, rachilla length is inherited as a straightforward quantitative character with an intermediate F1 and no signs of segregation in the F2. The number of major factors when the extremes of length are hybridized appears to be in the neighbourhood of four.

5. Hybridization of “Archer” and “Chevallier” type parents has given “dominance” of length and a possible heterotic effect. Long rachilla in these crosses appears to be linked with the “Chevallier” rachilla type.

Two field experiments were made to examine differences in wheat variety response to applied superphosphate. In the first experiment, conducted under dry conditions, both yield and yield response to superphosphate were low; in the second experiment some semi-dwarf wheats showed a greater response than standard-height wheat varieties. The semi-dwarf wheats had a greater proportion of plant phosphorus in the reproductive sections of the plant at maturity. The semi-dwarf variety Israel M 68 also showed the greatest increase in root production following the application of superphosphate.

1. Attention is drawn to Mason's modification of Livingston's soilpoint method of directly estimating the water-supplying power of a soil in situ. Mason used ordinary lead writing pencils as soil-points.

2. This method, heretofore tested only in the laboratory, has been employed by the writer in an ecological field study. Details of the procedure adopted are described, and the reliability of the method is indicated by the presentation of a series of mean results with their corresponding probable errors.

3. It is concluded that the method is practicable; it should prove of considerable usefulness to workers in ecology.

The moisture regimes of three soils under grassland in midland England were investigated using a neutron probe moisture meter from May 1976 until August 1978. The main aim of the experiments was to compare the differential build-up of moisture deficits in the three soils of different texture by monitoring moisture extraction down to 1·50 m depth. The moisture deficits measured by neutron probe were also compared with those predicted from meteorological data using the Grindley (1970) model.

The sandy (Newport) soil dried out more quickly and more completely than the clayey (Worcester) or fine loamy over clayey stagnogley (Salop) soil, particularly in 1976. This reflected the fact that the former had the smallest available water, most of which is held at low suctions, whereas the Salop soil, with much of its water bound at high suctions, continued to supply small amounts to plant roots when the available water in both the other soils was exhausted.

The soil moisture deficits determined from neutron probe measurements were much larger at all three sites in 1976 than in the following 2 years. The deficit increased more slowly in the Salop soil than in the other two in the early part of 1976 and more slowly than predicted by the Grindley model. However, during July and August of the same year, deficits in the Salop and Worcester soils increased more quickly than predicted and maximum deficits were in proportion to the available water capacities of the three soils. Deficits in 1978 were very small (less than 70 mm) in all three soils because of the wetter weather.

The results of this neutron probe study clearly show that the patterns of moisture extraction and the maximum deficits which developed in the three soils, particularly in 1976, are closely related to their physical properties, as determined from undisturbed soil cores.

Efforts were made to obtain forage cultivars with high production capacity and quality and to determine the ideal time to start animal grazing, respecting the morphological characteristics of the grasses. For this purpose, the nutritional value, digestibility and characteristics of the forage canopy of Aries and Aruana (Megathyrsus maximus (Jacq.) or Panicum maximum) cultivars kept under rotational stocking with sheep were evaluated and the management height was determined based on 95% light interception (LI). The experiment was evaluated with repeated measures over time (grazing cycles by season, in 2 years) with a treatment factor (grass cultivar) in a completely randomized block design with eight replicates, using 800 m2 paddocks. The height of the forage canopy before grazing (pre-grazing) determined by 95% LI stabilized around 29 cm. The highest proportion of Aruana leaf blades was observed in winter. Aries grass presented similar leaf blade percentages in summer, autumn and spring. Similar forage accumulation (FA) was observed for both cultivars, decreasing in spring, autumn and winter. Higher crude protein and in vitro dry matter digestibility (IVDMD) were seen in Aries grass, while Aruana grass presented higher neutral and acid detergent fibre and cellulose and lower IVDMD. The nutritional quality of the grasses was maintained throughout the year. The height of the forage canopy of Aries and Aruana recommended for entry into the paddock is 29 cm to maintain nutritional quality. The successful management strategy adopted for grasses combined with nitrogen fertilization provided a greater forage mass quality.

The incidence of various infectious and non-infectious diseases as causes of death in lambs up to 8 months of age was studied in relation to breed, inbreeding and other factors. The data from an upland grazing flock covered 6 years and involved the Scottish Blackface, Cheviot and Welsh Mountain breeds and the crosses among them.

Infectious and non-infectious diseases were directly responsible for almost a quarter of the mortality and their presence contributed to many more deaths. The organisms mainly responsible were Escherichia coli, Pasteurella spp. and Fusobacterium necrophorum.

The incidence of infectious diseases in general and enteritis in particular varied significantly between the breeds and was lower in the cross-breds than in the purebreds. Variation between the breeds in the incidence of non-infectious diseases was statistically significant only in respect of digestive upsets for which there was a similar ranking of breeds to that for infectious disease.

Inbreeding of the lamb (25–59%) significantly increased the incidence of infectious diseases, especially respiratory diseases, but not of non-infectious diseases. There was little difference between singles and twins in susceptibility to disease. The lower the birth weight of the lamb the greater the risk, particularly of non-infectious disease.

Six pairs of gilts were taken at first mating. One of each pair was given about half the A.R.C. recommended amounts of protein and energy during pregnancy and lactation until she became anoestrus (thin group). The other gilt of each pair was given the same amount of protein, but double the amount of energy (standard group).

All the thin sows lost condition and became infertile. Their appearance conformed to that of sows with the ‘thin sow syndrome’. This took up to three reproductive cycles. There was no clear effect on the number of piglets born, but the litters of the thin sows contained an increasing proportion of small piglets. One of the thin sows died in her second pregnancy. The standard sows performed well producing an average of 10·3 piglets weighing 1·4 kg over three parities.

There were no differences between the two groups in their digestive efficiency. The thin sows retained less nitrogen in the later stages (days 80–100) of their first pregnancy than did the standard sows.

There were no differences between the groups in milk production during the first lactation when litters were standardized at eight piglets. There was some evidence that in the second lactation the thin sows secreted less fat and lactose.

The five remaining thin sows were repleted at the end of the experiment when their average weight was 96 kg. They were mated as quickly, produced litters which were as large, and piglets which were as heavy as those produced by the standard sows whose mating weight was 182 kg.

Six late pregnant and six non-pregnant Finnish Landrace × Dorset Horn ewes were fed a standard diet. Blood and liver samples were taken and the concentrations of the following metabolites measured: adenine monophosphate (AMP), adenine diphosphate (ADP), adenine triphosphate (ATP), citrate, 2-oxoglutarate, phosphoenol-pyruvate, pyruvate, lactate, 2·phosphoglycerate, 3·phosphoglycerate, malate, β·hydroxybutyrate, acetoacetate, glutamate, alanine, NAD+ and NADH. Comparing non-pregnant with pregnant ewes the liver of the pregnant animals had reduced concentrations of lactate, ADP, NAD+ and NADH, and in the blood there were reductions in lactate, pyruvate, lactate/pyruvate ratio and urea. The concentrations of the other metabolites of the pregnant ewes receiving adequate nutrition were little changed from those of the non-pregnant ewes. The significance of these findings is discussed.

Two spring wheat varieties, Cardinal and Kolibri, were inoculated with Septoria nodorum Berk and S. tritici Rob. & Desm. at Growth Stages 3, 7, 10.1 and 10.5 of the Feekes' scale. The treatments included single inoculations at each growth stage and multiple inoculations at 2, 3 and 4 of the above growth stages.

Thousand-grain weights of both varieties were reduced by inoculation with either pathogen, S. nodorum causing the largest reduction. Numbers of grain per head in Cardinal were severely reduced by S. nodorum, particularly after the multiple inoculations. In Kolibri, there was evidence of increases in numbers of grain with S. tritici inoculation which nullified the grain size reductions. The results are discussed in relation to compensatory mechanisms and disease tolerance.