1. In an experiment conducted on an established perennial rye-grass/white clover sward close cutting was carried out over a 3-year period (1956–58), either with a lawn mower to simulate gang mowing or with a reciprocating-knife mower. The sward was cut either six or eight times in each season, and received 0 or 2 cwt. ‘Nitro-Chalk’/acre for each cut.

2. Swards cut with the gang mower yielded from 3·5 to 12·5% more herbage dry matter than swards cut with the reciprocating-knife mower and also gave a greater mean yield of crude protein.

3. The difference in dry-matter yield between swards cut with each of the mowers is attributed to the slightly closer cutting level of the gang mower having a greater inhibiting effect on flower development in the grasses and hence stimulating leaf production and increasing total yields.

4. In the second and third years of the experiment swards cut with the gang mower outyielded those cut with the reciprocating-knife mower by a proportionately greater amount when eight cuts rather than six cuts were taken in the season.

5. When no nitrogenous fertilizer was applied the proportion of broad-leaved weeds in the sward increased more rapidly over the 3-year period where the herbage was cut with the gang mower rather than the reciprocating-knife mower. This disadvantage of gang mowing did not apply where the fertility was maintained at a high level by applications of nitrogenous fertilizer.

6. It is concluded that the gang mower is a more suitable machine than the reciprocating-knife mower for close cutting on a field scale.

The activity of alanine aminotransferase (Al. T) was determined in serum and liver biopsy samples collected from cows over a period of more than a year. There were statistically significant fluctuations in both liver and serum activities during the period of observation. On the whole serum and liver activities appeared to fluctuate independently of one another and of climatic changes. The only possible correlation was between the rate of increase in hours of daylight and the increases in serum and liver activities in the period January to March. The cows were calving at intervals throughout the year, and their liver and serum Al.T activities did not change significantly during the last three months of pregnancy and the first 3 months of lactation.

Six ewes were milked over a lactation period of 12 weeks beginning 2 weeks after parturition. Milk fat, total crude protein, and protein fractions were determined in each weekly milk sample.

Milk fat and total crude protein in whole milk increased significantly over the lactation, attaining mean values of 5.8 and 5.9% respectively. The concentration of the caseins, total albumins and β-lactoglobulin in the whole milk also increased significantly over the lactation, with mean concentrations of 4.67, 0.80 and 0.54% respectively. The mean concentrations of these fractions, expressed as a percentage of the total crude protein, were, caseins 78.7, total albumins 13.5 and β-lactoglobulin 9.1.

The following fractions, whose mean percentage concentrations in whole milk are given in parentheses, showed no significant trends over the lactation: α-lactalbumin + serum albumin (0.26), proteose-peptones (0.05), globulins (0.06) and non-protein nitrogen (0.35). Expressed as percentages of total crude protein, these concentrations are 4.4, 0.8, 1.1 and 5.6 respectively.

The milk constituents synthesized in the mammary gland, i.e. fat, caseins and β-lactoglobulin showed significant correlations in concentration in whole milk as well as significant increases in concentration over the lactation.

Two experiments were carried out to examine the value of copper, cobalt and selenium contained in soluble glass boluses as a means of providing supplementary trace elements to goats.

In the first experiment 36 purebred Toggenburg goats were used and divided into two groups. One group was treated with soluble glass boluses while the other was left as control.

In the second experiment 46 Saanen half-bred goats were used, divided into three groups. The first group was treated with soluble glass boluses, the second was treated with selenium injectable compound and the third was left as control.

Blood samples were collected on four occasions, during an experimental period of almost 12 months and plasma copper, serum vitamin B12 and blood selenium concentrations were determined. All those measurements showed significant increases for about a year, and were due to treatment. The advantages of glass boluses were not shared by the selenium injectable compound.

Gestational age-related changes in plasma free thyroxine (FT4) concentration in maternal and foetal goats were determined for 65–140 days of pregnancy. The placental permeability to maternal thyroxine (T4) and iodine (I) during the last trimester of pregnancy was evaluated.

The presence of T4 in foetal circulation at 65 days' gestation, the absence of a significant correlation between maternal and foetal levels and the absence of any transplacental diffusion of 125I–T4 showed autonomous foetal thyroid function during pregnancy in goats. Significantly low maternal FT4 was measured at 95 and 110 days' gestation (32·7 and 31·5 pmol/1 respectively). Plasma concentration increased to 48·6 pmol/1 at day 125 then fell before parturition to a level similar to that of non-pregnant goats (41·9 pmol/1). In contrast, foetal FT4 increased with gestational age to 110 and 125 days when levels of 64·0 and 59·1 pmol/1 respectively were greater than those at all other ages, suggesting that the foetal hypothalamic-pituitary-thyroid is functioning at a higher rate than the maternal system around this time. This was supported by increased foetal thyroid affinity for I when compared with the maternal thyroid at 110–140 days' gestation.

A significant cubic relationship between foetal FT4 and gestational age was established.

There is evidence from solution culture studies that ammonium nitrogen is taken up by grass preferentially to NO3-N at low temperatures (Clarkson & Warner, 1979). In addition NH4 ions are less subject to leaching losses or denitrification (Ryden, 1982). It has been speculated therefore that ammonium N could be the best form of nitrogen for early grass, especially in wet springs. Field experiments have studied the efficiency of different nitrogen forms at the first application over a number of years (McAllister et al. 1965; Van Burg, Dilz & Prins, 1982). The yield response has tended to be variable and may have depended on climatic and soil conditions. Investigations of climatic effects on fertilizer efficiency have often necessitated long-term field studies, but it is proposed that the importance of rainfall in particular could be investigated by means of a short-term irrigation experiment. This paper reports such an experiment using irrigation to simulate a wet spring while keeping other conditions the same for all treatments.

Fifteen British Friesian steers were reared using grain and forages which had been grown on land which has had a long history of use for disposal of sewage sludges. The food consumption was recorded and samples of feedingstuffs analysed for Cd, Cr, Cu, Ni and Zn. The various components used in compounding the feedingstuffs were also analysed. After about 13 months the animals were slaughtered and samples of various organs and tissues obtained for analysis.

The majority of the Cd, Cr, Cu and Zn came from sources other than uptake into plants. The largest single contributor was the high phosphate mineral supplement. No animal health problem due to the feed regime was encountered. Concentrations of cadmium in liver and kidney were slightly higher than average. Muscle cadmium concentrations of Cr, Cu, Pb, Ni and Zn were within the range of published values.

Infection of pearl millet by downy mildew [Sclerospora graminicola (Sacc.) Schrot.] has been shown to be influenced by soil pH, soil bulk density, soil moisture content and addition of farmyard manure and nitrogen fixing bacteria. A pH value of 8·5 allowed disease to develop the most, with increases in acidity to pH 7·5 producing 70% reduction in disease. Higher soil bulk density and moisture content also led to reductions in disease but the effects were not as marked as for pH. The addition of farmyard manure to soil or the addition of Rhizobium, Azospirillum or Azotobacter inocula as combined seed and soil treatment also reduced disease with the best effects being from a cluster bean isolate of Rhizobium and from Azotobacter chroococcum. Assessment of rhizosphere microorganisms associated with the resistant and susceptible varieties of pearl millet showed that, overall, the fungal population was lower in the resistant varieties but that it was increased in both susceptible and resistant varieties by infection with downy mildew. Bacterial and actinomycete populations were also lower in resistant varieties but in this case downy mildew infection decreased the rhizosphere populations of both groups.

Dehydrogenase activity of rhizosphere soil was higher in susceptible varieties but was decreased in both variety types by infection with S. graminicola.

The results are discussed with reference to possible mechanisms to explain the observed effects.

The original object of the breeding investigations described above was to secure a new variety of oats exhibiting the resistance to winter conditions and the grain quality characteristic of Grey Winter, in combination, if possible, with straw of better standing power.

The characters of the hybrids studied in the course of the investigations were accordingly resistance to winter conditions, standing power of the straw, quality of the grain, and the early growth habit, particularly in relation to these three features.

The duration of the breeding season was studied in 33 Suffolk × Galway ewe lambs which had a mean live weight of 45·9 ± 1·4 kg. The mean dates of onset and cessation of oestrous activity were 8 November ± 1·4 days and 12 January ± 2·6 days, respectively. The mean number of heat periods exhibited was 4·37 0·3 and the duration of the breeding season was 81 ± 5·7 days. Only 18·2 % of animals had ≥ 6 heat periods while 45·5 % of animals had ≤ 3 heat periods. The incidence of silent heats was 9·2 %.

Micro-organisms from the rumen of a hay-fed sheep rapidly synthesized an intracellular polysaccharide (starch) when growing or resting suspensions of cells were incubated in vitro with easily metabolized sugars.

In 30 min incubation periods the optimum pH for the synthesis of starch by resting cultures was about 6·0 when glucose or fructose were substrates. Relative to glucose (as 100%) in ability to form the polysaccharide were, fructose, 75%; sucrose, 80%; soluble starch, 18·6%; maltose, 6·9%; cellobiose, 4%; and xylose, 2·1%. No starch was formed from galacturonic, acetic, propionic, butyric, lactic or succinic acids. A bacterial fraction of the microbes was reponsible for about 80% of the starch formed from glucose, fructose or sucrose.

In incubations of 24 h, resting cultures formed more starch per unit of microbial protein than growing cultures. The utilization of microbial starch and lactic acid, formation of which often accompanied starch synthesis, gave rise to volatile fatty acids. Acid production was maintained from these substrates at rates similar to those obtained from the fermentation of glucose. The acids were in molar proportions of 65–70% acetic, 20–27% propionic and 8–15% butyric. The maximum starch calculated to be synthesized by the microbes from 100 ml of rumen liquor, in media containing excess sugar, amounted to over 250 mg from glucose, 200 mg from fructose, 200 mg from cellobiose and 50 mg from xylose. It is calculated that under optimum conditions for synthesis about 25 g of starch would pass daily from the rumen of a sheep.

Field experiments were made during the rainy seasons of 1979 and 1980 at Hissar, India, to study the effect of time of weed removal on the yield of groundnut. Removing weeds from 2 to 8 weeks after sowing led to significantly larger yields than that of plots which were not weeded. Maximum pod yield in both years was obtained when weeds were removed 4 weeks after crop sowing.

At high northern latitudes, growing seasons are short with long days. In these conditions, tillering is an unwanted trait in barley (Hordeum vulgare L.), because the grains on tillers develop later than those on the main stem and are often harvested before they are fully mature, leading to reductions in overall quality. Hence, the uniculm growth habit has been considered an interesting option for boreal barley production. The aim of the present study was to determine the differences in the yield formation of conventional tillering and uniculm barley, using two pairs of near-isogenic lines and two controls. Uniculm and conventional tillering barley were grown in three experiments conducted at Suitia Experimental Farm, University Helsinki, Finland during 1999–2001. Samples were collected frequently to monitor the biomass and leaf area accumulation. Water-soluble carbohydrate content was analysed at anthesis and at maturity in different plant parts. At maturity, the numbers of spikes/plant and grains/spike were calculated and grain yield weighed. The grain yield of the uniculm barleys was stable over these growing seasons, but it was only half that of the conventional barley cultivars due to the absence of spike-bearing tillers, lower spike grain number and spike weight. In addition, the ability to transport photosynthesized carbohydrates to grains may have been reduced. Thus, it seems that uniculm barleys do not provide further improvement in barley yield.

An experiment was conducted with 63 July-born Friesian heifer calves, purchased at an average age of 10 days and fed cold reconstituted milk substitute for 4, 6 or 8 weeks. The sole ‘solid’ feed was dried grass, chopped and fed loose (a), milled through a 6 mm screen and pelleted (b) or milled through a 3 mm screen and pelleted (c). The experiment was of 3 x 3 factorial design.

Calves fed milk for 4, 6 or 8 weeks consumed mean amounts of 20, 42 and 63 kg milk D.M. respectively. During the first 10 weeks the mean daily intake of grass b was significantly greater than that of grasses a or c (0.77, 1.09 and 0.89 kg D.M. for grasses a, b and c respectively) and during weeks 11 to 21 the mean intake of grasses b and c was greater than that of a (3.1, 4.1, 3.7 kg D.M. for grasses a, b and c respectively). Also during weeks 11 to 21 the previous milk feeding had a small but significant effect on the mean daily intake of grass (3.4, 3.7, 3.8 kg D.M./head/day for 4, 6 and 8 weeks of milk feeding respectively).

Increasing the period of milk feeding significantly increased the rate of live-weight gain during the first 10 weeks, but subsequently had no effect. During the first 10 weeks and during weeks 11–21, feeding grass b or c significantly increased the rate of liveweight gain compared with grass a but had no effect during a period of uniform feeding, weeks 23–34.

During the first 21 weeks feed conversion efficiency was positively related to duration of milk feeding, and was greater for calves given grass b or c than, for thoso given grass a.

During weeks 23–34, 36 calves (4 from each original treatment) were fed another uniformly milled and pelleted dried grass. There were no significant differences in voluntary intake, live-weight gain or efficiency of food conversion between the groups of calves during this period. Hence the results of this experiment support previous observations, that when only forage diets are fed the effect of level of early nutrition is still evident in live weights of calves at 6 months of age.

Milk yields determined by a lamb-suckling and an oxytocin technique were compared using a control group of four ewes. Both methods showed a similar linear decrease in yield with advancing lactation, but the oxytocin method gave 23% more milk presumably because residual milk was included.

When the diet of lactating ewes was changed so that the amounts of hay and commercial concentrates were reduced in favour of flaked maize, such severe acidosis developed when 39·5% of this food was introduced abruptly or 53% more gradually over one week, that the trials were discontinued.

Rolled barley, which probably ferments more slowly, was therefore used instead of flaked maize. Levels up to 62·9%, gradually introduced over a period of 3 weeks, also produced acidosis whose severity varied greatly in individual ewes.

Milk yield was also determined by the oxytocin technique for ewes receiving normal diets followed by those rich in rolled barley, and the milk was analysed for fat, protein and lactose. The composition of the milk was extremely variable during rolled barley feeding, but there was an indication of an increase in the percentage of crude protein and also fat, after a marked fall in the latter in the milk of two ewes with the change to the low-fibre diet.

Diet had little effect on yields of milk and its components but, on the rolled barley diets, the rate of decrease of these yields was arrested (or even reversed in the case of fat), with a high degree of significance (milk yield P < 0·05, fat yield P < 0·01, protein yield P < 0·01). These observations are discussed, in the light of knowledge on the effect of diet on molar proportions of volatile fatty acids in the rumen.

Crosses between eelworm-resistant tetraploid red clover plants varied significantly in corolla tube length and in the distance between the top of the nectar and mouth of the corolla tube. Variability between plants in height of nectar above the base of the corolla was positively correlated with corolla tube length but a significant residual variance in nectar height was independent of corolla tube length.

Tetraploids had higher nectar but longer corolla tubes and greater distances for bees to reach than those in related diploids which were previously reported.

The implications of the findings are discussed in relation to the improvement by breeding of the attractiveness of tetraploid red clover to honey-bees.

1. The question whether the amount of cystine in the wool grown may exceed that in the diet is discussed.

2. When 1 gm. of laevo-cystine was added to the daily ration of a ewe on a low protein diet, the wool grown upon a circumscribed area was 14 per cent, more than that grown during a similar period immediately preceding. Four-fifths of the sulphur in the added cystine was absorbed, about half of which was excreted in the urine during the period the cystine was being fed.

3. When 1 gm. of laevo-cystein was injected subcutaneously each day for 10 days, a 34 per cent, increase in wool growth occurred. During three succeeding periods, of 10 days each, immediately after the injections had been discontinued, the increases were 30, 18 and 7 per cent, respectively. Of the 2.6 gm. of sulphur in the cystein injected during the 10 days, 1.7 gm. was retained and could be accounted for by the extra amount of wool grown during that and the succeeding periods.

The Journal of Agricultural Science, Cambridge has been a fixture in dissemination of crop simulation models and the concepts and data upon which they are built since the inception of computers and computer modelling in the mid-20th century. To quantify the performance of a crop simulation model, model outputs are compared with observed values using statistical measures of bias, i.e. the difference between simulated and observed values. While applying these statistical measures is unambiguous for the experienced user, the same cannot always be said of determining the observed or simulated values. For example, differences in accessing crop development can be due to the subjectivity of an observer or to a definition that is difficult to apply in the field. Methods of determining kernel number, kernel mass, and yield can vary among researchers, which can add errors to comparisons between experimental observations and simulated results. If kernel moisture is not carefully determined and reported it can add error to values of grain yield and kernels per unit area regardless of the protocol used to collect these data. Inaccurate determination of kernel moisture will also influence computation of grain protein or oil content. Problems can also be associated with input data to the simulation models. Under-reporting of precipitation values from tipping bucket rain gauges, commonly found on automated weather stations, can introduce errors in results from crop simulation models. Using weather data collected too far from an experimental site may compound problems with input data. The importance of accurate soil and weather input data increases as the environment becomes more limiting for plant growth and development. Problems can also arise from algorithms that calculate important parameters in a model, such as daylength, which is used to determine a photoperiod response. Errors in the calculation of photoperiod can be related to the definition of sunrise and sunset and the inclusion or exclusion of civil twilight or to the improper calculation of the solar declination. Even the simple calculation of the daily mean air temperature can have an impact on the results from a non-linear algorithm. During a period when crop simulation modelling is moving in the difficult direction of incorporating genomic-based inputs, the critical importance of careful and accurate collection and reporting of field data and the need to develop robust algorithms that accommodate readily available or easily acquired input data should not be forgotten. As scientists we have an obligation to provide the best available knowledge and understanding as possible. Avoiding potential pitfalls will assist us as we develop new knowledge and understanding and incorporate these concepts into new or modified crop simulation models.

Three soya-bean (Glycine max L.) genotypes (Bragg, Type I and Hark) were grown in Mollisol supplemented with 0, 2·5, 5·0 mg Zn/kg in pot-culture experiments. The genotypes showed significant differences in their capacity to absorb Zn. Maximum Zn accumulation was found in the genotype Bragg and minimum in Hark. The pattern of Zn distribution in plant parts was also different in the three genotypes and was differently affected by Zn application. The uptake and percentage distribution of 66Zn followed more or less the same trend as that of total Zn. The genotypes differed significantly in R(recovery), A(availability of native Zn) and L(labile soil Zn) value indicating that these three genotypes differed in their capacity for recovering applied and native Zn. The genotype Bragg had maximum R, A and L values. These results correspond well with the reported tolerance of these genotypes to Zn deficiency (Bragg > Type I > Hark).

Varietal identification is an important aspect of crop research and utilization. Identification using computer-based image analysis could be an alternative to visual identification. However, the effectiveness of image analysis systems needs to be established under various real conditions. Three wheat varieties were sown on three different dates. Variation in the grain size and shape of these varieties, brought about by changes in the environmental conditions, was measured using Comprehensive Image Processing Software (CIPS). Some parameters showed considerable grain-to-grain variation, which was either inherent or due to environmental changes during grain filling. Euclidean distances were calculated using either means of all the parameters (ED1), or using only those parameters that did not show a high coefficient of variation (ED2). For samples of the same variety sown at different times, Euclidean distances were smaller compared with samples of different varieties, indicating that grains of the same variety resembled one another. By using the criterion of minimum Euclidean distance it was possible to distinguish between varieties, in spite of variation in grain shape and size due to environmental conditions. It was possible to identify correctly an unknown sample, taken as a test case.