In this paper an examination is made of the processes operative and the limits of accuracy of the electrical method of determining soil moisture.

The resistance over a small plot is found to vary under similar conditions and it is concluded that these differences are most probably due to actual differences in moisture or other factors.

The effect of the distance apart of the electrodes is investigated and a probability of a minimum resistance between two electrodes being observed under certain conditions is indicated.

In a small plot experiment in which the crop was protected from rain, the application of large amounts of water to keep the soil water stress to a minimum gave very large crop yields. One-fifth of this amount of water gave 80% of the maximum yield. Small, frequent applications of water appeared to give higher yields than the same amount of water in one large application. Yield differences were due to differences in leaf areas rather than to differences in net assimilation rates.

1.Within a flock of 55 Welsh Mountain ewes maintained under lowland conditions the first ewecame into oestrus on the 14th October. The mean cycle length of 44 normal cycles was 16 days 3 hr.

2. The onset of oestrus as assessed by the time of mounting of the ram does not appear to beevenly distributed throughout the day (24 hr.).

1. The moisture equivalent of pure clay preparations varies with (a) the chemical composition, (b) the method of separation if centrifuged, (c) the replaceable bases.

2. The imbibitional water content also shows a close connection with the above variables.

3. Good additive relationships can only be obtained from series of soils of the same nature and in some cases, if taken at the same depth. This is, at any rate in part, due to differences existing in composition and properties between clay separated from soils and subsoils.

4. Pure silt fractions from different soils showed marked differences in their chemical composition and moisture equivalent.

A field experiment was conducted on a saline sodic soil at Kanpur to study the effects of sedimentary pyrites and Zn on the yield, Zn and Ca utilization by rice and wheat crops and on the amelioration of saline sodic soil. The grain yield of the first crop of rice increased from 1·55 t/ha for the ‘control’ to 3·44 and 4·01 t/ha with the 40 and 80% gypsum requirement pyrites treatments. The grain yield of succeeding wheat and rice crops also increased significantly owing to pyrites residues. The favourable effect of pyrites on crop yield was associated with an appreciable decrease in the pH, electrical conductivity and exchangeable and soluble sodium content of the soil resulting in greater utilization of Zn and Ca by the crops. Zinc applications also greatly increased grain yield and Zn uptake by the crops. The higher levels of pyrites with adequate N, P and K fertilizers but without Zn did not give yields that were obtained by adding 11 kg Zn/ha.

Significant yield responses were observed in the succeeding wheat and rice crops to Zn residues from the higher Zn treatments. The ‘pyrites+Zn’ treatment was most effective in decreasing the Na content and enhancing Ca uptake which increased the Ca/Na ratio in plants. The Zn treatment alone also decreased soil pH, electrical conductivity and exchangeable Na.

1. The attack on the organic matter of different soils using varying strengths of hydrogen peroxide has been investigated.

2. Starting with the most dilute peroxide, a complex of constant composition is oxidised in increasing amount.

3. Above a certain strength of peroxide there is no further attack on the nitrogenous compounds of the organic matter, but a progressive decomposition of non-nitrogenous carbon compounds or complexes.

4. The fraction oxidised up to the point at which no further decomposition of nitrogenous matter occurs is termed the “oxidisable complex”, and, whilst apparently specific for a given soil, varies somewhat in composition in different soils.

1. The compositions and digestibilities of ten selected typical Northern Irish meadow hays have been ascertained and compared with similar data published by other workers for meadow hays produced in the British Isles.

2. It is suggested that average Northern Irish meadow hay of reasonably good quality has a starch equivalent value in the region of 35 on a drymatter basis. Poor samples will have a value in the region of 25.

An impermeable continuous-culture artificial rumen was constructed and rumen microbial populations were cultured in vitro for periods of up to 23 days. Diets of hay and 20:80 hay:cooked flaked maize (concentrate diet) were fed to the in vitro cultures and also to sheep, and the performance of the in vitro fermentation compared with that of the in vivo fermentation.

With the hay diet, changing the initial inoculum from strained rumen liquor to unmodified rumen contents (containing solid ingesta) reduced the time required to attain a steady-state fermentation in vitro from 13 to 4 days. VFA molar proportions and the CO2: CH4 ratio indicated that the type of fermentation taking place in vitro was remarkably close to in vivo fermentation. However, rates of cellulose digestion, CH4 production and number of bacteria/unit volume (as judged by DNA concentration) were much less in vitro than in vivo, showing that the rate of fermentation was reduced in the artificial rumen. Total VFA concentration and the osmotic pressure of fermentor liquor were slightly higher than the maximum values found in vivo, and it was concluded that these were responsible for the reduced rate of fermentation.

Regardless of the duration of culture, a satisfactory steady-state fermentation was never attained when the concentrate diet was administered. DNA concentration in fermentor liquor declined to very low levels after 4 days; CH4 production rapidly declined and was replaced by H2 production after 5 days. VFA molar proportions bore little resemblance to those found in vivo. Both the osmotic pressure of fermentor contents and total VFA concentration rapidly increased with time, and by day 3 were approximately 2·5 times the values found in vivo. It was concluded that high VFA concentration, and the associated increase in osmotic pressure, were the main factors responsible for the unrealistic in vitro fermentation, and that this problem was much greater than encountered with the hay diet due to starch being digested at a faster rate than cellulose and hemicellulose.

Methods of regulating VFA concentration in continuous culture in vitro rumen systems are discussed and some improvements suggested.

A study was made of the live-weight gains of four ¾-bred Brahman and four purebred Hereford steers over a 12-month period. At 950 lb live weight each animal was slaughtered, after which the carcass characteristics of the two breed types were compared.

The Herefords showed the highest live-weight gains over the whole year but during autumn, when nutritional levels were poor, the Brahmans had an advantage in average daily gain.

Although both breed types varied greatly in body conformation, there was little appreciable difference in weight distribution of joints on the carcass. A higher dressing percentage was observed in the Brahmans, this being attributed to their smaller alimentary tracts. The Brahmans had a greater carcass muscle and smaller carcass fat content than the Herefords. The necessity for fat trimming of the Hereford carcasses reduced their calculated retail value index to a level below that of the Brahmans in a market which discriminated against excess fat.

Thus it was concluded that even in a temperate climate, Brahman cattle can have a place in improving productive efficiency. Apart from the heterosis developed in crossbreeding, benefits should flow from the Brahmans superiority on poor pastures and the improved production of lean meat on their carcasses.

A factorial experiment on Vicia faba L. cv. Alameda with three plant densities at three levels of nitrogen fertilization was done for three years (1984–87) at Granada. Yield varied markedly from 403 to 579 g/m2 between seasons. The mean increase in plant population density from 10 to 16 plants/m2 raised seed yield, but a further increase to 21 plants/m2 did not increase yield significantly. There was, however, considerable variation in the response to increasing density (Dl to D3) within each N level (N0, N1 and N2). Application of 30 kg N/ha at the start of flowering increased mean seed yield only at the lowest plant density and in 1986, but 60 kg N/ha increased yield by 135% on average over the 3 years. The highest N application rate resulted in consistently higher overall yields at each plant density. Leaf area index (LAI) showed a significant increase at 20 seeds/m2 compared with that at 10 seeds/m2 but there was no further increase at 30 seeds/m2. Harvest index (HI) was mainly affected by the annual weather conditions, and ranged from 47–4 in 1986 to 62–6 in 1987. HI was related to the mean temperature at flowering (April).

Experiments were done on three sheep fed several diets to determine the usefulness of the marker 51Cr-EDTA in the caecum of the sheep to study changes in weight of digesta and its turnover time. The activity of the marker decreased exponentially with time, indicating that it had mixed with a pool of digesta. Variation in the results was attributed mainly to the slowness of mixing and to the periodic nature of filling with digesta from the ileum.

Most estimates of weight of digesta were compatible with the digesta being contained in the caecum and the proximal colon but in one sheep some estimates obtained by one method of calculation were so large as to be unrealistic. Both the estimated weight and the rate of turnover of digesta varied with the weight of the sheep and the level of food intake.

Relationships among quality number, crimp frequency and. fibre diameter of sale lots are reported for a wide range of Australian wools, the quality number appraisals being those of the selling broker and the successful bidder at auction.

Results show that sale lots classified as having the same quality number exhibit a 95% confidence interval of ± 2·5 μm about the mean value. This variation is attributed first to the dependence of quality number on staple crimp frequency and secondly to the strength of the relationship between crimp frequency and fibre diameter.

A model is presented which considers the effects of competition between pairs of individuals in binary mixtures. Competitive effects are defined in terms of two parameters; a monoculture effect (Mo) which measures competition between like individuals and a mixture effect (Mi) which relates to competition between unlike individuals. If the data from a particular density replacement series conform to the proposed model the ratio of Mi to Mo can be used to determine whether it would be more advantageous to grow a mixture of the two components concerned or a pure stand of the better component. Where appropriate the optimal composition of the mixture may also be estimated. Theoretical considerations suggest that a 50:50 ratio only represents the optimal composition of a mixture when the two components possess a similar expression for the character concerned.

The model has been applied to dry weight data collected over two growing seasons from a glasshouse experiment which contained 5 genotypes of Lolium perenne grown as monocultures and in all 10 binary combinations. Each combination was represented by three mixture proportions. For the majority of these density replacement series the model was satisfactory, with mixture effects tending to be of greater significance during the first of the two growing seasons. Failure of the model was in general due either to a specific form of competition, which maintained the performance of the mixtures at the level of the better monoculture, or to the presence of more complex forms of competition.

The implications of this model for the development of productive herbage mixtures are briefly discussed, whilst the possible effects of invasion by unsown grass species upon the productivity of a pure sward are also outlined.

Twenty-three experiments between 1968 and 1971 compared the effect of no magnesium, 50 and 100 kg/ha magnesium as kieserite and 100 and 200 kg/ha magnesium as calcined magnesite, on yield and magnesium uptake by sugar beet. On average, 100 kg/ha magnesium as kieserite increased the mean sugar yield of 7·55 t/ha by 0·17 t/ha whereas 200 kg/ha magnesium as calcined magnesite increased it by only 0·08 t/ha; on fields with less than 15 ppm exchangeable magnesium the magnesium fertilizers increased sugar yield by 0·34 and 0·10 t/ha respectively and there was no response to either fertilizer when the soil contained more than 25 ppm of exchangeable magnesium.

100 kg/ha magnesium as kieserite or calcined magnesite increased magnesium in the dry matter of tops by 0·091 and 0·040% and of roots by 0·013 and 0·004% respectively. Giving 100 kg/ha magnesium as kieserite or calcined magnesite increased uptake of the element in August by 5·1 and 2·6 kg/ha respectively. Differences in soil pH did not influence the uptake of magnesium from kieserite but they greatly affected uptake from calcined magnesite. On the slightly acid soils, the fertilizers were almost equally effective but at pH > 7·6 little magnesium was taken up from calcined magnesite. Glasshouse experiments showed that grinding the calcined magnesite increased the availability of the magnesium.

1. The attraction between spheres, due to surface tension forces, in a lenticular drop between them is calculated for spheres in contact and at increasing separations up to the point of rupture of the drop. Hence the work of separation of the spheres is calculated.

2. Experimental measurements confirm the validity of these calculations, down to very small drop sizes, where it is likely that the failure is in the experimental method. As predicted by Fisher, the force decreases with increasing drop size, while the work of separation increases. Since, however, it is shown that the smaller lenticels are more easily ruptured, no discrimination is provided between the differing explanations of Haines and Fisher of measurements made with the Atterberg apparatus for measurement of soil cohesion.

An experimental verification of the validity of Fisher's calculation of the pressure deficiency inside the drop is also given.

3. It is pointed out that these results depend on the geometry of the system; types of contact other than that of spheres will show different behaviour. Hence generalizations about the behaviour of a real soil, based on an idealized soil of packed spheres, may lead to erroneous conclusions.

Results are described of an experiment made at the Indian Agricultural Research Institute, New Delhi, for 4 years under semi-arid seasonally dry tropical conditions to explore the possibilities of double cropping in the traditionally monocropped areas. Use of straw mulch did not increase mung yield in the monsoon season with welldistributed rainfall but increased its yield in a year when the monsoon receded early. Irrespective of rainfall pattern, mulching helped conserve enough moisture in the top 30 cm of soil to enable germination and quick establishment of the rapeseed crop. Mulching continued in the rapeseed crop conserved soil moisture until the flowering stage and increased the yield of rapeseed by 23%. Kaolin, a reflectant material applied at the preflowering stage, also increased seed yield of rapeseed.

Pod yield of groundnut and grain yield of wheat grown in that sequence was compared as affected by date of sowing and response to direct, residual and cumulative P application over 3 years in a field experiment. Total yield of groundnut and wheat was higher when groundnut was sown on 22 June and the following wheat on 1 November than when groundnut was sown on 6 July, followed by wheat sown on 16 November. Limited P requirement of groundnut was indicated by the small and inconsistent response to applied P on soil low in available P. Wheat responded to the second increment of P and direct application to wheat proved more effective than residual effects of previous application. Differential response of wheat to direct and residual P application in the groundnut-wheat cropping sequence indicates that P applications are more effective for wheat than groundnut, and groundnut can grow well on the residual P that remained in the soil.

The number of spermatozoa in bull semen was determined by electronic counting, light scattering and absorptiometry. Electronic counting was found to be accurate, fast and reliable and seems to be the method of choice.

Determination of the light scattering was found to be the more sensitive of the indirect methods, but absorptiometry also yields consistent and reliable results. The accuracy obtained by absorptiometry was found to be independent of the sensitivity of the instrument.

Effects of set size, density of planting, harvest date and spatial arrangement on yield and size grading of potatoes were examined using the cultivar Maris Peer. The results indicate that highest economic returns would be obtained by growing crops at between 70 and 110 eyes/m2, using small sets for late season production and large ones only for very early production, with as near a square pattern of planting as possible.

Based on these findings four growing systems were tested on a field scale, a 1·5 m raised bed with four rows, a 0·6 m ridge, a 0·9 m ridge containing two rows 0·3 m apart, and a 0·75 m ridge. Highest yields and returns were obtained from the two-row, 0·9 m, ridge system, which also had certain cultural advantages.

The percentage of natural cross pollination was estimated in the Alexandria area (Egypt) in two sites near and far from an apiary. The Egyptian cotton variety Giza 45 and the glandless strain Bahtim 110, as a marker parent, were used during three growing seasons. The average natural crossing within the square of the marker parent were 3·54 and 0·34% near and far from the apiary respectively. For the plants around the square of pollen source, however, the average of natural crossing was 0·56% near the apiary, while it was 0·21% far from the apiary. The natural crossing steadily decreased as the distance from the marker variety increased.