The variable viscosity which is shown by colloids generally as the rate at which they are sheared is varied leads to more striking anomalies in the behaviour of concentrated suspensions such as clay pastes when they are subjected to forces tending to make them flow. Bingham and Durham (l) first showed that when clay pastes were forced through capillary tubes, not only did the amount of clay squeezed out per second increase more slowly than the pressure applied, indicating a diminishing coefficient of viscosity, but also that there was evidence of a limiting shear, due to the consistency or cohesion of the particles, below which no flow would take place. It is the existence of this latter criterion that distinguishes clay from a weak suspension, e.g. of sand grains in water. This combined effect of cohesion and viscosity Bingham calls plasticity, and modifies Newton's law of viscous flow by the addition of a constant to allow for the cohesive force. Nevertheless, owing to the fact that the coefficient of viscosity is a function of the velocity gradient instead of being constant as in a homogeneous liquid, and that this velocity gradient is not known in the capillary tube viscometer, results as between one viscometer and another, or between two flow tubes of different size cannot be reduced to a common basis for comparison except by empirical trial. Keen and Scott Blair(2), Scott Blair and Crowther(3), and Schofield and Scott Blair(4) have repeated Bingham's experiments in an improved apparatus of the flow tube type, which they call a “plastometer.”

1. Two lots of twenty sheep each were fed indoors on rations known to produce satisfactory growth. The calorific value of the two diets was the same. One lot received 52 per cent, more digestible protein than the other. The diet of the low protein group was protein deficient according to the calculations of Wood.

2. The sheep were shorn at the beginning of the experiment and again at its conclusion. Fibre measurements were made on samples taken at the same two periods from the same body area. The fleece and fibres grown during the experimental period were compared in each case with the fleece and fibres grown during the pre-experimental period. The fibre measurements included fineness, length and fibre weight.

The effect of 200, 400 and 600 mg dietary copper sulphate/kg was studied in 64 Japanese quail (Coturnix coturnix japonica) in 1987. The results indicated that addition of 200 or 400 mg/kg to conventional diets of quail 7–42 days old significantly increased (P < 0·05) body weight gain and significantly decreased (P < 0·05) feed intake. There were significant (P < 0·05) increases in carcass, breast and leg weights in some cases; the first two characters had the highest values in the quail fed the diet containing 200 mg Cu/kg. The addition of 600 mg Cu/kg to the diet had an adverse effect on liver weight compared with the addition of 200 and 400 mg/kg. Copper concentration in the liver was not influenced by any rate of copper supplementation.

The conclusions that have been arrived at from the foregoing statistical examination of the available data on the physical properties of the Natal soils used by Coutts are:

(1) The base exchange capacity of the soil, as measured by Schofield's potassium phosphate buffer method, appears to be of predominant importance for predicting several of the soil properties, as for example the sticky point and the moisture content at 50 per cent. relative humidity. On the other hand, the clay content seems to be of quite minor importance in predicting these soil properties.

(2) The information from the data supplied by the Keen-Raczkowski box indicates that ω, the weight of water held per gram of soil in the box is very closely correlated with the base exchange capacity of the soil, while the swelling and pore-space parameters are more complex. The swelling υ seems to be dependent on the base exchange capacity of the soil and a term probably representing the structure of the soil, while the pore space p seems to be dependent on the clay content and a soil structure term. By choosing an appropriate definition of the pore space practically all the structure information given by the swelling parameters is contained in it.

1. Experience raised doubts as to the usefulness of filling gaps in bad stands of cotton at Barberton and experiments were conducted in two seasons to measure its effectiveness. The experiments gave clear-cut results.

2. Randomized gaps ranging from 20 to 40% of the stand were filled and left open for comparison, the filling being done 13 and 19 days after planting.

3. Any reduction in stand, though reducing yield per acre, led to large and significant increases in yield per plant, even when the spacing was 3 by 3 ft., wider than that normally used on the Station.

4. Replanting the gaps in a bad stand did not lead to any increase in yield per acre; there were, in fact, indications that this practice actually reduced yield per acre, the refills preventing plants of the original sowing from benefiting fully from the extra space available to them in a bad stand.

5. The general conclusion is that no useful purpose is served by refilling the gaps in poor stands of cotton with up to 40% of gaps.

Beverage tea is produced from the immature shoots manually harvested from the perennial shrub Camellia sinensis (L.) O. Kuntze. Fresh green leaf is mechanically comminuted and converted to the black tea of commerce by a series of partially controlled biochemical oxidation reactions (Sanderson, 1972). The final, unrefined dried product represents some 20% of the initial fresh weight of crop, the actual dry-matter content of the harvested shoots determining the percentage made-tea return (Keegel, 1955). Dry-matter content, hence, influences yield in terms of black tea produced. Although theeffectsof environmental, agronomic and cultural factors on green leaf yield have been studied intensively, little work has been done on the influence of such factors on dry-matter content. The present study examines the effects of nitrogen application rates on dry-matter content in four genetically diverse clonal populations throughout the main production season and during the first period of the Central African off-season.

1. Considerable differences were found in the specific conductivities of different soils at any one time of the year, and considerable differences in any one soil at different times of the year, the specific conductivities being highest in March and lowest in June and July. Hence it is only possible to compare different soils when samples of these soils are taken at the same time of the year.

2. A relation has been found between the specific conductivities of the soil extracts and the mean weights of lint per plant per row in the case of 2 strains of Ishan cotton. Other data are presented showing that the specific conductivity of a 1 to 5 soil extract is an index of the fertility of the soil.

3. It has been found that the specific conductivity of a soil decreases under continuous cultivation. There is evidence that the rate of solution also decreases under the same condition.

Between weeks 3 and 18 of lactation, 141 British Friesians all received concentrate (metabolizable energy (ME) 12·9 MJ/kg dry matter (DM), 202 g crude protein (CP)/kg DM) at 8·0 kg fresh weight/day. In addition, cows received ad libitum either grass silage (ME 11·7 MJ/kg toluene DM; 219 gCP/kg DM) or a mixture containing grass silage and 15, 25 or 40% (DM basis) of winter barley straw (cv. Igri) either untreated (UTS) or treated (TS) with 4% NaOH. Forage treatments were imposed at either week 3 or week 9 of lactation.

The mean forage DM intake of cows receiving grass silage only was 8·60 kg/day. When 15, 25 and 40% UTS was introduced into the rations at week 3 or 9 of lactation, forage DM intakes were 884, 8·43, 7·62 and 8·63, 8·83, 819 kg/day, respectively; the corresponding values for TS were 8·88, 855, 8·99 and 8·97, 8·98, 9·35 kg7sol;day. The milk yield of cows receiving grass silage only was 22·1 kg/day. When 15, 25 and 40% UTS was introduced into the rations at week 3 or 9 of lactation, milk yields were 21·1 kg/3, 20·1 kg/1, 20·1 kg/5 and 20·1 kg/1, 21·4, 20·5 kg/day, respectively; the corresponding values for TS were 21·8, 22·1, 21·3 and 22·5, 21·4, 22·6 kg/day. When averaged across the three inclusion rates, TS significantly increased forage intake (P < 0·05) and milk yield (P < 0·01) compared with UTS. Intermediate values were recorded for the diet with grass silage alone. The inclusion of TS in the ration did not affect milk yield compared with grass silage alone. No major changes in milk composition were recorded by the inclusion of either TS or UTS. However, the yields of milk fat, protein and lactose for the TS treatments were higher than for UTS and were significant for protein (P < 0·01) and lactose (P < 0·001). Cows with UTS in their ration tended to have lower live weight gains than either the control group or treatments with TS.

When compared with grass silage only, the inclusion of TS or UTS decreased digestibility coefficients and ME contents, determined in vivo using wether sheep fed at maintenance. However, the treatment of straw with NaOH (4%) increased its digestibility coefficients of dry matter from 0·-393 to 0·668, of organic matter from 0·445 to 0·686, of acid detergent fibre from 0·442 to 0·713, gross energy from 0·438 to 0·640 and ME content from 7·0 to 9·4 MJ/kg DM.

Three groups (1, 2 and 3) of weaned Hereford steers were grazed separately on pasture. Groups 1 and 2 were supplemented with hay and oats during autumn and winter in an attempt to maintain two rates of live-weight gain, namely 0·8 and 0·4 kg/day, respectively. Group 3 was not supplemented and gained at zero and 0·11 kg/day during corresponding periods in the 2 years in which the experiment was repeated (years 1 and 2).

Supplementation ceased at the end of winter (September). Group 1 steers were slaughtered at the end of the growing season (January) when their mean live weight was 420 and 450 kg in years 1 and 2 at 19 months of age. Thereafter, groups 2 and 3 were removed from the plots and grazed together on another pasture at a reduced stocking rate until they attained the slaughter live weights of group 1 when they were slaughtered at 25 and 27 months of age, respectively.

Mean depth of fat cover over the eye muscle at the 10–11th rib in groups 1, 2 and 3 were 8, 6 and 4 mm in year 1, and 12, 5 and 6 mm in year 2, respectively. Group 1 carcasses had shorter skeletal dimensions, contained more fat and graded better than the carcasses of groups 2 and 3. The Longissimus dorsi muscles from group 1 were found to be the most tender in year 1 but no treatment effects were detected in year 2.

The effects of six amounts (0, 17, 34, 51, 68, 85 kg N/ha) of fertilizer N, applied at sowing time, on the crude protein (N × 6·25) content of barley grain sown as the first, second and fourth or later tillage crop after grazed pasture were studied over three seasons at a total of 126 sites. In addition, non-protein N in the grain was measured at 24 sites.

The overall crude protein content was 11·3% without N, increasing to 13·4% with 85 kg N/ha. The first increment of 17 kg N/ha gave the least increase in grain protein content. The year which gave the largest yields gave the lowest grain protein contents and vice versa. The mean grain protein contents without N for 1971–3 inclusive were 10·8, 11·5 and 11·8% respectively.

The mean grain protein contents without N when barley was sown as the first, second and fourth or later tillage crop after pasture were 12·6, 11·5 and 10·0% respectively; the corresponding values with 85 kg N/ha were 14·4, 13·9 and 11·8%. There was a positive relationship between grain protein content and lodging, especially in barley sown as the first tillage crop after pasture, where lodging was most severe.

Non-protein N was low and only accounted for 5–8% of the total grain N content. The mean grain. N uptake with no fertilizer N applied was 82, 70 and 49 kg/ha in barley sown as the first, second and fourth or later tillage crop respectively. The apparent recovery of fertilizer N was largest in fourth or later barley.

Six experiments on winter wheat, three in 1974 and three in 1975, evaluated aqueous ammonia, aqueous urea and a solution of ammonium nitrate and urea, using ammonium nitrate granules as the standard. Aqueous ammonia and aqueous urea were injected 8–10 cm deep in bands either 25 or 50 cm apart during April. The ammonium nitrate/urea solution was sprayed and the ammonium nitrate granules were broadcast (a) partly in April and partly in May or (6) wholly in May. All were applied at 50, 75, 100 or 125 kg N/ha. Yields and % N in grain were measured and N removed by grain calculated. In two experiments lodging diminished yield and complicated the comparisons.

Elsewhere, aqueous urea and aqueous ammonia were of similar value, and each gave a larger yield when injected in bands 25 rather than 50 cm apart. Both fertilizers gave yields similar to those from broadcasting the ammonium nitrate granules, but larger yields than from spraying the ammonium nitrate/urea solution. Yields were slightly larger when divided rather than single topdressings were given, but % N in grain and the amounts of N removed were smaller. Yields and % N in the grain were smallest when the ammonium nitrate/urea solution was sprayed. The other three fertilizers were each of greater value judged by N uptake, the ammonium nitrate granules having a slight advantage.

One of the main problems confronting the advocates of silage in this country is the selection of crops suitable for being grown for ensilage purposes, particularly in view of the fact that attempts to produce maize silage in this country have frequently been unsuccessful. It has been demonstrated, in trials extending over a number of years at Cambridge, that the mixed oat and tare crop can be used for the production of silage with success. The silage from oats and tares, when made under favourable circumstances, is possessed of great palatability and excellent nutritive value, and moreover, the process, considered from the point of view of losses of ingredients as a result of silo fermentation, is, if anything, more economical than that by which maize forage is converted into silage (1).

Efficiency of food utilization from 2 to 18 weeks of age has been examined in 12 MZ and 7 DZ pairs of twin calves fed standard rations. Mean efficiency reached a maximum at about 6 weeks of age; weaning brought about a rapid decline followed by a recovery. Animals became more alike in efficiency as their ages increased.

Those animals least efficient shortly after birth were most adversely affected by weaning, although they tended to be relatively more efficient when fully established on either milk or solid food.

Relative to the fairly closely replicated age-efficiency trends of identical twins, different pairs followed different trends. These trends, which primarily reflected the variable success with which the calves adapted to new diets, were subject to some genetic control.

Studies were conducted to evaluate the effect of 50% restriction of normal daily water intake on nitrogen balance, plasma urea concentration and excretion of different urinary nitrogenous constituents (ammonia, creatine, creatinine, urea and undetermined nitrogen) in the Marwari breed of sheep of the Rajasthan desert, India. The results indicated that the reduction in feed intake in water-restricted sheep leads to a reduction in intake and excretion of nitrogen through faeces (P < 0·01) and urine (P < 0·01) of these animals. No sigficant differences in the excretion of most urinary nitrogenous constituents between ad libitum watered and water-restricted animals were observed, except for creatine which was excreted in significantly higher concentrations in the urine of the water-restricted animals. On offering water ad libitum for 3 days to the restricted animals, the plasma urea in these animals dropped from 33·0 to 20·7 mg/100 ml, i.e. almost to the level in the animals watered ad libitum (18·7 mg/ 100 ml). The daily dry-matter intakes of the ad libitum watered and restricted animals were 790 and 488 g, respectively. The digestibility coefficients for dry matter and crude protein of the feed were 47·1 and 27·2%, respectively in ad libitum watered and 56·6 and 39·5%, respectively, in restricted animals. This improvement in the efficiency of digestion in water-restricted sheep may not be due to any enhanced microbial activity in the rumen, but may possibly be due to an increased absorption of feed nutrients in the hind gut of these animals.

Three preliminary experiments at Cambridge (1904–70) indicated that several varieties and breeding lines of sugar beet differed in their response to fertilizers. Three factorial experiments were therefore made at Broom's Barn (1970–2) to measure response by four widely differing varieties of sugar beet (Sharpe's Klein ‘E’, Maris Vanguard, V.T.137 and Anglo-Maribo Poly) to nitrogen (0, 75 and 150kgN/ha), sodium (0 and 250 kg N/ha) and potassium (0 and 400 kg K/ha) fertilizers. Increases in sugar yield from 75 kg N/ha by each of the varieties were remarkably similar and giving a further 75 kg N/ha neither increased nor decreased the yield of any variety on average over the three experiments. The yield response to sodium and potassium was greatest in Sharpe's Klein ‘E’ and least in V.T.137; however, as with nitrogen, varieties responded inconsistently from year to year and the interactions were not statistically significant for data pooled over the three experiments. These experiments indicate that varietal differences in fertilizer requirement are unlikely to be important in commercial practice.

Twenty alfalfa cultivars were tested, under rainfed conditions in central Greece, for forage yield, agronomic and nutritive value in order to identify adaptive responses contributing to high resilience and productivity. From 2014 to 2017, five harvests (H1 to H5) per season were conducted. Two cultivars were also grown as irrigated checks. Annual and total dry matter (DMA and DMT) and harvest ratios (RH) were estimated. DMT was reduced by 42.9–48.1% under ambient rainfall compared to irrigated checks, which received 50.2% more water. The seasonal yield distribution demonstrated two contrasting strategies, however, equally effective for high resilience under rainfed conditions. The winter-active imported cultivars were the most resilient in the driest year, potentially due to their ability to exploit autumn rains, whereas the locally adapted genotypes were more productive in summer. The spring harvest ratio (RH1) was more indicative (r = 0.94, P < 0.01) of cultivar productivity, compared to plant survival (r = 0.65, P < 0.01), whereas the autumn harvest ratio (RH5) was representative of productivity under extreme drought (r = 0.53, P < 0.05). RH1 and RH5 were increased by 11.8 and 12.3%, respectively, whereas the summer ratios (RH3, RH4) were reduced by 47.3%, under rainfed v. irrigated conditions. Two Australian cultivars (‘Blue Ace’, ‘Icon’) achieved the highest RH5 suggesting an adaptive response by being more productive in autumn. However, the development of specifically adapted cultivars in terms of higher summer yield and plant survival may be necessary to cope with future climatic changes in the Mediterranean region.

Winter wheat (Triticum aestivum L.) production on the Loess Plateau in China has been threatened by water scarcity and climate change during the last decade. Sustainable crop production in this region requires managerial practices that can provide high yield and high water productivity (WP). A 7-year (2001–2008) study at the Loess Plateau Research Station of Lanzhou University investigated the effects of various conservation tillage practices on grain yield, soil water content (SWC), WP and economic return of winter wheat production. Tillage treatments included: conventional tillage (T), conventional tillage followed by stubble retention (TS), no-till (NT) and no-till followed by stubble retention (NTS). Over the entire experimental period, grain yield and WP of winter wheat ranged from 1279 to 4894 kg/ha and 0·32 to 2·41 kg/m3, respectively. Both were significantly affected by tillage treatment and year, while SWC was only affected by year. Grain yield and WP in TS was increased by 4·9, 12·1, 0·9% and 13·7, 20·4 and 3·9% compared with NTS, NT and T, respectively, over seven growing seasons. Additionally, a multiple linear regression analysis indicated that grain yield is mainly limited by SWC during planting. Despite its lower grain yield, the NTS treatment increased economic benefit by US$ 328, US$ 23 and US$ 87/ha compared with TS, NT and T, respectively. Therefore, it is suggested that increasing soil water storage at wheat sowing time and encouraging the use of NTS could improve economic returns in this region.

Experiments are described which analyse the effects of date of sowing and of a black petroleum soil mulch on the growth of two maize hybrids. The two hybrids used were Anjou 210, which is late maturing in S.E. England, and Kelvedon 75A, which is an early hybrid.

As sowing was delayed from mid-April until the end of May, so there was a greater development of vegetative tissue (mainly stem) and leaf area which reached peaks at a later stage after silking. In Anjou 210 early sowing led to higher grain yields (12%) as the production of peak vegetative weight near to the time of silking allowed dry matter produced after that stage, still at a time of high radiation, to move direct to the oars. Also, the remobilization of the secondary source of grain dry matter, namely previously stored photosynthate from the stem, occurred earlier with early sowing and to a greater extent when a longer grain-filling period was allowed.

The hybrid K 75A had a lower vegetative weight, and earlier silking coincided with higher levels of radiation, and the resultant increase in net assimilation rate led to a higher proportion of dry matter being partitioned into the ear. Because this hybrid flowered and senesced early, reserves of stem carbohydrate were low and the time available to transfer carbohydrate to the ear was short, resulting in lower yields than in the later maturing Anjou 210. K 75A also responded unexpectedly to the sowing treatments. Although late sowing gave higher grain yields in both hybrids up to 156 days after sowing, in the case of K 75 A, the early senescence curtailed the continuation of grain fill that would normally give early sowing an advantage and hence the late sown K 75 A produced 10 % more grain.

The application of a black petroleum mulch to the surface of the soil to raise soil temperature enhanced the benefits derived from early sowing. Plants given this treatment produced greater leaf areas and vegetative dry weights. As a result more carbohydrate was translocated from the stem during the grain-filling period, increasing grain yield by 13% following an increase in both number of grains and individual grain weight.

Eight experiments, comprising four randomized-block feeding trials each with 20–45 animals and four changeover-design nitrogen (N) balance trials each with 6–10 animals, were used to study the effect of the addition of formaldehyde to fishmeal and to casein, of severe heating of fishmeal, and of tannin treatment of a mixture of vegetable protein-rich foods on the utilization of N for growth. Added in moderate amounts to rations demonstrated within the experiments to be deficient in N, quantities, but not the preparations, of N in the diet were critical to growth save at very low N intakes when the untreated foodstuffs were used more efficiently. Additional energy given in isonitrogenous rations increased growth, reducing N losses in the urine.

Evaluating the effects of crop successions in no-tillage system (NTS) is essential for the correct recommendation of agronomic practices, such as top-dressing nitrogen fertilization. The aim was to evaluate the effect of the crop succession and the splitting of top-dressing N fertilization on the agronomic performance and economic viability of common bean crop. The experiment was conducted in southeastern Brazil for two agricultural seasons in an area under NTS, using a split-plot in randomized complete block design. The plots represented three cropping successions (maize in sole crop, maize intercropped with Urochloa ruziziensis and U. ruziziensis in sole crop) and the subplots composed of ten combinations of splitting of top-dressing N, at the stages V3, V4 and R5 of the common bean crop. In relation to the single application of the N dose of 90 kg ha−1, the common bean had higher response as a function of the N splitting schemes adopted, regardless of the previous cropping succession. The cropping successions evaluated did not interfere with the seed yield of common bean as subsequent crop, even at the beginning of the establishment of NTS. To obtain higher seed yield and economic viability, the N dose of 90 kg ha−1 indicated for the crop must be split and applied among the phenological stages V3, V4 and R5.