Signal grass (Brachiaria decumbens Stapf.) given 100, 200, 300 and 400 kg N/ha and protected from defoliation by growing in cages was evaluated for tiller height, tiller density and dry matter (DM) yield in 1979 and 1980.

Nitrogen rate had highly significant linear effects on tiller height and density and DM yield of the grass at each age of pasture regrowth and at all the ages of pasture regrowth combined in 1979 and 1980. The quadratic effect of N rate was not significant in either year.

The positive linear responses shown by the growth of tillers and the overall yield of the grass at N rates up to 400 kg/ha suggest that further work, using N rates above 400 kg/ha, is needed to ascertain the optimum N requirement of this grass.

is generally used to describe the lactation curve in cattle, where yn (kg) is the average daily milk yield in the nth week of lactation (n = 1, 2, 3, …, N), a is a scale parameter, and b and c are shape parameters. The model was first proposed by Wood (1967) and is widely used in practice to describe the lactation curve for fat, protein, lactose and wholemilk production; it has also been used as a basis of a mathematical model for poultry egg production (McNally, 1971). Having estimated a, b and c by regression analysis, the total lactation yield Y (kg) can then be calculated as

Oestrone sulphate, progesterone, total protein, Na and K concentrations in mammary secretions of Friesland sheep have been determined from 11 days before until 8 days after parturition. Mammary secretions were obtained on most days for at least 1 week before parturition in 9 of 14 ewes, and in all animals after lambing. Oestrone sulphate concentration had doubled on the morning of parturition compared with the value 24 h earlier, and this sharp rise was a useful indicator that delivery was imminent. Values continued to rise during the day of delivery, remained high for a further 24 h and then declined over the next 2 days. Progesterone, in contrast, decreased linearly between day –2 and day +2 when it reached baseline values.

Total protein concentration in pre-colostral and colostral mammary secretion (10–15 g/100 ml) was higher than that in goats, and decreased to a mean value of about 6 g/100 ml by day +8 after delivery. Na declined from about 55 mM on day –10 to 36 mM on day 0, whereas K increased from 20 to 29 mM. There was a sharp rise in K/Na, but this occurred after rather than before parturition and was not a useful predictor of parturition.

The onset of copious milk secretion occurred when oestrone sulphate in mammary secretions was high and progesterone was low, which is consistent with the hypothesis that the cessation of progesterone secretion is an important regulator of the onset of lactogenesis in sheep. Efficiency of milk secretion in the first 14 days of lactation was correlated, however, with the maximum oestrone sulphate concentration in colostrum on the day of parturition.

Fifteen cultivars of orchardgrass (Dactylis glomerata L.) were grown in the field at Hiroshima University, Japan, to investigate seasonal changes in leaf water relations and cell membrane stability (CMS) measured by the polyethylene glycol (PEG) test. Leaf water potential and osmotic potential were measured from August 1988 to August 1989. Solute concentration in leaf cell sap was also estimated.

Cell membrane stability increased, leaf water potential and osmotic potential decreased and turgor potential increased with decreasing environmental temperatures during autumn and winter. The significant increases observed in CMS may enable plants to tolerate freezing temperatures during winter. Decrease in leaf water potential may be a result of water-deficit effects due to soil freezing at low temperatures and the decrease in osmotic potential may help plants to maintain turgor and tolerate freezing conditions. Plants maintained higher turgor as the osmotic potential decreased to values as low as – 3·98 MPa during winter; the maintenance of turgor helps to maintain water uptake under water deficit conditions at low temperatures.

Sugar and K were the major osmotic contributors in orchardgrass leaves. Sugar and Ca concentrations increased and Mg and P concentrations decreased at cold temperatures. K concentration increased in six cultivars and decreased in nine others at cold temperatures. Sugar concentration in cell sap was negatively correlated with osmotic potential. It was concluded that seasonal changes in CMS may be mainly associated with the osmotic potential of the leaf tissues.

The digestibility coefficients of old barley straw fed with a basal ration of oats, bran and maize to two adult horses and of the same straw after treatment by Beckmann's method were ascertained. The coefficients of the nitrogen-free extractives and the crude fibre of the untreated straw were 33·23 and 38·24 respectively and of the treated straw 54·14 and 63·71. There was a reduction in the digestibility of the small quantity of protein and fat.

Taking into account the 14·5% of dry matter lost during treatment, the starch equivalent value of the treated material was somewhat higher than that of poor quality meadow hay.

The digestibility coefficients were considerably lower for an immature horse previously maintained entirely on fresh grass.

Experiments on spring barley at Rothamsted over the years 1974–81 were used to study how sources of powdery mildew inoculum affected responses to fungicide sprays applied at different times. Reinfection of early-sprayed plots was generally faster where they were close to a potent source of inoculum than where they were not. Conversely, effects of sources on yield, although not always significant, occurred mainly in the later-sprayed plots. Sources thus had their most important effects before these later sprays were applied, and probably during the very early stages of the epidemic. This implies that if experiments are to approximate to fields, they should, initially, be part of a large, uniformly-susceptible area of crop.

Regression analyses showed that delaying the application of fungicide sprays after the optimum date caused smaller yield losses in plots near minimal sources of inoculum than in plots near more potent sources. There was no conclusive evidence for effects of inoculum sources on the optimum date to apply a fungicide spray but the tendency was for the optimum to become later as inoculum pressure increased.

Separating fungicide-treated plots with mildew-resistant barley resulted in larger treatment effects and smaller residual mean squares than where there was no separation. Judged by residual mean squares alone, precision was approximately doubled by separation.

To evaluate the accuracy of various techniques for determining the sexual state of sows, four multiparous Landrace sows were housed in stalls 2–5 weeks after weaning. Catheters were inserted under anaesthetic into a prominent ear vein on each sow. Four days later blood and urine sampling commenced, along with other measurements to assess the oestrous state of the animals.

Oestrus was detected in all four sows and so were corresponding oestradiol·17β peaks (22–49 pg/ml) in serum of the three sows from which blood was successfully sampled during the complete 25·day collection period. Serum progesterone concentrations were highest between days — 5 and — 12 (day 0 = 1st day of standing heat) (peak values of 33·1–58·2 ng/ml), with values of 3·55 ng/ml or less on day 0. Urinary oestrogen was less well correlated with oestrous state than were serum hormone concentrations, but progesterone derivatives in urine corresponded well to serum progesterone with peaks between days —5 and —9. Vulval redness, vulval size, social interest and the occurrence of flehmen were markedly greater during the oestrous period than at other times in the cycle. Body temperature, vaginal pH, the presence of vaginal mucus and behavioural manifestations of oestrus (with the exception of back pressure test) were less well correlated with sexual state. A combination of vulval colour and size, back pressure test, a more detailed study of behaviour and possibly with urinary progesterone derivatives, should give the best indication of the incidence of oestrus in sows.

An experiment was carried out to study the effect of early weaning on body weight and growth rate of Awassi lambs raised at Abu-Ghurib Experiment Station, Baghdad, Iraq. Sex, type of birth and weaning age significantly influenced the body weight and growth rate of lambs at all the ages studied. Dam's age and weight at lambing, however, did not affect the growth rate of the lambs. The average body weights of lambs at 4 and 6 months of age were 23·8±0·28 and 32·3 ± 0·36 kg. The average daily gain in weight up to 120 and 180 days of age was 162·3 ±2·57 and 153·7 ±1·94 g/day respectively. Males were heavier than females and singles were heavier than twins at all the ages. Lambs weaned at 60 days of age were heavier and had a faster growth rate than those weaned at 90 or 120 days of age. Males born to 2-year-old dams grew fastest while the females born to them had the lowest body weights and growth rate.

1. Four experiments in 1958 and five in 1959 compared responses to potassium (as combinedrilled muriate of potash) in the absence of nitrogen and in the presence of single and double doses of nitrogen (as broadcast sulphate of ammonia) on soils selected because they contained very little acid-soluble potassium.

2. Responses to 0·5 cwt. K2O/acre were obtained at six centres (two significant), but the effects of a further 0·5 cwt. K2O/acre were more variable and gains and losses (each at four centres) were almost equally balanced.

3. Gains from nitrogen were associated with previous cropping. N1 raised yields at seven centres (six significantly), but N2 raised yields further at only five centres (three significantly) and depressed yields significantly at three centres where barley followed a root crop or ley.

4. Potash did little to improve the strength of straw and therefore standing capacity in a wet season (1958) and had little effect upon the size of the grain, whereas nitrogen increased lodging and reduced the average size of the grain.

5. Increases in potassium uptake were associated with yield increases, whereas increases in nitrogen uptake were associated with both higher nitrogen percentage in grain and higher yields.

The paper reports a laboratory study on miscible displacement of reactive solutes during leaching a highly saline-sodic soil rich in soluble sodium carbonate with solutions of calcium chloride. The effect of varying flow velocities, initial soil moisture content and concentration of calcium in the leaching water on the extent of carbonate precipitation and replacement of sodium by calcium from the exchange positions was studied in soil columns. The results showed that precipitation of soluble carbonates in the soil increased with increasing flow velocity, initial soil moisture content and concentration of calcium in the leaching solution. The results further showed that the calcium exchange capacity of the soil was reduced significantly and nearly proportionally with decrease in the degree of water saturation as a consequence of decreased water application rate and initial soil moisture content. In view of the results obtained, a simple model to describe calcium-sodium exchange under unsaturated flow conditions in saline-sodic soils under consideration has been proposed. Possible implications of the results in actual field situations is discussed.

The effect of morphactin sprayed at 0, 0·5, 1·0, 1·5 or 2·0 mg/1 on the concentrations of several nutrients in snapdragons (Antirrhinum, majus L.) were studied under glasshouse conditions. Snapdragon plants treated with morphactin increased in K, and Mg but decreased in Ca, Mn, Cu, Fe, and Zn. Action of morphactin and nutrient element relationships are suggested.

1. The degree of dispersion on shaking of the heavy clay Gezira soil has been studied in relation to its initial moisture content when it is added to the water. A minimum dispersibility was found at about 7% initial moisture content. Such behaviour is different from that found with certain English soils by Puri & Keen.

2. Spontaneous dispersion was studied using the same soil, and by this method it was found that the dispersion decreases with increasing moisture content over a range of zero to 9% moisture.

3. This relation between dispersion and water content is discussed in relation to possible effects in the field of practice. Attention is drawn to possible seasonal and daily differences in the effect of rainfall.

Field experiments made for 4 years between 1976–7 and 1979–80 in a semi-arid environment of north-west India showed that the productivity of dryland unirrigated wheat can be increased considerably by adjusting the date of sowing to conducive atmospheric temperatures. Sowing in the middle of November when daily mean temperatures ranged between 19 and 21 °C produced yields ranging between 2·6and 3·5t/ha (averaged over the 4 years) compared with 1·4–3·3 t/ha obtained from the crop sown by mid-October when the daily mean temperature ranged between 24 and 26 °C. The tall cultivar C 306, a derivative of winter x spring wheat cross, could withstand sowing at higher temperatures (mid-October) more than the spring wheats. High temperatures prevailing during the seedling stage of spring wheats shortened their vegetative growth and initiated early differentiation. Night temperatures above 13 °C coupled with day temperatures of 33–35 °C in the last fortnight of October adversely affected the tillering of spring wheats sown on 15 October and produced smaller spikes with few fertile spikelets.

In the application of the Scholander pressure chamber technique to cassava water relations studies, the leaf water potential measured on central lobules was initially compared with that measured on entire leaves (including petiole). Measurements made using both a Campbell-Brewster hydraulic press and a pressure chamber of the leaf water potential in six different cassava clones were also compared. Although the central lobules showed a greater sensitivity to moisture loss after sampling than entire leaves, their leaf water potential was in close agreement with those measured on the entire leaves (r3 = 0·96). Therefore, for routine and field estimates in cassava, measurements made on the central lobules may be used to avoid the large reduction in total leaf area. The Campbell-Brewster hydraulic press satisfactorily estimated leaf water potential in M.Col. 1684 clone, which had the longest and narrowest lobules, but in other clones the leaf water potential was overestimated at high leaf potential (> -12·5) and underestimated at low water potentials (< -12·5). Over a wide range of leaf water potentials, a poor relationship between leaf water potentials estimated with hydraulic press and with the pressure chamber was observed for cassava because press estimates are influenced by lobule length and lobule width.

Non-breeding groups, I, II and III, each with six high-potassium (HK) and six lowpotassium(LK) Chokla ewes were given water once in 24, 48 and 72 h respectively. In the next summer, seven ewes (4 HK and 3 LK) from each group I, II and III were switched over to a watering schedule of once in 24, 72 and 96 h respectively and were naturally bred. All the animals were maintained on grazing alone.

Water deprivation for 72 h caused 18·8 and 19·2% body weight loss in HK and LKewes respectively; an overall average maintenance of weight loss in LK ewes was significantly higher than in HK ewes from the same group. There were significant differences in water intake due to treatments only. The HK and LK ewes from groups I and III showed a similar trend.

Pregnant ewes of HK and LK types given water once in 96 h lost 21·7 and 23·8% of their body weights respectively. Corresponding weight loss in aborted ewes were 23·8 and 33·3%. Two ewes, each from 3 LK and 4 HK animals aborted owing to water deprivation for 96 h. The water intake reached 30 and 36·5% of body weight in LK and HK pregnant ewes given water intermittently.

The wool attributes of non-pregnant ewes did not indicate a significant influence of blood potassium types. Four out of five ewes of the LK phenotype died during 3 years, irrespective of watering schedule.

In four consecutive experiments, plasma uric acid (PUA), hepatic xanthine dehydrogenase (XDH) and body-weight gains (WG) of broiler chickens were measured under varying dietary methionine, protein and energy. In Expt 1, increases in WG with increasing dietary methionine peaked at 0·60%, a level where the initial decreases in either PUA or XDH reached a minimum. PUA and XDH in broiler finishers (Expt 2) decreased between 0·26 and 0·50% dietary methionine while WG improved between 0·26 and 0·50% methionine. XDH in the 18% protein and 0·68% methionine + cystine (MC) diet combination for Expt 3 was 66·4 μtmol/10 min/total liver weight, a value higher than either the 43·5 or 46·5 μtmol/10 min/total liver weight, respectively obtained in the 21% protein + 0·68% MC and 24% protein + 0·68% MC diet combinations. Both PUA and XDH, however, increased with increasing dietary protein when MC was either 0·76 or 0·84% diet. XDH in Expt 4 decreased between 11·7 and 13·4 MJ ME/kg diet that contained either 0·76 or 0·84% MC, tending not to vary between 13·4 and 15·1 MJ ME/kg diet. This enzyme activity remained essentially similar between 11·7 and 15·1 MJ ME/kg diet that contained 0·68% MC.

Effects of mepiquat chloride on gradients of shoot growth within spring barley plants (cv. Koru) were determined in two small-scale field experiments. Mepiquat chloride was applied at either the lemma primordium stage or the late carpel primordium stage of spike development in the main shoot. The shoot dry weight, stem length, spike length, number and size of florets and floret developmental score were measured for all shoots, over the period from the lemma primordium stage of main shoot spike development to the late milk stage of grain development.

Lemma primordium mepiquat chloride increased the size and developmental score of later-formed shorter shoots pre-anthesis while delaying the spike development of the main shoot and other longer shoots by up to 4 days. The overall effect was to produce plants with a reduced range of shoot and spike sizes from the end of floret initiation in the main shoot until maturity. In addition, there was a slight increase in the number of shoots per plant in both experiments. Gradients of carpel development and carpel width along the spike were reduced in all treated spikes by the time of floret abortion in the main shoot but the effects were more noticeable in shorter shoots. The number of florets initiated per plant was increased by 21–22%. All shoots contributed to the larger number of florets but again the major additions came from the shorter shoots. The few extra florets initiated in longer shoots were lost during abortion of distal florets while the 2–5 extra florets on shorter shoots were retained to give extra grains at maturity.

Application of mepiquat chloride at the late carpel primordium stage had little effect on gradients of spike size or on number, size and development of florets.

Colchicine induced 64-chromosome white clover was compared at a number of centres with control material (2n = 32), as spaced plants and in broadcast plots with and without companion grasses.

The chromosome-doubled material generally conformed to the well-known reaction of polyploids; the plants were later flowering, had thicker petioles and stolons, broader leaflets and spread less vigorously. Yield of green matter of spaced plants was much less, and in broadcast plots the gross yield (grass + clover) and that of the clover fraction was 7% less than in comparable S. 100 plots. The Finlay-Wilkinson analysis indicated that the chromosome-doubled form did not respond to improved conditions to the same extent as did the control varieties. The presence of grass in the mixture partly compensated for low clover yield, but was insufficient to increase total yields to that of S. 100 controls.