Four field experiments in 1972–6 investigated the effect of undersowing trefoil or ryegrass in barley, and of fodder radish sown after barley, on yield and nitrogen requirement of following sugar beet. Autumn applications of isobutylidene diurea or glycoluril (slow-release nitrogen fertilizers) were also included for comparison with green manures. The plots were split in the following spring and dressings of 0, 50, 100 and 150 kg N/ha as ‘Nitro-Chalk’ tested on the sugar-beet crop.

The undersown green manure crops slightly decreased the yield of barley but, at the time of ploughing, returned up to 3·7 t dry matter/ha and 50 kg N/ha. In the absence of spring-applied nitrogen fertilizer for the sugar beet, green manures increased root and sugar yield, but when more than 50 kg N/ha was applied for the sugar beet they had no effect on yield. Autumn applications of nitrogen fertilizers such as isobutylidene diurea decreased the requirement for nitrogen in spring, but yields were no greater than from spring-applied nitrogen alone. Top and subsoils sampled in late winter and early summer from plots where green manures had been grown showed no detectable increase in soil organic carbon or total nitrogen, but soil mineral-nitrogen concentrations were increased slightly by green manures as was the potentially available mineralnitrogen released in an incubation test. It is concluded that, on loamy soils, green manures decrease the nitrogen requirement of sugar beet but give no benefits in yield which cannot be obtained from nitrogen fertilizer in spring before sowing the crop. assistance and Miss G. Smith for statistical analyses.

Simazine and prometryne applied to the soil surface in pots at 1·6 and 3·2 kg/ha. 2 days after sowing, did not affect germination or early seedling growth of chickpea. Reductions were noticed under all treatments in the leaf dry weight after 28 days and in the length of the main stem after 42 days. Dry-matter accumulation in the shoot was drastically reduced with simazine but not with prometryne. All treatments retarded dry-matter accumulation in the roots with time. Prometryne reduced chlorophyll content during early growth stages and simazine during later stages.

Growth of the rhizobial culture was reduced with increasing concentrations (1–20 mg/1) of both simazine and prometryne. Root nodule initiation was not affected by either of the herbicides but the later production of new nodules and growth of the nodules were reduced in different degrees by various treatments. Overall nodulation was drastically reduced with simazine. Reductions in nodulation with simazine and prometryne appeared to be primarily a case of general root growth reduction. The pink pigment, leghaemoglobin, did not develop at all in the nodules of simazinetreated plants and its concentration was not affected in the nodules of prometrynetreated plants. The N2-fixing efficiency (acetylene reduction) of the nodules was more in the case of prometryne-treated plants and was nil in the case of simazine-treated ones.

Spring-born Friesian heifer calves were turned out to grass at either 3 or 4 months of age. In the summer of 1976 the experiment had 20 calves per treatment and in 1977 there were 22 calves per treatment. The calves remained outside for both day and night. They were the leaders in a leader–follower rotational grazing system based on nine paddocks. The followers were yearling heifers and sheep. Each calf was offered a daily grazing supplement of 1·8 kg concentrates. Housing was in mid-September.

There were no management problems and summer growth rates were within the range 0·55–0·74 kg/day. Calves turned out at 3 months of age grew slightly better than calves turned out at 4 months. This difference was not statistically significant, but it does suggest there is no harm in turning calves out at an early age. From a practical viewpoint the result indicates that all spring-born calves could be turned out in one batch in early summer.

A grazing study, comparing a naturalized and a sown pasture at three stocking rates, was conducted under a uniform stand of 65-year-old coconuts on a fertile soil in the Russell Islands. In a plot trial on this site there was no significant response to application of up to 400 kg N/ha/year over 2 years to Brachiaria decumbens. Average daily transmission of photosynthetically active radiation through the coconut canopy was 60% of full sunlight. The sown pasture consisted initially of para (Brachiaria mutica), signal (B. decumbens) and koronivia (B. humidicola) with the legumes Centrosema pubescens, Pueraria phaseoloides and Stylosanthes guianensis. The main species in the naturalized pasture were Axonopus compressus, Mimosa pudica, C. pubescens and Colopogonium mucunoides. Pastures were set stocked in two replicates over 3 years at 1·5, 2·5 and 3·5 animals/ha. There was no significant difference in live-weight gain between pastures in any year. Live-weight gain per head declined linearly with increasing stocking rate. Highest live-weight gain was 437 kg/ha/year in the 1st year at 3·5 animals/ha. The planted grasses declined from 60% at the start of grazing to 6% 8 months later. A. compressus increased from 2 to 24% over 3 years in the sown pasture, and from 12 to 34% of yield in the natural pasture. M. pudica increased from 27 to 44% in the sown, and remained approximately constant at 37% in the natural pasture. G. pubescens increased at 2·5 animals/ha, but was replaced by P. phaseoloides at 1·5 animals/ha and by A. compressus and M. pudica at 3·5 animals/ha. There were no significant effects of pasture treatments or stocking rate on copra yields. Where there is a cover of naturalized grasses and legumes under coconuts, cultivation and planting of exotic species cannot be recommended. Major improvement will come from thorough weed control and maintaining stocking rates between 1·5 and 2·5 animals/ha.

Field investigations were carried out to study the effect of partial defoliation on dry-matter production and seed yield of urd bean. Partial defoliation during the vegetative and/or reproductive phase reduced seed yield. The severity of yield reduction was dependent on the stage of crop development and the degree of defoliation. The reduction of total dry-matter production by defoliation was accompanied by a decrease in crop growth rate and leaf/plant weight ratio. The net assimilation rate was higher in defoliated plants from 40 to 60 days after sowing. The reduction in seed yield due to defoliation was highly due to a reduction in the number of pods per plant, and also sometimes in the number of seeds per pod and in 100-seed weight.

Experiments at Sutton Bonington in 1973 and 1974 compared the growth and yield of sugar beet which was handweeded at different stages with that where weed control was entirely by pre- and post-emergence herbicides, used alone and in various combinations. Data from the series of handweeding treatments enabled the crop's minimum weed control requirements to be specified. They indicated that an ideal herbicide would kill all the weeds present when applied at the six-leaf stage, persist in the soil to prevent weed infestation for 4 weeks, but not check the crop to the extent that recovery was incomplete. That the crop was capable of recovering from a degree of early check was clearly evident from the handweeded treatments; it proved possible for crops whose weights had been depressed by 25–30 % when first weeded to recover completely by harvest.

The performance of all post-emergence treatments fell short of these requirements. When the crop was at the six-leaf stage, the earliest emerging weeds were too far advanced to be killed by the herbicide. By themselves, pre-emergence herbicides gave weed control equivalent to only 2 or 3 weeks of handweeding but they did pave the way for more effective use of post-emergence treatments by restricting the spectrum of weed sizes present and sensitizing those plants which did establish. The most effective herbicide regime used in the experiments was the sequence of chloridazon applied pre-emergence followed by two post-emergence applications of phenmedipham. However, phenmedipham clearly checked the crop. Two weeks after application crop dry weight was usually depressed by one-third. Provided weed control was adequate, recovery was usually complete by the end of the season.

Oestrus and ovulation was controlled by progestagen-impregnated sponges in 279 adult dry ewes in late anoestrus: at pessary withdrawal, ewes received doses of 0, 250, 500 or 750 i.u. pregnant mare serum gonadotrophin (PMSG). Rams were introduced to half the number of ewes which did not receive PMSG at the time of sponge withdrawal and to the remainder 48 h later. A significantly lower (P < 0·05) oestrous response was observed in ewes which did not receive PMSG but were introduced to rams at 48 h, when compared with ewes introduced to rams at time of sponge withdrawal. With iams introduced at 48 h a greater precision of synchronization was achieved by the use of PMSG (P < 0·05). Differences in conception rates were not evident between the various treatment groups, but a significantly higher (P < 0·05) litter size followed the use of the 750 i.u. PMSG dose.

The results are reported of two experiments made on a silt loam soil over chalk on downland in southern England. Three primary tillage treatments (ploughing, deep or shallow tine cultivation) were compared with direct drilling for their effects on the growth of spring barley during the years 1969–74 and winter wheat during 1974–8.

No significant differences in barley population density or early growth were recorded. In the first 2 years more grain was produced on the shallow tined and direct-drilled plots than on those that were ploughed, but the differences did not persist into subsequent years. The mean yield of each treatment over the 4 years did not differ.

Significant differences in population density and winter mortality of wheat occurred but these were not consistently associated with differences in yield. In this crop also the mean yields of the cultivation treatments over the 4 years were not significantly different.

It is concluded that choice of primary tillage system on this chalk downland soil was not a significant factor in the production of either spring barley or winter wheat.

The effects of homozygous and heterozygous loci of 20 seedling lethal mutants on yield and yield components of barley (Hordeum vulgare L.) were studied. Nine of the 20 populations studied exhibited one locus heterosis (positive or negative advantages of Aa genotype compared with AA genotype) for yield per plant or one or more components of yield. In five instances of significance all showed positive single locus (Aa) heterosis for number of seeds per spike. Seedling lethal mutants, Ac ac and Alb,, p alb,, p showed three yield-component-heterosis. These two mutants might be suitable for hybrid barley production.

The effects of variety, plant density and time of N application on the yield and yield components of winter wheat were investigated in factorial experiments during 1977–8 and 1978–9, at Sutton Bonington. Armada produced substantially fewer vegetative tillers/m2 but the number of ears/m2, from anthesis onwards, was similar to that of Maris Huntsman. The effects of the time of N application on tiller production and survival differed between the 2 years and may have been related to the amount of residual N in the soil. A linear relationship was found between the number of tillers/m2 which died and the maximum number of tillers/m2.

Kador produced a lower grain yield than Armada or Maris Huntsman, owing to a combination of lower ratio of grain D.M. to total above-ground D.M. (harvest index) and lower total dry-matter production. Armada produced a higher grain yield than Maris Huntsman in response to earlier application of N. Grain yield was less variable when final plant densities were greater than 200/m2.

Grain yield was not particularly well related to individual yield components but showed a good linear relationship with number of grains/m2. Grain yield was also linearly related to total dry-matter production, with treatment effects on harvest index being relatively small. The results indicate that factors which influenced crop growth during grain site development were relatively more important than the factors affecting subsequent grain filling.

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.

Three spring oil-seed rape cultivars were drilled on five dates during 1979 and 1980. Delayed drilling (1) reduced seed yield, (2) increased the main stem contribution to seed production, and (3) increased the percentage of damaged pods at harvest. The results indicated that cultivars similar to those used in this trial should be drilled between the 3rd week of March and mid-April.

Least-squares estimates of the parameters of the Bertalanffy growth equation, adjusted for six sources of variation, were obtained for oryx, eland and zebu cattle.

Values for asymptotic weight were lower than the mature weights normally given for the species, particularly eland and cattle, owing to management constraints. The figures for females brought into the project were considered the most representative of the species in general. For this category of oryx, eland and zebu cattle respectively, the estimates were as follows: the coefficients of growth rate were 0·136, 0·112 and 0·114; asymptotic weights (W∞) were 146, 277 and 395 kg; and ages at maturity (0·98 W∞) were 33, 41 and 39 months. For females born on the project estimates of birth weights were 14·5, 24·1 and 28·7 kg; and of ages at zero weight were 3·55, 3·80 and 5·18 months prepartum, for oryx, eland and zebu cattle respectively.

When differences in size, and therefore metabolic rate were discounted, oryx grew at 3·2, eland at 3·1 and zebu cattle at 3·4 g/kg W∞0·75/day. Comparison with mean values for water turnover (ml/l0·82/day) on the same project revealed that oryx used about one third of the water required by eland and cattle, for the same amount of growth (g/kg W∞/day).

Significant sources of variation for W∞ were species, sex, and mode of entry into the project (capture or birth), all at P < 0·005. Season of birth was also significant at P < 0·01, with oryx born 2 months before a wet month achieving the largest W∞ whereas the highest average growth rate occurred when birth was 1 month before a wet month. The only significant source of variation obtained for growth rate was year of entry (P < 0·005).

Thirteen defoliation treatments were applied to a grass-white clover sward for 2 years to study some effects on the sward of cattle grazing compared with sheep grazing compared with various cutting treatments and to study the effect of height of defoliation.

Sheep actively sought out the clover in preference to grass whereas the cattle did not. The response of the clover to sheep grazing was a large reduction in the amount of stolon, shorter internodes, petioles and leaflets, and thinner stolon closer to the ground. Reducing the height of defoliation from 8 to 4 cm above ground level also reduced the dimensions of white clover. The clover, however, appeared to recover quickly and completely from the effects both of sheep grazing and of reducing the height of defoliation when these treatments were discontinued. In plots cut for hay the clover disappeared from the sward suddenly and completely in dry conditions following the 2nd-year hay cut. The effect of cattle grazing on white clover was similar to the effect of comparable cutting treatments. Cattle grazing, however, reduced the number of tillers of grass andincreased the proportion of bare ground, compared with cutting or sheep grazing. Grazing rather than cutting tended to encourage perennial ryegrass and to discourage Holcus. Cutting for hay encouraged Bromus mollis. Reducing the height of defoliation reduced leaf sheath and blade length and the rate of production of new blade per tiller in perennial ryegrass, but increased the numbers of tillers of grasses.

Nitric phosphates containing 80, 50 and 30% water-soluble phosphorus, and Mussoorie rock phosphate, alone or with Amjhore pyrites, farmyard manure or straw, were compared relative to concentrated superphosphate for each of three cycles of a clusterbean–wheat and a groundnut–wheat rotation. Both the field experiments were made on alkaline P-deficient Samana sands. All phosphatic fertilizers were applied to each crop at the rate of 10, 20 and 30 kg P/ha. Dry forage of clusterbean, groundnut pods and grain yield of wheat were measured. The model of concurrent straight line response was employed to calculate availability coefficient ratios which express the relative effectiveness of the different phosphatic fertilizers.

Nitric phosphate containing 80 % water-soluble phosphorus and concentrated superphosphate were almost equal in their effectiveness in both 3-year rotational studies of clusterbean–wheat and groundnut–wheat. The relative efficiency of the nitric phosphates increased with the amount of water-soluble phosphorus they contained. Mussoorie rock phosphate was the least effective source of fertilizer phosphorus, although its efficiency is considerably higher for the legume clusterbean and for groundnut than for the cereal wheat. The efficiency of Mussoorie rock phosphate increased when it was mixed with the soil together with Amjhore pyrites, farmyard manure and straw respectively. These materials were more effective for clusterbean and groundnut than for wheat.

A sample of twelve buffalo, nine O Friesian × ♀ Egyptian native Baladi (½ Friesian) and nine ♂ Friesian ×♀½ Friesian (¾ Friesian) bulls were individually penned and fed commercially cubed concentrates and roughages from weaning at 100 kg and slaughtered over the live-weight ranges 161–560 kg for buffaloes and 176–448 kg for cattle. Weights of gut fill (GFW), empty body (EBW), offals (TOW) and carcass were recorded. Right sides of all carcasses were jointed then dissected into muscle, fat, bone and ‘other tissues’. Analysis of covariance based on the allometric equation Y = aXb was applied to assess growth patterns (estimated from the slopes) and compositional differences (estimated from the intercepts).

The effect of genotype-group was not statistically significant on EBW at the same fasted body weight and cold carcass weight at the same EBW. However, the buffalo empty body contained (P < 0·05) more offal than the ¾ Friesian empty body and heavier TOW and lighter hot carcass than ½ Friesian empty body of the same weight.

No significant genotype-group differences were found in the slope of the regression of weight of total side muscle (TSM), total side fat (TSF), subcutaneous fat, intermuscular fat and total side bone (TSB) on dissected side weight (DSW) and ½ EBW. Comparison of adjusted means, however, showed buffaloes to have significantly more TSF and TSB but less TSM than the Friesian cross-breds. Most of the difference in TSF was due to more subcutaneous fat in the buffaloes than in the Friesian cross-breds. In all comparisons the two Friesian cross-bred groups did not significantly differ from one another.

The results indicate that Egyptian buffaloes may be earlier maturing than Friesian cross-bred cattle and buffaloes of other countries. It was also concluded that in order to produce desirable carcass of fat:muscle ratio of 1:5, Egyptian buffalo bulls should be slaughtered to produce carcasses of slightly more than 230 kg whereas ½ Friesian and ¾ Friesian bulls can be taken to heavier weights. Methods for reporting carcass compositional data are discussed.

Analyses of data on first peak yields of 1346 Holstein Friesian (HF) × Sahiwal crossbred cows belonging to four Indian military dairy farms were carried out. There were highly significant differences amongst different grades. The < ⅛ HF had the minimum (9·35 kg) and £ HF had the maximum (12·77 kg) peak yield during first lactation. Half-breds appeared to be most suited for peak production. Genetic grades, farms and periods of calving had highly significant, and season of calving had significant, influences on peak yield in cross-bred cows. Heritability of peak yield was 0·405±+ 0·023. Peak yield had highly significant and positive genetic and phenotypic correlations with total lactation yield, 300-day milk yield, milk yield per day of first calving intervaland milk yield per day of age at second calving. Interval, in days, between the dates of first and second calvings was considered the first calving interval. Age, in days, at the time of second calving was considered age at second calving. The high heritabilities and desirable correlations indicate the possibility of satisfactory correlated response in thesetraits, if selection is based on peak yield.

Efforts have been made to control the oestrous cycle of ewes so that breeding can be induced at most times of the year (Gordon, 1963, 1975; Cognie, Hernandez-Barreto & Saumande, 1975; Smith, Boland & Gordon, 1981). Despite a high oestrous response, conception rates have generally been low in lactating anoestrous ewes (Hunter, 1968; Land & McClelland, 1971; Cognie et al. 1975; Shevah, Black & Land, 1975). The ability to achieve conception in post-partum ewes appears to be related to season, breed and lactational status (Cognie et al. 1975; Evans & Robinson, 1980; Rhind et al. 1980). Early research has shown that conception rates of 90% can be achieved in Finnish Landrace × Dorset Horn ewes using exogenous hormones, early weaning and artificial lighting (Robinson, Fraser & McHattie, 1975). Subsequent studies have shown that similar results can be obtained under natural daylight conditions provided that each ewe received pregnant mare serum gonadotrophin (PMSG) at the time of sponge withdrawal (Fraser el al. 1976). Some breeds of sheep may be induced to lamb at 6-month intervals, when maintained under ideal conditions including artificial lighting (Evans & Robinson, 1980). There seems to be some conflict in the literature as to factors affecting conception rate in ewes. Kann & Martinet (1975) have shown that it is the problem of suckling rather than lactation that is responsible for the delay in return to normal reproductive activity. It has been shown that luteinizing hormone (LH) release is quantitatively less in lactating than in cyclic ewes (Cognie & Pelletier, 1976; Evans, 1980). Also the pattern of LH production has been shown to differ in ewes conceiving and those which fail to conceive (Rhind et al. 1980). Cognie & Pelletier (1976) have suggested that in lactating ewes, a proportion of eggs are shed abnormally late in relation to the LH surge and may not be fertilized. The purpose of the present experiment was to investigate some of the factors which may influence the induction of pregnancy in nursing ewes in the non-breeding season.

Soil samples were taken from four field experiments on the growth of cereals in direct-drilled and in mouldboard-ploughed soil. When sampled, one of the experiments had run for 5 years, one for 6, one for 8 and one for 10 years. Sampling was to just below plough depth and was done on an ‘equivalent depth’ basis, i.e. the more compact direct-drilled plots were sampled more shallowly than the ploughed plots in such a way that both samples represented the same weight of soil per unit area. No significant differences in total nitrogen or in total organic carbon were observed between cultivation treatments at any of the four sites.

In three of the four sites, there was no significant difference in microbial biomass carbon, adenosine 5'-triphosphate (ATP), or mineralizable nitrogen between directdrilled and ploughed soils. In the fourth, which contained more clay than the others, there was slightly more biomass carbon and ATP in the direct-drilled soil. As microbial biomass carbon (or ATP, which is closely correlated with microbial biomass carbon) responds more rapidly to changes in management than do total carbon and nitrogen, a change in biomass carbon should provide early warning of changes in soil organic matter, long before changes in total carbon and nitrogen become measurable. That no such change was observed, with one partial exception, is evidence that a change from traditional methods of cultivation to direct drilling has little effect on soil organic matter other than altering its distribution in the soil profile.

The yield of bone is an important aspect of lamb carcass evaluation studies. Hand boning is commonly done to compute this. However, it is often difficult to compare and draw conclusions on carcass bone content obtained by different groups of workers as this value is very sensitive to the extent to which bones are cleaned before weighing (Cuthbertson, 1975). The amount of residue remaining on the bones after hand boning and its effect on the final yield of bone in lamb carcasses has not been adequately investigated so far. Such information is of scientific interest to those involved in lamb carcass evaluation work. Therefore, the present study was planned to probe into this aspect.