Data from the chemical and dissection analyses of thirty-nine New Zealand Romney Marsh ewe carcasses are presented and compared. One side of each carcass was dissected into muscle, fat, and bone and the other side was totally ground and chemically analysed for water, fat, protein, and ash. There were strong statistical relationships between the two methods of carcass analysis and accordingly the quicker and more simple chemical technique could replace dissection in many carcass studies.

1. A survey of commercial crops of spring oats suggested tilth as a major factor affecting emergence.

2. In field experiments conducted on clay and sandy soils, the surface tilth was regarded as a population of aggregates characterized by size which was analysed by means of a five-point quadrat. A tilth index was calculated from the data thus obtained. Under the rough tilths on the clay soil emergence and tilth were directly related, but on the sandy soil there was an optimum degree of cultivation, the plots with the finest tilth had been over-cultivated and gave a low rate of emergence (Fig. 2).

3. A greenhouse pot experiment examined the effect of a cover above the seed of 21 tilths, of varying proportions of 0·03–0·25 in., 0·25–1·25 in., 1·25–2·25 in. diameter aggregates, the soil below the seed being uniform in all treatments. This confirmed that emergence rates were higher under fine surface tilths than under very rough tilths (Fig. 3). An increase in the proportion of 0·03–0·25 in. fraction increased emergence regularly whereas an increase in the proportion of the 1·25–2·25 in. fraction reduced emergence regularly. The presence of 0·25–1·25 in. aggregates reduced emergence compared with that where 0·03–0·25 in. only were present, but the effect of an increase in the proportion was not regular (Fig. 4).

4. A second greenhouse pot experiment compared the effect of 3 tilths above the seed and 2 irrigation treatments. The low emergence rate (58%) caused by a very rough tilth under restricted irrigation was raised to 86% by liberal irrigation.

5. From the evidence of both pot experiments it is postulated that a covering tilth above the seed of 25% or more by weight of fine soil (0·03–0·25 in.) and not more than 40% of coarse aggregates (1·25–2·25 in.) will permit a rate of emergence of at least 80%.

6. As the fine covering tilths in the pot experiment gave high rates of emergence as compared with rougher tilths, it is suggested that the low rate of emergence, on the sandy soil field experiments, was due to a lack of soil moisture induced by over-cultivation.

1. Ten experiments were carried out on grassland in various parts of England and Scotland to compare ammonium nitrate, ammonium sulphate, urea with less than 1% biuret and urea with about 4% biuret. The grass was cut a number of times during the season and each nitrogen fertilizer was applied at rates supplying 30 and 60 lb. per acre of nitrogen in spring and after each cut except the last.

2. Total yield and yields at most individual cuts of both dry matter and nitrogen in the herbage were increased by each increment of applied nitrogen.

3. Ammonium nitrate and ammonium sulphate gave similar dry-matter yields at all cuts in six experiments, while in four on calcareous soils ammonium sulphate gave lower yields than ammonium nitrate at one or more cuts. Ammonium sulphate gave lower yields at the second or third cuts in more experiments than at the first cut.

4. Urea with < 1% biuret gave lower dry-matter yields than ammonium nitrate at one or more cuts in eight of the ten experiments. Urea became less efficient relative to ammonium nitrate as the season advanced.

5. The efficiency of urea with < 1% biuret relative to ammonium nitrate in each experiment was positively correlated with the ammonia absorption potential of the soil.

6. Urea with < 1% biuret and urea with about 4% biuret gave similar yields.

1. 4 g. of Mg per day given as either magnesium oxide or magnesium nitrate failed to increase plasma magnesium levels of fourteen lactating ewes which had initial values of about 1·0 mg. Mg/100 ml.

2. Increases which were recorded 4 hr. after drenching were not sustained for the full 24 hr. period between drenches.

1. An experiment is described which investigated the effects of potassium fertilizer, age of ewe, and a small magnesium supplement, on the plasma magnesium and calcium levels of ewes shortly after lambing.

2. Three potassium treatments (0, 1, and 2 cwt. muriate of potash/acre) were used, each being replicated six times, which gave a total of eighteen plots. Each plot was grazed by two old and two young ewes. One ewe of each age in every plot was given supplementary magnesium in the form of two magnesium heavy pellets, which released a total of 150 mg. Mg/day.

3. 22% of the ewes had plasma magnesium values below 1·0 mg. Mg/100 ml. on at least one sampling occasion during the experimental period. There was only one clinical case of tetany.

4. Neither potassium fertilizer use, nor magnesium supplementation influenced plasma magnesium and calcium levels of the ewes. Old ewes had greater temporary falls in plasma magnesium values and had consistently lower plasma calcium values.

5. Attention is drawn to the large individual variation between animals and the consequent need for providing adequate statistical analysis of experiments of this type.

1. An experiment, lasting 3 years, was carried out to investigate the control of hypomagnesaemia on a medium-heavy loam soil in Northern Ireland, using as criteria herbage analysis and analysis of blood sera of grazing dairy cows.

2. Applications of calcined magnesite and magnesian limestone as soil treatments raised the magnesium contents of herbage slightly but not to levels judged to be safe. Low blood sorum magnesium levels were recorded for cows grazing this herbage although no cases of tetany occurred.

3. Magnesium sulphate, appliedas a spray, temporarily raised the ‘apparent’ magnesium content of the herbage but was easily washed off by rain.

4. Finely powdered calcined magnesite applied as a dust to the herbage immediately before grazing appeared to be a promising method of control under Northern Ireland conditions.

1. A survey was carried out on dairy farms in the south of Scotland during the period 1958–59 to obtain information on: (a) the mineral element composition of spring pastures associated with grass tetany or staggers and hypomagnesaemia, and (b) the influence of magnesium supplements on the incidence of these conditions and on serum magnesium levels.

2. Pastures associated with grass tetany had a significantly lower average magnesium and sodium content and a higher potassium content than those which were classed as normal. These differences were magnified in the values of the ratios K/(Ca + Mg) and (K + Ca + P)/(Mg + Na) which were considerably higher in tetany pastures. The incidence of tetany was positively correlated with the value of the former ratio. These results are similar to those obtained in Holland.

3. The analytical results for pastures associated with hypomagnesaemia in clinically normal cows were not significantly different from those for normal pastures and there was no evidence of any association between the composition of the pasture and the incidence or severity of the hypomagnesaemia or the serum magnesium levels.

4. The magnesium and sodium contents of the majority of the pastures examined would be judged as inadequate in the light of available information on the requirement of these elements.

5. There was no evidence of any correlation between the magnesium content of the pasture and that of any of the other elements studied.

6. Cases of grass tetany occurred in 25% of the 108 herds studied, the mean incidence in affected herds being 4·5 ± 0·65%. The overall incidence was 1·1 ± 0·25% and was significantly lower when a magnesium supplement was given as a prophylactic measure.

7. Hypomagnesaemia was detected in clinically normal cows after turning out in 41·2% of the herds, the overall incidence being 8·7 ± 1·0%. On tetany free farms the feeding of calcined magnesite or magnesium-rich mineral mixtures did not appear to reduce the incidence of hypomagnesaemia or the fall in serum magnesium levels which occurred after turning out.

8. These results emphasize the wide individual variation in the susceptibility of different cows to the factors causing hypomagnesaemia and grass tetany and also the differences between the two conditions in their dietary relationships. It is suggested that dietary factors may be responsible for producing the clinical signs of grass tetany in hypo-magnesaemic cows.

Twenty-nine digestibility trials were carried out on various tropical forages and the results obtained were used to investigate possible prediction of nutritive value from chemical composition.

1. The digestibility coefficient of crude protein could be predicted from the level of dietary crude protein. This prediction could be slightly improved by the incorporation of crude fibre in the expression. Results were somewhat higher than those reported from temperate areas.

2. In order to investigate the above phenomena, a value for metabolic faecal protein was calculated. This was found to be similar to values reported from temperate areas. There was no correlation between faecal crude protein and either level of dietary crude fibre or undigested crude fibre.

3. No significant relationships could be obtained to predict total digestible nutrients from either crude fibre or crude protein.

4. There was a low (non-significant) negative correlation between the content of dietary crude fibre and the digestibility coefficient of organic matter; comparison of this value with those in the literature suggested that the effect of crude fibre in tropical areas was different to that reported from temperate areas.

5. Results obtained were compared with standards of intake and nutrient requirements as recommended by the N.R.C. It was concluded that the factor most frequently limiting was digestible crude protein whilst total digestible nutrients were adequate in the greater part of the samples considered.

1. A ‘reference plot’ rotation experiment was begun at Rothamsted in 1956 on a field where grass had grown for many years. The soil contained very little HCl-soluble P and K but much N. The soil had been acid, but was limed to pH 6·5 immediately before the experiment started; this pH has been maintained. Very small individual plots (0·00128 acre) were used and nearly all work was done by hand. The results showed that such small plots can be used to do complicated rotation experiments satisfactorily provided that all work is done carefully and movement of soil over plot boundaries is prevented.

2. Responses to combinations of N, P and K fertilizers and farmyard manure (FYM) were measured on wheat, kale, barley, grass-clover ley, and potatoes grown in rotation. Two rates of N were tested. A strip of permanent grass had the same treatments as the arable crops.

3. Winter wheat yielded most dry matter, but wheat yields were increased least, proportionally, by added nutrients. Potatoes gave the smallest yield without manure and responded most to nutrients, yields being increased almost sixfold by NPK fertilizer plus FYM. Kale, barley and grass-clover ley were intermediate in their unmanured yields and in their responses.

4. All crops except the grass-clover ley responded to N; kale responded most and wheat least. Potatoes kale and barley responded roughly equally to P and needed this nutrient more than did wheat and the ley. Potatoes responded most to K, yields of wheat and clover ley were also small without K, but barley and kale needed K less. Interactions between nutrients were large with most crops, particularly with N on kale and K on potatoes, wheat and clover.

5. FYM greatly increased yields of all crops but responses were less when fertilizers were also given. Potatoes responded most to FYM whether or not fertilizers were also used. FYM also caused large increases in yields of grass-clover ley, kale, and permanent grass.

1. The amounts of N, P and K recovered by five arable crops and by permanent grass from soil alone, and from fertilizer and farmyard manure (FYM) dressings were measured. All the crops responded well to P and K fertilizers and all except clover responded to N. Uptakes from soil alone are therefore the maximum amounts of each nutrient that each crop could remove when supplied with other fertilizer nutrients (the exchangeable Ca and Mg in the soil were adequate).

2. Permanent grass (free from legumes) obtained about 114 lb. N/acre each year from soil and other natural sources; winter wheat obtained 1001b. N, kale and potatoes about 80 lb. N and spring barley only 57 lb. A 1 year ley of clover and grass fixed at least 1 cwt. N/aere/year. Permanent grass removed most P from soil (17 lb./acre a year), potatoes removed least (6 lb. of P) and other crops intermediate amounts. Most K was taken from soil by kale (70 lb. K/acre/year) and least (20 lb.) by potatoes. Annual variations in the amounts of nutrients recovered from soil by any one crop were much greater with K than with N or P.

3. Most fertilizer N was recovered by kale and least by potatoes; with these crops two-thirds and one-third respectively of the light dressing was recovered, percentage recovery from the higher rate of N tested was less. Kale and the 1 year ley recovered nearly one-quarter of the P applied, permanent grass recovered little more than one-tenth. Clover-grass ley recovered most fertilizer K, apparently taking up four-fifths of that applied. Potatoes, kale and permanent grass all recovered more than half of the fertilizer K given, cereals were least efficient although both responded well to K dressings.

4. Farmyard manure supplied large amounts of nutrients to all crops. Similar amounts of N, P and K appeared to be recovered from FYM whether or not NPK fertilizer was also used. A rough estimate was that crops like kale, potatoes and permanent grass, which received FYM each year, recovered about 30 lb. of N, 4 lb. of P and 75 lb. of K from a 10 tons/acre dressing.

1. From 1955 to 1957 a cattle grazing experiment was carried out on lucerne and cocksfoot pastures. Hereford-cross steers were used. Results obtained on the assessment of herbage intake either by the use of chromic oxide and faecal index methods or by herbage sampling are presented here.

2. Except in 1955, when techniques were being developed, the digestibility of the herbage on offer to the bullocks was estimated by cold storing herbage, cut with an Allen Autoscythe and later feeding it to sheep in indoor digestion trials. The in vitro digestibility of herbage samples cut in 1955 and 1956 was also determined.

3. In 1956 the mean intake of organic matter (lb.) per 100 lb. live weight by faecal methods was 2·38, 2·07, 2·20 and 2·29 on pastures of lucerne, cocksfoot, lucerne/cocksfoot (broadcast) and lucerne/cocksfoot (alternate 1 ft. drills), respectively, and 1·99, 1·76, 2·02 and 1·97, respectively, in 1957.

4. In 1956 the mean intake of organic matter (lb.) per 100 lb. live weight by herbage sampling methods was 2·14, 1·70, 2·11 and 1·99 on the same pastures of lucerne, cocksfoot, lucerne/cocksfoot (broadcast) and lucerne/cocksfoot (drills), respectively, and 2·49, 1·32, 2·35 and 2·03, respectively, in 1957. The modified Tarpen trimmer, cutting to within 1 in. of the ground was used for sampling in 1956 and the Allen Autoscythe cutting to within 2 or 3 in. of ground level in 1957.

5. Detailed botanical separation of herbage samples showed that the bullocks were selecting the more digestible parts of the plants; the top 4 in. of lucerne and the ends of leaves and stems of cocksfoot. This and other factors which could affect the estimates of digestibility of herbage eaten by the cattle are discussed together with possible sources of error in the herbage sampling methods.

1. A series of three experiments were performed to examine grass as a food for dairy heifers.

2. Indoor feeding resulted in lower intakes of herbage and slower growth but gave greater outputs per acre of animal days and live-weight gain than grazing.

3. The maximum consumption and growth rate, obtained on young grass, were 2·84 lb. herbage dry matter per 100 lb. live weight per day and 2·2 lb. live-weight gain per day for grazing stock. The corresponding figures for indoor feeding were 2·49 lb. herbage dry matter per 100 lb. per day and 1·34 lb. live weight gain per day.

4. Live-weight gain per day was linearly related to herbage dry matter intake from 1·48 to 2·48 lb./ 100 lb. live weight/day.

5. Intake of herbage and growth rate only fell after the herbage came into full flower.

6. Increased stocking rate had small effects on growth rate because the animals grazed the paddocks more heavily.

7. 2·6–3·0 lb. grass dry matter offered per 100 lb. live weight per day was judged an adequate ration for yearling heifers. This gave growth rates of 1·60 lb./day on herbage up to the flowering stage and a consumption of 88% of the available herbage.

8. As an experimental technique zero grazing was found inadequate to replace grazing since it fails to reproduce similar intakes and rates of production. It permitted the reduction of intake to sufficiently low levels that live-weight gain per animal and per acre were reduced.

9. The greatest output per acre was found to occur between limits of intake per day of 1·8–2·4 lb. herbage dry matter per 100 lb. live weight. Above the point of maximum output per acre level of feeding had little effect on production per animal and rate of stocking controlled output per acre. Below this point level of feeding controlled production per animal. The case is advanced that these latter levels of feeding are necessary in grassland experiments.

The methods proposed by Pereira for unirrigated coffee have been followed in a study of water use by this crop for the 12 years 1950–62. Soil sampling has shown that the procedure provides a reliable measure of evapotranspiration from unirrigated coffee.

A modification is proposed which has enabled the rate of water use by irrigated coffee to be followed satisfactorily for the 5 years 1957–62. Occasional soil sampling showed that the modified procedure provided an estimate of the soil moisture status sufficiently reliable and accurate for the regulation of irrigation timing and amount.

Irrigation to maintain a favourable soil moisture status has had a marked and beneficial effect on the production of Grade ‘A’ coffee in dry years.

The mean daily rate of evapotranspiration from irrigated coffee is estimated to range from 0·15 in. in hot weather to half this rate during the cool and cloudy season.

The maximum computed annual totals of supplementary irrigation which were required over a 12-year period ranged from 5·5 in. to 31·5 in. with a mean value of 16·0 in. per year.

1. A co-ordinated trial has been carried out at 17 centres to compare the effects on performance and carcass quality of feeding growing pigs once or twice daily.

2. No significant differences were found between growth rate, efficiency of food conversion or length of pigs on the two treatments.

3. Killing out percentage was on average 0·92% worse for the pigs fed once daily, a significant effect, probably because the pigs on the two treatments received different amounts of food at the last feed before slaughter.

1. In the winters of 1959–61 three randomized block experiments were carried out to study protein requirements of heifers of 800–1000 lb. live weight. 24 animals were used in each experiment. Half the animals were kept indoors; the remainder stayed out of doors except for 1 hr. per day when they came into covered yards to receive their concenrates ration.

2. Rations were based on straw, cereals and roots. The intake of crude protein was varied by replacing cereals by decorticated ground nut meal. The estimated level of energy intake varied from 7·2–8·2 lb. starch equivalent/day between experiments, but the level was constant for all treatments within an experiment.

3. At the end of each feeding trial the nitrogen balance was measured for 2 animals from each treatment. The results confirmed the estimated levels of digestible crude protein intakes upon which the experiments were based.

4. An increase in intake of digestible crude protein (as determined in the metabolism trials) from 0·35 lb./day to 0·72 lb./day gave a marked response of 0·45 lb./day in the rate of live-weight gain. Further increases in protein intake gave little response in live-weight gain. It was concluded that for heifers of 800–900 lb. live weight the protein requirement for maintenance and a live-weight gain of 1·2 lb./day was 0·70 lb. digestible crude protein/day.

5. Comparison of the estimated starch equivalent intakes in the three experiments showed that in heifers receiving 0·52 lb. digestible crude protein per day the rate of gain increased from 0·25 to 0·90 lb./day as the level of energy intake increased from 0·78 lb. starch equivalent/100 lb. live weight per day to 1·01 lb./100 lb. live weight.

6. Biological value of the dietary nitrogen decreased as level of protein intake increased. The values for individual animals ranged from 61·3 to 82·4. The mean value was 69·5.

7. The weather during these experiments was typical of winters in south-east England with mean minimum ground temperatures about 30° F. and mean maximum and minimum air temperatures of about 50° F. and 35° F., respectively. Snow fell occasionally only; 3½–5½ in. of rain fell in the period 1 January to 31 March. In 2 years out of 3 the outdoor group grew slightly faster than the indoor groups. In the third year this trend was reversed.

1. A field experiment on an acid soil long in arable cropping at Rothamsted measured residual effects of superphosphate, applied at several rates, and Gafsa rock phosphate applied at a single rate. Residues were valued after 1 year with barley, and after 2 years with rye-grass. In each year, the value of the residues was related to yields from fresh superphosphate dressings taken as standards. ‘Percentage fresh superphosphate equivalents’ of the residues were determined using yields and P uptakes of both crops. An isotope dilution method with 32P was also used with barley. The experiment was continued for 2 further years without applying phosphate fertilizers, to measure yields and P uptakes from the residues and yields and P uptakes from rock phosphate relative to superphosphate.

2. ‘Percentage fresh superphosphate equivalents’ of residues of superphosphate for barley varied with the growth of the crop and with the method used to calculate them. They were 21–24%6 weeks after sowing, measured from yield, P uptake or isotope dilution. At harvest, they were 26% from yield, 43% from P uptake and 49% by isotope dilution. ‘Percentage fresh superphosphate equivalents’ 6 weeks after sowing increased with the rate of superphosphate but at harvest were independent of rate. ‘Percentage superphosphate equivalents’ of Gafsa rock phosphate were much smaller; they increased from 2–3% 6 weeks after sowing to 7–12% at harvest.

3. With rye-grass ‘percentage fresh superphosphate equivalents’ of residues of superphosphate applied either 1 or 2 years previously also varied with growth. All methods of valuation showed that residues were about twice as effective after 1 year as after 2 years in the soil. ‘Percentage fresh superphosphate equivalents’ derived from P uptake remained constant during growth and were 37–38% for superphosphate applied 1 year before and 18–20% for superphosphate applied 2 years before. Values derived from rye-grass yields decreased during growth from 76 to 45% (1-year residues) and from 38 to 21% (2-year residues).

4. After cropping with barley for 2 more years, there was little difference between yields or P uptakes from equal amounts of superphosphate whether applied 3 or 4 years previously. Residues from rock phosphate were almost equivalent to those from superphosphate after 3–4 years.

5. Apparent recoveries of superphosphate, as percentages of the amount applied, decreased with rate. The apparent recovery of P by crops in 5 years was about 21% from superphosphate and about 10% from rock phosphate when both were applied at 3·0 owt. P2O5 per acre.

1. Analyses and a greenhouse experiment on soils taken from a field experiment to estimate residual values of phosphates were used to show changes in the amount and distribution of residual phosphate in the soil.

2. Total and NaHCO2-soluble P were large in the top 0–3 in. of soil after applying superphosphate. Total P was large, but NaHCO3-soluble P much less, where rock phosphate had been applied in the field. Ploughing distributed total and NaHCO3-soluble P more uniformly through the 0–6 in. layer of soil.

3. Soil analysis and crop yields in the greenhouse showed that the residual value of equal amounts of P2O5 as rock phosphate and superphosphate, three years after application, were very similar.

4. At the end of the field experiment the sand fraction of the soil (2000–75 μ) contained about 80% of the phosphate that was applied as rock phosphate in this particle-size range.

Projects carried out in the Lake Province of Tanganyika for breeding Upland cotton resistant to bacterial blight are described.

A programme in which Albar 51 was used as resistant parent was more successful than one in which an attempt was made to transfer the major gene B6m to breeding stocks.

Backcrossing was found to be of limited value as a breeding technique with rain-grown cotton, line breeding in segregating stocks being preferred.

It is demonstrated that resistant types can be synthesized by the systematic exploitation of residual genetic variability in locally adapted populations.

Correlations between stem, boll andleaf resistance are discussed and some deviations attributable to environmental effects described. It is inferred that there is a basic resistance mechanism in all tissues which is under the same genetic control but that results may be confused by genotype-environment interactions and by other factors operating in particular tissues.

The approach to resistance breeding is discussed in relation to the evolution of resistance in African Upland cotton. It is concluded that improvement by straight selection should be given equal emphasis with improvement by hybridization in resistance breeding programmes.