1. Early transplanting of seedlings resulted in the production of rice plants with greater total tiller and leaf number, greater total leaf area, leaf area per shoot and per leaf lamina, greater height, greater total fresh weight yield and yield of grain than late transplanting.

2. Early transplanting reduced the number of days from seeding to ear emergence.

3. Deep transplanting favoured greater leaf area per shoot and per leaf lamina and greater maximum tiller number and reduced the percentage tiller mortality.

4. Deep placement of fertilizer resulted in the production of plants with greater tiller and total leaf numbers, greater height, greater total leaf area, leaf area per shoot and per leaf lamina and greater total fresh weight and grain dry weight than surface placement.

5. Deep placement of fertilizer hastened the time of ear emergence of late transplanted seedlings.

6. The practical significance of these findings is that early transplanting of seedlings (30 days old), shallow transplanting, and deep placement of fertilizer will lead to greater yield of the rice variety BG 79.

1. A review of land restoration problems in relation to the soil depth required for successful crops showed that factual information on this orthodox method of restoration was inadequate.

2. A field trial sited on pulverized fuel ash is described in which the relationship between crop yield and soil depth at a range of fertilizer levels was determined; kale, oats, rape, barley and potatoes were the test crops.

3. The crops were divided into two groups, sensitive (kale and barley) and tolerant (oats, rape, potatoes) to ash toxicity, on the basis of their response to soil depth at the high fertilizer level. Quadratic expressions relating yield to soil depth, over the range 3–36 in. at each fertilizer level were fitted to the data for each crop group.

4. Yield isoquants, derived from the fertilizer response curves at each soil depth, enabled soil depth-fertilizer level combinations to be ascertained for producing a given level of crop yield. Fertilizer could be substituted for soil more effectively for tolerant than sensitive crops.

5. A 12 in. cover of soil together with 1½ times the normal farm fertilizer dressing for the crop was the minimum for acceptable yields. Fertilizer use may have to be increased to twice normal dressings to maintain yields if soil depths are reduced to below 12 in.

6. Crop yields were not increased by a soil covering greater than 24 in. deep.

1. The problems involved in conservation of fodder in Northern Rhodesia are discussed in relation to climate and present day practices. Special reference is made to the conservation of grassland herbage.

Climatic conditions do not appear suitable for haymaking.

2. A number of silage samples were collected from dairy farms in the territory and from Mount Makulu Research Station. Chemical analyses of these samples are given and their nutritional value is discussed with special reference to their crude protein contents. The majority of the silages were found to have low crude protein.

3. A type of miniature tower silo designed for experimental work is described.

4. Three crops commonly used for ensilage, i.e. maize, maize with legume and Napier grass, were compared with giant Rhodes grass (Chloris gayana Kunth.) when ensiled in these miniature silos. The type of fermentation and loss of nutrients was studied. Rhodes grass ensiled at the early flowering stage was found to compare favourably with the other three. Napier grass (Pennisetum purpurem) cut when over 6 ft. high did not ensile well and had a low crude-protein content.

5. Giant Rhodes grass was ensiled in miniature experimental silos at two different stages of growth. Cutting the grass at a height of 20 in., three times during the season, resulted in a higher yield of dry matter and crude protein per acre than cutting once at a height of 40 in. even when the resultant aftermath growth was included.

1. Observations were made during the autumn and spring of 1959–60, 1960–61, and 1961–62 on pregnant and lactating Clun ewes of mixed ages grazing under natural conditions. The pattern of food intake during pregnancy and lactation, the output achieved in the form of weight of lambs produced at parturition, milk yield, and bodyweight change of the ewes themselves was investigated. The interrelationships between these factors, as influenced by the feeding of supplementary concentrate, either for 7 weeks before or 7 weeks after lambing, or during both periods, was elucidated.

2. Daily dry-matter intake was found to be of the order of 1·5–2·0 kg. for this type of ewe, but there was considerable individual variation (coefficient of variation about 20%). Intake did not increase concurrently with the demands of the foetus during the later stages of pregnancy, and even became depressed as parturition approached. Immediately after lambing there was a spectacular increase in intake, which, after rising to a peak, was maintained at a high level during the lactation. Ewes receiving supplementary concentrates showed an increase in food intake over those unsupplemented, but this increase was less than the amount of dry matter fed in the supplement, even on rather bare pasture.

3. During the early stages of pregnancy there was no apparent difference in the weight gains of singleand twin-bearing ewes, but during the last 8 weeks prior to lambing twin-bearing ewes made greater weight gains. In relation to weights taken just after parturition ewes producing twins had lost most weight. Unsupplemented ewes lost more weight than those receiving supplements. Lack of supplementation prior to lambing only limited production in the case of twin-bearing ewes.

1. A study was made of the effects of feeding regimen and the composition of the diet on the ruminal production of V.f.a.'S in cattle.

2. The day-to-day variations in the pattern of rumen fermentation in cows given a diet of hay and concentrates indicated that within-cow differences in the molar proportions of the acids from diet to diet are of significance if they exceed about 3% (of the mean value) for acetic acid, about 10% for propionic and butyric acids, and about 25% for valeric acid. The results emphasized also the important differences to be found between cows given the same diet.

3. A change in the frequency of feeding from once to four times daily at a constant daily drymatter intake had little effect on the daily mean values for pH, concentration of total V.f.a.'S, or the molar percentages of the individual acids, but almost invariably decreased the range of values observed between feeding.

4. With diets of hay and of hay and concentrates an increase in daily dry-matter intake was associated with a fall in pH and an increase in the concentration of total V.f.a.'S; with the diet of hay and concentrates there was a considerable decrease in the molar percentage of acetic acid and a corresponding increase in N-butyric, but there was little change in the molar percentages of the acids with the diet of hay.

1. Soil samples were incubated at 60% W.h.c. at 20° C. and leached after 8 and 20 weeks. On subsequent incubation, the rate of nitrate production in the leached samples was greater than that in unleached control soils. The increase in nitrate production seems to be due to an increased rate of ammonification.

2. Adding 100 p.p.m. of nitrate nitrogen to the soil before incubating had no effect on mineralization.

3. Adding a leachate of incubated soil to new soil samples reduced the rate of mineralization on incubation. This reduction is not due to nitrate or any other anion, since deionized leachate was equally effective.

1. The effect of applications of liquid manure during the winter months was studied and compared with the application of dry artificial fertilizers on six different swards in two experiments in each of the years 1960, 1961 and 1962.

2. The liquid manure supplied an average of 69 lb. N and 114 lb. K/acre at each application and plots received one dressing only applied in November, December, January, February or March. Further treatments consisted of applying conventional dry fertilizer supplying the same weight of nitrogen and potassium as the liquid manure and applied on the same day. A control plot received no added fertilizer or liquid manure.

3. All plots were cut in May and a second cut was made 8–10 weeks later to measure residual effects of treatments.

4. The maximum increase in dry-matter yields at cut 1 occurred with the February application although the January and March applications gave only slightly lower yields. The dry-matter yield/lb of N applied even from some November applications was comparable to the response obtained from applications of inorganic nitrogen made in summer in earlier experiments by other workers.

5. The production of crude-protein followed a similar pattern to that of the dry-matter, and the maximum increase was from the March application.

6. With similar rainfall conditions but different winter soil temperatures a mixture of Italian and perennial rye-grasses under average fertility conditions gave the highest response to liquid manure. This was followed by the later growing cocksfoot sward and the permanent pasture, on both of which yields were increased by all the monthly applications. The two swards containing grass and clover mixtures showed a response to the later dressings whereas a vigorous Italian rye-grass ley in the mild winter of 1961 was unaffected by treatment.

1. Seed production stands of S 37 cocksfoot were obtained with varying plant densities by utilizing two drill widths, removing sections of drill, or over-sowing drilled material. All density treatments were operative at two levels of N, 87 or 174 lb. N per acre per annum.

2. Tillers in selected quadrats were labelled at monthly intervals during autumn and/or winter for 3 years. Performances of tiller populations were assessed from these quadrats.

3. Seed yields were increased in many cases by reducing plant density from a continuous drill pattern. Increased plant density reduced yields. With plant communities on a 1 ft. square arrangement at the high level of nitrogen, an increase of 33%, or 243 lb. seed, per year over a 3-year period was obtained compared with continuous rows at any level of N. The yield of gapped stands increased over the 3-year period, whilst the yields of continuous rows dropped in the final year.

4. Nitrogen significantly increased the yield of cocksfoot, except in the third year, by increasing the weight of seed per ear.

5. Tiller numbers per quadrat increased in most treatments over the course of the experiment, both within years and from year to year; seasonal peaks of tillering were apparent. The effect of N on tiller numbers differed each year, presumably due to the state of the populations when the N was applied.

6. Higher tiller numbers per plant were obtained with lower plant numbers per unit area. Percentage fertility of tillers was generally higher with lower plant densities, and lower tiller numbers per plant, other factors being equal. The only significant effect of N on fertility was to decrease it in the third year.

1. The concentrations of 131I in milk, urine, and faeces were compared to the total and non-proteinbound radio-iodine of blood after a single dose of radio-iodine to cows that were being maintained on diets providing about 3·5 or 12-16 mg. of stable iodine per day.

2. In general, the 131I concentrations in milk and urine tended to parallel the non-protein-bound 131I of blood. Faecal 131I levels of the low-iodine cows tended to parallel that of the whole blood, whereas it followed the non-bound radio-iodine of blood for cows on the higher stable iodine diet.

3. Compartmental analysis of the concentration curves showed a component with a T½ of from 10 to 22 hr. being common to both groups of cows. The second component of the curves constructed for the cows on the higher iodine intake had a T½ of from 41 to 58 hr. The second component for the low-iodine cows had a T½ that ranged from 83 to 169 hr. for the urine, faeces and non-bound radio-iodine of blood and 1200 and 1580 hr., respectively, for the faecal and whole-blood curves.

4. A greater proportion of bound radio-iodine was observed in the milk and blood of cows on the low-iodine diet than for the cows on the higher iodine intake. The proportion of bound 131I in blood increased with time, but the bound 131I of milk was relatively constant.

1. Twenty-one experiments were carried out in various parts of England and Scotland in 1959–61 comparing two or more of the nitrogen sources ammonium sulphate, ammonium nitrate, calcium nitrate and urea, combine-drilled in compound fertilizers for spring barley.

2. Ammonium sulphate and ammonium nitrate combine-drilled at rates from 35 to 105 lb./acre of nitrogen checked early growth slightly in some of the experiments, with no important difference between the two sources, which also gave similar grain yields.

3. Calcium nitrate and urea combine-drilled at 45 lb./acre of nitrogen had no large effect on early growth, while at 70 and 90 lb./acre both fertilizers seriously delayed brairding and reduced the plant population in many of the experiments, especially in eastern England. They gave lower yields than ammonium sulphate and ammonium nitrate in many of the experiments in which early growth was affected, and gave lower mean yields at all rates of application.

4. In eleven of the experiments, broadcast applications of two or more of the four nitrogen fertilizers were compared. All sources gave similar mean yields.

5. There was a slightly smaller yield from combine drilling than from broadcasting ammonium sulphate and ammonium nitrate, and a markedly smaller yield from calcium nitrate and urea.

1. Urea containing less than 1% biuret was compared with ammonium nitrate in field experiments on barley, sugar beet, winter wheat and grassland, and with ammonium sulphate on potatoes, in various parts of Great Britain in the years 1957–61.

2. When broadcast on the seed-bed for barley at rates supplying 25–45 lb./acre of nitrogen in twenty-five experiments, urea and ammonium nitrate gave similar mean increases in grain yield on acid soils, while on alkaline soils urea gave smaller increases than ammonium nitrate. The relative effect of the two sources was similar on light and heavy soils and in the east and west of the country.

3. When broadcast on the seed-bed for sugar beet at 50–60 lb./acre of nitrogen in nineteen experiments, mostly on alkaline soils in eastern England, no difference was detected between the mean increases in yield of sugar and tops from urea and from ammonium nitrate.

4. In twenty-two experiments on potatoes urea gave slightly smaller mean increases in yield of tubers than those from ammonium sulphate when applied at 40–60 lb./acre of nitrogen, with a larger difference at 80–120 lb./acre. No influence of soil pH, soil texture, region of the country or method of application (broadcast on the flat or over the open ridges) was detected.

5. When broadcast as spring top dressings in seventeen experiments on winter wheat, mostly in western England and Scotland, at rates supplying 34–45 lb./acre of nitrogen, urea and ammonium nitrate gave similar mean increases in yield of grain.

1. In 1958, leys of late flowering red clover (S. 151) and of Italian rye-grass (S. 22) were undersown in barley. In 1959, yield and N and K uptake by clover, and by rye-grass given 0·0, 0·75 or 1·5 cwt. N/acre, were compared; rye-grass, given 1·5 cwt. N/acre, yielded most dry matter and removed three times as much K, but rather less N than did clover.

2. In 1960, wheat given 0·0, 0·25, 0·5 or 0·75 cwt. N/acre as a top-dressing measured residual effects of the N left by each ley. When no N was given to wheat, most grain and straw was obtained after clover ley and least after rye-grass given no N. The residual N from clover was equivalent to 0·14 cwt. N/acre as a fresh top-dressing; N given to rye-grass left only a small residue. When the wheat had 0·5 or 0·75 cwt. N/acre as a top-dressing, N given to rye-grass in 1959 decreased yield, probably because the rye-grass removed much K, but K uptake at harvest was independent of ley.

3. In 1960, leys of early flowering red clover (Dorset Marl) and of Italian rye-grass (S. 22) and a mixture of the two were under-sown in barley. In 1961, yields and N and K uptakes of clover, and of rye-grass given 0·0, 1·0 or 2·0 cwt. N/acre and of clover-rye-grass given 0·0 or 1·0 cwt. N/acre were compared. Rye-grass given 2·0 cwt. N/acre yielded most dry matter and removed one-third more K than did clover, but clover yielded one-third more N.

1. The sodium and potassium content of longissimus dorsi (lumbar), psoas major, rectus femoris, triceps (lateral head) and extensor carpi radialis from 6 pigs each at pork, bacon and manufacturing weights were determined: these varied significantly and systematically between muscles and between groups.

2. Since the concentration of potassium may differ by at least 30% between muscles, it is concluded that assessment of total muscle mass may be inaccurate if based on the integration ofγ-ray emission from 40K.

1. Muriate of potash applied at rates of 0, 1 and 2 cwt./acre to herbage which had also received similar treatments in the previous year did not influence plasma magnesium or calcium values in lactating ewes.

2. 24 Cheviot ewes had slightly lower plasma calcium and magnesium levels than 24 Half-bred ewes of the same age both before and after lambing.

3. 6·6 g. of magnesium oxide given as a daily drench did not increase plasma magnesium values as measured by blood samples taken 24 hr. after drenching. Values were however increased by 0·5 mg. Mg/100 ml. four hours after drenching.

4. No clinical cases of hypomagnesaemic tetany occurred, even although the mean plasma magnesium level of all the ewes in the experiment was only about 1·0 mg./lOO ml.

5. Plasma magnesium values of ewes before lambing were significantly (P < 0·001) correlated with post-lambing levels. Values for the ewes during 1962 were equally significantly correlated with levels for the same sheep at comparable dates in 1961.

1. A preliminary study of the protein requirements of young steers of two breeds of African cattle has been described. These requirements were assessed by studying body weight changes of groups of animals fed for 140 days on rations varying in protein content.

2. There were only small differences between the breeds in their voluntary food intake while appetite seemed to be linearly related to protein content.

3. The two breeds were equally efficient in food and protein utilization.

4. Live-weight gain improved significantly as the protein content of the ration increased from 6 to 10%, but a further increase to 14% produced only a small subsequent improvement in growth.

5. Maintenance of weight was estimated to occur at a digestible protein intake of only 48% of that recommended by Brody (1945), while the required digestible protein for one pound daily gain was in agreement with the National Research Council (1950) standard.

1. A range of soils were cropped exhaustively by perennial rye-grass for up to eleven months in the glasshouse; some were also cropped with Dutch white clover.

2. At least 100 lb./acre of magnesium was taken up from most soils, and some soils supplied more than 200 lb./acre. The amounts of magnesium taken up decreased with successive harvests, suggesting that the available magnesium was progressively depleted. Although the ‘exhaustion’ magnesium (Mg taken up by crops+residual exchangeable magnesium) was greater than the initial exchangeable magnesium, these two measurements were closely correlated (r = 0·99). If non-exchangeable magnesium was released during cropping, the releases were proportional to the initial exchangeable magnesium contents. However, the exchangeable magnesium measurements may have extracted only a proportion of the magnesium available naturally.

3. Any releases of magnesium were small compared with the amounts available from the outset, and the crops obtained magnesium mainly from the exchangeable form. Rye-grass and white clover gave similar results.

4. The exchangeable magnesium in some exhausted soils was increased by wetting and drying. This effect may occur in the field, where the magnesium lost in cropping could be replenished by only small releases of non-exchangeable magnesium.

1. Methods of fitting certain yield-density relations are given which are appropriate when the proportional rather than the absolute standard error of the yields is constant.

2. These methods are applied to relations discussed by Jarvis in connexion with his data on lucerne, and it is shown that no clear advantage can be claimed for any of the relations.

3. The role of significance tests in the interpretation of the data is briefly discussed.