The influence of growing plants on nitrification in the soil was studied by means of small lysimeters of which four were planted to a perennial grass, four to an annual millet crop and four were left fallow.

Nitrification was entirely repressed under the grass from the second season after its establishment onwards, and did not take place even when the grass was dormant in winter. This was due to a direct influence of the living root, since in the fallow soil which was treated similarly, nitrification took place freely throughout the winter. Under the annual crop a repression of nitrification could be detected only towards maturity of the crop and the soil solution was completely depleted of nitrates at this period. Nitrification was resumed, however, immediately after the crop was ripe and had died off and continued through the winter.

During the period that nitrification was depressed replaceable ammonia made its appearance in the soil in more than normal quantities. This fact is hold to indicate that the plant exerts its influence on the mineralization of nitrogen in the soil by paralysing the autotrophic dehydrogenase system of the nitrifying organisms without interfering with the process of ammonification and not, as has been claimed, by excreting such quantities of carbonaceous matter that nitrates are reassimilated by micro-organisms.

By virtue of the constancy of the carbon-nitrogen ratio in soils this influence of plants on the mineralization of nitrogen has a very important bearing on the conservation of soil humus and consequently on any system of alternate husbandry. Some of its implications were discussed with particular reference to local fertilizer practice and field experience.

1. Chicks from commercial sources were housed intensively and fed on a series of rations containing decorticated extracted groundnut meal as the main supplementary source of protein, with and without additions of animal by-products and aureomycin. Parallel groups received rations conforming to Government regulations in their content of sources of animal protein.

2. Growth and feed efficiency up to point of lay were as good in groups fed on all-vegetable rations, containing 18% of crude protein in the starting ration and 16% in the growing ration, as in groups fed on regulation rations of the same protein content.

3. Performance on the all-vegetable ration up to 6 weeks of age was not as good as on the regulation ration. This inferiority could be largely or wholly corrected by adding extra groundnut meal and condensed fish solubles to the ration. Growth and feed efficiency over the whole rearing period were not improved by the addition of these supplements.

4. Addition of aureomycin stimulated growth over the whole rearing period but failed to improve feed efficiency.

5. Protein levels in the ration, the provision of animal protein factor(s) and aureomycin were without effect on the age at which laying began.

6. Current estimates of the chick's requirement for certain amino-acids appeared to be too high when this type of ration was used.

7. The addition of riboflavin to these starting rations was essential. When this was done mortality was low, leg weakness absent and feathering rate normal.

An attempt was made to determine what becomes of the nitrogen added to a poor soil in moderate quantities of organic manures or of ammonium sulphate. Losses by drainage, in two successive barley crops, and by fixation in an unavailable form in the soil were determined, and it was found that with every material used (including tare residues containing 3½% nitrogen, mustard plant residues containing 1½–2¼ nitrogen and pure ammonium sulphate) and with intensive cropping and leaching, not more than 40–51% of the added nitrogen could be accounted for at the end of the experimental period. The balance, it is suggested, must have disappeared from the system, possibly as gaseous nitrogen.

Incidentally to the above, it would appear that after the first crop of barley the presence of the manurial additions of tare residues, and especially of ammonium sulphate, tends to hinder the formation of leachable nitrogen in the soil.

Designs are given for factorial experiments with three, four or five factors at two levels each, using thirty-two plots in a 4 × 8 lay-out on the ground. The effects of both rows and columns can be eliminated from the estimate of error. Provided that three-factor interactions can be ignored, information can be retained on all two-factor interactions.

1. The relation between the soluble-nitrogen content of grass silage and the pepsin digestibility has been investigated, and formulae have been derived for calculating the protein digestibility in the silage dry matter from the determined solublenitrogen content.

2. Comparisons have been made between the calculated results for protein digestibility, the results using the formulae of Watson and Dijkstra and the digestibility as determined on sheep.

3. The peculiarities of molassed silage in the above connexion have been noted.

During the period 1942–50 some thirty-seven multifactorial field experiments have been carried out to determine the conditions under which weeds in fibre flax can be selectively controlled by herbicides. In order to assess the direct effects of treatment on flax, some experiments have been undertaken in weed-free crops, while others have been sited in weed-infested crops so that the increases in productivity following on weed suppression could be evaluated.

In almost all experiments, the total crop weight, the yield of de-seeded straw and the amount of scutched fibre per plot were determined, while in a proportion seed yield was also measured. Where weeds were present, counts were made to establish the degree of control.

The preliminary experiments demonstrated that sulphuric acid, ammonium sulphamate and ammonium thiocyanate were far too toxic to flax. An examination of a range of cupric salts suggested that the most promising compound was cupric chloride, while of the formulations of dinitro-o-cresol investigated only the sodium salt appeared to be sufficiently selective. It was also found that in terms of fibre production sodium 2-methyl-4-chlorophenoxyacetate was less toxic than sodium 2:4-dichlorophenoxyacetate. In consequence, the bulk of the investigations have related to determining the optimal conditions for the use of cupric chloride, sodium dinitro-o-cresylate and sodium methylchlorophenoxyacetate.

For all three compounds it has been observed that flax is least liable to injury at a height range of 2–6 in. There are limitations to the amounts which can be safely employed, namely, 20 lb. of cupric chloride or 6 lb. of sodium dinitro-o-cresylate applied in 100 gal. of spray solution per acre. With sodium methyl-chlorophenoxyacetate the corresponding limit is 1 lb./acre, and the evidence suggests that the crop may be injured if the volume of application is reduced below 25 gal./acre.

Within these limitations of concentration volume and stage of development of the crop, the suppression of annual weeds has led to significant increases in the yield of straw, seed and scutched fibre. Larger gains resulted from the use of sodium methyl-chlorophenoxyacetate and sodium dinitro-ocresylate. This superiority over cupric chloride is in part attributed to the wider range of weed species which are killed by the two sodium salts and in part due to the greater liability of crop damage if the limits on amount and time of application are not strictly observed.

The results have also clearly established that for fibre flax the weight of total crop, the yield of straw, the amount of seed or plant height cannot be taken as reliable criteria for the evaluation of herbicides, for while all these may be little affected by treatment yet there may still be large reductions in the amount of recoverable fibre. A preliminary anatomical examination of the internal changes in the stems of flax has shown that when treatment with dichlorophenoxyacetic acid is delayed, a marked but localized curvature of the stem results and in this zone fibre formation is abnormal: thus breakages either during pulling or processing may occur at this point of weakness.

1. Trials made near Cambridge in 1949 and 1950, under ‘mild’ and ‘hard’ spring weather conditions respectively, have confirmed that the findings of Aberg & Denward in Sweden, and of Pedersen, Andersen & Hermansen in Denmark, concerning distortions in barley caused by MCPA and 2,4-D, are also valid under English conditions.

2. Damage to barley caused by the application of MCPA and 2,4-D up to the 2-leaf and early 3-leaf stages may be recognized by the occurrence of many tubular leaves and bowed or trapped ears. As little as 2 lb./acre of 2,4-D, as the amine salt, applied at this stage may also cause severe stunting of theplants with distortion of the roots.

3. Damage to barley by the application of MCPA and 2,4-D at the 3–4-leaf stages may be recognized by the occurrence of tweaked ears. The application of as little as 2 lb./acre of MCPA, as the sodium salt, at these stages may cause tweaking in over 50% of the ears. 2,4-D (as amine) at the same dosage causes more distortion. Although the reduction in yield due to such tweaking may be slight, the grain sample is irregular in size, with a number of naked grains, and malting quality may be reduced.

The importance of conducting studies on the behaviour of grazing animals has been stressed by several authors. Stapledon & Jones (1927) indicated the need for such work; while more recently Stapledon (1948, 1949) has made further reference to this need.

Adequate reviews of the work conducted prior to 1939 are to be found elsewhere (Castle, Foot & Halley, 1950; Tribe, 1950), and only the more important aspects need be considered here. The main weakness on the part of many of these earlier studies was that they were based on few observation periods, and that few animals were observed during each period. Many workers (Cory, 1927; Hodgson, 1933; Sheppard, 1921) carried out their observations during the daytime only, on the assumption that little or no grazing occurred after dark. In spite of this and the fact that the methods of study adopted varied considerably, some correlation exists between the results reported by the different workers.

In view of the present interest in the development of commercial poultry flocks by crossing inbred lines, at least two questions of importance arise. One is, how well does a successful cross between two inbred lines repeat itself with successive generations of the particular parental lines involved? The other, bound up with the manifest degenerative change that seems to be the fate of most inbred lines, is related to the possibility of determining minimal and/or optimal degrees of inbreeding necessary to produce commercially satisfactory offspring.

As a preliminary to a major investigation of these problems it would perhaps be useful to record briefly observations on small groups of pullets derived from such a cross, which has been repeated at intervals over 11 years within the Centre's flock of Brown Leghorn fowls, and to compare them with the parental lines.

1. If a crop varies in respect to a character which shows simple Mendelian inheritance then it is possible to estimate the proportion of cross-fertilization within the crop from the data obtained by (i) drawing plants from the crop and scoring them in respect of the character, then (ii) growing their separate progenies and scoring them.

2. Maximum likelihood expressions are given for the estimation of p and f { = (1 — α)/(l + α)} from the genotypic classification of the parents and from the phenotypic classification of the progenies; where p is the gametic frequency of the dominant allel and α is the proportion of fertilizations in which the pollen is equally likely to come from any plant in the population.

3. When the above expressions are applied to a case in winter beans, in which the parent plants were selected for high yield it is found that the different estimates of p agree, but those of f do not.

With the installation of more factories for the decortication of cotton-seeds in Pakistan, the utilization of cotton-seed hulls as a feed is likely to assume great importance. During 1949–50, the writers made determinations of the chemical composition and the feeding value of Pakistan cottonseed hulls by conducting a digestibility trial on dry Sahiwal cows. They are found to contain 39.89–56.47% total digestible nutrients (mean value = 48.68%) and 0.0–0.38% digestible protein. It was observed during the trials that the cows could eat about 20 lb. of hulls per head per day without difficulty. The cows also ate hulls in preference to wheat straw.

Being low in calcium and phosphorus, cotton-seed hulls should not be used as a sole roughage for long periods, unless supplemented with calcium or phosphorus in mineral form, or preferably with silage, legume hay or green fodder of good quality.

Pakistan cotton-seed hulls appear to be equal, if not better, than wheat straw as a cattle feed. From the economic point of view, hulls should be used as a cattle feed only if they are purchasable at about the same price as wheat straw.