The layout of experiments for the study of the growth of four crops in the central rainlands of the Sudan in 1965 is described. The treatments, different levels of flooding prior to sowing, were replicated within blocks. Standard procedures for estimating within plot, between replicate plotswithin block and treatment x block components of error are set out and an example is given of the analysis employing data on kenaf. Using typical values for components of error found in these experiments, increases in precision obtainable by varying the number of plants sampled per plot, and the number of replicate plots per treatment, are considered in relation to their costs. It is concluded that excessive replication would be required to establish differences of interest and that attention should be given to sources of error variation when such large errors are found.

The response of cassava to CCC was investigated by applying concentrations of 0, 500, 1000, 1500 and 2000 ppm twice or four times as a foliar spray, which resulted in a significantly greater tuber yield than the control with most marked effects at the final harvest. CCC at 1500 ppm, applied four times at various growth stages, gave the best increase in tuber yield. Application of CCC tended to cause greater RGR and dry matter content (percentage) of tubers.

Two groundnut varieties, the small-seeded, early-maturing Natal Common and the large-seeded, late maturing ‘pops’-susceptible Makulu Red, were cultivated in nutrient solution, Application of calcium, labelled with 45Ca, to the roots and the fruit-medium respectively, showed that both varieties absorbed most of their seed-Ca from the fruit-medium. The translocation of calcium from the shells to the nuts was greater in the small-seeded variety Natal Common, which showed less susceptibility to ‘pops’. Calcium absorbed by pods and gynophores also migrated to a certain extent into the vegetative parts.

Following preliminary work in the previous year, further field trials were carried out with strains of the pearl lupin (Lupinus mutabilis Sweet) at Oxford, England. Two strains originating in Argentina and one in Bolivia were considered to show promise for development as crop plants in England if toxic alkaloids can be bred out of them. The seeds harvested had a crude protein content from 38·6 to 41·8% and an oil content from 13·1 to 14·4%. Advice is given, based on these trials, on sowing date and spacing.

Dry weight, stem and branch length and node number, and flower and fruit number where appropriate, were recorded through the season on cotton, groundnuts, kenaf and sesame in the central rainlands of the Sudan in 1965. For each sampling date variation within plots and betweenreplicate plots within blocks and treatment x block interaction have been studied, together with the effect of these components on the magnitude of the residual root mean square in the analysis of treatments x blocks. The main components were usually within plot and between replicate plots within block errors. Uncontrolled variation was unacceptably great, and was thought to be in large part the result of irregular surface drainage conditions. It seems more likely to be useful to include surface drainage contrasts in field experiments subject to high intensity rainfall on this impermeable clay soil than to attempt to increase precision alone.

Mechanical disintegration seems to be the most effective way of damaging the cells in potato tubers so that their juice can be expressed. If disintegration is too intense the pulp is intractable; a grater makes a uniform pulp with suitable texture. With existing continuous equipment it is necessary to press in two stages to get to 40% dry matter and further batch pressing is needed to get to 50%, but experience suggests it should be possible to make a press that would press to > 50% in one operation. Much less energy is needed to press out water rather than evaporate it, but about one-sixth of the tuber dry matter and more than one-half of the N is in the juice.

The rapid post-harvest deterioration of cassava roots, which usually prevents their storage in the fresh state for more than a few days, is poorly understood. Two types of deterioration are defined, namely primary, shown by internal root discoloration, and secondary, caused largely by wound pathogens. Information is presented on the influence of such factors as mechanical damage and plant cultivar upon the development of the two types. Control of primary, and a reduction in secondary, deterioration is achieved during a curing process, but none of the chemical treatments examined gave consistent practical control of deterioration.

The yield, variability and quality of 16 sweet potato cultivars, harvested after 21 weeks growth, were evaluated in sub-tropical Australia. The coloured-flesh cultivars L8-92, Centennial, HAC-Pink, Copperskin Goldrush and Nemagold produced yields of marketable storage roots in excess of 19,000 kg ha−1, which was three to four times the yield of the local commercial cultivar, White Maltese. The high variability in mean yield per plant of all cultivars offers scope for selection within cultivars. Those with a deep orange flesh and high soluble solids content, i.e. L8-92, Copperskin Goldrush and Centennial, were preferred by members of a taste panel. A high carotene cultivar L8-92 has the greatest commercial potential because it produced the highest yield of marketable storage roots and had the highest taste panel rating for eating quality of stored roots.

Mechanically dehydrated potato pulp containing up to 50% dry matter was stored, without visible deterioration, for up to 25 weeks after treatment with at least 0·3% of propionic acid. Wetter pulps required more acid for satisfactory preservation. Thorough mixing was important if maximum storage periods were to be achieved. Ammonia was less satisfactory as a preservative. No visible deterioration occurred while ammonia vapour was present, but bacterial growth was still found even after the addition of about 0·7% ammonia to pulp containing 40–45% dry matter.

Temperature effects on coleoptile development were studied in 18 genotypes of spring and semi-winter wheats, illustrating a simple experimental approach for choosing genotypes and management practices that would minimize genotype–environment interactions for stand establishment.

Herbicides tested at Kenana Agricultural Research Station (K.A.R.S.) from 1968 to 1972 showed that pre-emergence application of oxadiazon, nitrofen, linuron, phenobenzuron, prometryne, nitralin, diuron and fluorodifen gave satisfactory weed control. Applications of oxadiazon at 2·38 kg/ha, fluorodifen at 7·14 kg, nitrofen at 4·76 kg and nitralin at 3·8 kg had no adverse effect on growth of groundnuts, but prometryne, diuron, phenobenzuron and linuron at relatively lower rates caused phytotoxicity symptoms. Residues from treatment with 7·14 kg fluorodifen, 2·38 kg oxadiazon and 4·76 kg alachlor did not injure test crops, but growth of sorghum and maize was reduced 9 months after applying 3·8 kg nitralin. Phenobenzuron was persistent in soil and most test crops were injured following an application of only 1·9 kg.

Effects of daylength and night temperature on the onset of flowering of selected cowpea cultivars have been investigated, using automatically controlled glasshouses at Reading. The results show close agreement with those from field trials in Nigeria, wherein low intensity incandescent lighting was used to extend the natural daylength. As the field technique has proved an effective screen for daylength insensitivity, future screening work in glasshouses can be for effects of night temperature on time to first flower and for day temperature on the rate of leaf senescence and components of seed yield. This integrated approach can accelerate the screening of cowpea cultivars for sensitivity to environmental factors over ranges characteristic of the low altitude, humid tropics.

Despite large visual differences in size and form of shoot and root systems of young clonal plants and of older seedlings, there was no convincing evidence that tea plants, brought into bearing by pegging, are necessarily more susceptible to water stress than similar plants that have been pruned, though the sap tension in pegged plants of one clone was often greater than in similar pruned plants. Further studies are needed to show whether this is the case in drier areas, but differences in responses to dry conditions by individual clones appear to be of greater significance.

In field experiments at Pantnagar, India during 1968–70, evapo-transpiration (ET) in wheat was significantly correlated with U.S.W.B. class A pan evaporation (E0) when the crop was in an active stage of growth and moisture was non-limiting (50 or 25% depletion of available moisture). The estimated ET was higher than E0, probably due to ‘oasis’ and ‘clothesline’ effects. When ET measurements were made at varying distances from the upwind side during the subsequent three years, it was found that ET decreased with increasing distance downwind with a conspicuous border effect up to about 25 m distance. In the absence of advective heating, i.e. in extreme downwind locations, the actual ET was 480, 533 and 530 mm during 1970–71, 1971–72 and 1972–73 respectively.

The crude protein contents of four Nigerian edible leafy vegetables were high, with values ranging from ao to 30% on a dry weight basis and maximum yields of crude protein ranging from 428 to 602 kg/ha. The percentages of leaf protein extracted ranged from 41 to 70%, whilst the highest yields of extractable edible protein varied from 199 to 332 kg/ha. The crude protein levels, as well as yields of extractable proteins, were slightly affected by the season of growth, but greatly by the age and species of plants.

Ureaform, applied twice a year, in early spring and late summer, was compared with poultry manure and (NH4)2SO4 top dressings as nitrogen suppliers in a banana plantation. No significant differences between the treatments were obtained in any of the plant criteria, but nitrate concentrations in the soil were higher in the ureaform treatment at the standard nitrogen level than in the standard treatment, within the root zone as well as below it. The spring application of ureaform affected the nitrate concentration in soil for 8 months and was better utilized by the crop than the autumn application, which left a greater residual effect. It therefore seemed that one spring application might be sufficient to meet the banana's nitrogen requirement.

The magnitude of heterosis for 15 characters was studied in ten sorghum hybrids, produced by crossing ten restorer varieties with male-sterile Combine Kafir 60 as a common female parent. The most evident expressions of heterosis were higher yield and increased vegetative growth, often associated with delay in flowering. The increase in yield of the hybrids over their superior parents, ranging from 35 to 238%, resulted mainly from an increase in number of grains per head, rather than from an increase in the weight of individual grains. The regressions of hybrids on male parents, and the correlations of yield with other characters were studied, and the prospects of producing adapted hybrids for the Sudan are briefly discussed.

The yields of extractable protein, and its rates of production, were measured with seven crops given large dressings of nitrogen, which produced lush plants with small fibre to juice ratios, increased the nitrogen content (as percentage of dry matter) in five species, improved the extractability of protein N in three, and gave significant increases in both dry matter and protein yields of non-legumes. However, yields were affected more by climate than by the N fertilizer. It is felt that non-legumes given large dressings of fertilizer N, as well as leguminous fodders, could be used efficiently if their excess protein was extracted and used for human consumption.

In experiments conducted in the Ord River Valley, North Western Australia, the extent of egg laying, larval numbers and grain damage from Heliothis armigera was studied with three sorghum varieties of different head densities. Total numbers of eggs laid were similar for each variety, larval infestation was highest on a very dense-headed variety Pickett 932045 and similar in the semi-dense headed RS610 and the open-headed E57 varieties. Greater losses per larva were estimated with varieties E57 and Pickett 932045 than for RS610, where lesser susceptibility was associated with ability to compensate, mainly by increased grain size, for grain loss. This paper reports the results of experiments at Kimberley Research Station to measure infestation and damage caused by H. armigera on three varieties of sorghum with head types ranging from dense to open, and the effectiveness of biological and chemical control practices are also discussed.

A study was made of the effect of micronutrients such as boron, copper, zinc, manganese and iron, applied as foliar spray or directly to peat soil, on growth and yields of pepper under greenhouse and field conditions. Combinations of micronutrients were applied in two forms, as salts or as chelates. Results showed positive effects on yield and quality of red pepper, and soil chemical tests substantiated the results.