Two different collections of local sorghum strains, grown in 1975/76 and 1976/77, showed considerable and useful variation in plant height at maturity, head type and exsertion, grain colour, and days to flowering and maturity. A close and positive correlation was found between days to flowering and to maturity, and x2 tests also showed close associations among other characters. Implications of these variabilities for sorghum improvement are briefly discussed.

Colour development in fruits of dark purple eggplant cultivars was greatly influenced by temperature conditions. During the cool season, colour development was much slower than during the hot season, corresponding to slower fruit growth and much lower final weight. There were varietal differences in seasonal influence on the distribution of various colour shades, both during fruit growth and at harvest. Soil heating during the cool season improved fruit colour.

Fourteen varieties of cowpea (Vigna unguiculata (L.) Walp.) were compared for yields of forage and seed from two sowing dates, using various agronomic parameters. Yields ranged from 1048 to 5044, 185 to 920 and 864 to 3321 kg/ha for dry matter, crude protein and seed respectively, with advantages from spreading as against semi-erect types, and early rather than late July sowing. IVu 1283-1 and IVu 1283-2 effectively combined vegetative and seed yield, and appeared most suitable for fodder and seed production. A simple forage yield index (FYI), useful in yield prediction, was evolved.

Maize and cowpea were grown in mixed and pure stands, using the same overall density in all plots. Four fertilizer treatments N0P0, N1P0, N0P1 and N1P1 were imposed in experiments carried out during the early growing seasons of 1976 and 1977 at Ibadan in the rainforest zone of Nigeria. There was no competition between the crops for nitrogen or phosphorus and yields in mixtures were significantly higher than the means of the species monocultures, as shown by relative yield total (RYT) and C (complementation) values.

Combined effects of nitrogen at 25 and 50 kg/ha as calcium ammonium nitrate and phosphorus at 30, 60 and 90 kg/ha as triple superphosphate were studied on the composition, germination and emergence of sunflower seeds. Maximum protein (26·2%) and lipid (45·8%) with the maximum emergence (85·0%) was obtained from seeds produced by crops raised in soil with 50 kg/ha of nitrogen and 60 kg/ha of phosphorus. Lowest protein (21·6%), lipid (40·8%) and 45·0% emergence were obtained from seeds of crops raised on soil with the basal level of nitrogen and phosphorus.

Black polyethylene tunnels were used to subject Armore and Missionary strawberry cultivars to 21 short-day inductive cycles at either full bloom (7–28 May) or fruit swelling (1–21 June) stages. Regardless of application date, treatments induced a second bloom 8–10 weeks after treatment in both cultivars. The second crop of Armore was as large as the first, but Missionary produced only a small second crop that would not be worth commercial harvesting. Covering plants with black polyethylene reduced the vitamin C content of the first-crop fruits of Armore without affecting yield, while Missionary responded in an opposite way. Treating plants at full bloom hastened the ripening of the first crop of both cultivars by about 1 week and resulted in a larger second crop than was obtained by the later treatment.

Dark-firc-cured tobacco varieties produced acceptable tobacco when cured with the wood of the fast-growing tropical tree Gmelina arborea, with an aroma as good as from the best traditional curing timber in Malawi. The addition to the fire of slow-burning, wet banana stalks or Kingelia pinnata fruit to increase the smoke did not change the desirability of the aroma. Factors which increase the stickiness of the leaf increase the desirability of the aroma of cured leaf.

An experiment designed to study differences in water requirements between some clones of tea suggests that clones which showed visual symptoms of being more susceptible to drought had a greater demand for water. Supplementary irrigation applied during the dry seasons prevented plants from dying and stimulated better early growth of clones tested. As a result of better early growth, the irrigated tea gave persistently and significantly larger yields than non-irrigated tea in the first 2 years of recording.

Effects of plant population on mean yield and yield components of 2-year sole cassava crops were studied on Njala upland soils of Sierra Leone in two experiments. Increasing plant population of multi-shoot Cocoa cassava over 7000/ha decreased all the parameters studied except top/root weight ratio, which increased. The observed effects were attributed to competition for environmental resources, since area of land/plant unit decreased as plant population increased. The relations between plant populations and yields of fresh root and cortex dry matter were asymptotic, indicating that the respective yields were products of the vegetative phase of cropping.

The effects of delayed hand weed control at 30-, 45-, 60-, 90-day intervals, and no weeding, on sole-crop cassava, was studied in two experiments on the upland soils of Sierra Leone. Timing and frequency of weeding were important in influencing root number and root yield, and delayed weed control depressed both attributes. The critical period of competition was in the 45-day weeding interval, with six weedings in a 14-month growing period. Rottboellia exaltata was the predominant species amongst the permanent grasses on the no-weeding plots.

Field experiments were conducted for 4 years to study the yield of ‘kharif’ and ‘rabi’ crops grown in sequence on two soils differing in water-holding capacity. The results indicated that drought caused greater reduction in yield of rainy-season crops on loamy sand than on sandy loam soil. In low retentivity soil it was more profitable to raise a single crop of wheat on soil-stored water. In sandy loam soil of higher retentivity, two crops a year gave much higher yields than a single crop. Of the sequences tried, maize followed by wheat gave the highest and most stable yields. For ‘rabi’ crops, stored water showed a better yield response than an equivalent amount of rain during the growing season.

Grain maize in south-east England showed a markedly flat-topped curvilinear response between density and grain yield, maximum yields being obtained over a range of 80,000–120,000 plants/ha, but yields were reduced at less than 70,000 plants/ha. A general density recommendation of 80,000–90,000 plants/ha is suggested, or a seed rate of 95,000 seeds/ha to allow for germination losses. Yields of cv Anjou 210 and DeKalb 202 showed some decline when the density exceeded 100,000 plants/ha, whereas yields of Pioneer 131 increased above this value and 100,000 plants/ha can hence be recommended. Although planting above the optimum density markedly increased the incidence of stem lodging at harvest, only a minor delay in stage of maturity occurred.

The use of a durometer to assess hardness of onion bulbs is described, and compared with the use of a tensile testing machine. Results from the two tests were closely correlated, and significant varietal differences were detected in bulb hardness by both machines. The durometer is of particular value because of the simplicity and non-destructive nature of the test procedure.

Soil samples from Guneid Sugarcane Scheme, representing high- and poor-yielding sites, were collected and analysed. Yields of sugarcane were significantly and positively correlated with exchangeable potassium and clay content (P = 0·01), whereas there was a negative correlation between yield and exchangeable sodium percentage (P = 0·05). Multiple regression on soil clay content, exchangeable potassium and ESP accounted for 48·1% of the observed variability of yield of sugarcane, indicating that the clay content was the most important soil factor determining yield of sugarcane in this area.

A series of 17 crop-loss assessments was made under simulated farmers' field conditions in the three main rice cropping seasons of Bangladesh. The main insect pests were the rice stem borers (Tryporyza incertulas, Chilo polychrysa, Sesamia inferens) and in the monsoon rice gall midge (Pachydiplosis oryzae). Disease incidence was negligible. In the winter and early monsoon yield losses averaged 4 and 6% respectively, but economic benefit was only derived from insecticide application in the monsoon season, when there was an average yield loss of 16%. An economic threshold of 5–10% damaged tillers (‘deadhearts’ and ‘onion shoots’) was indicated for early attacks of stem borers and gall midge. Possible reasons are given for the usually low incidence of insect pests and diseases in Bangladesh rice.