The dependence of yields of sweet clover and alfalfa on environmental conditions, including soil acidity, at the germination stage has been studied over a period of 28 years. Results have been dramatic: sweet clover and alfalfa can grow well and produce large yields even on strongly acid soils (pHKCl 4.0) providing that the process of germination starts in a neutral medium.

Results clearly demonstrate that Crotalaria juncea (sunnhemp) is well adapted to the dry season paddy environment; peak dry matter production was 3170 kg ha−1 in a field experiment with rows 30 cm apart and 100 kg−1 ha of seed. A pot experiment gave yield responses of 179 and 16% to P and S application respectively but there was no response to fertilizer in the field. Cultivation increased DM production in one experiment from 86 to 1590 kg−1 ha, attributed to a reduction in bulk density from 1·65 to 1·19 g cm−3. This effect was not fully substantiated in a second experiment on a coarser soil, where good DM production of sunnhemp was achieved even on broadcast uncultivated plots. The toxicological implications of using sunnhemp as a forage legume are briefly discussed.

The best available varieties of barley, durum wheat, rapeseed, safflower and sunflower were compared for their yield of grain and oil and other traits under rainfed conditions and with supplementary irrigation in the relatively dry Mediterranean climate of Cyprus. The grain yields of the oilseed crops safflower and rapeseed when grown under conditions of plentiful rainfall or with supplementary irrigation were 3–5 t ha−l. Considering the high prices of oilseeds on the world market, the income from oil crops compares favourably with that from barley and wheat. However, under conditions of limited rainfall (300 mm) and without supplementary irrigation the yields of oilseed crops were extremely poor, at the most 0.6 t ha−1. Grain and oil yields of irrigated safflower and rapeseed were larger than those of sunflower. Among the oilseed crops, sunflower received most irrigation water and rapeseed the least. Under rainfed conditions, with precipitation less than 300 mm, cereals were the only successful crops. It is concluded that in the high rainfall areas of West Asia and North Africa, or with supplementary irrigation, including treated municipal wastewater, oilseed crops can be successfully grown.

Forty-six cultivars of linseed oil (Linum usitatissimum L.) were grown under wet and dry season conditions in the Sudan Savanna of Nigeria. Only during the dry season was production good and cv Dunes consistently outyielded all other cultivars in terms of seed and oil content. Trials of sowing dates gave maximum seed yield and oil content from plots sown during late October. In row spacing trials, rows 15–22 cm apart and seed rates of 58–78 kg/ha were found to be the most practicable. There was a linear relation between increasing rates of nitrogen and seed yield, maximum production being obtained at 55–88 kg N/ha, but oil content was slightly depressed at levels above 33 kg N/ha.

Forty-one factorial experiments on rates and forms of the three major elements and rates of some minor and trace elements were carried out over the period 1954–1962 in Iringa, as part of a project to introduce Virginian-type tobacco varieties into the area. There were major responses to nitrogen and phosphate, and a close relationship between their effects, but no responses to other elements. Nitrogen raised yield, particularly in wet seasons, but generally tended to reduce quality, severely above 44 lb N per acre and at lower levels in dry years. Phosphate raised yield and quality, and in some instances crop failures occurred in its absence. Data suggested the optimal N : P2O5 ratio in fertilizer mixtures to be 1 : 15. Despite lack of response to potassium a small amount was recommended, to cover requirements for leaf characteristics which were not measured. The programme amply succeeded in its aim of establishing ‘average’ fertilizer recommendations, which were fundamentally sound, for the whole of the Iringa tobacco growing area. These recommendations are summarized.

Observations on the relative degree of root nodulation were made for three successive years on tall and short cultivars of Pisum sativum and Phaseolus vulgaris sown at dates appropriate to each cultivar and grown under conditions of ordinary horticultural practice. In P. sativum, it was found that the shorter the cultivar, the greater were the number and weight of nodules per plant and the weight of nodules as a percentage of plant weight; dwarf cultivars also produced a greater weight of nodules per square metre of ground occupied and per square metre per day of crop growth. In Ph. vulgaris, differences in number and weight of nodules per plant between dwarf and climbing cultivars were not consistent between years. In a single comparison between Ph. uulgaris and Ph. multiflorus (scarlet runner beans), numbers and weights of nodules per plant were almost identical. Some agronomic implications of these findings are discussed.

Combined use of lime, animal manure and inorganic fertilisers is effective in replenishing the fertility of degraded acid soils. However, many smallholder farmers lack access to sufficient amounts of these inputs to improve the fertility and reduce the aluminium toxicity of Ferralsols. Organic manures are available but often have low nutrient content, which limits their ability to supply nutrients to soils. In a two-factor field experiment over four seasons on an Anthropic Ferralsol in Southern Province, Rwanda, we assessed (i) the effect of cattle manure on soil properties at a reduced rate affordable to smallholder farmers compared with that of NPK fertiliser applied, with and without lime also at a reduced rate, and (ii) the effect of supplementing grass in a basal cattle diet with legume leaves on manure quality and its effect on soil properties. Manure from cattle fed only the grass Chloris gayana (grass-only manure) and from cattle fed C. gayana supplemented with Acacia angustissima leaves (grass+legume manure) was applied at 5 t dry matter ha-1 (25% of the recommended rate) at the beginning of each growing season. NPK was applied as split doses supplying a total rate of 70 kg N ha-1. Lime was applied annually at a rate of 2.0 t CaO ha-1, which was 25% of the rate required to neutralise total acidity at the site. All amendments were applied only to the soil surrounding the maize plants (planting stations), which is estimated at 25% of the plot area. Maize stover was left on plots after harvest and planting stations were retained over all growing seasons. All treatments altered soil properties at the planting stations. Lime generally increased pH but there was no significant difference between lime plus manure treatments and non-limed manure treatments. Soil organic carbon concentration and cation exchange capacity were higher in manure and NPK treatments than in non-fertilised treatments. The manure treatment increased soil water-holding capacity compared with the NPK and non-fertilised treatments. There was no significant difference in total N, Ca2+, Mg2+ and K+ between the NPK and manure treatments. Micro-dosing animal manure can thus replace mineral fertiliser plus lime for soil fertility replenishment in smallholder farming. Grass+legume manure contained higher concentrations of total N, Ca, Mg, K and Na than grass-only manure, but its effect on soil properties did not differ significantly from that of grass-only manure.

An experiment is described on the establishment of cocoa on clear-felled land, using various ground covers on which 22 NP:KMg factorial treatments were later superimposed. Growth of cocoa was improved in mulched and clean-weeded plots and the unshaded trees began bearing two years after planting, which is exceptionally early for young cocoa in Ghana. In the third year responses to NP fertilizer were obtained and in the following year yields were very high, up to 2170 pounds dry cocoa per acre. This was partly responsible for K deficiency, particularly in plots without mulch and KMg, which led to declining yields especially on the NP plots. Significant increases were thence obtained from the KMg fertilized plots. Mulching at the rates used in this experiment is too expensive and uneconomic, but K fertilizer applied at rates higher than the present rate of 75 lb K2O/acre/annum may be needed on Ghanaian forest soils if they are clear-felled for growing unshaded cocoa.