The leaching of boron, studied after high rates of application under different management practices, indicated that leaching was rapid and that the presence of cover crops was likely to reduce the immediate availability of boron to the main crops.

Tall Nigerian Farafara and a dwarf line selected from the cross Combine Kafir 60 × Farafara were compared at Samaru in eight weekly sowings in 1969, which was a wet year, and 1970 which was rather dry. Whereas the dwarf line always gave more grain yield, its advantage over Farafara, and the effect of early sowing on its yield, were greater in the wetter year. In both varieties the date of flowering seemed to be determined mainly by photoperiod, but there was also a small but clear effect of sowing date.

The effects of different frequencies and rates of application of boron fertilizer were studied with regard to uptake of boron by the oil palm. The results indicated that annual or biannual application of this element maintained satisfactory levels in the leaf tissue. Heavy potassium fertilization was found to inhibit boron uptake but nitrogen had no effect.

The effects of irrigation on the yields of wheat and cotton were studied on a sandy clay loam soil, with a water-table at 7 ft below ground, under the arid conditions of Lyallpur. The conventional practice of providing 19-acre in. of water to Mexican wheat and 25-acre in. to American cotton proved to be a wasteful and unproductive practice on such soils. High yields of both these crops could be obtained without any subsequent watering after an initial 4-in. irrigation applied for seedbed preparation and sowing, while one 3-in. irrigation after sowing was needed to obtain maximum yields.

Soil analysis on samples taken from apple orchards in Khorasan and quince orchards in Esfahan, suggested that at a sampling depth of 20–45 cm., the critical soil concentration of calcium carbonate at which chlorosis might appear seems to be 14–15 per cent for apple and 39–40 per cent for quince. The incidence of lime-induced chlorosis was accompanied by lowered leaf Ca/K ratios. The application of various iron chelates to chlorotic trees not only benefited yield of apples but also exercised a residual effect in succeeding seasons.

Four trials are described on the effects of spraying and cultural practices on pests and yields of seed cotton. Precropping with sorghum or beans after opening from a ley did not reduce yields of cotton compared to the recommended practice of ploughing a ley 6 weeks before sowing, but late ploughing and late sowing reduced yields. Nitrogenous fertilizer after a successful ley did not increase yields, but multiple sprays (up to twelve) significantly increased them over the recommended standard four spray regime, and reduced the percentage of stained seed cotton. In general cultural practices did not affect the level of pest attack, but DDT spraying gave excellent control of Heliothis armigera, while dimethoate prevented the build up of red mite (Tetranychus telarius) and gave excellent control of tea mite (Polyphagotarsonemus latus) in the multiple spray regimes.

An experiment at Hudeiba Research Station in Northern Province for three consecutive seasons, testing the effects of form, rate and time of application of nitrogen, showed that grain yield of wheat was significantly influenced by rate and time of application but two forms of fertilizers behaved similarly. None of the factors examined affected the 1000 grain weights. A second order polynomial function, fitted to yields at different nitrogen levels to determine economic levels was quadratic, best described by Y = a + 11·809x − 0·1037 x2. When almost all relevant factors were considered, 30–40 kg. of N per acre appeared to be an optimum economic level.

Comparison of up to ten carrot cultivars at various sites in a three-year period did not show that any cultivar consistently outyielded the others. Investigations at Samaru between 1969 and 1971 indicated that application of 100 kg. of N was beneficial, response to P was not consistent and there was no response to K or trace elements. Economics of production by peasant farmers is discussed and conclusions drawn that irrigated carrots, grown in the dry season, could be very profitable. No successful control was found for blight (Alternaria dauci) which severely inhibits the production of a wet season crop.

Drought resistance in terms of yield and its components was studied in the field in twenty-one agronomically-adapted high-performance grain sorghum (Sorghum bicolor Moench) hybrids. Resistance was considered to be indicated by a minimal decrease in yield under stress as compared with non-stress conditions. Water stress, imposed by a decreasing amount of stored soil moisture during the growing season, decreased grain yield and number of panicles per unit area, increased the number of grains per panicle, the number of branches per whorl and the number of grains per branch, and decreased the number of whorls per panicle. Thus a compensatory effect was observed in some components for reduction in tillering under stress. Resistant hybrids performed better than susceptible ones under stress by producing a relatively higher number of panicles per unit area, and more grains per panicle branch. Susceptible hybrids performed better than resistant ones under non-stress (irrigated) conditions due to the relatively higher number of panicles per unit area and larger 1000-grain weight. Some of the implications regarding selection for yield performance under drought are discussed.

Glasshouse and field trials have been used to assess the effect of applying calcitic lime and gypsum on haulm weight, pod-filling and kernel yield of groundnuts grown in soils of Northern Malawi. Incorporation of lime prior to planting and topdressing gypsum at flowering both rectified poor pod-filling and improved kernel yield. Gypsum decreased haulm weight and usually produced lower overall kernel yield than lime. The relative merits of lime and gypsum application are discussed, together with the need for supplementation by phosphorus and sulphur.

The uptake of S followed a similar pattern to dry-matter production by groundnuts given enough fertilizer-S to prevent S-deficiency. The fastest rate at which dry matter was produced was 140 kg./ha./day. Of the 6857 kg./ha. at harvest, 3401 were in haulm, 967 in shells and 2489 in kernels. S was taken up fastest during the eighth week, when the daily average was 0·22 kg./ha.; at harvest, of the 11·6 kg./ha. in the plants, 5·4 was in the haulm, 0·8 in shells and 5·4 in the kernels. Of the 157 kg. N/ha. in the harvested crop 62 per cent was in shells and kernels and of the 13·5 kg. P/ha., 64 per cent was in shells and kernels.

Cynodon IB.8 was subjected to (i) various levels of N under cutting management, and (ii) various levels of K under grazing management. The results indicated significantly higher DM and CP production with 168 kg./ha. of N under cutting management, with resultant significant reduction in exchangeable and non-exchangeable soil K. Under grazing management, increased K application increased K content in the herbage, but showed a negative correlation with Ca uptake. Results indicated that the initial soil K status was adequate to supply the requirements of Cynodon, and that under grazing management the soil K status could be maintained at adequate levels to support lengthy cropping.

A number of crosses were made to study the mode of inheritance of flower colour and number of locules per capsule of sesame. Red flower colour was dominant to white, and 4-loculed dominant over 8-loculed pods, each of the traits being controlled by a single gene pair segregating in a 3:1 F2 ratio.

Crop growth rate of oil palm increases with leaf area index (LAI) to about 40 tons/ha./yr at the highest LAIs obtained. Net assimilation rate and dry matter production per palm decrease with increasing LAI, but the amount of dry matter per palm incorporated in vegetative tissues is unaffected by density. As a result the optimal LAI for oil yield is considerably below the critical LAI for maximum crop growth rate.

The efficiency of fertilizer N uptake by wheat, as affected by time and rate of application, was studied in the field using N15 labelled ammonium nitrate. Splitting the application was only beneficial at the maximum rate but two top dressings at tillering and boot stage were better for grain production than a basal dressing or single top dressing at stem extension stage, but uptake of fertilizer N was maximal from a single top dressing. The calculated effective rate of application (E.R.A.) was useful in evaluating the effect of time and rate of application and N availability to plants.

A method is described for estimating boron requirements of the oil palm, and factors influencing leaf boron concentration of the palm are discussed.

A field experiment was conducted to study the effect of irrigation with brackish water on the growth and composition of millet and corn, fertilized with various combinations of N and P. Millet irrigated with water of EC 3.30 mmho/cm. produced yields 79 to 93 per cent of the control (tap water of 0.61 mmho/cm.), depending on the N and P treatment applied. With water of EC 5.05 mmho/cm. yields equivalent to 52–72 per cent were obtained. Corn yields were 78–90 per cent of the control with irrigation water of 4.60 mmho/cm., and 55–64 per cent when irrigated with water of 7.06 mmho/cm. The N and P contents were mostly higher in plants grown on plots irrigated with brackish water.

Researchers commonly use unplanted alleys to separate plots in experiments with paddy rice. In studies in the Philippines and Thailand we compared the performance of rice plants grown in previously cropped areas of a field with that of plants grown in areas which were unplanted alleys in the previous season. The latter plants had yields and values for several agronomic characters that were significantly different from plants grown in the previously planted areas, with yields ranging from 8 to 25 per cent higher.

In a short-term competition experiment in large containers, growth of cotton planted 3 weeks after bermudagrass (Cynodon dactylon), johnsongrass (Sorghum halepense) or purple nutsedge (Cyperus rotundus), was severely reduced; after 10 weeks of competition, weedy cotton weighed only 15 per cent of the weed-free control. Cotton sown before weeds, or weeds planted before cotton, were only slightly affected by competition. Highly significant negative correlations were found between growth parameters of cotton and weeds. Inhibiting effects, and in some cases transitory stimulation, were produced on mustard seedlings by leachate from weed-infested soil and by extracts from subterranean weed parts, suggesting that the competitive effects of perennial weeds are due to nutrient depletion and to biologically active substances.

Data from uniformity trials on healthy and diseased wheat and oat crops showed that the coefficient of variation for yield decreased as plot size increased and became nearer to square in shape. Infection with Septoria leaf blotch of oats and powdery mildew of wheat did not appear to affect yield variability. Plots larger than rod row size (where 16 ft of the centre row of 3 rows is harvested) are recommended to detect differences of 10 per cent in yield between two treatments.