Two slow-release nitrogen fertilizers, isobutylidene diurea (IBDU) and sulphur-coated urea (SCU), and urea plus nitrapyrin were compared with urea alone for their effect on the growth and nitrogen uptake of ryegrass in a greenhouse experiment.

The IBDU and the SCU were applied in one dressing before sowing and the urea in five dressings (one after each cut). Dry matter yield and nitrogen uptake of the six cuts at the optimum levels of 3 and 6 g N pot−1 (equivalent to 1120 and 2240 kg N ha−1 on a weight basis) were similar for the slow-release fertilizers and urea, showing that SCU and IBDU can be effective sources of nitrogen for ryegrass at rates far above those regarded as safe for conventional nitrogen fertilizers when applied in a single dose.

Nitrapyrin at 20 ppm effectively inhibited nitrification for 12 weeks, then its effect rapidly declined, disappearing after 18 weeks. Ryegrass growth was retarded by nitrapyrin treatment, probably as a result of an accumulation of NH4-N in the soil.

Leaf scorch decline (LSD) is a disorder of coconut (Cocos nucifera) palms in Sri Lanka. The etiology of the disorder is not yet known. This study aimed to compare and quantify physiological and biochemical characters of LSD-affected palms with healthy palms. Thirty-year-old apparently healthy and LSD-affected (mild, moderate and severe) palms (variety typica) were compared at Bandirippuwa Estate, Coconut Research Institute, Sri Lanka. In LSD-affected coconut palms, the functional leaf area of the canopy, rates of photosynthesis and transpiration, leaf water potential, leaf chlorophyll and Zn contents were appreciably reduced with the development of the disorder, whereas stomatal diffusive resistances and abscisic acid concentrations in the xylem sap increased. The volume of inflorescence sap collected from LSD-affected palms was reduced compared to healthy palms, but the composition of the sap remained unaltered. Since altered stomatal behaviour might affect gas exchange and related processes, such as water movement, photosynthesis and the assimilate partitioning pattern, these results support the hypothesis that stomatal closure in LSD-affected palms may influence LSD symptoms. However, more research is needed to come up with conclusive evidence of its cause.

Under the three levels of submergence (0, 5 and 10 cm. depths), water requirement of rice was maximum at 10 cm. but crop performance was similar to that at 5 cm. With medium and high levels of fertilization the crop had a higher water requirement than under low level, for ‘aus’ and ‘aman’ crops. Compacted soil compared well with puddled soil, but water requirement was appreciably higher with shallow puddling. In the two seasons water requirement, transpiration, evaporation and percolation losses were greater under submergence, and only transpiration was greater under higher levels of fertilization. Transpiration was maximum at flowering stage.

An investigation for 2 years at Kano and 1 year at Samaru evaluated the effects of plant density on vegetative growth, development and dry matter production and distribution of five varieties of groundnut. Growth and branching of individual plants were reduced at high populations but more dry matter was produced per unit area. Dense plants, particularly Spanish 205, developed a larger leaf area earlier in the season and were presumably able to make better use of light. Varieties F439.4 and 439.2 suffered the least reduction in the number of vegetative branches but the extra branches contributed few useful reproductive nodes.

Bhutan is a small country in the Himalayan mountains where subsistence agriculture is practiced due to small land holdings and undulating mountainous terrains. Due to diverse altitudinal and agro-ecological environments, many food crops are cultivated. Wheat is currently a secondary cereal, grown over an area of 1,964 ha with a total production of 3,465 Mg. While there are enormous opportunities to increase wheat production in Bhutan, it is challenged by numerous biotic and socio-economic factors such as labour shortage and low economic return. Among the biotic constraints, stripe rust and leaf rust are the most important diseases. Stem rust has not yet been reported. Poor crop nutrition, both through low soil fertility and inadequate external supply, also results in low productivity. In addition, better remunerative crops and affordable-imported products discourage wheat production. However, the availability and accessibility to higher yielding disease-resistant varieties, fertilization (both organic and inorganic), appropriate seed rate, optimum planting time, mechanization, rotation with legumes and expansion of wheat area are some measures that will play a crucial role in managing sustainable wheat production in Bhutan. In this paper, we provide a brief overview of the current scenario of wheat production, discuss the constraints and provide strategic guidance to improve wheat production in Bhutan.

The pressure-chamber technique has been used for the first time to measure leaf-water potentials in chickpea under field conditions. Available soil-water contents at different depths for irrigated and non-irrigated crops are presented along with the diurnal variation in leaf-water status, to show that pressure-chamber measurements correspond closely with available soil water. Leaf-water potential has also shown differences in leaf-water status among different cultivars. The rapidity and ease with which measurements can be made in the field make the technique suitable for quick measurements of leaf-water status for chickpea.

Cowpea cvs Ife Brown and New Era were sown at a wide range of densities in 1976 and 1977 (early season) at Ibadan in the rainforest zone of Nigeria. In 1977 (late season), the experiment was modified and Ife Brown and Vita 5 were used. All the cultivars were indeterminate. Grain yields were higher at lower densities, especially in 1977 (late season). Numbers of leaves, branches and pods were also inversely related to density, but there were differences between varieties in flowering, branching and leaf and pod production.

A field experiment was conducted from 1979 to 1986 to compare the amelioration of a highly sodic soil by the application of gypsum compared with that achieved by growing Karnal or Para grass for between one and three years. After studies of the growth of rice and wheat on the experimental plots, the growth of four forage crops, less tolerant of sodic conditions, was studied between 1984 and 1986. The forage yields suggest that their order of tolerance to soil sodicity is Persian clover > Egyptian clover > teosinte > maize, the rabi (winter season) forage crops being more tolerant than the kharif (rainy season) ones.

This paper, concerned with agricultural development planning problems in the Sahelian and Sudanian (semi-desert and savanna) zones in Africa between 10 and 16° North, describes a plan for Darfur, Western Sudan. This aims to modernize a stagnant and primitive technology and out-dated land rights which, in the face of rapid population increase and climatic change, are reducing the long-term carrying capacity of the land. The development plan (H.T.S., 1974) has been based on a 2-year (1972–73) survey by a team of physical and social scientists, financed by the Overseas Development Administration of the United Kingdom and the Ministry of Agriculture in the Sudan.

In view of soil fertility problems and financial constraints identified in small-scale farming, on-station investigations on Low-External-Input and Sustainable Agriculture (LEISA) were started by the Farming Systems Research Team Luapula Province (FSRT-LP) in order to assess the potential of three annual and six perennial pasture legume species for green manuring purposes. Rhodes grass (Chloris gayana cv NIRS Boma) was used as a control. Over two seasons, a pasture legume-maize rotation trial was established. Different mineral fertilizer amounts were applied to the maize. Of all the species and cultivars tested, the perennial glycine (Neonotonia wightii cv Cooper) had the strongest green manure effect when no mineral fertilizer was applied. Of the annual pasture legumes, sunn hemp (Crotalaria juncea cv. NIRS 3) and velvet bean (Mucuna pruriens cv. NIRS 16) showed the greatest green manure potential at zero mineral fertilizer level. There were strong indications that the carbon:nitrogen ratio influenced the green manure potential of a species more than its ability to produce biomass. The need to assess the economics and sustainability of current mineral fertilizer practices on maize has been identified.

The effects of soil fertilization and plant age on the nutrient composition of various parts of five Nigerian cassava varieties were studied to identify suitable index plant tissue(s), sensitive growth stage(s) and optimum nutrient concentrations, to develop better fertilizer practices for the crop. The third month from planting was the most sensitive stage for diagnostic sampling, when N status was best reflected in leaf blades and K in petioles. N and P were most concentrated in leaf blades and least in root tubers. The largest root tuber yields after 12 months were associated with leaf blade analyses of 5% N, 0.4% P and 2% K at 3 months after planting.

The growth and development of a short-season sweet potato (Nemagold) and a long-season cultivar (White Maltese) were compared quantitatively in sub-tropical Australia and also with growth data for Nemagold in a temperate environment. Total and storage root dry matter production (DMP) followed autocatalytic equations, with similar whole plant DMP from planting to week 25 for both cultivars but plateauing (at 90% of asymptotic weight) at week 23 for Nemagold (448 g) with favourable temperatures and at week 38 for White Maltese (813 g) when temperatures were unfavourable. Storage root DMP of Nemagold plateaued at week 23 (246 g) and at week 36 (219 g) for White Maltese. Data are given on other attributes and on phasic development.

The effects of populations of 33,000–250,000 plants/ha on growth and grain yield of two cowpea genotypes of bush growth habit was studied in lowland Papua New Guinea. The optimum economic seed rate seems to be 100,000 plants/ha; increasing the plant population decreased pods/plant and lateral branch development, but increased seed number/pod. Genotype UV.53 yielded more than UV.19 due to a combination of all three yield components, and a large dry weight. Growth analysis showed that treatment effects were mediated by differences in growth between 8 weeks and harvest.

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.

This paper analyses the way the CGIAR system has incorporated social research in its agenda. Since 1995, the social science staff capacity in the CGIAR has decreased by 24 %, and the overall balance of social science research is still significantly tilted away from the core germplasm enhancement, production systems/natural resources management, and technology adoption work – the ‘bread and butter’ of technology generation and development effort – toward ex-ante and ex-post activities. Further, the bulk of the social science research has low social research content despite the significant expansion of the CGIAR initial goal of increasing the proverbial ‘pile of rice’ to poverty alleviation and sustainable food security. The paper concludes that a concerted effort is now required to mainstream social research in the CGIAR system, and this cannot occur without the full support of the CGIAR donors, the CGIAR senior managers, and the centre boards and executive staff.

The effects of three irrigation intervals (7, 10 and 15 days), four nitrogen levels (0N, 1N, 2N and 3N where 1N = 43.8 kg N/ha), and 0 or 11.9 tons/ha gypsum on leaf N, P and K uptake by forage sorghum grown on a highly saline–sodic clay soil were investigated in two successive seasons. The two seasons' data consistently showed that both leaf-N and leaf-K increased significantly with increasing N-rate and by splitting the same quantity of irrigation water into more frequent irrigations. Gypsum had no consistent effect. The responses of both leaf-N and leaf-K to nitrogen rates were significantly linear and a linear response of dry matter yield to leaf-N was also observed. P uptake was improved by more frequent irrigations in the first cutting of 1978, but was not otherwise affected by treatments.

Three experiments and five small trials on robusta coffee and four small trials on arabica coffee have confirmed that nitrogen is the main nutrient requirement in Uganda. Magnesium and sulphur were not deficient and mulching had no effect on responses to nitrogen fertilizers. Leaf and soil analyses confirm the yield results and indicate that the optimum time to apply nitrogen is in February and September. There was little difference between ammonium sulphate and urea, but the former tended to have greater effects on yields.

Tillage trials on sandy soils in Zimbabwe have shown that sheet erosion from arable fields under a no-till tied ridging treatment is negligible but that the system generates environmental conditions that have an adverse effect on crop potential. Tied ridging improves crop production by preventing waterlogging in high rainfall years and improving rooting depth when adequate water supply prevents soils from setting hard, but it causes high temperatures in the ridges and rapid drying during dry weather, resulting in poor or delayed emergence and thus in low and uneven crop stands. New strategies need to be developed to minimize these effects.

Sweetpotato (Ipomoea batatas, Convolvulaceae) is an important food crop in Sub-Saharan Africa (SSA). Lack of access to quality sweetpotato planting material after sweetpotato limits utilization of market oriented improved clones and new varieties. Obtaining clean planting material in the right quantity and quality is a challenge in the SSA region. Farmers often obtain planting materials from their own sources with multiple rooting, drawn from a previous crop or neighbors and face the risk of it being infected with sweetpotato viruses. The objective of this study was to examine the economic and physical yield performance of sandponics multiplication method by comparing with conventional soil method using optimal N-nutrient inputs. The performance of five sweetpotato cultivars (Irene, Delvia, Tanzania, Gweri, and Kabode) in the modified prototype sweetpotato nutrient media was evaluated. Vine production utilizing modified sandponics nutrient media with trellised plants was compared to the conventionally used soil media. Analysis of variance indicated that the main effects of cultivar and substrate were highly significant (p < 0.0001) for nodes produced, vine multiplication rate (VMR), number of cuttings produced, and vine length. In addition, cultivar by substrate interaction was highly significant at 0.01 probability level for nodes produced, VMR, and vine length. Vine multiplication rate was 33% higher in the sandponics system compared to the conventional soil method of multiplying sweetpotato vines. Among the cultivars studied, Irene was the most favorable cultivar with a VMR of 65.2 in sand and 45.5 in soil. The cost-effectiveness analysis indicates that the cost per cutting (i.e., 3–4 nodes) produced from sandponics method was 4.6 KSH (US$ 0.046) as compared to 3.1 KSH (US$ 0.031) per cutting produced from conventional method. Sandponics system is competitive due to its capability of increased VMRs. However, the optimal number of ratooning needs to be investigated to understand the economies of scale in future research.

The integration of a microcomputer-based data-capture and data-processing system into an existing mainframe computing environment in a crop research institute is described. The system includes hand-held data terminals and electronic balances. Some computing terms are explained in an appendix.