For Muguga, in Kenya, confidence limits of expected ‘twenty-day’ rainfall may be reliably derived through a logarithmic transformation of the skew rainfall data. Frequency distributions of rainfall totals received during specific crop-growing seasons are examined for three widely separated Kenya sites. It is shown that confidence limits for such seasonal rainfall cannot be obtained by summation of the corresponding limits for the successive twenty-day intervals included within the season. Twenty-day limits should not therefore be accumulated in seasonal comparisons of crop water requirements and precipitation. Such assessments of agricultural site potential must take account of the year-to-year variability of precipitation, but are best undertaken with actual rainfall amounts.

The failure of overdrilling techniques to improve poor pasture and the development of the dipyridylium herbicides, particularly paraquat, for controlling grass species, prompted research into oversowing techniques in 1963 and 1964. Rotary cultivation, although giving better establishment than any other oversowing technique, did not always reduce the more persistent weed grasses such as Agrostis spp., and so failed to produce a perennial rye-grass dominant sward. This was believed to be due to various factors such as unsatisfactory herbicide pre-treatments, the interval between spraying and cultivation, the high moisture content of the soil when cultivated, as well as the greater resistance of rhizomatous grass species to paraquat. In the absence of paraquat, rotary cultivation was able to establish a satisfactory number of seedlings. In both experiments, however, the subsequent botanical composition was considerably influenced by pasture management.

A selection programme conducted on young clonal tea plants grown in large sleeved bags and in a field trial established criteria for selecting high yielding field clones on the basis of their growth in early years. Bush area, number of branches and shoots per bush, and foliar phosphorus content at the second crop peak were correlated with yield but the correlation between stem circumference at ground level and yield was inconsistent. It is therefore concluded that all these bush and growth characters, apart from stem circumference, may be reliably used to predict and select high yielding tea clones.

The effect of a single grazing at the tillering stage on barley yield and economic returns was studied with two widely grown local landraces over five seasons at Tel Hadya and two seasons at Breda in northern Syria. In general, grazing reduced both grain and straw yield, particularly the latter. The percentage of grain yield reduction was similar at the two sites. Grazing increased net revenue on average, though there were marked seasonal differences. This increase was higher at Breda, the drier site, a finding which contradicts the commonly-held belief that grazing is unprofitable in dry areas.

The tuber yield of potatoes in a field experiment conducted at Jalandhar between 1981 and 1984 was greater following green manuring with either Crotalaria juncea or Sesbania aculeata than after fodder crops of Zea mays or Pennisetum typhoides. The residual effect of phosphorus applied to potato on subsequent wheat crops varied with the previous green manuring and fodder cropping treatments but was always sufficient for the wheat when applied at an economic rate; the lack of an application of phosphorus fertilizer to the wheat did not result in a decline in the availability of soil phosphorus. The use of C. juncea as a green manure increased the availability of phosphorus but decreased that of potassium. Pennisetum typhoides also depleted soil potassium reserves. Sesbania aculeata green manure improved the organic carbon status of soil whereas P. typhoides depleted it.

A series of experiments was designed to evaluate a wide range of possible cropping systems for deep Vertisols of the Indian semi-arid tropics. The introduction of a rainy season maize crop, compared with traditional fallowing, had little effect on the yields of post-rainy season crops of sorghum, chickpea and pigeonpea. Introducing a rainy season sorghum crop caused severe yield reductions of post-rainy season crops in one year but only slight reductions in two subsequent years. Intercrop systems of maize/pigeonpea or sorghum/pigeonpea, and a three-crop system of maize/pigeonpea/chickpea, appeared very promising. Gross returns were usually much higher for the improved systems that utilized both the rainy and post-rainy seasons, though differences in net returns were not quite so great because of the extra costs of growing the additional rainy season crops.

Farmers’ access to reliable information is crucial to improving rural livelihoods, food security, and national economies in West Africa. This paper discusses the dynamics of accessing and using agricultural learning videos from commercial channels, vs project and non-project channels in Benin and Mali. Using combinations of different models to assess the effectiveness of agricultural extension programs, the findings showed that farmers were motivated to pay for videos and watch them by themselves, without facilitation. Farmers who watched the videos through project support have also continued to watch on their own if the videos are of interest to them. Nevertheless, farmers were less motivated in the learning process when they received the Digital Video Disc (DVD) free and without support to watch them. We also found that the distribution of learning videos through commercial channels reaches more serious users and increases farmers’ self-determination for learning, and farmers are more motivated to provide feedback than viewers who receive DVDs for free or via project support, Non-Governmental Organizations (NGOs), or farmer organizations. Although buying a DVD is an individual action, they like to watch the videos in groups. After buying the DVD, about 43% of respondent borrowed DVD players and one person in five bought a DVD player to watch the videos. Efforts to promote improved technologies need to expand beyond the conventional focus on research and extension services. Support to agricultural technology dissemination must go beyond assistance to smallholder farmers and NGOs (practical implication). As the private sector has a role to play, both in making technologies available and in teaching farmers how to use them, their contribution would create space for innovation (theoretical implication). Our findings suggest that successful development intervention programs can be sell audiovisual material to farmers, who will use it proactively.

On the basis of a preliminary experiment with 20-day-old Cicer seedlings, wherein the values obtained by integrating the in vivo nitrate reductase (NR) activity with the duration closely approximated the actual reduced N, a field experiment was conducted with cv BG 203 (indeterminate type) to ascertain the extent to which the nitrate assimilated via the enzyme NR contributed to the total reduced N. Soil-derived N accounted for 15.1, 8.3 and 7.2% of the total reduced N at pre-flowering (I), profuse flowering (II) and seed filling (III) stages respectively. Out of the total soil-derived N, 10.1, 59.3 and 30.6% was reduced during stages I, II and III respectively.

The fixation of nitrogen in root nodules of pigeon pea, Centrosema pubescens and Styloxanthes gracilis were studied, and the transfer of nitrogen to other parts of the plant. Fixation reached a maximum of 14·5, 10·3 and 4·6 mg. per day per plant respectively, and the rate of transfer of nitrogen from the nodules was at a high constant rate throughout the experimental period. With pigeon pea and Centrosema younger plants seem to be more efficient fixers of nitrogen than older on, but the reverse was true with Styloxanthes.

In the Northern mountainous region of Vietnam, cassava–cowpea intercropping system has been widely promoted with support from the local agricultural department. However, cowpea yield is often limited because of a low Biological Nitrogen Fixation (BNF) activity due to its low natural nodulation and lack of available effective Rhizobium products. The aim of this study was to identify the most effective native rhizobia isolate nodulating cowpea with the potential to increase BNF and yield of cowpea. A greenhouse experiment was initially conducted with five treatments: three native rhizobia isolates (CMBP037, CMBP054, and CMBP065); a control (no inoculation and no N application); and N+ (no inoculation, application of N as KNO3). Field inoculations were carried out and the treatments were as follows: a control (no inoculation); CMBP (037+054) – a mixture of strains from Mau Dong; CMBP065 strain from Cat Thinh. CMBP054 and CMBP065 had the highest nodulation in the greenhouse (46.4 and 60.7 nodules plant−1, respectively) and were rated as effective with symbiotic efficiency (SEF) of 54.56 and 55.73%, respectively. In the field, CMBP (037+054) recorded significantly higher nodulation (19.4 nodules plant−1) than the control (11.7 nodules plant−1). CMBP (037+054) also increased cowpea shoot dry weight, shoot N, and yield by 28.6, 4.9, and 10.5%, respectively, compared to the uninoculated control. This effect was slope dependent (statistically significant in moderate and steep slope, not with gentle slope). Besides, the high expansion rate of intercropping with cowpea showed the high adoption level of these agroecological practices by local farmers. This study reveals the potential of native rhizobia inoculation to enhance soil fertility and sustainable agriculture in the Northern mountainous region of Vietnam and proposes enhanced efforts to promote the availability and utilization of effective inoculants for cowpea.

In this study, the effects of HA combined with NPK fertilizer (HANPK) on root growth and leaf quality of tobacco plants were investigated in tobacco fields. Results indicated that the application of HA alone did not enhance the growth of tobacco obviously, while HANPK increased tobacco biomass by 36.9% and stimulated the growth of lateral roots significantly. The number of the second-order lateral roots was increased by 89.3% compared with the control. Furthermore, HANPK raised the ratio of root biomass in 0–20 cm soil layer over the whole soil layer and increased the proportion of fine roots over the total roots. Tobacco leaf yield, output value, and benefit of HANPK were 12.2%, 29.4% and 35.5% higher than those of the control, respectively. The above results suggest that the combined application of HA and NPK chemical fertilizer is an economical pattern for improving tobacco growth.

Multiflorous spikelets are found in oat Avena sativa L. subsp. nudisativa, which is characterised by elongated rachilla and variable number of florets per spikelet. One of the main factors limiting the exploration of multiflorous spikelets in oats, aiming to produce naked grains, is its variable expressivity. This work aimed to detect the environmental influence on the variable expressivity of multiflorous spikelet formation in oats and to estimate the heritability of this trait by analysing its expression in lower, middle and upper third of the panicle in 94 inbred lines of two crosses each. Two populations of recombinant inbred lines were screened for the spikelet formation in 2 years and sowing dates under field experiments. The results demonstrate that the variable expressivity of the multiflorous spikelet formation was highly influenced by the environmental conditions. The variable expressivity varied according to the genetic background, as well as the panicle third where spikelets were produced. The upper third of the panicle showed greater stability for the multiflorous spikelet formation, which is confirmed by the highest heritability coefficients observed in this third, regardless of the assessed population. Our results provide substantial evidences of the contribution exerted by environmental conditions in multiflorous spikelet formation in oats.

Phaseolus vulgaris is considered an inefficient nitrogen fixer, and therefore farmers in Mexico use large quantities of synthetic nitrogen fertilisers. The aim of this research was to evaluate the performance of native isolates of Rhizobium spp. and Bacillus spp. as biological fertilisers in northern Mexico. A first test was carried out under greenhouse conditions to analyse 15 native isolates of Rhizobium and 15 native isolates of Bacillus. Based on their effects on the bean crop, the best treatments were tested under field conditions. In the field, the combination of Rhizobium and Bacillus (Rz + Bs) produced the highest grain yield, biomass production, number of nodules per plant and dry weight of nodules, statistically surpassing (p ≤ 0.05) the control (without inoculation and fertilisation). Furthermore, compared with synthetic fertilisation, no statistical differences were found, which suggests that the combination Rz + Bs can replace synthetic fertilisation.

Fourteen smallholder coconut plantations, subdivided into 27 uniform sub-units, were surveyed in an area around Dala, in Western Malaita, Solomon Islands. Most units (17 out of 27) had densities of 160–200 palms ha−1 with a median light transmission of 50–55%. Palm growth was poor due to low soil K, and copra yields averaged only 540 kg ha−1 year−1 Batiki (Ischaemum aristatum) was the most important sown grass, and its productivity was significantly related to stocking rate and weed control, but not directly with light transmission. Farmers should thin dense palm stands, adjust stocking rates in relation to actual areas of pasture available, and institute careful and adequate weed control.

Water depth at or shortly after planting is critical for the establishment and subsequent tolerance of excess water in rice. A crop transplanted early in the season produced twice as much grain as a later planted crop. A semi-dwarf variety (CR 1018) and a taller variety (CR 1030) performed similarly after early transplanting, but the tall variety performed better when planted late under excess water. Seedling age did not greatly alter the yields when crops were transplanted early, but after late planting 45-day-old seedlings were best.

The production of lentil (Lens culinaris) was examined in 24 on-farm trials conducted over three seasons (1985/86 to 1987/88) in northwest Syria to examine the main effects and interaction of sowing date, weed control, Sitona weevil control, and fertilizer application (phosphorus and nitrogen). Advancing the date of sowing from late winter (mid January) to early winter (mid-November) resulted in an increased yield of grain and straw in all years across locations. Responses to phosphorus application were also significant in all years. Controlling Sitona weevil increased grain yield by 20% in early sown crops and by 14% in those that were sown late. Weed control by the pre-emergence application of cyanazine and pronamide increased grain yield by 59% in early sowings and by 20% in late sowings. Economic analysis of the improved production practices showed that early sowing combined with the control of Sitona and weeds, and phosphorus application, gave the highest probability of an increase in net revenue with virtually no risk of economic loss to the farmer.

The objective of this study was to develop a basic variety selection decision support system (DSS) based on industry legalities, varietal characteristics and structured genotype-by-environment (G × E) analyses. Trial data extracted from a variety trial database at the South African Sugarcane Research Institute (SASRI) were categorized into different regions, harvest ages (12, 18, 24 months) and harvest seasons (early, mid, late season harvests). Restricted maximum likelihood analyses were conducted regionally to determine varietal adaptability to different harvest ages and seasons. Highly significant variety × harvest age and variety × season interactions allowed for the appropriate categorization of varieties. Varietal adaptability to different yield potential conditions was determined using the sites regression technique, and varietal adaptability was interpreted from the slope of the regression curves. The analysed data were used to create simplistic ‘yes/no’ spreadsheets, which were housed within a relational database. A web interface linked to the database allows users to specify characteristics of their production environment. The system then selects appropriate varieties that conform to specified criteria and eliminates non-compliers in a stepwise approach. The system was subsequently validated against expert extension specialist opinion and acceptable performance was observed.

Potassium chloride (KCl) is the most widely used fertilizer in oil palm (Elaeis guineensis) plantations and the rates applied are based on interpretation of leaf K contents. When no positive response on leaf K contents can be detected, no optimum content can be established whatever the yield response to KCl rates. We used data from 13 fertilization trials conducted on several continents to study the responses of leaf K, leaf Cl, leaf Ca and yield to KCl rates as a function of the soil properties of each site. We found that the abundance of exchangeable Ca in the soil expressed as a percent of the cation exchange capacity (CEC) was the best soil variable to predict if leaf K content would increase with KCl rates. In addition, we found that the leaf K contents of unfertilized controls at the end of the trials were also correlated with Ca/CEC. This ratio thus appears to be a better index of soil K reserves than soil exchangeable K content.