Initial and residual effects of phosphorus, lime and potassium were studied on Natal Common and Dodoma Bold groundnuts. Double superphosphate (D.S.P., 42% P2O5) considerably increased yields of the first two crops. Lime was noticeably beneficial on Dodoma Bold but less so on Natal Common, while K depressed yields of both when applied without P. The LPK treatment yielded best with each variety, but initially P alone was most economic. Comparing D.S.P., Tororo superphosphate (T.S.P., 21% P2O5, 13% S) and Minjingu phosphate (M.P., 15% citric soluble P2O5), T.S.P. gave the best response (625 lb/acre over 3 years), more than double that of equivalent P2O5 as D.S.P. T.S.P.'s superiority is attributed mainly to its sulphur content. Though initially inferior, M.P. proved as good as D.S.P. over 3 years. 224 lb/acre T.S.P. in alter-nate years is recommended. After two or three crops, light applications of lime and potassium together would be beneficial.

Many smallholder farm systems in Uganda produce coffee as an important cash crop. Yet coffee yields are poor. To increase farmers’ production, a range of agronomic practices have been recommended by national and international agencies. Yet the adoption potential of recommendations differs between farm systems. To understand the differences in adoption potential of recommended coffee management practices in Uganda, we provide a typology of farm systems with coffee, assess the diversity between the farm types, and evaluate the current use of existing management recommendations for each farm type. Through factor analysis and cluster analysis of farms producing coffee, we identified five farm types: large coffee farms, farms with off-farm activities, coffee-dependent farms, diversified farms, and banana–coffee farms. The farm types were based on differences in size, and on the relative contributions of coffee, banana and off-farm labour to total household income. They also differ in the availability of the resources labour, land and cash, in coffee production and revenue, and in current use of most recommended practices. Qualitative analysis indicates that farm types have different constraints and opportunities to adopt recommendations. Our results highlight that an analysis of different farm systems with coffee production, a degree of definition beyond the ‘smallholder coffee farmer’ as a homogenous entity, is important in order to understand the scope for success or failure of recommended practices.

Long-term field experiments were conducted at Agra, Solapur and Hisar from 2000 to 2008 to identify efficient tillage and nutrient management practices and to develop predictive models that would describe the relationship between crop yields and monthly rainfall for rainfed pearl millet grown on arid and semi-arid Inceptisol, Vertisol and Aridisol soils. Nine treatments comprising a factorial combination of three tillage practices, viz., conventional tillage (CT), low tillage + interculture (LT1) and low tillage + herbicide (LT2) and three fertilizer treatments viz., 100% N from an organic source (F1), 50% organic N + 50% inorganic N (F2) and 100% inorganic N (F3) were tested in a split-plot design at the three locations. Studies revealed that tillage and fertilizer treatments, and their interactions, significantly influenced pearl millet grain yields at the three locations. Prediction models describing the relation between grain yield and monthly rainfall indicated that rainfall occurring in June, July and August at Agra; June and July at Solapur; and June and August at Hisar significantly influenced pearl millet grain yield attained by different treatments. The R2 values of the model ranged from 0.64 to 0.81 at Agra; 0.63 to 0.92 at Solapur, and 0.75 to 0.89 at Hisar. When averaged over all the treatment combinations, mean pearl millet grain yields varied from 1590 to 1744 kg ha−1 at Agra; 1424 to 1786 kg ha−1 at Solapur; and 1675 to 1766 kg ha−1 at Hisar while their corresponding sustainability yield indice (SYI) varied from 35.4 to 42.2%, 19.9 to 45.6% and 64.1 to 68.3%, respectively. At Agra (Inceptisol), CTF3 resulted in significantly higher mean net returns (Rs 11 439 ha−1), benefit-cost ratio (2.33), rainwater use efficiency (RWUE) (3.52 kg ha−1 mm−1) and the second best SYI (39.9%). At Solapur (Vertisol), the LT1F3 resulted in significantly higher net returns (Rs 12 818 ha−1), benefit-cost ratio (3.52), RWUE (3.89 kg ha−1 mm−1) and the fourth best SYI (42.6%). At Hisar (Aridisol), the LT1F3 treatment gave higher net returns (Rs 3866 ha−1), benefit-cost ratio (1.26), RWUE (5.05 kg ha−1 mm−1) and the fourth best SYI (67.8%). These treatment combinations can be recommended for their respective locations to achieve maximum RWUE, productivity and profitability.

The complex dynamics of the sulphur (S) cycle has prompted several questions concerning its bioavailability and evaluation by different extraction methods, and few studies under field conditions have been performed to elucidate available S on Brazilian soils under no-till (NT) cropping systems. A field experiment examined the effects of phosphogypsum (PG) applications on nutrient uptake and availability of S to maize and wheat crops under an NT system aiming to establish critic levels of S on an Oxisol (clay, kaolinitic, Rhodic Hapludox) in Parana state, Brazil. PG at the rates of 0, 3, 6 and 9 t ha−1 was applied on the surface of the plots in 1998 upon conversion from pasture to an NT cropping system, and in 2004 subplots received either 0 or 6 t ha−1 of PG on the surface. Effects of PG applications on nutrient uptake and available soil SO4-S to the maize and wheat crops were evaluated in 2004–2005. Increasing the surface-applied PG rate in 1998 increased Mg uptake by maize, and N, K, Ca and Mg uptake by wheat plants. Reapplication of PG in 2004 increased the uptake of N and P by maize, and the uptake of N, K, Ca and Mg by wheat plants. The PG rates surface-applied in 1998 have resulted in a long-term residual effect on soil by increasing SO4-S in surface and subsoil layers 6.5 and 7.5 years after application, affecting aboveground biomass, S uptake and S content in the leaves of the wheat crop. The reapplication of PG in 2004 increased maize S uptake, S content in leaves and grains and S exported by maize harvest, and increased wheat aboveground biomass, S uptake and S content in leaves. These effects were due to increasing available soil SO4-S from different depths extracted by 0.5 M ammonium acetate (NH4OAc) along with 0.25 M acetic acid (HOAc) and 0.01 M calcium phosphate (Ca(H2PO4)2). Both extractants were very similar in their ability to assess available soil S in these crops, and the 0–0.20-m layer is shown to be adequate for evaluating the concentration of available SO4-S in maize and wheat cultivated under NT.

Twenty one genotypes belonging to Spanish, Valencia and Virginia groups of groundnut were studied at Patancheru and a further seventeen at Delhi. Their relative performance based on a large number of characters spanning the entire growth phase was assessed. Nitrogenase activity and nodule mass were measured at three stages of crop growth starting from first flowering, and these two characters alone when measured at 30 days after flowering closely matched the measure of relative performance based on the entire set of characters.

Maize (Zea mays)-mucuna (Mucuna pruriens) systems have been promoted to the smallholder farmers of the Los Tuxtlas region of southeastern Veracruz, Mexico. To determine on-farm performance, an agronomic assessment was conducted in 1995–97 replicating farmer conditions in four fields. Treatments were first- and second-season maize with first-season mucuna (system Zm-Mp/Zm), first-season maize with first- and second-season mucuna (system Zm-Mp/Mp), second-season maize following first-season mucuna (system Mp/Zm), and first- and second-season maize, no mucuna control. Data on mucuna biomass amount and quality as well as maize yield, yield components, and nutrient status were collected. Highest mucuna biomass was obtained in system Mp/Zm (leaf-stem-mulch biomass in 1996/97, 7.34 t ha−1, 147 kg ha−1 N), followed by systems Zm-Mp/Mp (5.06 t ha−1, 101 kg N ha−1) and Zm-Mp/Zm (2.75 t ha−1, 50 kg N ha−1). Second-season maize yield was increased over that of the control by 45–58% (0.15–0.23 t ha−1) in system Zm-Mp/Zm and by 118% (0.60 t ha−1) in system Mp/Zm. Mucuna did not increase first-season maize yield. Climatic constraints make second-season maize production risky and yield increases due to mucuna are low in absolute terms, perhaps not offsetting labour costs (systems Zm-Mp/Zm and Mp/Zm) or loss of first-season maize (Mp/Zm).

Prior on-station research showed that sowing dates, sowing density and applications of fungicide and phosphorus (P) increased groundnut (Arachis hypogaea) pod yield by 60–80%. Farmer-managed trials were conducted in the Wa district of the Upper West Region of Ghana from 2004 to 2007 to test the yield response to sowing density, fungicide and P and to assess economic returns of these technologies to farmers. Treatments included: an early maturing groundnut cultivar, Chinese, sown at farmers' density (5–8 plant m−2) without fungicide and without P application (T1, control), with fungicide sprays alone (T2), or with fungicide and P application (T3), cultivar Chinese sown at recommended (higher) density (20 plant m−2) with fungicide and P application (T4), and a full season cultivar, Manipinter, with fungicide and P application (T5). Soil fertility, sowing density, days from sowing to first weeding, incidence and severity of leaf-spot disease and plant population at final harvest were recorded. Relative to farmers' practice, pod yield of cultivar Chinese was significantly increased by 80% with fungicide sprays alone, 108% with fungicide and P application, and 113% with fungicide and P application at higher sowing density. Cultivar Manipinter treated with fungicide and P gave 107% increase in pod yield relative to farmers' practice. Correlation and stepwise regression analyses suggested that major determinants of groundnut pod yield in farmers' fields were plant density, leaf-spot disease and P availability. The increase in yield with fungicide and P application translated into a 4–5-fold increase in gross margin for farmers in the region. Returns to labour and labour productivity were doubled with combined use of fungicide and P fertilizer.

Agricultural research and development (R&D) would benefit from reliable yet cheap technology uptake indicators to guide decision making. The paper explores the use of village surveys to monitor technology use and illustrates this through two empirical case studies into tillage dynamics in the Trans-Gangetic Plains in northwest India. The first case study is a revisit of 50 communities surveyed earlier in Haryana State. The second case study is a new and wider representative sample of 120 villages across Haryana and Punjab States. The case studies illustrate that after an initial rapid spread of tractor-drawn zero tillage drills for wheat seeding in these intensive systems, the zero + reduced tillage area seems to have stabilized there at between a fifth and a quarter of the wheat area. Conventional tillage for wheat continues to decline, with an increased use of rotavators making up the difference – but its intensive shallow tillage goes against the conservation agriculture tenets. The paper illustrates the potential of village surveys to provide timely and cost-effective feedback to agricultural R&D.

A model predicting biomass production and water use in tea plantations is described. Biomass production is calculated from the amount of light intercepted and a radiation conversion efficiency. Available assimilate (current production plus reserves) is distributed according to the ‘potential’ demand of each of the shoots, stems and roots. Any excess is stored in the stem and root reserve pool. In the case of the demand for assimilate exceeding the supply, allocation is according to the relative demands of each component. Simulations with the model suggest that assimilate supply is unlikely to limit shoot growth under most conditions. Soil water movement and crop water uptake are simulated using the water balance sub-model used by the CERES crop growth models. The model calculates a water stress factor (Φ) as the ratio of actual to potential crop transpiration, and uses this factor to adjust various crop processes such as dry matter production and shoot development and extension rates. Predicted yields match observed yields well across a range of watering treatments and for different years at sites in Tanzania and Zimbabwe, providing some degree of confidence in the model's ability to predict tea yields for environments in East Africa.

Experimental data on tillage requirement of cocoyam (Xanthosoma sagittifolium) are needed to identify the most suitable tillage methods for managing the fragile Alfisols of the humid tropics to ensure sustained productivity. Hence, five tillage methods were compared as to their effects on soil physical and chemical properties, and growth and yield of cocoyam on an Alfisol at Owo in the forest-savanna transition zone of southwest Nigeria. The experiment consisted of five tillage methods: manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing + harrowing (P + H) and ploughing + harrowing twice (P + 2 H) were used for three years at two sites in a randomized complete block design with three replications. In the first two years (2007 and 2008), P + H produced the least soil bulk density and highest growth and yield, whereas in the third year (2009), MC produced the lowest soil bulk density and best performance of cocoyam. Manual clearing produced the best values of soil chemical properties in 2008 and 2009. Averaged over the three years, P + H, MR and MM had lower soil bulk density hence better growth and yield compared with P + 2 H and MC. Over the three years MC, MM, MR and P + H increased cocoyam cormel yield by 10, 21, 23 and 32%, respectively, over P + 2 H.The corresponding increases in corm yield were 7, 15, 13 and 21%, respectively. The multiple regressions revealed that bulk density and moisture content significantly influenced the yield of cocoyam. Soil chemical properties were not significant. Bulk density rather than soil chemical properties dictated the performance of cocoyam in an Alfisol of southwest Nigeria. Soil quality was degraded by P + 2H. For small farms, either MR or MM is recommended while P + H is recommended for large-scale farming of cocoyam.

The economics of coffee plantations is intrinsically linked to pruning, which can improve the canopy architecture and thereby increase productivity. However, recommended pruning times on conilon coffee plantations have been made on an entirely empirical basis. In this study, by evaluating growth, photosynthetic gas exchanges, starch accumulation and crop productivity, the effects of pruning at different times between harvest and flowering were investigated for six conilon coffee clones with distinct stages of fruit maturation (early, intermediate and late). Clones with an early maturation stage were pruned at four different times: 0, 30, 60 and 90 days after harvest (DAH). Intermediate clones were pruned at 0, 30 and 60 DAH, and late clones were pruned at 0 and 30 DAH. Overall, the rates of shoot growth and net photosynthesis, the stomatal conductance and the crop yield were not affected by the pruning treatments in any of the clones. In addition, pruning times did not affect the concentrations of starch or the photochemical efficiency of photosystem II. The carbon isotope composition ratio was marginally affected by the treatments. These results suggest that the pruning time after harvests is relatively unimportant and pruning operations can be scheduled to optimise the use of labour, which directly impacts the production costs of coffee.

During a period of dry weather, seedling tea bushes were generally less stressed than the clones which had been derived from those plants by vegetative propagation. There were interesting differences between the clones in their responses to dry conditions, but these could not have been predicted from similar observations made on the heterogeneous seedlings. However, it should be possible to use tests, based on measurements of the xylem water potential and stomatal resistance, to identify potentially drought-resistant clones at a later stage in the selection programme.

Extra-short-duration pigeonpea (Cajanus cajan) genotypes generally yielded more than short-season legumes when sown at the normal time on rainfed medium-deep Alfisols. However, their growth and yield were more reduced by delayed sowings and varied more widely between seasons than those of the short-season legumes, especially cowpea and black gram. All the crops gave lower yields on shallow Alfisols than on medium-deep Alfisols and none was consistently superior. Partitioning of dry matter into grain yield was less affected by time of sowing, soil and season in extra-short-duration pigeonpea genotypes than in short-season legumes. Less sensitivity of biomass accumulation to various abiotic constraints is therefore a major objective in improving the adaptation of extra-short-duration pigeonpea genotypes.

Cajanus cajan de duración extra-corta

Experiments were carried out to relate soil moisture to leaf water potential (Ψ1), and to determine the effects of varying Ψ1, on leaf conductances and photosynthesis in coffee. Stomatal conductance was maximum at 0900 h, but plants growing in drier soil showed marked mid-day stomatal closure. After 1500 h, stomata began closing although plant water status improved. Photosynthesis in relation to changing Ψ1 appeared to exhibit roughly three different rates. At the fixed experimental temperature (25°C) low Ψ1 reduced photosynthesis throughits influence on stomata, but under field conditions low Ψ1 and an accompanying rise in temperature could lower the rate by lowering both mesophyll and stomatal conductances.

By comparing flowered and non-flowered plants of the same age (where flowering was inhibited by photoperiod control), cane yield gains due to prevention of flowering were estimated to be 56·6% in a plant crop and 33·8% in a ratoon crop. Sugar gain due to prevention of flowering was 69·1% in the plant and 35·4% in the ratoon crop. A simple negative linear relation was found between cane (and sugar) yield per plant and the proportion of canes that flowered. There was no significant difference in fibre content of flowered and non-flowered canes. The influence of loss of growth, side-shoot production and pithiness on the yield of flowered canes are discussed.

Pot and field investigations were conducted to study the effects of vesicular-arbuscular mycorrhizal (VAM) inoculation and triple superphosphate fertilization on nodulation, dry matter yield and tissue nitrogen and phosphorus contents of Bradyrhizobium-inoculated soya-bean and lablab bean in the Sudan.

Inoculation of both crops with the VAM fungus Glomus mosseae in clay and sandy soils in pots increased nodulation, dry matter yield and tissue nitrogen and phosphorus contents more than triple superphosphate fertilizer, but even greater responses were obtained from G. mosseae combined with fertilizer. Crop responses in the two soils were similar, despite the large differences in soil physico-chemical properties.

In the field, inoculation of both crops with any of four VAM fungi enhanced nodulation, dry matter yield and plant nitrogen and phosphorus contents more than did triple superphosphate. Gigaspora margarita and Glomus mosseae were superior to Gigaspora calospora and Acaulospora species and resulted in more extensive root infection, especially in soyabean.

Nodule and plant dry weight of five photoperiodically different cowpea varieties increased with increasing day-length. There were no effective nodules on any varieties in 8-hour days and the response of nodulation to day-length was greater than plant dry weight. Nodule and plant dry weight also increased with increasing availability of water, but at the highest watering rate nodule weight was significantly lower under long than short days. Cowpea should nodulate well under tropical day-lengths provided enough water is available.

Establishment of young cacao trees in West Africa can be severely impeded by the onset of the dry season. To address this issue, a field experiment was conducted in Ghana to examine whether different mulch treatments and irrigation applied during the dry season combined with overhead shade could improve survival, early growth and yield of cacao. The mulch treatments used were polyethylene film and coffee husks placed around the young plants. Irrigation was used as a positive control, and no mulching or irrigation was a negative control. Three shade regimes were provided through different arrangements of Gliricidia sepium and plantains. Four different cacao clones were used in the study in a replicated split-plot design. Early growth of cacao was stimulated under the irrigation and plastic mulch treatments. Higher rates of photosynthesis during the dry season appeared to underlie these increases. Significantly higher early yields were also observed under the irrigation and coffee mulch treatments compared with the control. Plant survival varied significantly between treatments; irrigation was associated with the highest plant survival (94%), followed by the plastic mulch treatment (91%), coffee husk (82%) and the control (70%). There was also an increase in survival when more intense shading was used. Under zero mulch conditions, differences in survival were observed between clones. The clones P 30 [POS] and SCA 6 were more sensitive to drought (in terms of survival) than PA 150 and T 79/501. It is concluded that relatively simple mulching techniques or controlled irrigation in conjunction with appropriate shade management can significantly improve early establishment and cropping of cacao.

Principal component analysis is a mathematical technique for summarizing a set of related measurements as a set of derived variates, frequently fewer in number, which are definable as independent linear functions of the original measurements. Consideration of their mathematical nature shows that they do not, themselves, necessarily correspond to sensible biological concepts, though they are more amenable to statistical study than the original measurements. Further, by assessing the extent to which they are in accordance with biological hypotheses, or with the results of other, similar, analyses, they can be transformed into other linear functions which are meaningful in the biological sense, or consistent with other results. Thus the specific technique of principal component analysis is developed into a more general component analysis approach. With proper regard for the purpose the analysis is intended to serve and for the mathematical restrictions involved, this approach can lead to a useful condensation of a mass of data, a better under-standing of the observed individuals as entities rather than collections of isolated measurements, and to the formulation of new hypotheses for subsequent examination.

The small amount of on-farm research that has been carried out with fodder trees in Africa has mainly involved exotic species selected by researchers rather than farmers. In this study, farmers who had participated in a pre-planting survey chose, during feedback meetings, seedlings of indigenous, naturalized and some exotic fodder trees from a nursery. They planted them on-farm, where the planting niches, management, biomass production, and animal response were evaluated over a short period, and compared with the results of the earlier survey. The farmers came from three agro-ecological zones in central Kenya with respective mean annual rainfall totals of 775, 950 and 1300 mm. Data were collected at two months, one year and two years after planting. The feedback meetings proved important to the understanding of discrepancies between the earlier survey results and farmers' practices. Survival and growth of seedlings, manure application by farmers, and percentage of trees pruned for fodder, differed among species. The farmers showed a strong interest in experimenting with and actively cultivating local fodder trees.