Potassium application appeared to increase dry matter production and yield of oil palms, primarily by increasing leaf area, while nitrogen increased both leaf area and net assimilation rate. Responses to phosphorus and magnesium were harder to interpret. Production of vegetative dry matter attained a fairly constant level at the higher rates of fertilizer application, while the ratio of bunch yield to total dry matter production was little affected by fertilizer treatments. The importance of these results for oil palm breeding, and their possible value in diagnosing fertilizer requirements, are briefly discussed.

The possible use of tropical forage legumes in pastures based on Brachiaria decumbens and Andropogon gayanus pastures was tested on farms in the humid tropics region of Pucallpa, Perú. The pastures were established by farmers using manual labour. They were associated with maize in some cases and were normally grown without fertilizers. The pastures were established in areas where fallow regrowth was felled and burnt. These pastures, with grass-alone controls, were incorporated by farmers into their normal paddock rotation and were grazed by dual-purpose cows. Despite the variable terrain and soil conditions, all the pastures established and persisted well. Over a four year period under grazing, the legume contribution to the forage averaged 21% and ranged between 1 and 66%. Desmodium ovalifolium was the dominant legume in paddocks that were not burnt, whereas in pastures regularly burnt to control weeds it tended to disappear and Stylosanthes guianensis was the main legume present. It is concluded that where farmers ensure the maintenance of adequate levels of forage, grass-legume mixtures are a viable and persistent option even if the pasture is occasionally burnt.

The effect of no-tillage and mulch on soil properties and tuber yield of cassava was studied over a five year period on an infertile, acid Ultisol in south-eastern Nigeria. Mulch was applied at a rate of 12 t ha−1 as a split application once at planting and once six months after planting. No chemical fertilizers were used during the trial. Bulk density and proportion of micropores (pore radius, r, <1.4 µm) were greater, and proportion of macropores (r>14.4 µm) lower, with no-tillage. Water infiltration was increased by mulching, being greatest in tilled, mulched plots. Soil chemical properties were not significantly affected by tillage system, although levels of exchangeable calcium, magnesium and potassium were higher and acid saturation lower with mulching. Soil physical and chemical properties were best with tillage and mulching, and poorest when neither tillage nor mulch was used. Cassava tuber yield was unaffected by tillage system but increased by mulching.

Increasing transplanting costs in southeast Asia have encouraged farmers to adopt labour-saving crop establishment techniques for rice, such as wet seeding. This practice has been accompanied by an increase in weed problems and a shift in the dominant species to grassy weeds. Other problems are encountered with wet seeding but weeds are the most severe and most widespread constraint. It is impossible to produce rice economically without a well-planned weed control programme. The problems caused by weeds in wet-seeded rice and ways of controlling them by preventive, ecological, managerial, physical and chemical means are discussed in this paper. Herbicides are the most cost-effective weed control method in wet-seeded rice but there is a need to reduce the almost total reliance on them for weed control; cultural practices need to be integrated with judicious herbicide use. Worldwide concerns over environmental issues also need to be addressed.

Control de malezas en el arroz de siembra húmeda

Smallholders' acceptance of innovations depends largely on the approach used to take their needs and constraints into account. The adoption of integrated pest management (IPM) strategies by smallholders can lead to a reduction in pesticide use in cotton, as soon as the recommended cropping practices are adapted to local conditions and associated with a threshold-based use of chemicals. To achieve this goal, farmers need to be trained on the biological basis of IPM. To ensure effective and rational implementation of IPM by farmers, it is essential to overcome constraints associated with pest scouting, identifying and preserving beneficial insects, and gaining access to the right inputs on time. In the current African context, where the extension system is sometimes in very poor shape, participatory methods fostered by the ‘farmer field school’ concept could enable farmers to implement an integrated approach to pest management, while keeping researchers informed about farmers' needs and constraints. Our paper is an attempt to use such a participatory method as a tool to explore farmers' needs and constraints when smallholders are asked to adopt an integrated approach to cotton pest management.

Sustainable intensification (SI) of agriculture is the predominant objective for agricultural research and extension worldwide. Researchers and policymakers consider SI to be essential to avoid global hunger, improve human nutrition and reduce rural poverty while avoiding all manner of environmental disasters. To achieve these global public goods requires a large number of rural households – ‘small farmers’ – in less developed countries to improve their agriculture. Household size and farm size from 11,789 households in 15 countries from sub-Saharan Africa were used to calculate an intensification benefit index (IBI) that reflects how much a household will benefit if intensification occurs. IBI is defined as the increase in personal daily income (cents/person/day) as returns to land (dollars/hectare/year) increase. Actual net farm income from 160 rural households in each of three countries was compared with their IBI values to explore the gap between potential intensification and current smallholder farm performance. Fifty percent of all households had IBI values less than 0.075 cents/dollar, 70% less than 0.125 cents/dollar and 90% less than 0.225 cents/dollar. Returns of $1000/ha/year would result in fewer than 15% of households crossing a $2/person/day poverty line; $2500/ha/year would be required to lift 50% of the sample above the line; and even with $4000/ha/year, more than 30% of households would remain below the line. Since mean net returns from three sub-sampled sites were only $78, $83 and $424/ha/year the gap between potential- and actual performance is large but, theoretically, amenable to closure through adoption of improved technologies. However, surveys have shown that the available technologies would struggle to bridge the gap completely for rural households with small farms. For many small farms, the gains from adopting improved technologies are unlikely by themselves to lift them out of poverty and so might not be as attractive as scientists would wish.

Ten endophytic bacteria were isolated from different sugarcane varieties growing in the Crop Research Centre, Pantnagar on nitrogen-free medium. Plant growth-promoting potential of the isolates was reported in terms of indole acetic acid (IAA) production, phosphorus solubilization, siderophore production and antagonistic action against the pathogen Colletotrichum falcatum, which causes red rot disease in sugarcane in vitro. All the isolates were able to produce IAA (4.8–9 μg ml−1); three isolates (H3, H5 and H14) solubilized insoluble phosphorus on Pikovaskaya's agar; two isolates (H10 and H14) showed siderophore production on Chrome-azurol S (CAS) agar and antagonism against C. falcatum was exhibited by two isolates (H14 and H15) in a dual plate assay. 16 S rRNA sequencing identified isolates H3 and H12 as Pseudomonas spp., and H8, H14 and H15 as Bacillus spp. A field experiment on sugarcane was conducted with five plant growth-promoting bacterial endophytes Pseudomonas spp. (H3 and H12) and Bacillus spp. (H8, H14 and H15) along with standard strains of Gluconacetobacter and Azospirillum spp. Plant height, chlorophyll content, total nitrogen and cane length were significantly higher in almost all inoculated plants compared with the uninoculated control. An increase of 40% in cane yield over the control was obtained after inoculation with isolate H15 (Bacillus spp.). This was statistically on par with the standard endophyte Gluconacetobacter diazotrophicus, which resulted in 42% increased cane yield. Identification of new diazotrophs and their promising results towards improving plant growth in the field suggest their use as inoculants in future.

The effects of site and rate of application of fertilizer on the grain and straw production of barley were investigated in 75 trials on representative farmers' fields. Grain and straw production were strongly but curvilinearly correlated with growth-period rainfall over the range 136–568 mm, almost irrespective of soil type, previous crop or fertilizer rate, and responded positively to applied nitrogen and/or phosphorus in 74 of the trials. Responses to nitrogen increased and those to phosphorus decreased with increasing rainfall. Yields tended to be lower but responses to nitrogen were higher where barley followed barley and were influenced by the availability of phosphate and mineral nitrogen in the soil at planting time.

These results are summarized in regression equations, which express yield quadratically in terms of fertilizer rates, seasonal rainfall and their interactions over the full 75-trial data set and within representative sub-sets. The wide differences in crop response to fertilizer highlight the problem of recommending fertilizer rates for a low and variable rainfall environment. Simple second-order multiple regressions for different geographical areas, rainfall zones, crop rotations etc., based on mean rainfall values, account for around 40% of the variance in yield response to nitrogen and phosphorus fertilizer; only a small proportion of the remaining variance appears attributable to rainfall variability. Alternatively, yield may be expressed as a function of fertilizer rate and rainfall using rainfall probability values derived from long-term records. This can be used to estimate the probabilities of predetermined yield responses for specified sites and fertilizer rates and to produce maps of those probabilities.

The traditional crops of Oceania are asexually propagated and are losing their positions in cropping systems because of their genetic vulnerability. This paper reviews genetic reasons explaining the deterioration of their agronomic performance, using information mostly derived from surveys of genetic resources conducted in more than 50 Pacific islands, coupled with genetic investigations. More than 2000 cultivars have been analysed for isozyme variation. Cultivars and wild forms showed greater isozymic variation in Melanesia than in Polynesia and Micronesia but the genetic base for many of these crops was much narrower than morphological and chemical variation had suggested. No correlations were found between zymotypes, chemotypes, and morphotypes. Cultivars exhibited variation in qualitative traits as a result of human selection of somatic mutations. Accumulation of viral particles in propagules and build-up of pest and pathogen populations are often responsible for poor agronomic performance. If breeding of these traditional crops is to have any future, it is important to exchange genotypes to broaden the base of existing programmes.

Root development of maize (Zea mays), soyabean (Glycine max), cowpea (Vigna unguiculata), and pigeonpea (Cajanus cajan) was investigated with and without tillage. Observations were made at different growth stages by digging trenches normal to the rows, by core sampling, and by observing growth of roots against glass windows. There were more maize roots in the surface layer (0–10 cm) with no-tillage than in conventionally ploughed plots, but at 10–40 cm maize roots were more abundant and soyabean and pigeonpea roots less so in the no-tillage plots.

A field experiment was conducted to evaluate the comparative effectiveness of poultry manure, urea N and the integrated use of both in changing soil properties, nutrient uptake, yield and yield attributes of maize grown at Rawalakot, Azad Jammu and Kashmir, Pakistan. Treatments include control without any amendment (N0); urea N (UN) = 120 kg N ha−1 (N120U); UN = 150 kg N ha−1(N150U); poultry manure (PM) = 120 kg N ha−1(N120PM); PM = 150 kg N ha−1(N150PM); UN = 90 kg N ha−1+ PM = 30 kg N ha−1(N90U+30PM); UN = 60 kg N ha−1+ PM = 60 kg N ha−1(N60U+60PM); UN = 30 kg N ha−1+ PM = 90 kg N ha−1(N30U+90PM). N fertilization from different sources and combinations increased dry matter yield from 5206 kg ha−1 in the control to 5605–5783 kg ha−1 and grain yield increased from 1911 kg ha−1 to 2065–3763 kg ha−1. Application of the highest rate of urea N recorded the highest grain yields of 3763 kg ha−1, double the control. The proportional increase for N90U+30PM and N60U+60PM was 85 and 83% while PM alone gave lower yields (41 and 44%) than the respective urea N treatments. Integrated use of urea + PM proved superior to other treatments in enhancing the uptake of N, P and K in plants. Averaged across two years, uptake of N, P and K in N90U+30PM and N60U+60PM was 88 and 85, 16.5 and 17.5, and 48.5 and 53.5 kg ha−1, respectively compared to 52.5, 11.5 and 33.5 kg ha−1 in the control. Nitrogen use efficiency (NUE) varied from 29% in PM treatments to 30–39% in combined treatments while NUE of 40% was recorded for urea N treatments. Application of PM lowered soil bulk density from 1.19 t m−3 in the control to 1.10 and 1.05 t m−3 in N120PM and N150U, enhanced pH from 7.39 to 7.65 and 7.78 and increased soil organic matter (22 and 32%), total N (21 and 26%), available P (44 and 55%) and available K (10 and 15%) compared with the control. Economic analysis suggested the use of 50% recommended mineral N (60 kg N ha−1) with PM saves the mineral N fertilizer by almost 50% compared to a system with only mineral N application. In addition, increase in N efficiency, plant nutrition and soil fertility associated with combined treatment would help to minimize the use of high cost synthetic mineral fertilizers and represents an environmentally and agronomically sound management strategy.

This paper presents the main features of a unique decision-support tool developed for selecting tree species in coffee and cocoa agroforestry systems. This tool aims at assisting in the selection of appropriate shade trees taking into account local conditions as well as needs and preferences of smallholder farmers while maximizing ecosystem services from plot to landscape level. This user-friendly and practical tool provides site-specific recommendations on tree species selection via simple graphical displays and is targeted towards extension services and stakeholders directly involved in sustainable agroforestry and adaptation to climate change. The tool is based on a simple protocol to collect local agroforestry knowledge through farmers’ interviews and rankings of tree species with respect to locally perceived key ecosystem services. The data collected are first analysed using the BradleyTerry2 package in R, yielding the ranking scores that are used in the decision-support tool. Originally developed for coffee and cocoa systems of Uganda and Ghana, this tool can be extended to other producing regions of the world as well as to other cropping systems. The tool will be tested to see if repeated assessments show consistent ranking scores, and to see if the use of the tool by extension workers improves their shade tree advice to local farmers.

Breeding for high and stable yields is a major objective for cassava breeding programmes. Owing to the simultaneous formation of steins and leaves (source) and storage roots (sink), competition for assimilates implies that there is an optimum leaf area index for yield. This has led to the use of the harvest index as a practical criterion for selection. The optimal harvest index and leaf area index are discussed for selection for stressful environments. A successful strategy for developing high yielding varieties for favourable conditions is presented. Recent information has shown that selection for a slightly larger than optimal leaf area index, and hence greater biomass, can lead to stable yield in both favourable and stressful environments. Moreover, yield levels can be increased by selecting for moderate harvest indices (e.g. 0.5-0.65) and increased biomass. Longer leaf life is an integral part of this selection strategy. These concepts are discussed in detail.

James H. Cock y Mabrouk A. El-Sharkawy: Caracteristicas fisiológicas para la selección de la mandioca.

The on-farm evaluation of three feeding strategies for smallholder campesino dairy herds was undertaken in the highlands of Central Mexico with cooperating farmers: traditional, alternative and intermediate feeding strategies. All three incorporated grazing of cultivated pastures, but concentrate use was 4.0 and 7.0 kg per cow per day in the rainy and dry seasons respectively for the traditional feeding strategy, 3.3 for the alternative feeding strategy in both rainy and dry seasons and 5.0 and 9.0 kg per cow per day in the rainy and dry seasons respectively for the intermediate feeding strategy. Feeding during the dry season was based on maize straw in the traditional strategy, on pasture complemented with maize silage in the alternative feeding strategy, and with some maize silage but mostly maize straw in the intermediate feeding strategy. The trial ran between 25 September 1996 and 24 September 1997, divided by season into four, thirteen-week periods. Milk yields were recorded once per week, and live weight and body-condition score, every 28 days. Three cows per strategy that completed each period were blocked according to stage of lactation and used for the statistical analysis of a split-plot design with feeding strategies as main plots and weeks as split-plots. Overall mean milk yields were 15.5±2.05, 13.4±2.43 and 12.4±2.37 kg milk per cow per day for alternative, intermediate and traditional feeding strategies respectively, with significant interactions (P<0.05) for autumn, winter and summer. The alternative feeding strategy (with over 50% less concentrate) produced milk yields 0.24 and 0.38 higher than the intermediate and traditional feeding strategies in the dry season. In the rainy season, milk yields with the alternative feeding strategy (30% less concentrates) were 0.09 and 0.16 higher than the other two strategies. Margins per day of family labour were: alternative feeding strategy US$36.48 per day, intermediate feeding strategy US$9.22 per day and the traditional feeding strategy US$9.11 per day, although in the case of the last two there were two family members in charge of the dairy herds. Results demonstrate the successful integration of grazed pasture and maize silage for the efficient production of milk, and provide evidence on the productive use of limited campesino land resources in the face of unviable economic conditions for maize grain production.

Four methods of measuring crop production are reviewed in the context of different survey objectives. A popular technique, crop cutting, tends to overestimate yields and does not produce good estimates of individual plots. For high accuracy, harvest of the whole plot is the best method. If statistics of regional production are required output can be sampled after harvest, or, if the farmer harvests in consistent units, his own estimate can be taken. Limited evidence shows that farmers' estimates may be no more biased than crop cutting, but require fewer resources and supervision. There is no best method. The method used must be chosen for the purpose of the study. Whichever method is chosen a distinction should be made between biological and economic yield and correction must be made for threshing and moisture content.

Field studies were conducted during the 2014 and 2015 wet seasons at Zaria in the northern Guinea savanna and at Iburu in the southern Guinea savanna of Nigeria to determine the productivity of maize–soybean intercropping system. There were four treatment combinations in the experiment: sole maize; sole soybean; maize spaced at 50 cm and intercropped with soybean; and maize spaced at 65 cm and intercropped with soybean. The experiment was laid out in a randomized complete block design with three replications. The results showed that sole cropped maize and soybean generally outperformed the intercropped component crops. Land Equivalent Ratio (LER) was greater than 1 for all the intercrop treatments, indicating that it is advantageous to grow maize and soybean in association than in pure stands. Except for 2014 in Zaria, LER for intercropped maize spaced at 50 cm was higher than that for maize spaced at 65 cm. Gross Monetary Value (GMV) was generally higher for intercrops than sole crops except in Iburu in 2015 where GMV for intercropped maize spaced at 65 cm was similar to those of sole maize and soybean. Monetary Advantage Index (MAI) was positive for all intercrop treatments in both locations and years, which shows definite yield and economic advantages compared to the sole cropping systems. This suggests that farmers can intercrop soybean and maize with maize spaced at 50 cm and 65 cm.

Rainfed wheat is frequently exposed to periods of water stress that generate low and variable grain yields. Field experiments (with studies in Tunisia and Morocco) carried out in the context of a European research project of co-operation with Mediterranean partner countries (WatNitMED) showed that nitrogen (N) fertilization may be a tool to increase productivity of rainfed wheat in Mediterranean environments. However, most farmers in Northern Africa do not fertilize their rainfed cereals. In the present study, we aimed to analyse whether the generally accepted positive yield response to N fertilization in rainfed Mediterranean conditions corresponds to actual advantages achieved in the fields of working farmers, attempting a further up-scaling of knowledge from field experiments to real fields. We attempted to apply research results to Tunisian working farmers’ fields by conducting a farm pilot experiment. The pilot experiment was conducted in two different regions (a low-yielding region and a relatively high-yielding region) of cereal production in Tunisia, where wheat production represents typical rainfed Mediterranean agro-ecosystems in North Africa. First, we compared the yield response to N fertilization against unfertilized conditions (a common situation for many of the farmers in North Africa), and secondly we compared what the farmers suggested as an optimal N fertilization practice in their fields against the WatNitMED's recommendation which was based on an N-fertilization scheme derived from field experiments from the European research project in Mediterranean conditions. The WatNitMED fertilization scheme suggested higher rates of fertilization than those considered optimal by farmers (on average 40 kg N ha−1 higher). Unfertilized grain yield across both locations ranged from about 1 to 3.5 Mg ha−1 (typical of farmers’ yields in the region), and fertilizing increased grain yields in most situations. Within the two alternative fertilization treatments, WatNitMED fertilization produced higher yields than the fertilization rate considered optimal by farmers. This trend was observed at the low-yielding location as well as at the high-yielding location. These responses demonstrated that fertilization in working farmers’ field conditions may be a reliable means of improving dryland wheat grain and straw yields. They also showed that rates of fertilization regarded as optimal by real farmers were below the optimum for these regions.

Straws and stovers are often called ‘by-products’ of grain production even though they are increasingly important, e.g. for animal feed, thatching, soil improvement, mushroom production and industrial use. As a result, plant breeders, agronomists, economists and animal nutritionists have to pay more attention than before to the total value of crops, i.e. whole plant value in which straws and grain both play a part. This paper reviews literature about the technical potential of breeding and/or management for more or better straw. It then discusses issues of the economic value (EV) and nutritional value (NV) of straw and stovers for livestock feed to guide research and development in cereal breeding and management. It is mainly based on experiences from the Indian subcontinent and semi-arid regions of the Near and Middle East. The paper shows that the quantity and quality of straw produced has changed considerably over recent decades as a result of breeding policies, new cultivation patterns and choice of cultivars. Both EV and NV depend on type of grain, animal production system and access to other feeds. A classification of these factors is provided and suggests that the EV of straw is particularly important in low-input systems with stovers from coarse grains.

In a 2 row cereal: 1 row pigeonpea intercropping system, four sorghum and two millet genotypes were examined with four of pigeonpea on a medium-deep Alfisol during 1978 and 1979. The cereals usually produced a large proportion of their sole crop yields. Millets matured relatively early which allowed large yields of later-maturing pigeonpea. A tall millet gave the best total Land Equivalent Ratio (LER) of 1.78 and most monetary returns. Early and/or short sorghums produced large LERs (1.51–1.59) and combinations with an early hybrid also gave good returns. A tall late sorghum gave poor yields of both components, smallest total LER (1.30), and little return. Pigeonpea intercrop yields became larger as the maturity difference between the cereal and pigeonpea increased. A combination of a short, early but large-yielding cereal with a pigeonpea that is as late as possible without incurring undue risk of moisture stress may be ideal.

Seedling growth in the nursery and the magnitude of shock experienced by the seedlings after transplanting can affect subsequent growth and development of transplanted rice (Oryza sativa). These two processes have not been adequately represented by rice growth simulation models. In this study, seedling growth in the nursery was described with respect to endosperm mobilization, dry matter (DM) distribution and seed size. In addition, the transplanting shock process was represented describing the crop development and growth in relation to seedling age at transplanting. These relationships, as two sub-models, were incorporated into CERES-Rice, a rice growth model, and their performances compared with independent field data. The nursery growth sub-model was also evaluated with another model, RIBHAB. Results of the comparison showed that the nursery growth sub-model, either with CERES-Rice or RIBHAB, closely predicted observed seedling growth. On the other hand, CERES-Rice overestimated root and leaf DM and underestimated culm DM, while RIBHAB underestimated all the growth traits considered in the evaluation. Transplanting shock period predicted by the sub-model closely mimicked observation, whereas CERES-Rice highly overestimated it. It is concluded that the developed nursery growth and transplanting shock sub-models can be incorporated into CERES-Rice and other rice growth models for better simulation of those growth processes.