Seed-oriented planting provides a manner to influence canopy structure. The purpose of this research was to improve maize light interception using seed-oriented planting to manipulate leaf azimuth across the row thereby minimizing leaf overlap. To achieve leaf azimuths oriented preferentially across the row, seeds were planted: (i) upright with caryopsis pointed down, parallel to the row (upright); and (ii) laying flat, embryo up, perpendicular to the row (flat). These treatments were compared to conventionally planted seeds with resulting random leaf azimuth distribution. Seed orientation effects were contrasted with three levels of plant population and two levels of hybrid specific canopy structures. Increased plant population resulted in greater light interception but yield tended to decrease as plant population increased. The planophile hybrid produced consistently greater yields than the erectophile hybrid. The difference between planophile and erectophile hybrids ranged from 283 to 903 kg ha−1. Overall, mean grain yield for upright and flat seed placement increased by 351 and 463 kg ha−1 compared to random seed placement. Greater cumulative intercepted photosynthetically active radiation (CIPAR) was found for oriented seeds rather than random-oriented seeds. At physiological maturity upright, flat and random-oriented seeds intercepted 555, 525 and 521 MJ m−2 of PAR, respectively. Maize yield responded positively to improved light interception and better radiation use efficiency. Under irrigated conditions, precision planting of maize increased yield by 9 to 14% compared to random-oriented seeds.

Grain sorghum [Sorghum bicolor (L.) Moench] is the major cereal crop used as staple crop in the arid and semi-arid regions of Ethiopia. Low sorghum yields are attributed to soil, climate and topographic factors. We investigated sorghum yield response to factorial combination of nitrogen and phosphorous (NP) as well as potassium (K), sulphur (S) and zinc (Zn), and how the position of farmers’ fields belonging to different landscape positions (i.e., upslope, mid-slope, and foot slope) could explain fertilizer response and yield variability. The analysis in this study made use of dataset from two sets of on-farm experiments where trials were set at two farmers’ fields for NPKS and three farmers’ fields for NPZn experiments in each landscape position. The experiments were implemented at two sorghum-growing locations (i.e., Hayk and Sirinka) in parts of the north-eastern Amhara region in Ethiopia. Sorghum yield response to fertilizer application was strongly linked to the spatial variation along landscape positions and varied over locations. Fertilizer response was significantly higher at foot slopes compared to mid-slopes and upslope positions, where fields at foot slopes exhibited relatively homogeneous responses. Application of combined nitrogen (N) and phosphorus (P) fertilizers, landscape position and the interaction of fertilizer application and landscape positions strongly affected sorghum yield. There was a linear and significant increase in sorghum yield with the increase in the NP rates. The combined application of NP with different levels of KS as well as NP with Zn fertilizer rates did not result in significant yield difference. The results indicated that local factors were much more influential when accounting for the heterogeneity in sorghum yield response to fertilizer. This further acknowledges the importance of a landscape-based fertilizer management approach to respond yield potential variability related with the farmers’ fields and landscape environment. Further investigation is needed to develop homogeneous fertilizer response units based on spatial variability of soil and topographic attributes along the landscape.

A technique for observing the effects of soil physical and other factors on root growth was evaluated, using glass tubes packed with soil. The number of root intersections observed on a grid at the interface between the soil and glass was correlated with the number of root ends counted within the soil core. Comparatively small differences in the dry bulk density of a structureless sandy loam (1.25 and 1.50 g cm−3) had much larger effects than differential watering treatments on the pattern of root growth of lettuces (Lactuca sativa). Loosening the soil to depth (with additional fertilizer) increased the availability of water, under both wet and dry conditions, and improved water use efficiency, primarily through effects on root activity.

Growth variability in pearl millet (Pennisetum glaucum) over short distances is a severe constraint on the interpretation of agricultural experiments in the West African Sahel. The purpose of this study, therefore, was to compare different non-destructive methods to estimate, spatially, millet growth and final yields. Aerial photography, georeferenced radiometric measurements and a chlorophyll meter were tested during three rainy seasons in a nitrogen rate×density×genotype experiment in western Niger. For the radiometric measurements, normalized difference vegetation indices (NDVI) obtained and calibrated for individual millet hills spaced 1.5 m apart were aggregated for the entire experiment with 6000 samples per hectare. A simple calibration procedure was used to correct for variation in soil background reflectance and incident light. For NDVI measurements of individual planting hills, the correlation between plant total dry matter (TDM), leaf weight, leaf area and NDVI was high (r2 = 0.89–0.91) and regression parameters were genotype-specific. Aggregated georeferenced NDVI measurements at the plot level correlated with grain and TDM at harvest (r2 = 0.40–0.87). The analysis of true-colour and infrared aerial photographs permitted the monitoring of millet growth and the quantitative evaluation of treatment responses throughout the growing season. The infrared images were the most efficient in the detection of vegetation followed by the normalized green band of true-colour images. The red band was the least effective because of the influence of soil albedo and image vignetting. Although chlorophyll meter measurements reflected relative differences in plant nitrogen status between treatments, their interpretation required destructive sampling and proved unsuitable to predict millet yields. The results demonstrate the potential of georeferenced radiometric data and aerial photographs to improve soil sampling strategies, sequential plant growth monitoring and the statistical design and analysis of experiments. By providing intermediate data sets, the tested tools can also help in the upscaling of ground truth to satellite data in yield prediction studies.

Cassava, a crop widely adapted in the tropics, has the important attribute of withstanding adverse environmental conditions better than do many other staple crops. The performance of an individual genotype, however, is influenced by the environment in which it grows. In Malawi, the heterogeneity of agro-ecologies requires the cumbersome and costly assessment of new cassava genotypes at many sites. This study was conducted, therefore, to test the feasibility of selecting only a few locations for cassava evaluation that would be representative of all the agro-ecologies in which cassava is grown in Malawi. Enormous environmental effects, largely contributed by the interaction between season and location, were manifested. Genotype×environment interaction, due largely to a third level interaction (genotype×season×location), was highly significant for all the traits studied. A principal component analysis scatter plot showed no particular grouping of environments, but a pair-wise comparison showed that some of the locations had limited genotype×environment interaction, indicating that it would be sufficient to use one of these sites for evaluating these traits. The value of the residual was often large, probably as an effect of environmental heterogeneity in the test sites. The authors conclude that cassava genetic improvement will continue to be slow if Malawi is used as a single breeding zone. They recommend a much finer grouping of the locations and the use of smaller plot sizes to allow more clones to be tested at more sites for the same cost. Locations may be selected for intensive cassava breeding work from those that give the best discrimination between genotypes while having insignificant genotype×environment interactions in a relatively large number of environments.

Objectives of different intercrop experiments need to be kept in view while analysing the data from them. There is no single straightforward way of analysing the data and certain situations require innovative approaches. Types of situations that are encountered in dryland agricultural research are exemplified and methods of meaningful analysis and interpretation of data from them are indicated here. Agronomically-sound meanings are imputed for different ways of calculating LER. Use of the concept ‘Staple Land Equivalent Ratio’ for assessing intercrop systems in particular situations is illustrated.

A field experiment was conducted in 2002/03 (year 1) and repeated in 2003/04 (year 2) to study the competitive ability of 10 winter barley (Hordeum vulgare) cultivars against common poppy (Papaver rhoeas) and ivy-leaved speedwell (Veronica hederifolia). The phytotoxic (or allelopathic) activity of barley extracts was also determined in the laboratory using a perlite-based bioassay with barnyard grass (Echinochloa crus-galli). In the field, biomass of both weeds was reduced more (65–79%) by the competition of Alpha, Esterel, Terova or Lignee 640 barley cultivars, than with Aspen or Tersey. Biomass of ivy-leaved speedwell in competition with each barley cultivar was significantly lower than that of common poppy. In year 1, the six-row barley cultivars caused greater weed biomass reduction than the two-row, but this was not the case in year 2. Grain yield of Tersey, Aspen and Goldmarker cultivars in herbicide treatments was greater by 41, 33 and 17%, respectively, than from the corresponding herbicide untreated plots. However, grain yield of Terova, Alpha, Esterel and Lignee 640 was not significantly affected by the presence of weeds. In the laboratory, barley extracts affected the total fresh weight or root length of barnyard grass more than its germination. The germination, root length or total fresh weight inhibition on barnyard grass caused by the two six-row barley extracts was greater (43, 48 and 56%, respectively) than that caused by the eight two-row extracts (22, 34 and 43%, respectively). The results of this study indicated that barley cultivars with great competitive and/or phytotoxic ability could be used in sustainable cereal production systems in order to minimize herbicide usage.

Biomass burning has links with a number of global concerns including soil health, food security and climate change. In central Côte d'Ivoire (West Africa), we conducted a field study to compare nutrient losses, soil fertility and yam yield in slash-and-burn versus slash-and-mulch agriculture. Trials involved five sites established in the dominant Chromolaena odorata fallows of the region, each consisting of paired plots: slash and burnt biomass (SB) versus slashed and unburnt biomass, but left to serve as mulch (SM). Carbon and five elemental nutrients were assessed in the aboveground biomass prior to burning and in ash after fires; losses were assessed by subtraction. The greatest proportions of loss occurred with C (95%), N (95%) and K (74%), corresponding to losses into the atmosphere of 3532 ± 408, 200 ± 36, 132 ± 36 kg ha−1. Six weeks after the fire, soil properties were assessed: soil organic C, total N and Mg2+ were higher in SM than in SB sites. At final harvest, yam tuber yield was twice as large in SM as in SB (18 ± 4 vs. 9 ± 2 Mg ha−1) with soil C, total N and K+ as the main influential soil parameters. The key finding was that the elements lost in greatest proportion during burning were those mostly influencing yam yields. Because a clear negative relationship between biomass burning and yam production has been established the promotion of the more productive, alternate slash-and-mulch system compared to slash-and-burn system, is warranted. The findings of our research can be used in support of developing a sustainable yam production system in the region and in West Africa more generally.

The present study is to characterise the non-structural carbohydrate (NSC) status and its catabolism along with elongation growth in rice cultivars either possessing or not possessing the Sub 1 quantitative trait locus (QTL), i.e. Swarna and Swarna Sub1 exposed to seven days of complete submergence. During submergence, Swarna accelerated the rate of stem and leaf elongation and rapidly consumed NSC. In contrast, Swarna Sub1 consumed energy resources more slowly and maintained similar growth rate to that of non-submerged plants. Swarna Sub1 showed better utilisation of carbohydrate than that of Swarna by progressive induction of alcohol dehydrogenase, starch phosphorylase and total and α-amylase enzyme activity during submergence. Overall, submergence tolerance conferred by the Swarna Sub1 QTL is correlated with better maintenance and utilisation of NSC than that of Swarna.

Maize (Zea mays) seed orientation at planting can influence emerging leaf angle. If leaf angle were consistent among plants without leaf overlap, large numbers of these bilaterally symmetrical plants could be arranged to optimize light interception and possibly increase grain yields or maintain grain yield with a lower population. The objectives were to evaluate the effect of seed orientation in soil on the angle of maize leaves relative to the planted row and on emergence rate. Seeds were planted 2.5 cm deep in diverse combinations of flat, cotyledon down, cotyledon up, on their side, radicle up and radicle down. Each seed orientation was repeated 10 times. Data on days to emergence and leaf angle were collected. In three experiments, maize seeds planted flat with the cotyledon up resulted in homogenous and faster emergence, and maize leaves aligned perpendicular to the direction of the maize row. Similar results were achieved with maize seeds planted parallel to the row with the radicle down. Random placement of maize seeds resulted in random orientation of maize leaves and lower emergence rates. The effects of controlled leaf geometry could facilitate planting higher populations with the potential for increasing grain yield and/or allow the maintenance of grain yields while reducing seed rates.

This study identified decision variables influencing fertilizer adoption and optimal fertilizer rates among smallholder farmers in the Ethiopian highlands. The fertilizer adoption and fertilizer use were examined in four regional states using a questionnaire survey, which was administered to 2880 farm households. A double hurdle model was used to analyze factors influencing the two independent decisions of adoption of fertilizers and use of fertilizers. The model estimates of the first hurdle revealed that the probability of fertilizer adoption increased by 1.2% as household education status improved, by 1.4% for an increased number of active family members, by 5.6% with improved access to credit, by 3.4% with cooperative membership, by 3.3% with an increase in farm size, by 4.6% when soil and water conservation practices are employed, and by 3.4% when agroecology of the farm is located in the medium to highland zone. Conversely, the probability of fertilizer adoption reduced by 0.9% for an increase in family size, 0.6% with 1 km distance from all-weather road, 1.6% for a kilometer further to farm plots, and 0.9% for an increase in number of parcels. The intensity of use of fertilizers was influenced by education status of the household head, family size, access to credit, membership to cooperatives, use of crop rotation, annual income, number of farm plots owned, use of soil and water conservation, and agroecology. Therefore, a concerted effort is needed to encourage fertilizer adoption and optimum fertilizer use intensity by improving households’ resource endowment, institutional capacity to deliver services, and infrastructure development.

Seedlings of 48 genotypes of barley were grown in a glasshouse in different rooting media to determine the possible range of variation in root and shoot systems. Plants grown in nutrient solution produced shoots which were larger than those grown in sand and perlite, but in sand and perlite almost twice as much root length was produced per unit of shoot area. There were large differences between genotypes in both root and shoot growth.

The effects of growing medium on rooting were studied in more detail on six of the genotypes. Plants grown in soil and nutrient solution had longer lateral roots than those grown in sand and perlite. Genotypic variation in growth was large but the range of root and shoot growth in a particular medium was similar. Generally, the ranking of the genotypes was similar in both studies and in all media.

The combined effect of soil moisture stress in the root zone and atmospheric evaporative demand on the growth and yield of two chickpea cultivars was investigated using four sowing dates and three irrigation regimes within each sowing date during the 1980–81 and 1981–82 seasons at the ICRISAT research centre. Total water use was different for different irrigation regimes and sowing dates and there were differences in the total dry weight and seed yield of chickpea between the sowing dates and the irrigation regimes. The cultivars did not differ in dry matter production. However, cv. Annigeri yielded more than cv. L-550 under all irrigation regimes. Differences in seed weight were observed between irrigation regimes and sowing dates and there were interactions between sowing dates and cultivars and between irrigation regimes, sowing dates and cultivars. High air temperatures during the period from flowering to maturity reduced the time to maturity of late-sown chickpea and led to reduced seed size and lower yields. The efficiency of use of applied water was also low for the late-sown crop.

Availability of soil water was investigated and the methods of determining the lower limit of availability by biotic and standard 15-bar pressure were compared. Greenhouse-grown sunflower and okra were the test crops for the biotic method. The pressure membrane equipment was used for standard 15-bar moisture determination. Okra and sunflower took up water beyond the standard 15-bar tension, thus lowering the moisture content at moderate wilting below the generally accepted values. In topsoil okra wilted at very high tensions, but at somewhat lower tensions in subsoil samples, unlike sunflower which wilted at higher tensions in subsoil samples. An equation is given which may be used to estimate the moisture content at the moderate wilting point of plants with known wilting tensions.

Turkish (Origanum onites L.) and Greek oregano (Origanum vulgare L., ssp. hirtum (Link.) Ietswaart) species were investigated to determine herbage colour, essential oil content and composition changes due to sage leafhopper (Eupteryx melissae) (Hemiptera: Cicadellidae) infestation. Sage leafhopper population on both Turkish and Greek oregano did not significantly vary. The sage leafhopper damage was more severe in the lower part of the canopy than the middle and upper parts. Extensive sage leafhopper feeding dramatically reduced essential oil contents, resulting in 28.8 and 34.8% reductions for Greek and Turkish oregano, respectively. Carvacrol, the major essential oil component of both oregano species, did not remarkably vary between leafhopper infested and non-infested plants. With respect to herbage colour, the brightness, redness and yellowness values were significantly different between infested and non-infested plants. Sage leafhopper damage increased brightness and yellowness but decreased greenness of the oregano herbage. To avoid the feeding damage, it is essential to detect the sage leafhopper problem as early as possible and certain control practices are necessary when the infestation is high.

The effects of ten rootstocks on tree development, leaf nutrient levels, fruit internal quality and yield were studied. Plantings of the mandarin cultivar ‘clementine’ were established at the Agricultural Research Station of Rhodes on the rootstocks Cleopatra mandarin, Troyer and Carrizo citranges, rough lemon, Palestine sweet lime, Volkameriana, Citrus macrophylla, Rangpur lime and C. moi with sour orange as a standard for comparison. Data indicated that rootstocks significantly influenced tree development and fruit quality characteristics as well as foliar nutrient concentrations. The largest trees were on Volkameriana and the smallest on the two citranges. In terms of trunk cross-sectional area, the most vigorous trees were on C. moi and the least on Palestine sweet lime and the two citranges. Cleopatra mandarin, the two citranges, and Palestine sweet lime showed a tendency to biennial bearing. The highest cumulative yield of clementine trees was on C. macrophylla and Volkameriana and the lowest on Troyer and Carrizo citrange. C. macrophylla and Volkameriana produced the most efficient trees with the largest and heaviest thin-skinned almost seedless fruit. Fruit on C. macrophylla produced the highest juice content but also the lowest concentration of total soluble solids. Differences were observed in leaf nutrient contents between the rootstocks. These trials showed that C. macrophylla and Volkameriana could be used successfully as alternatives rootstocks to sour orange.

Farming systems in the wetter tropics may be divided into three simplified models: the irrigated paddy-rice multistorey homestead garden complex of Asia, the tree and cash crop plantations of Latin America, and the mixed root crop-bush fallow systems of Africa. In upland ecosystems, sustainable farming systems development rests on a delicate balance between conservation and utilization. To meet the basic food and nutritional needs of the indigenous population, there is great potential for the improvement and adaptation of multistorey homestead gardens and mixed systems which include trees and annual and perennial crops. The principle and practice of ‘alley cropping’ provide an ecologically sound basis for future farming systems research and development in the region.

A study was conducted in the humid-forest, forest-savanna, and Guinea savanna zones of West Africa from 1993 to 1999 to examine the effect of managing crop residues from cereal–legume cropping systems for mulch and fodder for sheep. Increasing the proportion of total crop residues produced from a unit area of land and used as mulch increased maize grain yield, soil organic carbon, nitrogen and available phosphorus. The extra increases obtained when more than half the crop residues were applied as mulch were relatively small, however, suggesting that 25–50% of the crop residues could be removed as feed without any detrimental effect. When any crop residues rejected by sheep were mixed with livestock urine and faeces and returned to the respective fields from where the crop residues had been removed, subsequent grain yield and soil organic carbon, nitrogen, and available phosphorus increased. The study demonstrated the possibility of managing crop residues for increased productivity in smallholder mixed crop–livestock systems.

Bambara groundnut (Vigna subterranea) is a grain legume crop, which is increasingly popular as food in rural areas across the African continent. However, reliable information pertaining to management of the crop is limited. Field experiments were conducted in Swaziland in the 1998/99 and 1999/2000 cropping seasons to determine the influence of sowing date and environmental factors on the growth, development and yield of bambara groundnut. In the 1998/99 season, seeds of one local landrace were sown on six dates between mid-September 1998 and mid-February 1999. In 1999/2000, seeds of two local landraces were sown on six dates between mid-October 1999 and late January 2000. The highest pod yield and total dry matter production were achieved in November sowings, with maximum pod yields of 1.3 and 0.64 t ha−1 for the 1998/99 and 1999/2000 seasons, respectively. Earlier sowing and successive delays in sowing from November caused substantial yield declines of as much as 72–75%. Sowing date influenced yields of bambara groundnut through the effect of temperature and daylength on plant development. For the landraces used in the study, while the rate of progress from sowing to flowering was influenced by temperature, the rate of progress from flowering to podding was influenced largely by daylength. The practical implications of the results for increased bambara groundnut production are discussed.

Conservation agriculture (CA) has been promoted as a strategy to cope with deterioration in soil fertility, but its adoption on smallholder farms in tropical areas remains limited. In Madagascar, livestock production is facing shortages in forage especially during the dry season. The value of cover crops used in CA as livestock feed could be an incentive to make this form of agriculture more acceptable in rural areas. To do so, farmers must find a trade-off between the use of biomass from cover crops for animal production and its maintenance on the soil to meet CA's criteria. In this study, we evaluated the impact of biomass flows (cover crops and manure) between cropping and cattle production in crop–livestock farms in the Lake Alaotra region. Surveys among crop–livestock farmers were used to calculate feed concentrate and mineral fertilizer equivalents. Our results show that on average 42, 22 and 10% of biomass production (dry matter basis) of Brachiaria spp., Stylosanthes guianensis and Vicia villosa, respectively, are used for livestock feeding. The economic benefit in feed concentrate equivalent is between €73 and €723/year per farm. The use of manure contributes, just as CA, to improve soil fertility without using external fertilizing resources. The economic benefit in mineral fertilizer equivalent is between €116 and €2365/year per farm. The integration of CA and livestock production shows, beyond the agronomic advantages, an obvious economic benefit, which is essential to secure the Malagasy agricultural systems. Moreover, this economic benefit is another argument for the dissemination of CA practices in rural areas.