After farmer-to-farmer training, farmers at an upland research site in the Philippines adapted and adopted contour hedgerows over a period of four years. They developed hedgerow establishment methods that required less labour, eliminated grasses that were too competitive with crops, stopped planting trees that were initially intended to produce green manures, and planted species that might provide direct cash returns. The different systems they used controlled soil erosion equally and effectively, although grazing of hedgerows by neighbours’ cattle was a problem. The farmers who learned about the technology but who did not establish contour hedgerows on their farms were those who had a higher proportion of flat land and/or off -farm or non-farm income opportunities.

Changes in seed quality were monitored during seed development and maturation in three genotypes of soyabean (Glycine max), the USA cv. Bossier, the Indonesian line TGm 737p, and their cross TGx 536–02D in a controlled environment of 30°/20°C (day/night temperatures). The capacity of seeds to germinate following desiccation and their potential longevity increased after the end of the seed-filling phase. Potential longevity reached a maximum close to harvest maturity (that is, when seed moisture content had declined naturally to 14–15%). The subsequent decline in potential longevity in all three genotypes was quantitatively similar to that predicted in post-harvest air-dry seed storage in similar environments, but was far less in TGm 737p than in the other two genotypes as a consequence of the lower moisture content of its mature seeds. These findings contradict the previously well-established hypotheses that seed quality in soyabean is maximal at the end of the seed-filling phase and that viability and vigour begin to decline immediately thereafter. They also infer that the desirable seed longevity characteristics of the Indonesian line TGm 737p may not have been successfully incorporated into the cross TGx 536–02D.

Calidad y desarrollo de similla en la soja

The results of research on the water relations and irrigation needs of olive are collated and summarised in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information on the ecology of the olive (it is native to the coastal areas of the eastern Mediterranean) and on crop development processes are presented, followed by reviews of the influence of water stress on gas exchange (stomatal conductance, photosynthesis and transpiration), crop water requirements, water productivities and irrigation systems. The olive has many attributes that help to protect it against drought, including the morphology of the leaf, and the capacity to conserve water under conditions of high evaporative demand through stomatal closure, osmotic regulation and resistance to cavitation. The concept of ‘deficit irrigation’ has been the subject of much research. Although vegetative growth is restricted, there is no convincing evidence that ‘sustained deficit irrigation’ or ‘regulated deficit irrigation’ or ‘partial root zone drying’ offer any advantages over conventional practices. Water productivities are very variable and difficult to reconcile due, in part, to biennial bearing, tree-to-tree variability and differences in tree population densities. Similarly, no clear consensus has emerged on how best to exploit the sensitivity of trunk expansion to water availability in irrigation scheduling. As production methods for this historical crop are intensified (high-density hedgerows, irrigated and mechanized orchards), so will the need to understand the role that water plays in the production processes become ever more critical.

Crop growth rate of oil palm increases with leaf area index (LAI) to about 40 tons/ha./yr at the highest LAIs obtained. Net assimilation rate and dry matter production per palm decrease with increasing LAI, but the amount of dry matter per palm incorporated in vegetative tissues is unaffected by density. As a result the optimal LAI for oil yield is considerably below the critical LAI for maximum crop growth rate.

Results are described of an experiment conducted for 2 years in North-West India where grain legumes increased the N and P status of the soil compared with cereal or fallow. Maize following legumes recorded increases in growth, yield attributes, yield and N uptake. Various winter grain legumes such as chickpea, lentil, pea and Lathyrus sativus reduced the need for fertilizer N in maize to the extent of 18–68 kg/ha compared with cereal (wheat) or fallow. Application of nitrogen to the maize promoted plant growth and increased both yield and N uptake.

The cyanide contents were determined quantitatively of the peeled roots of 108 cassava clones, which had been previously selected as low-cyanide by the picrate leaf-test, and compared with the qualitative picrate leaf-test scores used for rapid screening. The correlation coefficient between root tuber cyanide content (dry weight basis) and leaf-test score was r = 0·36 (P < 0·01). The picrate leaf-test, while useful for screening large numbers of clones in early stages of breeding, needs augmenting by more accurate methods. There was no significant correlation between root cyanide content and dry root yield (r = 0·18). The cyanide content varied considerably between roots of the same plant; and plants of the same cultivar grown under the same conditions. Possible improvements in the effectiveness of the cyanide screening procedure are discussed.

Mineral fertiliser is a scarce input for smallholder maize farmers in Malawi. A recent provision of small amounts of subsidised fertilisers by government programmes to farmers throughout Malawi has increased fertiliser access and raised maize production, but fertiliser management and yield responses frequently remain poor. To seek ways to use the fertiliser more efficiently, we analysed the effects of low rates of N (15 or 30 kg N ha−1) and P (9 kg P ha−1) fertiliser in combination with improved weed management on maize yields in experiments on 12 smallholder farms in Chisepo, central Malawi. Several indices of N and P use efficiency were computed from the above-ground crop components and nutrient contents. Maize yield simulations were conducted using long-term rainfall records in the APSIM crop-soil system model. NP fertiliser significantly (p < 0.001) raised maize grain yield from 0.65 to 1.5 t ha−1, and twice-weeding fertilised maize significantly (p < 0.001) raised maize yields by 0.4 t ha−1 compared with weeding once (0.9 t ha−1). The agronomic efficiency of applied fertiliser N (AEN) averaged 19.3 kg grain kg N−1 with one weeding but doubled to 38.7 kg with the additional weeding. The physiological efficiency of applied N (PEN) was 40.7 kg grain kg−1 N uptake. APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha−1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo. A financial analysis showed that the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded. Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding, although some farmers reported difficulty implementing this recommendation due to competing demands for labour. We conclude that to raise the productivity and sustainability of fertiliser support programmes in Malawi, initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems.

An experiment is described in which the productivity of maize–bean and maize–potato mixtures in alternate rows was compared with pure stands of the component species in four cropping seasons. In seasons with low rainfall, yield from the mixtures fell short of that from pure stands, but in one exceptionally wet season a yield advantage was found for maize–bean mixtures. The poor performance of mixtures in low rainfall seasons appeared to result from large reductions in maize yield attributable to competition from the potato or bean. In the one high-rainfall season, no such reduction in maize yield occurred. An implication of these findings for farming systems with mixed cropping is discussed.

The results of research on the water relations and irrigation need of avocado are collated and reviewed in an attempt to link fundamental studies on crop physiology to irrigation practices. Background information is given on the centre of origin (Mexico and Central America) and the three distinct ecological areas where avocados are grown commercially: (1) Cool, semi-arid climates with winter-dominant rainfall (e.g. Southern California, Chile, Israel); (2) Humid, subtropical climates with summer-dominant rainfall (e.g. eastern Australia, Mexico, South Africa); and (3) Tropical or semi-tropical climates also with summer-dominant rainfall (e.g. Brazil, Florida and Indonesia). Most of the research reported has been done in Australia, California, Israel and South Africa. There are three ecological races that are given varietal status within the species: Persea americana var. drymifolia (Mexican race), P. americana var. guatemalensis (Guatemalan race) and P. americana var. americana (Antillean, West Indian or Lowland race). Interracial crossing has taken place. This paper summarises the effects of water deficits on the development processes of the crop and then reviews plant–water relations, crop water requirements, water productivity and irrigation systems. Shoot growth in mature trees is synchronised into flushes. Flower initiation occurs in the autumn, with flowering in late winter and spring. Flowers form on the ends of the branches. A large heavily flowering tree may have over a million flowers, but only produce 200–300 fruits. Fruit load adjustment occurs by shedding during the first three to four weeks after fruit set and again in early summer. Water deficits during critical stages of fruit ontogeny have been linked to fruit disorders such as ring-neck. Reproductive growth is very resistant to water stress (compared with vegetative growth). Avocado is conventionally considered to be shallow rooted, although roots extend to depths greater than 1.5 m. The majority of feeder roots are found in the top 0.60 m of soil and root extension can continue throughout the year. Leaves develop a waxy cuticle on both surfaces, which is interrupted by stomata on the abaxial surface (350–510 mm−2), many of which are blocked by wax. Stomata are also present on the sepals and petals at low densities (and on young fruit). During flowering, the canopy surface area available for water loss is considerably increased. Stomatal closure is an early indicator of water stress, which together with associated changes in leaf anatomy, restricts CO2 diffusion. There have only been a few attempts to measure the actual water use of avocado trees. In Mediterranean-type climates, peak rates of water use (in summer) appear to be between 3 and 5 mm d−1. For mature trees, the crop coefficient (Kc) is usually within the range 0.4–0.6. The best estimate of water productivity is between 1 and 2 kg fruit m−3. Soil flooding and the resultant reduction in oxygen level can damage roots even in the absence of root rot. Avocado is particularly sensitive to salinity, notably that caused by chloride ions. Rootstocks vary in their sensitivity. Both drip and under-tree microsprinklers have been/are successfully used to irrigate avocado trees. Mulching of young trees is a recommended water conservation measure and has other benefits. A large proportion of the research reviewed has been published in the ‘grey’ literature as conference papers and annual reports. Sometimes, this is at the expense of reporting the science on which the recommendations are based in peer-reviewed papers. The pressures on irrigators to improve water productivity are considered.

Physiomorphological differences between crops in binary mixtures can influence grain yield. A two year field study considered intra-row mixtures of two sorghum varieties, one short (KSV4) and one tall (Yarwasha), with cowpea at Maiduguri in Nigeria. The performance of the component crops depended largely on the relative proportion of cowpea and sorghum in the mixtures. Comparison of actual and expected land equivalent ratios suggested that mutual compensation and cooperation prevailed within mixtures in most instances. The system productivity index of mixtures where the proportion of sorghum: cowpea was 1:3 showed that their yield stability was greater than that of other sorghum-cowpea mixtures.

Combination de sorgol caupi en la Sabana del Sudan

In general, olive trees are self-compatible, but under some climatic conditions a number of cultivars have demonstrated problems with pollination and fruit set. The Manzanillo cultivar is usually self-pollinating, but under hot conditions its pollen develops slowly, resulting in little or no fertilization. Trials were carried out in two hot, arid ecosystems (Arid Chaco in La Rioja, Argentina and Sonoran Desert in Arizona, USA) to determine if supplemental pollination of a Manzanillo cultivar has the potential to increase yields, and to assess the effectiveness of three different cultivars as sources of pollen. Branches that received supplemental pollination produced 21% more total olives than the control. In Arizona, total olive and shotberry (unpollinated olive) production were significantly different between treatments. Branches that received supplemental pollination produced 98% more olives, and had 58% fewer shotberries than did branches in the control rows. Significantly more olives were produced on branches pollinated with Sevillano and Arbequina pollen, compared with those pollinated with Ascolano pollen and with the control.

Soil Organic Carbon (SOC) is a major indicator of soil fertility in the tropics and underlies variability in crop response to mineral fertilizers. Critical SOC concentrations that interact positively with N fertilizer for optimal crop yield are less understood. A study was conducted on a Ferralsol in sub-humid Uganda to explore the critical range of SOC concentrations and associated fractions for optimal maize (Zea mays L.) yield response to applied mineral N fertiliser. Maize grain yield response to N rates applied at 0, 25, 50 and 100 kg N ha−1 in 30 fields of low fertility (SOC < 1.2%), medium fertility (SOC = 1.2–1.7%) and high fertility (SOC > 1.7%) was assessed. Soil was physically fractionated into sand-sized (63–2000 µm), silt-sized (2–63 µm) and clay-sized (<2 µm) particles and SOC content determined. Low fertility fields (<1.2% SOC) resulted in the lowest response to N application. Fields with >1.2% SOC registered the highest agronomic efficiency (AE) and grain yield. Non-linear regression models predicted critical SOC for optimal yields to be 2.204% at the 50 kg N ha−1 rate. Overall, models predicted 1.9–2.2% SOC as the critical concentration range for high yields. The critical range of SOC concentrations corresponded to 3.5–5.0 g kg−1 sand-sized C and 9–11 g kg−1 for clay-sized C.

The relation between soil mechanical impedance as a result of soil drying, and root system growth (mass and length density) of rice was investigated in greenhouse and field studies. In a greenhouse experiment, soil drying for 16 days increased mechanical impedance in the 0–20 cm soil layer from near 0 to 2.5 MPa, and decreased root growth by 47% compared to the continuously flooded control. Root length density decreased with decreasing soil moisture and increasing soil mechanical impedance. In a lowland field experiment using a sprinkler irrigation gradient treatment for 19 days during the vegetative growth stage, soil mechanical impedance as low as 0.01 MPa inhibited root growth while values greater than 0.3–0.5 MPa decreased root growth and extension by 75%. The relative loss of potential root growth was continued after reflooding. Root length density, measured at flowering, was linearly related to yield.

Accurate crop varietal identification is the backbone of any high-quality assessment of outcomes and impacts. Sweetpotato (Ipomoea batatas) varieties have important nutritional differences, and there is a strong interest to identify nutritionally superior varieties for dissemination. In agricultural household surveys, such information is often collected based on the farmer's self-report. In this article, we present the results of a data capture experiment on sweet potato varietal identification in southern Ethiopia. Three household-based methods of identifying varietal adoption are tested against the benchmark of DNA fingerprinting: (A) Elicitation from farmers with basic questions for the most widely planted variety; (B) Farmer elicitation on five sweet potato phenotypic attributes by showing a visual-aid protocol; and (C) Enumerator recording observations on five sweet potato phenotypic attributes using a visual-aid protocol and visiting the field. In total, 20% of farmers identified a variety as improved when in fact it was local and 19% identified a variety as local when it was in fact improved. The variety names given by farmers delivered inconsistent and inaccurate varietal identities. Visual-aid protocols employed in methods B and C were better than those in method A, but greatly underestimated the adoption estimates given by the DNA fingerprinting method. Our results suggest that estimating the adoption of improved varieties with methods based on farmer self-reports is questionable and point towards a wider use of DNA fingerprinting in adoption and impact assessments.

Intercropping cereals with legumes for forage or food production is extensively used as a cropping practice in many parts of the world. A 2-year field study was conducted using common vetch (Vicia sativa), winter wheat (Triticum aestivum), triticale (× Triticosecale), barley (Hordeum vulgare) and oat (Avena sativa) sole crops as well as common vetch intercrops with each of these cereals in a 35:65 cereal:common vetch ratio based on seed numbers, to determine their ability to compete with sterile oat (Avena sterilis spp. sterilis). At nine weeks after planting, fewer sterile oat plants emerged in common vetch sole crop than in cereal sole crops. Intercropping of cereals with common vetch generally did not affect sterile oat stem number and biomass compared with cereal sole crops. At harvest, cereal sole crops provided greater total dry biomass (DB) than the common vetch sole crop. However, triticale and oat produced more DB than winter wheat and barley. In most cases intercropping reduced total DB compared with cereal sole crops. The results of this study indicated that intercropping of the four winter cereals with common vetch did not provide any significant competitive advantage against sterile oat. However, common vetch sole crop showed the greatest suppressive ability against sterile oat among the sole crops or intercrops studied.

Oil palm has become an important source of revenue for smallholders in Indonesia, but productivity of smallholder plantations is generally poor. Nutrient limitations have been suggested as an important agronomic constraint to yield. Our research aimed to quantify fertiliser use, soil and tissue nutrient status, and palm growth and yield in a sample of independent smallholder plantations. We selected 49 plantations in Indonesia in two provinces with contrasting soils. For all plantations, we obtained self-reported fertiliser use and yield data, collected soil and tissue samples, and analysed vegetative growth. More than 170 kg N ha−1 year−1 was applied in one site, and P was applied in excess of recommended quantities in both sites, but on average farmers applied less than 100 kg K ha−1 year−1. Soils in the palm circle were poor in N, P and K in 29, 40 and 82% of the plantations, and deficiencies were measured in 57, 61 and 80% of the leaflet samples, respectively. We found statistically significant correlations between tissue nutrient concentrations and vegetative growth, but a large part of the variation in the data remained unaccounted for. Single leaf area was reduced in >80% of the plantations. Average yields were estimated to be 50‒70% of the water-limited potential. Our results demonstrate that widespread nutrient imbalances and deficiencies, especially potassium and phosphorus, occur in smallholder oil palm plantations, due to inadequate and unbalanced fertiliser application practices. These deficiencies may be an important underlying cause of the overall poor productivity, which threatens the economic and environmental sustainability of the smallholder sector.

Thirty one soils from the Savanna Zone of Nigeria were low in exchangeable potassium, ΔK°, and ΔK°° and had very low potassium buffer capacities. The soils were low in clay, which was kaolinitic. Two soils high in 2:1 layer clay minerals contained higher quantities of labile potassium. Total potassium varied with parent material. Release of non-exchangeable potassium was low. After cropping, wet/dry cycles released exchangeable potassium. Potassium deficiency is expected to occur commonly with intensive cropping in the field.

In this study, we compared the weed emergence, water input, water saving, water productivity, panicle sterility, yield outputs and economic returns of transplanting with alternate wetting and drying (TRAWD) and dry direct seeding (DSR) with transplanting under continuous flooding (TRCF) using three fine-grain rice cultivars: Super Basmati; Basmati 2000; and Shaheen Basmati. Higher weed infestation was recorded in DSR than in TRCF and TRAWD. Raising rice as TRAWD and DSR had considerable water savings but a lower grain yield than TRCF. High panicle sterility was primarily responsible for low grain yield in TRAWD and DSR systems. Nonetheless, water productivity was better in DSR and TRAWD than TRCF. Shaheen Basmati in the DSR system and Basmati 2000 in TRCF fetched the highest economic returns during 2008 and 2009, respectively. In conclusion, fine-grain rice cultivars can be grown in water-saving production systems (e.g. TRAWD and DSR); however, these water-saving production systems might incur a yield penalty.

Experiments were made in glasshouses, growth cabinets and growth rooms to study the differential responses of the broad bean to water stress during the vegetative and flowering phases of growth. Plants in the flowering phase proved to be more sensitive to drought than in the vegetative period, and there were different responses (Relative Growth Rate) to temperature at different stages of plant growth. Day length and temperature influenced the position of the earliest flower initials on the stem, and intensity of flower shedding was aggravated by high temperature.

Pearl millet was grown on stored water at Niamey, Niger, using three row spacings. Water extraction based on neutron probe readings was compared with crop transpiration using a porometer and allied measurements. Between 23 and 52 days after sowing, plants at the narrow and medium spacings used about 77 and 100 mm of water, respectively, and those at the wide spacing used between 59 and 75 mm. Estimates of seasonal crop evaporation from leaf resistances and from the green leaf area index (GLAI) of the crops were 103, 130 and 123 mm for the narrow, medium and wide spacings, respectively. The water use per unit of dry weight produced was similar for both narrow and medium spacings but water was used more efficiently in the wide spacing. Dry weight increased in proportion to intercepted radiation with the same efficiency (1·3 g MJ−1) irrespective of spacing.