West Asia-North Africa Research Articles

A Multi-Model Based Stability Analysis Employing Multi-Environmental Trials (METs) Data for Discerning Heat Tolerance in Chickpea (Cicer arietinum L.) Landraces.

Identifying a congenially targeted production environment and understanding the effects of genotype by environmental interactions on the adaption of chickpea genotypes is essential for achieving an optimal yield stability. Different models like additive main effect and multiplicative interactions (AMMI 1, AMM2), weighted average absolute scores of BLUPs (WAASB), and genotype plus genotype-environment (GGE) interactions were used to understand their suitability in the precise estimation of variance and their interaction. Our experiment used genotypes that represent the West Asia-North Africa (WANA) region. This trial involved two different sowing dates, two distinct seasons, and three different locations, resulting in a total of 12 environments. Genotype IG 5871(G1) showed a lower heat susceptibility index (HSI) across environments under study. The first four interactions principal component axis (IPCA) explain 93.2% of variations with significant genotype-environment interactions. Considering the AMMI stability value (ASV), the genotypes IG5862(G7), IG5861(G6), ILC239(G40), IG6002(G26), and ILC1932(G39), showing ASV scores of 1.66, 1.80, 2.20, 2.60, and 2.84, respectively, were ranked as the most stable and are comparable to the weighted average absolute scores of BLUPs (WAASB) ranking of genotypes. The which-won-where pattern of genotype plus genotype-environment (GGE) interactions suggested that the target environment consists of one mega environment. IG5866(G10), IG5865(G9), IG5884(G14), and IG5862(G7) displayed higher stability, as they were nearer to the origin. The genotypes that exhibited a superior performance in the tested environments can serve as ideal parental lines for heat-stress tolerance breeding programs. The weighted average absolute scores of BLUPs (WAASB) serve as an ideal tool to discern the variations and identify the stable genotype among all methods.

On Academic Research, Legitimacy, and Fieldwork in Times of Crisis

In thinking through the stark differences in how a research project in Lebanon was received in 2018 versus 2020, this paper seeks to reflect on the fragile relationship between academic researcher and community, on the legitimacy of research in moments of crisis, and on the complexity of pursuing decolonial research in the contemporary West Asia North Africa region.

Soil fertility, crop nutrition, and cropping systems: Research for Mediterranean dryland agriculture

AbstractThe mission of the Consortium on Global International Agricultural Research (CGIAR) is to reduce poverty and enhance food, water, nutritional security, and environmental health in the face of global challenges, including climate change. It operates worldwide through a network of 15 international research centers. One of these institutions, The International Center for Agricultural Research in the Dry Areas (ICARDA) has focused on dryland agriculture in the Mediterranean region, specifically in West Asia–North Africa (WANA). Soil fertility, agronomy, and crop nutrition were key areas of its research program. This mini review highlights the research achievements at ICARDA with respect to nitrogen, phosphorus, micronutrients, nutrient dynamics, fertilizer use, soil testing, sustainable cropping and/or crop rotations, and conservation tillage. Despite the destruction of the Center's headquarters in the ongoing civil war and its dispersion in the region, the legacy of ICARDA will survive through documentation of its research in the international literature.

The relationship between flag leaf senescence and grain yield of some durum wheat varieties under drought stress during grain filling period

This study aimed at investigating genotypic differences in the leaf area duration of durum wheat genotypes during grain filling periods and their relation to grain yield under two different irrigation conditions. The experiments were designed randomized complete block design for four replication in 2009/2010 and 2010/2011. Irrigation levels in main plots, cultivars were included in the sub plots. The study gathered data of six genotypes with similar anthesis times in Antakya/Hatay-Turkey. During the growth period, the two groups of plants received general management techniques and 60 kg ha -1 phosphorus and 80 kg ha -1 nitrogen (ammonium sulphate) fertilizer. Two different irrigation regimes were applied; the control group received full irrigation until reaching physiological maturity, while the experiment group was not irrigated after anthesis but instead received rainfall characteristic of WANA (West Asia North Africa). Results showed that flag leaf area (FLA) and lower leaf area (LLA) were not significantly related to spike grain yield (SGY) under control conditions. Flag leaf area duration (FLAD) was not related to grain yield, while the increase in lower leaf area duration (LLAD) reduced grain yield. Meanwhile, a positive relation was observed between FLA and SGY under experimental conditions, since SGY significantly increased according to the increase of FLAD. Moreover, high FLAD positively contributed to grain filling under both the conditions, while high LLAD partly contributed only under control conditions. These results suggest that the genotypes with low leaf number or short plant height and low tillering capacity should receive significant irrigation, while genotypes with middling plant height should be planted during conditions of drought stress. Under both the sets of conditions genotypes must have high FLAD.

Center of Origin and Centers of Diversity in an Ancient Crop, Brassica rapa (Turnip Rape)

Brassica rapa is the most widely distributed and has the longest history of domestication of the agricultural Brassica species. Molecular genetic diversity, based on 51 simple sequence repeat primer pairs and 715 alleles at polymorphic loci, was used to predict the center of origin and centers of diversity in a global collection of 173 B. rapa accessions. The accessions were separated into 3 molecular genetic groups based on STRUCTURE analysis-group 1 from the classical Old World (Europe and west Asia-north Africa), group 2 from east Asia, and group 3 from east, central, south, and southeast Asia. Accessions classified as "wild" (B. rapa var. sylvestris) were found only in group 1 and this group had the highest number and richness of private alleles. Each group included a diverse range of agricultural morphotypes (oilseed, root, or leafy vegetable types), flowering habit (winter, semi-winter, or spring type), self-compatibility or incompatibility, and seed color. The Old World and east, south, and central Asia were distinct subpopulations based on analysis of shared unique alleles. This study supports the theory that the classical Old World is the center of origin of B. rapa, with centers of diversity in east Asia and along ancient trade routes in Asia, with recent migration to the New World.

QTL for yield and associated traits in the Seri/Babax population grown across several environments in Mexico, in the West Asia, North Africa, and South Asia regions

Heat and drought adaptive quantitative trait loci (QTL) in a spring bread wheat population resulting from the Seri/Babax cross designed to minimize confounding agronomic traits have been identified previously in trials conducted in Mexico. The same population was grown across a wide range of environments where heat and drought stress are naturally experienced including environments in Mexico, West Asia, North Africa (WANA), and South Asia regions. A molecular genetic linkage map including 475 marker loci associated to 29 linkage groups was used for QTL analysis of yield, days to heading (DH) and to maturity (DM), grain number (GM2), thousand kernel weight (TKW), plant height (PH), canopy temperature at the vegetative and grain filling stages (CTvg and CTgf), and early ground cover. A QTL for yield on chromosome 4A was confirmed across several environments, in subsets of lines with uniform allelic expression of a major phenology QTL, but not independently from PH. With terminal stress, TKW QTL was linked or pleiotropic to DH and DM. The link between phenology and TKW suggested that early maturity would favor the post-anthesis grain growth periods resulting in increased grain size and yields under terminal stress. GM2 and TKW were partially associated with markers at different positions suggesting different genetic regulation and room for improvement of both traits. Prediction accuracy of yield was improved by 5 % when using marker scores of component traits (GM2 and DH) together with yield in multiple regression. This procedure may provide accumulation of more favorable alleles during selection.

Training and Capacity Building: An Essential Strategy for Development at an International Research Center

In order to be meaningful, agricultural research has to provide solutions to problems, especially in the international agricultural research system which is designed to contribute to enhanced food production and improved rural livelihoods in the lesser-developed world. Training and human resource development, whether at the technical support or research scientists/managerial level, is fundamental to an effective agricultural research and technology transfer system. By comparison with the developed world, the national agricultural research systems (NARS) in developing countries are weak, often with ineffective extension programs, as typified by the West Asia-North Africa (WANA) region, which is served by the International Center for Agricultural Research in the Dry Areas (ICARDA). Despite the potential benefits of enhancing human skills, training and human resource development activities are often under-valued and under-funded in international research centers that serve developing countries. By highlighting training at ICARDA and its mandate countries, we sought to give renewed focus on this important component of the mission of the Consultative Group on Agricultural Research (CGIAR). In this article, we considered ICARDA’s philosophy and concepts on training, collaborating institutions, educational materials, categories of training, development of training courses, significant outcomes of training, shifting paradigms, and future directions. ICARDA’s innovative collaborative approach is a model to be emulated not only by the Centers but by other international institutions involved in agricultural and rural development in the developing countries. At this crucial time of restructuring of the CGIAR, renewed emphasis on training has never been more urgent.

Fertilizer Best Management Practices: A Perspective from the Dryland West Asia–North Africa Region

AbstractChemical fertilizer use has contributed significantly to increased global food output in the past half century, especially in climatically favourable regions of the world. However, in drier agro‐ecological zones, such as in West Asia and North Africa (WANA) with a Mediterranean‐type climate, fertilizer use has been low but has increased rapidly in the past few decades. Chemical fertilizer use is now widely adopted in rainfed and irrigated agriculture. As elsewhere, fertilizer use is underpinned by concerns about biological and economic efficiency. Fertilizer use efficiency is central to the current concept of fertilizer best management practices (FBMP), which embraces right source, right place, right timing and right application method. In this brief review, we highlight such FBMP concepts as related to agriculture of the WANA region, with emphasis on the key nutrients for crop production. Rainfall has a dominant influence on dryland crop yields. Nitrogen (N) use efficiency increases with increasing rainfall and is influenced by crop rotation. Under rainfed conditions, modest N losses by volatilization can occur. Leaching losses are usually minimal. Phosphorus use (P) efficiency is higher with band application than with broadcasting. Balanced fertilization, especially involving potassium (K) and micronutrients, is fundamental to efficient nutrient use. Fertilizer efficiency is also influenced by soil test values and agronomic factors that influence crop yields, e.g. sowing date and varietal differences. Rational fertilizer application rates are guided by calibration–response trials. Effective fertilizer use in the region is also dictated by external factors such as government policies and a functioning extension service. In contrast to other regions of the world, environmental impacts from the overuse of fertilizers are relatively minor, while developments in fertilizer formulations that promote efficiency have yet to have impact. Despite the relatively low fertilizer use intensity in dryland areas such as the WANA region, the FBMP comprehensive approach is a logical framework within which to achieve the most efficient management and use of fertilizer in the region’s agriculture.

Differential Responses of Barley Landraces and Improved Barley Cultivars to Nitrogen-Phosphorus Fertilizer

ABSTRACT Barley is traditionally grown in the Mediterranean region as a dryland crop, invariably under drought-stressed conditions and often without inputs such as fertilizer. Following research that demonstrated the benefits of fertilization, even under less-than-favourable rainfall condition, fertilizer use on cereals has increased dramatically in the past few decades in countries of West Asia-North Africa. With developments in breeding new barley cultivars for higher yield, combined with disease resistance and environmental adaptability, it is crucial to assess the extent to which such cultivars respond to fertilizer inputs as this may affect aspects of a breeding strategy, particularly the choice of germplasm for adaptation in any particular environment. Thus, we assessed the yield potential of 30 barley cultivars with a range of germplasm types, including new cultivars and landraces, in a greenhouse in two soil types with and without adequate nitrogen and phosphorus fertilizer, i.e., low and high fertility. By comparison with the unfertilized low fertility soils, the fertilizer treatment increased yield parameters by about 10-fold. However, the rankings of some cultivars changed markedly with fertilization; some increased, others showed poor responses and decreased relatively, and two performed well with and without fertilizer. Based on the differential responses at the initial screening stage in the greenhouse, it is possible to identify lines or cultivars that are highly responsive to fertilizers and to incorporate such germplasm for further development to produce high-yielding cultivars for commercial adoption by farmers.

Sunflower production: Hybrids versus open pollinated varieties on dry land

Sunflower (Helianthus annuus L.) is an important oilseed crop. It was grown on more than 20 million ha in the world in 1997, of which over one million ha were in West Asia-North Africa (WANA) countries, where Iran grew 60,000 ha and Syria 50,000. There is potential for substantial increase in sunflower area and production on dry land if optimum management practices are applied. An important management consideration is choosing a high yielding, good quality variety that will maximize seed yield and minimize seed costs. This study investigated the influence of hybrids and open pollinated varieties on yield and other agronomic traits of sunflower. Ten hybrids and eleven open pollinated varieties were compared, under rainfed conditions (Jindiress) and with minimum supplementary irrigation (Tel Hadya, ICARDA Aleppo, Syria) in 1993. Soil at Tel Hadya is red clay loam characterized as Calcixerollic Xerochrept (Inceptisol), Chromic Calcixeret (Vertisol); at Jindfiress, the soil is Calcixerollic Xerochrept (Inceptisol). All of them are thermic and clayey to very fine clay. At both stations, equally good and statistically similar yields were obtained with hybrids and varieties. The average yield of the 21 cultivars was 2,207 kg/ha at Jindiress and 2,080 kg/ha at Tel Hadya. The average yield of the 11 OPVs was 2,073 kg/ha and that of the 10 hybrids was 2,220 kg/ha, which was similar. Thus, less costly OPVs can be used instead of costly hybrid seed. Farmer can also produce their own seed with little training; the cost will be one fourth of that of hybrids, which are imported and seldom available on time. In the absence of hybrids, F2 seed is resorted to by farmers which reduces the yields considerably. The rainfall during 1993 was lower than the long-term average; it was 277 mm (TH) and 417 mm (Jindiress). The information obtained are important to farmers, allowing them to maximize economic returns from rainfed areas by using limited supplementary irrigation in lowrainfall locations and during dry years.

Global adaptation patterns of Australian and CIMMYT spring bread wheat

The International Adaptation Trial (IAT) is a special purpose nursery designed to investigate the genotype-by-environment interactions and worldwide adaptation for grain yield of Australian and CIMMYT spring bread wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var. durum). The IAT contains lines representing Australian and CIMMYT wheat breeding programs and was distributed to 91 countries between 2000 and 2004. Yield data of 41 reference lines from 106 trials were analysed. A multiplicative mixed model accounted for trial variance heterogeneity and inter-trial correlations characteristic of multi-environment trials. A factor analytic model explained 48% of the genetic variance for the reference lines. Pedigree information was then incorporated to partition the genetic line effects into additive and non-additive components. This model explained 67 and 56% of the additive by environment and non-additive by environment genetic variances, respectively. Australian and CIMMYT germplasm showed good adaptation to their respective target production environments. In general, Australian lines performed well in south and west Australia, South America, southern Africa, Iran and high latitude European and Canadian locations. CIMMYT lines performed well at CIMMYT's key yield testing location in Mexico (CIANO), north-eastern Australia, the Indo-Gangetic plains, West Asia North Africa and locations in Europe and Canada. Maturity explained some of the global adaptation patterns. In general, southern Australian germplasm were later maturing than CIMMYT material. While CIANO continues to provide adapted lines to northern Australia, selecting for yield among later maturing CIMMYT material in CIANO may identify lines adapted to southern and western Australian environments.

Effect of supplementary irrigation and variety on yield and some agronomic characters of sunflower grown under rainfed conditions in Northern Syria

Sunflower is an important edible oil crop. Its yield on dry lands of West Asia-North Africa is low due to limited rainfall at the time when this crop is in full growth during May-June, thus supplementary irrigation (SI) must be used. However, this region lacks river/canal water and irrigation, when possible, is from underground water storages, which, due to their quantitative scarcity, have to be used judiciously. This trial was conducted to assess the minimum SI application needed to produce optimum economic yields. The study was made for three years (1995-1997) at Tel Hadya, ICARDA, in northern Syria, on a soil characterized as fine clay (montmorillonitic, thermic Calcixerollic Xerochrept) with a pH around 8.0. We tested two open pollinated varieties, HO-1 and Record, and three water level treatments, rainfed, 50% of crop water requirement and 100% of crop water requirement. Effects of environment (years), variety and water level were observed on plant height, head and stem diameter, 200-seed weight, leaf area and sunflower grain yield. The results show that plant height, head diameter, stem diameter and leaf area differed significantly due to year effects while seed weight and yield differed non-significantly. The cultivars were significantly different only regarding seed weight and stem diameter. Grain yield obtained under rainfed conditions was highly significantly lower than those obtained under SI, with both lower and higher quantity of irrigation water. The average yield increase with 50% SI was 150% and with 100% SI was 312%. However, the yield difference between the two irrigation levels was 66%. This trial showed that 50% SI irrigation level can increase the yield substantially and economically, and can be resorted to in the absence of water for full irrigation.

Optimizing wheat productivity in two rain-fed environments of the West Asia–North Africa region using a simulation model

The performance of a crop simulation model (agricultural production systems simulator model, APSIM-Nwheat) was tested using data obtained from several locations in the rain-fed environments of West Asia and North Africa (WANA) in Morocco and Jordan. The model was able to simulate wheat grain yields reasonably well except at one site in one season in Morocco. The model was subsequently used to analyze the effect of soil type (soil water-holding capacity), rate and timing of nitrogen (N) fertiliser, initial soil moisture storage, cultivars (early versus late), sowing dates and density and supplemental irrigation (SI) in optimizing wheat production using 20 years of historical weather records from Morocco. The simulation indicated that yields were often limited by the amount and timing of rainfall. While the effect of N fertiliser was minimal or detrimental in dry years, it improved grain yields in wet years and when crops were sown early combined with pre-sown stored plant available water in the soil. The analysis showed that early sowing is important for achieving high yields by avoiding terminal water deficit. There is little difference between grain yields when current practice of about 300 plants/m 2 was compared with a density of 150 plants/m 2. This implies that there is scope for reducing current planting density to save seeds without reducing yields. The simulation analysis highlighted that 40 mm of SI at sowing significantly improved average grain yields as a result of enabling early crop establishment, in particular with a N fertiliser application of 40 kg N/ha. The analysis indicated that wheat grain yields in the arid and semi-arid rain-fed regions of WANA can be improved compared to current yield levels by adjusting N management to soil type, pre-sowing soil water availability, sowing opportunity and the availability of SI.

Application of Soil and Plant Analysis for Applied Research and Development in West Asia–North Africa: An International Center's Perspective

The networks of 15 international research centers around the globe that are sponsored by the Consultative Group for International Agricultural Research (CGIAR) seeks to alleviate poverty in the developing world through enhanced production, while maintaining biodiversity and the sustainability of natural resources. The mandate of the International Center for Agricultural Research in the Dry Areas (ICARDA) is to focus on improving semi‐arid cropping systems in the drought‐prone West Asia and North Africa region. Since its inception in 1997, ICARDA's soil laboratory played a pivotal role in backstopping the institution's on‐station and on‐farm research in Syria and its collaborative research with the region's national programs. This article gives an overview of the evolution of soil and plant analysis in serving the center's mission. A major effort was the regional soil test calibration program, which set the basis for rational use of fertilizers and the identification of related nutrient constraints. Such analyses were extensively employed in all the long‐term dryland cropping system trials and later in irrigated agriculture and the interface between plant nutrition and crop breeding. Major emphasis was given to improving and upgrading analytical services in the region's laboratories. Despite advances made in analytical methodology, the challenge is to apply to solving real problems in the service of humanity.

Carbon sequestration in dryland ecosystems of West Asia and North Africa

AbstractThe West Asia–North Africa (WANA) region has a land area of 1.7 billion ha, and a population of 600 million. Desertification and soil degradation are severe problems in the region. The problem of drought stress is exacerbated by low and erratic rainfall and soils of limited available water holding capacity and soil organic carbon (SOC) content of less than 0.5 per cent. The SOC pool of most soils has been depleted by soil degradation and widespread use of subsistence and exploitative farming systems. The historic loss of a SOC pool for the soils of the WANA region may be 6–12 Pg compared with the global loss of 66–90 Pg. Assuming that 60 per cent of the historic loss can be resequestered, the total soil‐C sink capacity of the WANA region may be 3–7 Pg. This potential may be realized through adoption of measures to control desertification, restore degraded soils and ecosystems, and improve soil and crop management techniques that can enhance the SOC pool and improve soil quality. The strategies of soil‐C sequestration include integrated nutrient management (INM) and recycling, controlled grazing, and growing improved fodder species on rangeland. Improved technologies for cropland include use of INM and biofertilizers, appropriate tillage methods and residue management techniques, crop rotations and cover crops, and water and nutrient recycling technologies. Through adoption of such measures, the potential of soil‐C sequestration in the WANA region is 0.2–0.4 Pg C yr−1. Copyright © 2002 John Wiley & Sons, Ltd.

Yield performance and adaptation of some Australian and CIMMYT/ICARDA developed wheat genotypes in the West Asia North Africa (WANA) region

A set of 29 advanced breeding lines and named cultivars from different breeding programs in Australia was compared with 18 genotypes developed by the CIMMYT/ICARDA breeding programs for their adaptation and yield performance using 5 locations in the WANA region for 2 years. Classification analysis identified 13 CIMMYT/ICARDA genotypes that had a pattern in yield performance similar to 2 Australian cultivars, Leichhardt and Hartog. The classification of environments effectively identified trials that experienced heat stress and received supplementary irrigation. Most of the genotypes developed by the CIMMYT/ICARDA breeding programs showed wide adaptation in the WANA region. Genotypes developed for Australian Mediterranean environments failed to show wide adaptation in the WANA region. However, many Australian genotypes showed specific adaptation to heat-stressed environments. Variation among Australian genotypes for disease resistance and heat tolerance couldbe used for wheat improvement in the WANA region.

Stabilizing Rainfed Wheat Yields with Supplemental Irrigation and Nitrogen in a Mediterranean Climate

AbstractThe West Asia‐North Africa (WANA) region, with a Mediterranean‐type climate, has an increasing deficit in cereal production, especially bread wheat (Triticum aestivum L.). Rainfed cropping coincides with the relatively cool, rainy winter season, usually from October to May. Cereal yields are low and variable in response to inadequate and erratic seasonal rainfall and associated management factors, such as lack of N and late sowing. In an area where water is limited, small amounts of supplemental irrigation (SI) water can make up for the deficits in seasonal rain and potentially produce satisfactory yields. This field study (1992–1993 to 1995–1996) on a deep clay soil (a Calcixerollic Xerochrept) in northern Syria was conducted for four growing seasons to assess the effects of SI (rainfed, 1/3, 2/3, and full irrigation) combined with N rate (0, 50, 100, and 150 kg ha−1) and sowing date (early, normal, and late) on one traditional (Mexipak 65) and three improved bread wheat cultivars (Cham 4, Cham 6, Gomam). Yields of rainfed wheat varied with seasonal rainfall and its distribution, with all main factors having significant effects. A delay in the sowing date from November to January consistently reduced yields and the response to both SI and N. With irrigation, crop responses were generally significant up to 100 kg N ha−1, while optimum response for rainfed conditions was with 50 kg N ha−1. An addition of only limited irrigation (1/3 full irrigation) significantly increased yields, but near maximum yields were obtained by 2/3 of full irrigation. Responses to N and SI were greatest for the higher‐yielding cultivars. Use efficiency for both water and N was greatly increased by SI. Thus, with minimum irrigation during the winter growing season combined with appropriate management, inputs, and varieties, wheat output could be substantially and consistently increased in the semiarid Mediterranean zone. Production functions developed from this dataset can help predict the effects of changing any of these parameters in other locations in the region.

Establishment and yield of wheat ( Triticum turgidum L.) after early sowing at various depths in a semi-arid Mediterranean environment

Shallow sowing and in ridges are common practices in the west-Asia north-Africa (WANA) region in rain-fed cereal farming. Soil water is often limited in the top soil layer at the optimum sowing time, and stands of wheat may be established poorly and have low yields unless sowing is delayed until later rainfall. Sowing more deeply may enhance establishment due to higher soil water content in the seed zone, leading to better germination and emergence of seedling. Otherwise, a grain yield reduction will occur due to the delay in sowing after the optimum time. In a 2-year field experiment at Tel Hadya, Syria, the optimum time of sowing for rainfed cereals was between early November and early December. The establishment of plants sown 3, 9, and 12 cm deep and in ridges was poorer than that of plants sown at 6 cm, causing reductions in tiller numbers, leaf area index (LAI) and yield. Grain yield from ridge planting was 40% lower on average than from sowing at 6 cm. At this depth, yields declined by 5% per week with delay in sowing after the optimum time at 6 cm depth, but by lesser amounts for other depths, and varied little for the ridge method of planting. To maximize yield in this environment, i.e., 2.5 t ha −1, it is important that crops are sown early at the appropriate depth, even when pre-sowing rainfall is less than enough to wet the profile fully.

Effect of fertilizer rate and form on the recovery of 15N-labelled fertilizer applied to wheat in Syria

15N-labelled fertilizer was applied at different rates (0, 30, 60, 90 kg N ha−1) and in different forms (urea or ammonium sulphate) to wheat grown in Syria in three seasons (1991/92, 1992/93 and 1994/95).Recovery of 15N-labelled fertilizer in the above-ground crop at harvest was low (8–22%), with the amount of 15N-labelled fertilizer recovered in the crop increasing as the rate of application increased. Fertilizer application caused a significant increase in the amount of unlabelled soil N in the crop, suggesting that the application of N fertilizer caused a ‘real’ added nitrogen interaction. Recovery of 15N-labelled fertilizer in the crop was unaffected by the form of the fertilizer.On average 31% (14–54%) of the 15N-labelled fertilizer remained in the soil at harvest, mostly in the 0–20 cm layer. At the lowest application rate (30 kg N ha−1) most of the residual fertilizer was as organic N, but at the higher application rates (60 and 90 kg N ha−1), a greater proportion of the 15N-labelled fertilizer was recovered as inorganic N, presumably as the result of top-dressing N in dry conditions in the spring. The amount of 15N-labelled fertilizer remaining in the soil increased as the fertilizer rate increased, but was unaffected by the form of fertilizer applied.Losses of 15N-labelled fertilizer were large (>35%), probably caused by gaseous losses, either through volatilization of N from the calcareous soil, or through denitrification from wet soils rich in organic residues.N fertilization strategies in the West Asia/North Africa (WANA) region should take note of the low recovery of N fertilizer by the crop in the season of application, and the resultant large quantities of residual fertilizer.

PROPORTION OF TOTAL NITROGEN AND FIXED NITROGEN IN SHOOTS OF LENTIL AND CHICKPEA GROWN IN A MEDITERRANEAN-TYPE ENVIRONMENT

Shoot dry matter yield, shoot nitrogen yield and amount of nitrogen derived from fixation are collated for chickpea (Cicer arietinum L.) cv. ILC482 and lentil (Lens culinaris Medic.) cv. ILL8 grown at the ICARDA research station Tel Hadya, Syria over a period of 17 years. Regression analyses of shoot nitrogen yield on shoot dry matter and of the amount of nitrogen fixed on shoot nitrogen yield were undertaken for both species. The intercepts for both analyses with lentil were not significantly different from zero, so the slopes of the lines represented the concentration of nitrogen in the plant tissue (20.6 g kg−1 dry matter) and the proportion of nitrogen derived from fixation 0.75. Data for other cultivars of lentil grown at Tel Hadya and at four other locations in Syria fell within the 95% confidence limits of the original analyses. The intercept of the regression of shoot nitrogen yield on shoot dry matter yield for chickpea grown at Tel Hadya was not significantly different from zero, so the concentration of nitrogen in the plant tissue was constant (17.8 g kg−1 dry matter). The proportion of nitrogen derived from fixation increased asymptotically as the shoot nitrogen yield increased. Data for other cultivars of chickpea grown in different locations were generally similar to those for cv. ILC482 grown at Tel Hadya. It is proposed that generalized relationships between shoot nitrogen yield and shoot dry matter yield, and between amount of nitrogen fixed and shoot nitrogen yield can be established for lentil and chickpea grown in the West Asia–North Africa region. Consequently the amounts of nitrogen fixed by the two crops could be predicted from a knowledge of dry matter production alone.