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Very little information is available for Mediterranean areas about the soil N dynamics and crop N use efficiency during the transition phase from conventional tillage (CT) to no-tillage (NT). Hence, a 2-yr experiment was conducted under semiarid Mediterranean conditions in three sites to study how soil N dynamics, crop N uptake, grain yield, and N use efficiency vary with N-fertilization rate and crop genotype in the switch year from CT to NT. Treatments consisted of two tillage systems (CT and NT), five N-fertilization rates (0, 40, 80, 120, and 160 kg N ha−1), and two durum wheat (Triticum durum Desf.) genotypes (one modern variety and one old landrace). Irrespective of the genotype, NT reduced compared to CT both wheat N uptake and grain yield under low soil N availability. The greater soil N supply under CT was the main reason for this outcome, so much so that the differences between CT and NT for these traits gradually decreased with the increase of N fertilization rate, practically disappearing at 80 kg N ha−1). The analysis of the N use efficiency components corroborated this hypothesis showing clearly that the yield advantage observed in CT depended mainly on the increase in N supply in soil under CT than NT condition. The two wheat genotypes responded similarly to varying soil tillage system. However, the adverse effects of NT practice were more evident in the modern variety than the old landrace. This study ultimately indicates that in the Mediterranean areas the switch year from CT to NT regime is rather delicate. Given that the lack of soil cultivation considerably reduces the soil N availability, hence, using NT technique alone as a substitute for CT is not agronomically feasible. Instead, an optimal application of NT is achievable by acting simultaneously on other factors of the cropping management, particularly the N-fertilization strategy, to maximize the crop N use efficiency and increase crop yield, which are essential requirements for a more sustainable agriculture.

Conservative tillage techniques have several agro-ecological benefits for organic farming. The application of these techniques, however, can create quite a few challenges due to the increased weed competition. Here, we report the results of an organic field experiment in which the responses of wheat and weeds to no tillage (NT) were evaluated compared with conventional tillage (CT). We also tested the hypothesis that, under NT, moving up the sowing date, compared with using the ordinary sowing date for the study area, can result in increased competitiveness of the crop against weeds. Two wheat genotypes, a modern variety and an ancient landrace, were tested.Substantial reductions in grain yield and protein content were observed in wheat under NT than under CT when the ordinary sowing date was used. This was mainly due to the considerable increase in weed biomass under NT. The tillage system also altered the composition of weed flora, with some species favored under NT and others under CT. In general, early sowing mitigated the detrimental effect of NT on yield. The two genotypes responded differently to the treatments. The early sowing in the modern variety reduced but did not eliminate the advantages of CT over NT, whereas no appreciable differences in grain yield were observed between CT and NT in the landrace.Our results show clearly that, under organic management, using NT alone as a substitute for CT is not agronomically feasible. Moving up the sowing date and using a competitive genotype can help mitigate the negative effects of NT, but surely a more effective application of NT could be achieved by acting simultaneously on other factors of the cropping management system (e.g. crop rotation, fertilization strategy, type of seeder). © 2022 The Authors. Journal of The Science of Food and Agriculture published by John WileySons Ltd on behalf of Society of Chemical Industry.

The arbuscular mycorrhizal (AM) symbiosis is generally considered effective in improving salt tolerance in plants; however, the advantages it offers can vary greatly depending on the context in which it occurs; furthermore, the mechanisms underlying these responses are still unclear. A study was conducted to investigate the role of nitrogen (N) availability on the effectiveness of AM symbiosis in durum wheat (Triticum durum Desf.) plants grown under salt stress. Plants were grown in pots in the absence or in presence of salt stress (soil electrical conductivity of 1.50 and 13.00 dS m−1, respectively), with or without AM fungi inoculation (Rhizophagus irregularis and Funneliformis mosseae), varying the N dose supplied (0 or 80 mg N per pot). Results indicate that AM symbiosis can alleviate the detrimental effects of salt stress on the growth of durum wheat only when plants are grown under sufficient N availability in soil; in such conditions mycorrhizal symbiosis determined an improvement of leaf traits (leaf area, SLA, stability of plasma membranes and SPAD), N uptake, N fertilizer recovery and water use efficiency. On the contrary, when wheat plants were grown in conditions of N deficiency, the mycorrhizal symbiosis had no effect (under salt stress) or even depressive effect (under unstressed condition) on plant growth and N uptake, highlighting how, in some cases, competition for nutrients between plants and AM can arise. This study suggests that N availability in the soil can drive the effects of AM symbiosis in assisting the plant with containing saline stress.

Determining the best conservation agriculture practices for increasing soil organic carbon (C) and hence soil quality is of paramount importance in the semi-arid Mediterranean environment, where soils are experiencing a continuous decline in organic matter. Therefore, the aim of this long-term study was to assess the combined effects of tillage system and crop sequence on soil organic C and biochemical properties of soil generally used as indicators of soil quality. After 23 years of continuous application of contrasting tillage systems (conventional tillage [CT], vs. no tillage [NT]) and crop sequences (wheat monoculture vs. wheat-faba bean rotation), soil samples were collected from topsoil (0–15 cm) and subsoil (15–30 cm) at three different times during a cropping year. Soil samples were analyzed for total and labile organic C pools, microbial biomass C (MBC) and microbial biomass N, basal respiration, and the abundance of main microbial groups by phospholipid fatty acids. Long-term NT increased total organic C (TOC) at a yearly rate of 0.17 g kg−1. This in turn stimulated microbial biomass, in particular Gram-negative bacteria. This suggests a higher soil quality in NT, as was confirmed by the increase in MBC/TOC and the decrease in stress indices. In contrast, no differences were observed with regard to fungal biomass. These findings suggest the need to reconsider the role of specific bacterial groups in organic C accumulation in soils of semiarid environments. It is interesting that the effects of long-term NT varied widely by crop sequence, whereas in CT changes in biochemical characteristics and in the main microbial groups due to crop sequence were modest. Thus, the interaction among various aspects of agronomic management modulates the effects of substrate quality on chemical and biological properties of soil.

Summary Knowledge of the effects of agricultural practices on weed seedbank dynamics is essential for predicting future problems in weed management. This article reports data relative to weed seedbank structure after 18 years of continuous application of conventional tillage (CT, based on mouldboard ploughing) or no tillage (NT) within three crop sequences (continuous wheat, WW; wheat–faba bean, WF; and wheat–berseem clover, WB). Tillage system did not affect the size of the total weed seedbank, but altered both its composition and the distribution of seeds within the soil profile. In particular, the adoption of CT favoured some species (mainly Polygonum aviculare), whereas the continuous use of NT favoured other species (Papaver rhoeas, Phalaris spp. and Lactuca serriola). The effects of tillage system on weed seedbank size and composition were less pronounced in the WB cropping system than in either the WW or WF. Compared with WF and WB, WW resulted in an increase in total weed seedbank density (about 16 000 seedlings m−2 in WW, compared with 10 000 and 6000 seedlings m−2 in WF and WB, respectively) and a reduction in weed diversity, with a strong increase in some species (e.g. Polygonum aviculare). Our results for the effect of NT application on weed seedbank size and composition suggest that farmers should only apply such a conservative technique within an appropriate crop sequence.

SUMMARYArbuscular mycorrhizal (AM) fungi increase nitrogen (N) uptake by their host plants, but their role in plant N capture from soil organic material is still unclear. In particular, it is not clear if AM fungi compete with the host plant for the N coming from the decomposing organic matter (OM), especially when the AM extraradical mycelium (ERM) and plant roots share the same soil volume. The goal of the present research was to study the effects of AM fungi on wheat N capture after the addition of 15N-labelled OM to soil. Durum wheat (Triticum durum) was grown under controlled conditions in a sand:soil mix and the following treatments were applied: (1) AM inoculation with Glomus mosseae and uninoculated control; and (2) soil amended with 15N-enriched maize leaves and unamended soil. The addition of OM reduced plant growth and N uptake. The AM fungi increased both plant growth and N uptake compared with uninoculated control plants and the effect was enhanced when wheat was grown in soil amended with OM compared with the unamended control. Although AM fungi increased soil N mineralization rates and total plant N uptake, they strongly reduced wheat N recovery from OM, suggesting that AM fungi have marked effects on competition between plants and bacteria for the different N sources in soil.

This paper reviews the main results from a set of experiments carried out in a semiarid Mediterranean environment during the past 25 years on faba bean (Vicia faba L.), a crop traditionally grown in southern Italy and Sicily under rainfed conditions. These experiments focused on the residual effects of faba bean on subsequent crop(s) and assessment of the nitrogen (N) balance during the crop cycle, paying attention to both the environmental release of N (losses via volatilisation and denitrification) and estimates of N2 fixation as influenced by tillage system, intercropping, and presence/absence of mycorrhizal inoculum. Faba bean relied on N2 fixation more than other grain legumes typically grown in the Mediterranean region (e.g., chickpea). Contributing reasons were the higher plant N demand of faba bean and its lower capacity to use soil mineral N. This implies higher N benefits for subsequent crop(s) as well as higher risk of N losses from the plant–soil– atmosphere system via leaching, denitrification, and volatilisation. Results from these experiments contribute to better defining the role of faba bean in Mediterranean agro-ecosystems and to identifying technical solutions that maximise the potential benefits of faba bean as a fertility-building crop.

A better understanding of the genotype response to N fertilization under weed competition is necessary to identify varieties that exhibit high N use effi ciency even when weeds compete for available N. Such varieties may be more suitable for low input or organic systems. Th is study assessed the variations in nitrogen use effi ciency (NUE) (and its components) and the recovery of 15 N-labeled fertilizer in three durum wheat (Triticum durum Desf.) genotypes (one landrace and two varieties that diff er in terms of plant growth, grain yield potential, and adaptability to stressful environments) grown in the presence or absence of interspecifi c competition and varying soil N availability (0 or 80 kg N ha –1 fertilization). Th e results showed that wheat genotypes had diff erent grain yield potentials and the yields were similar when plants were grown in conditions of low N availability and in presence of interspecifi c competition. Diff erences among genotypes in N uptake effi ciency were very small, and the low NUE value observed for the landrace seemed to be due to its reduced ability to use absorbed N for increasing grain yield compared with the two varieties. Furthermore, the genotypes showed diff erent competitive abilities against competitor, and seemed to depend on the genotypes’ ability to reduce resource availability (N) for their competitors rather than on their ability to tolerate a reduction in contested resources due to competitors.

No tillage (NT) soil management has largely been promoted because of its potential to generate both economic and environmental benefits. However, it often leads to reductions in crop yield and quality, which in many cases have been attributed to the effects this technique has on the nitrogen (N) dynamics in the soil–plant system. This 2-year study, performed within a long-term experiment in which NT was continuously applied for over 15 years, aimed to verify whether and to what extent the use of NT affects soil N availability, recovery of 15 N-labeled fertilizer, and N use efficiency (NUE) and its components (N uptake efficiency, NUpE; N utilization efficiency, NUtE). Durum wheat was the focal crop. NT was evaluated and compared with conventional tillage (CT) within three crop sequences: continuous wheat (WW), wheat–faba bean (WF), and wheat–berseem clover (WB). At the same time, the timing of N fertilization was varied (either distributing 100 kg N ha −1 all at once at crop emergence or applying 50% at crop emergence and 50% at the end of tillering; no N-fertilizer treatment was included as a control). The data indicated that, compared to CT, NT had a detrimental effect on wheat productivity in WW but improved yields in WF and WB. NT was associated with less N uptake by wheat, mainly attributable to a decrease in soil N availability, and to a lesser extent, to a decrease in the 15 N-fertilizer recovery. This reduction in uptake was markedly more evident in WW than in WF or WB, and when all of the 15 N-fertilizer was applied at crop emergence. The effects of tillage system on NUE varied by crop sequence: NT increased NUE (+18% on average compared to CT) in WF, but had the opposite effect in WW (−17% on average). These results suggest that the adoption of the NT technique by farmers must be accompanied by a reorganization of the components of crop management, such as crop rotation and the rate and timing of N fertilization.

Although sulla (Hedysarum coronarium L.) has many interesting features that could support the production of biofuels (e.g., a high yield and soluble sugar content, N-fixation capacity, low input requirements for its cultivation), no study has assessed the possibility of its use for that purpose. Our objective was to evaluate the potential value for energy production of sulla cut at various stages of growth. Furthermore, the potential of sulla as a dual purpose crop (energy and feed) was investigated. The crop was grown in rainfed conditions in a typical Mediterranean environment (over two complete 2-year crop cycles) and was cut at four different phenological stages. The biomass was divided into two fractions (stems and leaves), weighed, and analyzed to estimate the theoretical production of bioethanol and biomethane and the feed value of the whole biomass and of the two fractions. The total dry matter yield in the 2-year crop cycle was about 18 Mg ha−1; this level of production is similar to or higher than that of most other crops grown in the same environment in rainfed conditions. The stems had a high content of total soluble sugars (even higher than 200 g kg−1) and cell wall polysaccharides, markedly higher than the leaves. The leaves contained most of the protein of the plant, representing an actual protein concentrate. Thus, the crop seems particularly suitable for dual purpose use if stems are allocated to the production of biofuels and leaves to the production of livestock feed. Moreover, the results showed that the early seed set stage is the most appropriate cutting time for maximizing yield both for energy and for livestock use.

Medicago arborea is one of the most potentially valuable fodder shrubs in a Mediterranean environment because of its high preference by small ruminants and its nutritive value. Edible biomass production is affected by agronomic and environmental factors. A study, carried out in an inland area of Sicily in the growing seasons of 1994/95, 1995/96 and 1996/97, evaluated the forage production and canopy modification in a M. arborea plantation after (i) commencing defoliation 1 or 2 years after transplanting and (ii) defoliating only in autumn (A), only in early summer (S) or in both seasons (A and S). Six clones derived from five different Mediterranean populations were used. Plant age at the first defoliation did not significantly influence forage production. The genotypes differed in growth rate and forage production. The season and frequency of defoliation markedly influenced forage production and canopy size. The highest annual production was obtained by defoliating once a year in early summer (on average, 1Æ65, 2Æ85 and 4Æ50 tonnes ha)1 respectively in the three growing seasons). With the A and S, and A defoliation treatments, production decreased over 3 years by, on average, 0Æ19 and 0Æ57 respectively, but the differences became more marked over a 3-year period. Defoliating only in early summer, however, resulted in an excessive shrub height (>120 cm, 3 years after transplanting), thereby increasing problems of accessibility to small grazing ruminants, and possibly necessitating cutting. On the contrary, the A and S defoliation made it possible to limit the height to

In vivo digestibility trials were carried out using six young rams fed with Atriplex halimus biomass harvested in summer (A) and in early autumn (B), and with a mixture of mid-autumn Atriplex halimus and wheat straw (5[ratio ]1 ratio on fresh matter basis) (C). Atriplex halimus had a high protein content (139·0, 135·9 and 193·4 g/kg DM in A, B and C respectively), but was rich in sodium chloride, especially in summer (145·9 g/kg DM), limiting its use as feed. The summer forage had a higher organic matter (OM) digestibility coefficient than the autumn forage (0·663 v. 0·530) but lower digestible OM intake (16·8 v. 29·4 g/day per kg BW0·75). In autumn forage, the combination with straw did not influence the digestibility of organic matter, whereas it enhanced DOM intake in comparison with the Atriplex halimus on its own (35·7 v. 29·4 g/day per kg BW0·75).

Conservation tillage techniques are becoming increasingly popular worldwide as they have the potential to generate environmental, agronomic, and economic benefits. In Mediterranean areas, studies performed on the effects of conservation tillage [in comparison with the conventional tillage technique (CT)] on grain yield of cereal crops have reported contradictory results as well as considerable year-to-year variation, demonstrating how the impact of different soil tillage techniques on crop productivity is strongly site-specific. The present paper summarises the main results from a set of experiments carried out in Sicily during the last 20 years in which we compared no tillage (NT) to CT in terms of their respective effects on the productivity and quality of durum wheat, while at the same time varying some other crop management practices ( e.g. crop sequence, N fertilisation, wheat genotype, sowing time). On average, no differences were observed between the two tillage techniques; yields were 3.84 and 3.87 Mg ha –1 for CT and NT, respectively. However, NT guaranteed superior yield when water stress during the crop cycle was high, whereas CT led to higher yields when water availability was adequate. Moreover, the results suggest that the use of NT needs to be accompanied by a rational crop sequence. In fact, a cumulative detrimental effect of NT over time was found for continuous wheat. Finally, grain quality in terms of protein content was slightly higher for CT (15.1%) than NT (14.4%). Thus, when using NT, the rate of nitrogen fertiliser application should be increased to offset this difference.

Much research around the world has compared the performance of cereals grown under conventional and conservation tillage systems; however, relatively few long-term experiments have been conducted in Mediterranean areas, and little attention has been given to interactions among tillage techniques and other system components across space and time. In this study, we investigated the effects of the long-term (18-yr) use of three tillage techniques (conventional tillage, CT; reduced tillage, RT; and no-till, NT) on wheat (Triticum durum Desf.) grain yield and quality within three crop sequences: continuous wheat, faba bean (Vicia faba L.)–wheat, and berseem clover (Trifolium alexandrinum L.)–wheat. In addition, we investigated the effects of climatic variability on the treatments and evaluated whether cumulative effects occurred from continuous treatment. On average, NT resulted in a grain yield advantage over CT when water stress was high and, conversely, a disadvantage when water stress was low. The effect of the tillage system on grain yield varied by crop sequence. Grain yield differences between NT and CT when wheat was grown after faba bean or berseem clover were explained primarily by climatic variability without a cumulative effect over time. In contrast, in continuous wheat, NT resulted in a progressive decrease in grain yield compared with CT. On average, wheat grain protein content varied significantly by tillage system (CT > RT > NT). This suggests that fertilizer N requirements increase with NT compared with CT because of changes in N cycling that lead to a reduction in plant-available soil N.

The seed yield of berseem clover (Trifolium alexandrinum L.) is usually obtained from regrowth after forage utilization. In stockless, cereal-growing, or specialized seed farms the forage is not needed and the mowed herbage is seldom marketable. Three different experiments were conducted in a Mediterranean environment to evaluate the effect of returning the cut biomass to the soil/crop on the regrowth, seed yield, and seed quality of berseem clover. Different forms of cut and post-cut management were examined, in which the time of cutting, the amount of biomass returned to the crop/soil, and the size of the returned material (unchopped or chopped) all varied. In addition, the effect of the berseem management on the grain yield and N content of a subsequent durum wheat (Triticum durum Desf.) crop was evaluated. The study showed that when cutting takes place during the early spring, removing and returning the herbage both result in similar seed yields but when cutting takes place later it is necessary to chop the herbage to eliminate or strongly attenuate the negative effects of mulching on seed yield. In farms in which it is not convenient or possible to use the cut herbage, returning the herbage to the crop/soil (without detrimental effects on seed yield) would increase N availability for subsequent non-legume crops. This option appears to be particularly relevant to organic farming.

Published in Agron. J. 104:1459–1466 (2012) Posted online [DATE] doi:10.2134/agronj2012.0070 Copyright © 2012 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. I agricultural practices that involve the use of agrochemicals such as fertilizers, pesticides, and herbicides have greatly increased the global food supply but often with detrimental effects on the environment, such as contamination of ground and surface water, air pollution, and loss of biodiversity. Thus, there is a need to give more attention to the sustainable agricultural systems that rely, as much as possible, on the use and effective management of internal resources (Bohlool et al., 1992). Cultivating N-fixing plants is a valuable approach to curbing the increasing reliance on chemical inputs. Introducing legumes into cereal-dominated cropping systems can provide many advantages, such as fixing great amounts of atmospheric N which will then be partly available to the subsequent crop; reducing the occurrence of pests and weeds; and improving the quality of the soil (Peoples et al., 1995; Stevenson and van Kessel, 1996; Unkovich et al., 1997; van Kessel and Hartley, 2000). Unfortunately, legumes are often considered crops of secondary importance, particularly in the Mediterranean regions (Lopez-Bellido et al., 2003), and as a consequence, they are usually grown without adequate crop management. To take advantage of all the benefits legumes can provide, it is necessary to develop more sustainable and environmentally friendly crop management methods, such as conservation tillage and NT. Reducing the intensity of tillage helps mitigate soil erosion (Jordan et al., 2000), increase soil organic matter (West and Post, 2002), improve soil biodiversity (Kladivko, 2001), enhance aggregation and aggregate stability (Madari et al., 2005), and increase water storage in the soil (Radford et al., 1995). Although these improvements often have positive effects on crop growth and yield (De Vita et al., 2007; He et al., 2011; Cullum, 2012; Giambalvo et al., 2012), contradictory results (as well as considerable year-to-year variation) have been reported for comparisons of conservation tillage and CT. For instance, in environments with a cold spring and poorly draining soil, plowing can result in quick soil warming and rapid drainage, leading to an increase in crop yield (Lal, 2007). Much research around the world has compared the performance of cereal crops grown under CT and conservative tillage, but few studies have examined legume crops, particularly in Mediterranean regions, and even fewer have done so by investigating more than one species. Thus, we studied the effects of the use of NT on the productivity of four grain legumes (chickpea, faba bean, field pea, and lentil) typically grown in semiarid Mediterranean regions. As the value of legume crops lies in great part in their ability to fix N2, an ability that can be affected by agronomic management practices such as soil management systems (Horn et al., 1996; Matus et al., 1997; van Kessel and Hartley, 2000), we also studied the effects of the tillage system (NT vs. CT) on N2 fixation and N accumulation by the four species and constructed a simple N balance to assess the incremental changes in soil N associated with each species and tillage technique. AbSTrACT

Sulla (Hedysarum coronarium L.) is a short-lived perennial forage legume that plays a key role in cereal-based systems in semi-arid Mediterranean regions, particularly in organic production and low-input oriented agriculture. In Sicily, the species is widespread both as a wild and cultivated plant. The present study assessed the phenotypic and genetic variation among natural populations of sulla collected from different environments throughout Sicily and analysed how the patterns of phenotypic diversity varied according to the environmental parameters of each collection site. Two commercial varieties and two Sicilian agro-ecotypes were also included in the study as controls. Principal components analysis (PCA) was performed on the sites using geographic, climatic, and pedological data to assess the differences in types of collection sites. PCA was also performed on the accessions (using pheno-morphological and agronomic data) to establish the importance of different traits in explaining multivariate polymorphisms. The results showed a large degree of genetic diversity (based on ISSR markers) and variability in pheno-morphological and agronomic traits. PCA did not clearly differentiate the accessions according to their habitats of origin, but in some cases accessions from the same habitat had a tendency to group together. The agronomic attributes of several populations were more pronounced than those of the controls. The observed variability may be valuable when selecting for H. coronarium varieties suitable for various uses (e.g., hay production, grazing, soil protection).

Defoliation management of forage crops affects endogenous reserves (in the root and in the stubble), the residual leaf area, and, consequently, the regrowth and biomass yield. The aim of this study was to evaluate the effect of cutting frequency (28-d vs. 35-d intervals) and stubble height (3 vs. 6 cm) on forage yield, regrowth, and persistence of berseem clover (Trifolium alexandrinum L.). Neither cutting interval nor cutting height affected plant survival during the crop cycle. Frequent clipping reduced crop yield. Residual biomass and leaf area were less when plants were cut at a height of 3 cm compared with 6 cm, but stubble height did not affect the total amount of dry matter (DM) removed. However, with a cutting interval of 28 d, DM yield was greater with a stubble height of 6 cm compared with 3 cm, whereas stubble height generally had no effect with a cutting interval of 35 d. This study shows that severe defoliation, which substantially reduces residual photosynthetic area, forces berseem clover plants to mobilize reserves from the taproot. With frequent clipping, taproot reserves are depleted and regrowth is impaired, whereas less frequent clipping enables taproot reserves to be restored. In contrast, less severe defoliation, which results in a considerable residual leaf area, promotes rapid regrowth regardless of the frequency of defoliation.

SUMMARYPrickly scorpion's tail (Scorpiurus muricatus L.) is a self-reseeding annual legume widely distributed in natural pastures of the Mediterranean area and appreciated by farmers for its productivity, forage quality and palatability. Twenty-eight natural populations were collected throughout Sicily in 2005; two field experiments were carried out in 2005/06 in a hilly area of the Sicilian inland to assess the genetic variation based on pheno-morphological and agronomic characters. The pheno-morphological traits observed were analysed using a principal component analysis (PCA). The first four components of PCA (eigenvalues >1) explained 0·84 of the total variation. Similarities obtained by PCA were investigated by means of cluster analysis, which clearly identified five clusters.The pheno-morphological and agronomic traits were mainly affected by latitude of the collection site (0·69 of the correlations were significant), spring rainfall (0·63) and rain days per year (0·63). Altitude was not significantly correlated with any of the traits.A strong positive correlation was found between the days to the first flower and spring rainfall at the collection site. Populations originating from subhumid or dry-subhumid Mediterranean climate zones showed greater leaf dimensions when compared with those originating from semi-arid zones. Seed weight decreased with increasing number of rain days per year and spring rainfall. Populations from drier environments showed, on the whole, a more prostrate growth habit. Dry matter yield at spring cut exhibited a significant correlation with latitude (positive) and longitude (negative). Seed production was highly correlated with spring rainfall, number of rain days per year and latitude of collection site. The presence of a large diversity among populations appears to be valuable when searching for suitable S. muricatus material to exploit in pastures and crop–livestock farming systems of Mediterranean areas.

The present study assessed the diversity of pheno-morphological and agronomic traits among 31 natural populations of burr medic (Medicago polymorpha L.) from different environments throughout Sicily, and analysed the patterns of phenotypic diversity in relation to the environmental parameters of each collection site. Three commercial cultivars (Cavalier, Santiago, and Anglona) were also included in the study as check cultivars. Two field experiments were performed in 2005–06 in a hilly area of the Sicilian inland. Principal components analysis (PCA) was performed on the sites using geographic, climatic, and pedological data to assess the differences in types of collection sites. PCA was also performed on the accessions using pheno-morphological and agronomic data to establish the importance of different traits in explaining multivariate polymorphisms. Sicilian burr medic populations showed highly significant inter-population differences for all of the recorded pheno-morphological and agronomic traits, and several populations had agronomic attributes that were more pronounced than those of the check cultivars. PCA did not clearly differentiate the accessions according to their habitats of origin, but in some cases, accessions from the same habitat had a tendency to stay together. Populations from drier and warmer habitats flowered earlier and were less productive than those from wetter and colder ones. The large variability in both pheno-morphological and agronomic traits among Sicilian populations may be valuable when searching for suitable M. polymorpha material to exploit in pastures and crop–livestock farming systems in the Mediterranean region.