Abstract The agronomic performance, biological nitrogen fixation (BNF

A 2 &amp

F 2 Fayad

L 1 Al-Bitar

N 1 Abou Driouech

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16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 
Archived at http://orgprints.org/view/projects/conference.html 
 
 
Agronomic performance of annual self-reseeding legumes and 
their self-establishment potential in the Apulia region of Italy 
Driouech, N1. Abou Fayad , F2. Ghanem, A2. & Al-Bitar, L1.  
Key words: annual self-reseeding legumes, Trifolium spp., Medicago spp., biological 
nitrogen fixation, Mediterranean region.  
Abstract  
The agronomic performance, biological nitrogen fixation (BNF) ability and self-
establishment potential of seven species of annual self-reseeding legumes were 
investigated in Apulia region, Italy. For the first cropping cycle (2005-2006) preliminary 
results showed that Trifolium spp. performed better than Medicago spp. Among the 
seven species, five were more suitable to the site’s conditions.  T. angustifolium and 
M. polymorpha gave the best results. T. angustifolium fixed 131.7 kg ha-1 year of 
nitrogen (15N isotope dilution method), produced 1976 kg ha-1 of seeds and 8.7 t ha-1 
of dry matter (DM). M. radiata and M. rigidula were the less performing. During the 
second cropping cycle (2006-2007) results showed that Trifolium spp. self-established 
better than Medigaco spp. Regenerated species appeared to sustain optimum level of 
BNF. Again T. angustifolium was the best performing species producing the highest 
DM (7.7 t ha-1) and fixing nitrogen (146.7 kg) N ha-1 symbiotically. In contrast, M. 
polymorpha, was the less performing (0.3 t ha-1 of DM and 11.5 kg ha1 of BNF) while 
M. rigidula and M. radiata did not regenerate. Given the overall performance of all 
species, it was determined that T. angustifolium had the greatest potential for further 
development in this environment. 
Introduction  
Successful establishment of annual legumes is achieved only with the use of varieties 
that have both high persistence and high productivity within the specific environment 
in which they are used (Rochon et al., 2004). In the Mediterranean areas, native 
ecotypes are more persistent and better adapted than commercial varieties (Fara et 
al., 1997). Self-reseeding annual legumes can play an increasingly important role in 
Mediterranean organic farming systems. They are flexible components within the 
whole farm systems, and can be used as cover crop, living mulches, green manure 
and forage crops to increase economic, environmental and social sustainability 
(Caporali et al., 2004). Nitrogen fixed by legumes is the main nitrogen source in 
organic farming systems (Loges et al., 2000). Moreover, in order to design strategies 
for optimizing management of biological nitrogen fixation (BNF) for maximal 
production with minimal nitrogen pollution of water resources, it is essential that 
nitrogen inputs by legumes and the subsequent fate of this nitrogen be quantitatively 
assessed (Unkovich and Pate, 2001).Therefore, the agronomic performance, ability of 
nitrogen fixation and self-establishment potential of seven self-reseeding legumes 
(four Trifolium species as well as three Medicago spp.) were investigated in 
                                                 
1 Mediterranean Agronomic Institute of Bari-  Via Celgie, 9 Valenzano (BA) 70010, Italy, E-Mail driouech@iamb.it, 
   Internet : www.iamb.it 
2 Master students at Mediterranean Agronomic Institute of Bari-Italy 
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 
Archived at http://orgprints.org/view/projects/conference.html 
 
 
comparison with Trifolium subterraneum cv. Antas (T.su.) used as reference crop 
during the period between autumn 2005 and spring 2007 in South of Italy. 
Materials and methods  
The experiment was carried out at the experimental field of IAMB located in Apulia 
region, South of Italy (41°03’16”N, 16°52’45”E, 72 m a.s.l.). Apulia region is 
characterized by a Mediterranean climate with humid mild winter and hot dry summer. 
Precipitation varies from 400 to 500 mm/ year and is mainly concentrated between 
October and April. Annual average temperature ranges from 15 to 16 °C, with a 
maximum of 35°C recorded in July and a minimum of 0°C in January (IAMB’s 
Agrometerological Station). The soil type was a sandy clay. Soil pH was 8.1, soil 
organic matter 1.6%, P and K (0-20 cm) were approximately 85 and 514 mg kg-1, 
respectively at experimental site. 
Seven accessions of annual self-reseeding legumes (Trifolium angustifolium (T.a.),  
T. campestre (T.ca.), T. cherleri (T.ch.), T. stellatum (T.st.), Medigago polymorpha 
(T.p.), M. rigidula (M.ri.) M. radiata (M. ra.) and two reference crops Trifolium 
subterraneum (T.su) cv. ANTAS (Crl1) and Barley Hordeum vulgare (Crl2) (as 
reference for 15N isotope dilution method) were arranged in a randomised completely 
block design with four replicates. Each block was composed of 9 plots of 9 m2.   
Legumes were sown in November 2005 at a rate of 28 kg ha-1. The first growth cycle 
extended over seven months until the end of May 2006. Legumes were left on the field 
over the summer after seed production. In autumn (October 2006), legumes self-
established after the first rain and grew until April 2007. Legumes were then 
incorporated (no cutting regime) as a green manure for further investigation. 
During the two growing cycles, plant height and crop ground cover were measured 
every two weeks. Before full-flowering stage April 2006 and March 2007, BNF was 
quantified using 15N isotope dilution method (Unkovich and Pate 2001). In each plot, a 
quadrat of 2.25 m2 was identified and two grams of ammonium sulphate (15NH4)2SO4 
diluted in 10 liters of water were sprayed. At the end of each growing cycle a 
representative sample per plot was used to measure DM, seed yield (only for the first 
cycle) and 15N (mass spectrophotometer) for BNF quantification. Statistic analysis was 
performed on each variable by analysis of variance. The observed measurements 
average were compared according to Duncan test. 
Results and brief discussion 
Highly significant differences of DM production were obtained between T.a, T.ca, M.p. 
and T. su (Crl1) in which Crl1 showed the lowest DM value. Highly significant 
differences were also observed between the Crl1 and M.ri and M. ra, in which Crl1 
showed a higher value (Tab.1). The lowest DM production of M. p. and M. ri. were far 
inferior to these reported by Walsh et al., (2001) in a study for annual medic 
production, with large differences in experimental design and sites conditions (i.e. soil 
pH=6.1) in Western Australia.  
Amount of BNF ranged from 0.7 to 147 kg ha-1 (Tab.1 & 2) and this is confirming 
results of Peoples et al., (1998) and Evers (2003). 
T. a. resulted in the highest BNF (146.7 kg ha-1 year), M. p. and T. ca. resulted in the 
lowest amounts (11.5 and 9.9 kg ha-1 year) in the second cropping cycle while (90 and 
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 
Archived at http://orgprints.org/view/projects/conference.html 
 
 
70 kg ha-1 year) in the first, respectively. This is due to the high DM production of M. p. 
and T. ca. in the first cropping cycle (5.5 and 5.1 t ha-1) in comparison with only (0.3 
and 0.3 t ha-1) in the second cycle, respectively. A clear reduction in BNF was also 
determined for T.ch. and T. st. for the second cropping cycle. 
Tab. 1: Agronomic performance of annual self-reseeding legumes (at the end of the 
1st growth cycle November 2005- May 2006) 
 Species Plant 
height 
 (cm) 
Crop ground 
cover 
 (%) 
DM 
(t ha-1) 
Seed 
yield 
(kg ha-1) 
BNF 
(kg ha-1 
year) 
T. angustifolium 43.4   b 100 a 8.7 a 1976    a 131.7 a 
T. campestre 33.9   b 100 a 5.1 b 472  cd 66.7 c 
T. stellatum 32,6   c 100 a 3.2 c 683   d 35.2 d 
T. cherleri 28.5 cd 99 a 3.6 c 1089   b 47.2 d 
M. polymorpha 55.6   a 100 a 5.5 b 732   c 89.6 b 
M. rigidula 23.6   d 53 b 0.9 d 60   e 1.9 e 
M. radiata 6.1   e 8 c 0.2 d 22   e 0.7 e 
T. subterraneum 
cv. Antas (Crl1)  
51.4   a 100 a 2.8 c 527 cd 32.6 d 
Means with different letters are significantly different (Duncan test, α=0.05)  
Highly significant differences were assessed between T. a. and T. su. (Crl1) for mainly 
DM and BNF in which the Crl1 showed the lowest value. Highly significant differences 
were also obtained between the Crl1 and the rest of the tested species in which the 
Crl1 showed the highest value (Tab. 2). 
Tab. 2: Self-establishment of annual self-reseeding legumes (at the end of the 2nd  
growth cycle September 2006- April 2007) 
 Species Plant height
 (cm) 
Crop 
 ground cover
 (%) 
DM 
(t.ha-1) 
BNF 
(kg ha-1 
year) 
T. angustifolium 40.6 a 97.5 a 7.7 a 146.7 a 
T. campestre 3.0 c 20.6 b 0.3 c 9.9 d 
T. stellatum 6.8 b 63.8 b 1.2 c 39.6 c 
T. cherleri 7.0 b 55.0 b 1.7 c 40.8 d 
M. ploymorpha 3.8 c 4.6 b 0.3 c 11.5 c 
M. rigidula 
M. radiata 
Not regenerated 
T. subterraneum  
cv. Antas  (Crl1) 
39.8 a 100.0 a 5.4 b 125.2 b 
Means with different letters are significantly different (Duncan test , α=0.05)  
Generally, the legumes (except T.a) did not perform as well during the second 
cropping cycle compared to the first. This result confirms the results of an experiment 
conducted by Thorup-Kristensen and Bertelsen (1996) in Denmark, as well as the 
results of another experiment conducted in Italy at Mediterranean Agronomic Institute 
of Bari (IAMB) (Al-Bitar, 2005). These results are not only based on the amount of 
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008 
Archived at http://orgprints.org/view/projects/conference.html 
 
 
nitrogen fixed, but also on others parameters like legumes plant height, crop ground 
cover and DM production. 
Conclusions  
The genus Trifolium appeared better adapted to the pedo-climatic conditions of the 
studied area than the genus Medicago. Both Medicago radiata and Medicago rigidula 
did not regenerate while Medicago polymorpha regenerated very poorly. 
We conclude that Trifolium angustifolium is suitable for Apulian conditions due to 
highest BNF and rapid soil covering. After their incorporation, all legumes treatments 
(except T. ra. and T. ri.) showed a positive precrop effects on all growth parameters of 
the subsequent crops (Zucchini and lettuce) compared to controls without legumes 
preceding. T.a induced the best effect on the zucchini and lettuce crop yields  (42.66 
and 48 t ha-1 ) respectively. Consequently, T.a. may play an important role in 
managing soil fertility and be considered as a key-element in enhancing field 
biodiversity. It can further be recommended to integrate T.a  as a winter cover crop, 
for the purpose of green manure, in apulian organic cropping systems (i.e. rotation of 
organic vegetable crops). 
Acknowledgements 
This work was carried out in the framework of a joint PhD programme (Driouech, 
2005-2007) between Tuscia University-Viterbo and Mediterranean Agronomic Institute 
of Bari (IAMB). Gratitude is also extended to International Center of Agricultural 
Research in the Dry Areas (ICARDA) for legume seeds supply.  
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Agronomic performance of annual self-reseeding legumes and their self-establishment potential in the Apulia region of Italy

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Agronomic performance of annual self-reseeding legumes and their self-establishment potential in the Apulia region of Italy

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