Various agronomic factors can affect the productivity and the efficiency of legume-grass intercropping systems. This research was carried out in a Mediterranean semi-arid environment (37°30’N; 13°31’E; 178 m a.s.l.) with the aim to study on berseem clover- annual ryegrass mixture (Trifolium alexandrinum L. – Lolium multiflorum Lam subsp. wersterwoldicum) the effects of different plant arrangement (sowing of the two components in alternate rows or in the same row) and seeding ratios (100:0; 75:25; 50:50; 25:75; 0:100) on forage yield, nitrogen content and nitrogen fixation. The experimental design was a split-plot with four replications. The 15N isotope dilution technique was used to estimate nitrogen fixation by berseem clover. All plots were cut four times (first cut 85 DAS; rest period of four weeks).
The DM yield of mixtures and pure stand clover were similar; annual ryegrass in pure stand produced the lowest yields. No significant differences for DM yield were observed due to the plant arrangement and seeding ratio in the mixture. Intercropping berseem had always a significant higher percentage of Ndfa than monocropped berseem. The %Ndfa of mixed berseem was not influenced by plant arrangement but gradually decreased when proportion of berseem in the mixture increased

ATTARDO, C

FRENDA, Alfonso Salvatore

GIAMBALVO, Dario

SCARPELLO, Carmela

STRINGI, Luigi

TRAPANI, Piero

Archivio istituzionale della ricerca - Università di Palermo

Integrating efﬁcient grassland farming and biodiversity 533Berseem-annual ryegrass intercropping: effect of plant arrangement and seeding ratio on N2 ﬁxation and yieldSTRINGI, L., GIAMBALVO, D., SCARPELLO, C., ATTARDO, C., FRENDA, A. S. AND TRAPANI, P.Dipartimento di Agronomia Ambientale e Territoriale, Università di Palermo, Viale delle Scienze, 90128 Palermo, ItalyAbstractVarious agronomic factors can affect the productivity and the efﬁciency of legume-grass intercropping systems. This research was carried out in a Mediterranean semi-arid environment (37°30’N; 13°31’E; 178 m a.s.l.) with the aim to study on berseem clover- annual ryegrass mixture (Trifolium alexandrinum L. – Lolium multiﬂorum Lam subsp. wersterwoldicum) the effects of different plant arrangement (sowing of the two components in alternate rows or in the same row) and seeding ratios (100:0; 75:25; 50:50; 25:75; 0:100) on forage yield, nitrogen content and nitrogen ﬁxation. The experimental design was a split-plot with four replications. The 15N isotope dilution technique was used to estimate nitrogen ﬁxation by berseem clover. All plots were cut four times (ﬁrst cut 85 DAS; rest period of four weeks). The DM yield of mixtures and pure stand clover were similar; annual ryegrass in pure stand produced the lowest yields. No signiﬁcant differences for DM yield were observed due to the plant arrangement and seeding ratio in the mixture. Intercropping berseem had always a signiﬁcant higher percentage of Ndfa than monocropped berseem. The %Ndfa of mixed berseem was not inﬂuenced by plant arrangement but gradually decreased when proportion of berseem in the mixture increased.Keywords: berseem clover, annual ryegrass, mixture, plant arrangement, seeding ratio, nitrogen ﬁxationIntroductionIntercropping is the growing of two (or more) crops together on the same area of ground and often produces an advantage in terms of more yield and less variation in yield than comparable areas of sole crops (Willey, 1979; Bulson et al., 1997). The most commonly accepted reason explaining why it is possible to obtain better yields with crop mixtures is that the component crops can use more efﬁciently the limiting resources differing in their growth requirements. Systems which combine grass and legume crops are highly regarded because of their potential for replacing fertilizer N with symbiotically ﬁxed atmospheric N2 and the economic and environmental beneﬁts which may result from this (Stern, 1993). However, in the literature there are few data available on biological nitrogen ﬁxation by annual forage legumes in Mediterranean environments. As well as few data is available on the contribution of biological nitrogen ﬁxed by annual legume to the nitrogen nutrition of a non-legume grown in mixed stand and on the effects of intercropping with grass on the quantity of N2 ﬁxed by forage legume component. Moreover the productivity and efﬁciency of grass-legume intercrop system are affected by various agronomic variables such as component crop density, plant spacing and arrangement, time of sowing of component crop, N fertilization (Ofori and Stern, 1987).The aim of this research was to evaluate on berseem clover – annual ryegrass mixture the effects of different plant arrangement and seeding ratios on forage yield, nitrogen content and nitrogen ﬁxation in a typical rain-fed Mediterranean environment.Grassland Science in Europe, Vol 10534Stringi et al.Materials and MethodsThe research was carried out during 2002/03 in a hilly area of Sicily (37°30’N; 13°31’E; 178 m a.s.l.) on a Vertic haploxerepts soil and with wheat as previous crop. The topsoil (0–40 cm) had the following characteristics: 38% clay, 25% silt, 36% sand, 8.4 pH (in water), 1.27% organic matter, 0.85‰ total nitrogen.The experiment was set up in a complete randomized block design with four replications. Treatments were: berseem (Trifolium alexandrinum L. cv Lilibeo) in pure stand (B); annual ryegrass (Lolium multiﬂorum Lam. subsp. wersterwoldicum cv Elunaria) in pure stand (R); and their mixture with different plant arrangement [sowing of the two components in alternate rows (BRAR) or in the same row (BRSR)] and seeding ratios (B25-R75; B50-R50; B75-R25). Pure stands were seeded at 50 kg seeds ha–1. Mixed and pure stands were sown by hand on 16 December 2002. No herbicide treatments were used; all plots were kept free of weeds by hand-weeding.The 15N isotope dilution technique was used to estimate nitrogen ﬁxation by clover. 15N fertilizer [(NH4)2SO4 with an isotopic composition of 10 atom% 15N] was uniformly applied in a liquid form, following the application procedure described by Hogh-Jensen and Schjoerring (1994). 15N fertilizer (8 kg N ha–1) was applied to a 2.88 m2 microplot in the middle of each plot at the emergence of the crops and again two days after the 1st and 2nd utilizations. The rest of the plot outside the 15N-labelled area received a top-dressing of ammonium sulphate in an amount equivalent to the microplots. After each application of labelled fertilizer an irrigation of all plots was used in order to avoid the retention of 15N fertilizer on the plant leaves. All plots were cut simultaneously at 85d after sowing and defoliation frequency of 28d was used (4 times). All plots were harvested by hand at 5 cm stubble height and total fresh weight was determined. At each harvest, a sample of plant material, taken in the centre of microplots, was hand-disaggregated into its botanical components (B, R), dried at 60 °C for 36 h, weighed and ground to a ﬁne powder (sieved using a 0.1 mm mesh size) in a fast running mill and analysed by the Iso-Analytical laboratory (EA-IRMS technique) for 15N enrichment and total N content. Data on 15N enrichment of biomass were used to calculate the percentage of clover nitrogen derived from symbiotic N2 ﬁxation (%Ndfa) according to Fried and Middleboe (1977).The GLM procedure of the Statistical Analysis System (SAS) was used to analyze the variance. Least signiﬁcant difference (LSD at P≤0.05) was used to make comparisons among treatments.Results and DiscussionDuring growing season total rainfall was close to the long-term mean (532 mm vs 550 mm) and distribution was generally favourable for crop growth.Dry matter yield (kg ha–1) for annual ryegrass and berseem clover in pure and mixed stands in relation to the different plant arrangement and seeding ratio are reported in Table 1.The yield of sole-cropped berseem was signiﬁcantly higher than ryegrass in pure stand (9449 vs 4826; P<0.0001). The DM yield of mixture and pure stand clover were similar. No signiﬁcant differences for DM yield were observed due to the arrangement of plants and to the different seeding ratio in the mixture.The legumes competed very well in the mixed stands, producing on average 80% of the total yield. Both seeding ratio and plant arrangement had small effects on %clover on DM basis.Annual ryegrass intercropped with berseem consistently had a higher nitrogen concentration in the dry matter than ryegrass grown in pure stand (P<0.001). This is in agreement with the Integrating efﬁcient grassland farming and biodiversity 535Berseem-annual ryegrass intercropping: effect of plant arrangement reports of Jorgessen et al. (1999) and Malhi et al. (2002). Moreover, mixing the components within the row, compared to sowing in alternate rows, signiﬁcantly increased the N content in annual ryegrass. On the contrary, the N concentration of berseem was much greater in pure stand than in mixture; similar results have been found by Scarpello (2003) for berseem clover intercropped with annul ryegrass in a Mediterranean semi-arid environment.In the mixture the N concentration (g kg–1 DM) of berseem and ryegrass forage increased signiﬁcantly with increase in berseem portion of stand.Table 1. Dry matter yield (kg ha–1), N concentration (g kg–1 DM) and percent of N uptake derived from atmospheric nitrogen ﬁxation (%Ndfa) for annual ryegrass and berseem clover in pure and mixed stands as affected by plant arrangement (alternate rows – BRAR; same row – BRSR) and seeding ratioDry matter yield (kg ha–1) N concentration (g kg–1 DM) Ndfa (%)Berseem Ryegrass Total Berseem Ryegrass BerseemBerseem (B) 9449 – 9449 35.0 – 73.3Ryegrass (R) – 4826 4826 – 20.6 –BRAR (B25-R75) 6746 2000 8746 31.6 29.9 81.1BRAR (B50-R50) 7083 1707 8790 32.6 29.2 80.7BRAR (B75-R25) 6948 1718 8666 33.5 31.3 78.8BRSR (B25-R75) 6824 2458 9282 31.4 28.4 84.1BRSR (B50-R50) 7980 1266 9246 33.7 33.3 80.2BRSR (B75-R25) 8258 1438 9696 33.9 33.6 78.8LSD0,05 970 852 811 1.3 2.5 3.0Mean effect of plant arrangementAlternate rows 6925 1809 8734 32.6 30.1 b 80.2Same row 7688 1721 9409 33.0 31.8 a 81.0Mean effect of seeding ratio     BR (B25-R75) 6785 b 2228 a 9013 31.5 b 29.1 b 82.6 aBR (B50-R50) 7531 a 1487 b 9018 33.1 a 31.2 a 80.4 abBR(B75-R25) 7603 a 1579 b 9182 33.7 a 32.5 a 78.8 bDifferent letters within the columns indicate signiﬁcant different at the P≤0.05 levelOn average, Trifolium alexandrinum achieved a higher proportion of its N from nitrogen ﬁxation when grown in mixture with ryegrass than when it was grown in monoculture (P<0.0001). In mixture ryegrass has been found to be stronger competitor for soil nitrogen (data not shown), and berseem relied more on N2 ﬁxation as N source. Similar observations were made by Papastylianou (1988), Loiseau et al. (2001), Carlsson and Huss-Danell (2003) and Stringi et al. (2004). This suggests that nitrogen competition plays a key role in intercropping legume-nonlegume systems and its knowledge can enable to manage better N inputs in order to make the intercropping system more efﬁcient.No signiﬁcant differences for %Ndfa were observed due to the arrangement of plants in the mixture. The percentage of nitrogen derived from N2-ﬁxation decreased with increase in berseem portion of stand. Such result seems related to the increase of soil N uptake by Grassland Science in Europe, Vol 10536Stringi et al.ryegrass as its density increased in the mixture; this, on turn, encouraged the legume to obtain a greater proportion of its nitrogen through biological ﬁxation.The apparent transfer of ﬁxed nitrogen from clover to grass was negligible in all treatment. In fact, no signiﬁcant lower values for % atom 15N of intercropped annual ryegrass compared to monocropped were observed, indicating that transfer of the nitrogen from legume to grass was marginal or nonexistent (Cowell et al., 1989). This is in agreement with the reports of Peoples and Herridge (1990), Danso et al. (1993) and Stringi et al. (2004) that highlighted how in annual grass-legume intercropping N transfer may not be common phenomena.AcknowledgementsThis research was supported by Patti territoriali “Magazzolo-Platani”.ReferencesBulson H. A. J., Snaydon R. W. and Stopes C. E. (1997) Effects of plant density on intercropped wheat and ﬁeld beans in an organic farming system. Journal of Agricultural Science, 128, 59–71.Carlsson G. and Huss-Danell K. (2003) Nitrogen ﬁxation in perennial forage legumes in the ﬁeld. Plant and Soil, 253, 353–372.Cowell L. E., Bremer E. and Van Kessel C. (1989) Yield and N2 ﬁxation of pea and lentil as affected by intercropping and N application. Canadian Journal of Soil Science, 69, 243–251.Danso S. K. A., Palmason F. and Hardason G. (1993) Is nitrogen transferred between ﬁeld crops? Examining the question through a sweet-blue lupin (Lupinus angustifolium L.) – oats (Avena sativa) intercrop. Soil Biology and Biochemestry, 25, 1135–1137.Fried M. and Middleboe V. (1997) Measurements of amount of nitrogen ﬁxed by a legume crop. Plant and Soil, 4, 713–715.Hogh-Jensen H. and Schjoerring J. K. (1994) Measurement of biological dinitrogen ﬁxation in grassland: Comparasion of the enriched 15N dilution and the natural 15N abundance methods at different nitrogen application rates and defoliation frequencies. Plant and Soil, 166, 154–164.Jorgensen F. V., Jensen E. S. and Schjoerring J. K. (1999) Dinitrogen ﬁxation in white clover grown in pure stand and mixture with ryegrass estimated by the immobilized 15N isotope dilution method. Plant and soil, 208, 293–305.Loiseau P., Soussanna J. F., Lounault F. and Delpy R. (2001) Soil N contributes to the oscillations of the white clover content in mixed swards of perennial ryegrass under conditions that simulate grazing over ﬁve years. Grass and Forage Scence, 56, 205–217.Malhi S. S., Zentner R. P. and Heier K. (2002) Effectiveness of alfalfa in reducing fertilizer N input for optimum forage yield, protein concentration, returns and energy performance of bromegrass-alfalfa mixtures. Nutrient cycling in agroecosystems, 62, 219–227.Ofori F. and Stern W. R. (1987) Cereal-legume intercropping systems. Advances in Agronomy, 4, 41–90.Papastylianou I. (1988) The 15N methodology in estimating N2 ﬁxation by vetch and pea grown in pure stand or in mixes with oat. Plant and Soil, 107, 183–188.Peoples M. B. and Herridge D. F. (1990) Nitrogen ﬁxation by legumes in tropical and subtropical agriculture. Advances in Agronomy, 44, 155–223.Scarpello C. (2003) Efficienza biologica della consociazione trifoglio alessandrino-loiessa e stima dell’azotofissazione in rapporto a diversi livelli di azoto minerale nel suolo. PhD thesis, University of Palermo, Palermo, Italy.Stern W. R. (1993) Nitrogen ﬁxation and transfer in intercrop systems. Field Crops Research, 34, 335–356.Stringi L., Giambalvo D., Scarpello C., Di Miceli G. and Attardo C. (2004) Nitrogen fixation by beersem clover in pure and mixed stand in a semi-arid Mediterranean environment. In Jacobsen S.E., Jensen C.R. Porter J.R. (eds) Proceedings of VIII ESA Congress: European agriculture in a global context Copenhagen, Denmark 11–15 July , 671–672.Willey, R. W. (1979). Intercropping – its importance and research needs. Part 1. Competition and yield advantages. Field Crop Abstracts, 32, 1–10.

Berseem-annual ryegrass intercropping: effect of plant arrangement and seeding ratio on N2 fixation and yield

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Berseem-annual ryegrass intercropping: effect of plant arrangement and seeding ratio on N2 fixation and yield

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