Background and aims Grasses and legumes co-exist in grasslands partially because of nitrogen (N) niche partitioning and facilitation. Grasses stimulate legume biological N fixation (BNF) by depleting soil N, simultaneously benefiting from the N that legumes fix. While these responses and mechanisms are maximized at ~ 40% legume proportion in temperate grass-legume mixtures, they have remained little studied in warm climates. Here, we explored N niche differentiation and overyielding along a legume proportion gradient in a subtropical grass-legume pasture. Methods Bahiagrass (Paspalum notatum Flügge; C4 grass) and rhizoma peanut (Arachis glabrata Benth.; C3 legume) were studied in pastures encompassing a legume gradient of zero (grass monoculture) to 60% (grass-legume mixture). Twenty-four sites were clipped at 4-week intervals during four periods per year over two years (n = 192). Samples were analyzed for total and atmospheric N concentration using the natural abundance technique (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11104_2025_7234_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">${\updelta }^{15}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="normal">δ</mi> </mrow> <mn>15</mn> </msup> </math></EquationSource> </InlineEquation> N). The proportion of soil-derived N was estimated by the difference between total and atmospheric N concentration in shoot biomass. Results Nitrogen niche differentiation and overyielding were maximized between 33–41% legume. Within this optimum range, the atmospheric and soil-derived N content in shoot biomass overyielded the grass monoculture by 84–148% and 75–79%, respectively, during both years. Within this range, the whole-season-BNF averaged 10.0–13.8 g N m−2 during both years, overyielding sites with maximum legume proportion by 27–50%. At 35% legume, the soil-derived N yield was 225–285% and 73–134% greater than for grass monoculture and legume-dominated sites. Conclusion Moderate legume proportions (30–40%) maximize N niche differentiation and overyielding compared with subtropical grass monocultures and legume-dominated grasslands.

Nitrogen niche differentiation and overyielding along a legume proportion gradient in a subtropical grass-legume mixture

期刊论文
发表日期：

2025年1月31日

查看全文

Nicolas Caram,
Lynn E. Sollenberger,
Marcelo O. Wallau,
Jose C. B. Dubeux

摘要

Background and aims

Grasses and legumes co-exist in grasslands partially because of nitrogen (N) niche partitioning and facilitation. Grasses stimulate legume biological N fixation (BNF) by depleting soil N, simultaneously benefiting from the N that legumes fix. While these responses and mechanisms are maximized at ~ 40% legume proportion in temperate grass-legume mixtures, they have remained little studied in warm climates. Here, we explored N niche differentiation and overyielding along a legume proportion gradient in a subtropical grass-legume pasture.

Methods

Bahiagrass (Paspalum notatum Flügge; C4 grass) and rhizoma peanut (Arachis glabrata Benth.; C3 legume) were studied in pastures encompassing a legume gradient of zero (grass monoculture) to 60% (grass-legume mixture). Twenty-four sites were clipped at 4-week intervals during four periods per year over two years (n = 192). Samples were analyzed for total and atmospheric N concentration using the natural abundance technique ( ${\updelta }^{15}$ $δ^{15}$ N). The proportion of soil-derived N was estimated by the difference between total and atmospheric N concentration in shoot biomass.

Results

Nitrogen niche differentiation and overyielding were maximized between 33–41% legume. Within this optimum range, the atmospheric and soil-derived N content in shoot biomass overyielded the grass monoculture by 84–148% and 75–79%, respectively, during both years. Within this range, the whole-season-BNF averaged 10.0–13.8 g N m⁻² during both years, overyielding sites with maximum legume proportion by 27–50%. At 35% legume, the soil-derived N yield was 225–285% and 73–134% greater than for grass monoculture and legume-dominated sites.

Conclusion

Moderate legume proportions (30–40%) maximize N niche differentiation and overyielding compared with subtropical grass monocultures and legume-dominated grasslands.