A study of 15N transfer between legumes and grasses

By F. Paynel, F. Lesuffleur, J. Bigot, S. Diquélou, J. Cliquet. Agronomy for Sustainable Development, 2008

88 citations recorded by the source corpus.

The overuse of classical N fertilisers contributes substantially to environmental degradation by pollution of groundwater by nitrates. This leaching of N in waters is also an economic flaw for farmers because only a part of the fertiliser is used by the plants. Here, systems involving mixtures of legumes and grasses represent a sustainable alternative because legumes can fix atmospheric N2 using symbiotic microbes. N transfer in those mixtures has been thoroughly investigated but little is known concerning the effect of N fertiliser on N transfer between N-fixing legumes and companion grasses. In white clover (Trifolium repens L.) — perennial ryegrass (Lolium perenne L.) associations, N is transferred mostly through rhizodeposition into the soil by clover followed by re-uptake by ryegrass. Rhizodeposition of N occurs through senescence and decomposition of legume tissue or through exudation of N compounds by living cells. Ammonium and amino acids are the main compounds exuded and their exudation is thought to occur by passive diffusion attributed to a concentration gradient from root to soil. In this study, we test the hypothesis that greater N transfer from clover to grass, as seen in N-rich soils or nutrient solutions, is due to greater N rhizodeposition brought about by higher ammonium and amino acid content of roots. The relations between N input, root N content, N net exudation and N transfer between legumes and grasses were investigated using 15N by growing white clover and perennial ryegrass with increasing N application in axenic microlysimeters or in pots. Ammonium and amino acid concentrations were measured in root tissues, in root bathing solutions and in soils. We found that mineral N application strongly reduced atmospheric N fixation by clover, from 3.0 to 0.9 mg per plant, and root amino acid content, from 164 to 49 nmoles per g dry weight, but had no effect on ammonium and amino acid concentrations in sterile exudates, showing for the first time that amino acid net exudation is independent of root content. In contrast, ammonium and amino acid concentrations in clover soils increased with N fixation, showing the link between N fixation and N rhizodeposition in soils. Nitrate application increased ryegrass root growth by 7–8 times, and transfer of N between clover and ryegrass (by 3 times). It is concluded that N fertiliser does not modify N exudation but decreases N fixation and ammonium rhizodeposition in soil by clover. N fertiliser increases N transfer between clover and ryegrass by increasing soil exploration by ryegrass and giving a better access to different available N sources, including the N compounds exuded from clover.

Subfields: Plant Science, Soil Science

View Paper: https://www.semanticscholar.org/paper/ee1feed2e8410357a50f81e9124d3c6e43893e25

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Plant Science

1. S. Mahieu
2. J. Fustec
3. J. Cliquet
4. F. Lesuffleur
5. Jesper Rasmussen
6. F. Akinnifesi

In Soil Science

1. S. Mahieu
2. J. Fustec
3. J. Cliquet
4. F. Lesuffleur
5. Jesper Rasmussen
6. E. Nkonya
7. F. Akinnifesi

Citations in the corpus

• Biological nitrogen fixation and socioeconomic factors for legume production in sub-Saharan Africa: a review (2011, background): “Rhizobium inoculants have been used to address the problems of soil fertility and inadequate fertilizer application in grain legume production and have been found to be a cheaper and usually more effective agronomic practice for ensuring adequate N nutrition of legumes, compared with the application”
• Nitrogen rhizodeposition of legumes. A review (2011, methodology): “(i) In the 15 N dilution technique, the label is provided directly to the soil and N fixation is estimated by the input of 14 N from the atmosphere (Fig. 1). This method is reliable for measurement of N2 fixation by legumes and transfer to companion plants (Giller et al., 1991; Moyer-Henry et al., 2”
• Nitrogen Rhizodeposition of Legumes (2011, methodology): “method is reliable for measurement of N2 fixation by legumes and transfer to companion plants (Giller et al., 1991; Moyer-Henry et al., 2006; Paynel et al., 2008 ) but is strongly influenced by small differences in the spatial and temporal distribution of soil 15 Nw hen used”
• Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland (2011, background): “an increase in N transfer after nitrate application was positively correlated with root dry weight ( Paynel et al. 2008 ), which supports the hypothesis that root characteristics of receiver plant species strongly determine N transfer.”