Dinitrogen fixation and nitrogen transfer among red clover cultivars

Farnham, Dale E.; George, J. R.

doi:10.4141/cjps93-136

Cited by 26 publications

(8 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The suggested mechanisms for this genetic variability have been proposed to include slow decay of roots and stolons in the large-leaf cultivars (Laidlaw et al 1996); effective competition from the large-leaf cultivars with grasses for available N (Laidlaw et al 1996); differences in root and nodulation profiles (Thilakarathna et al 2012a); and a higher herbage-to-root ratio of large-leaf cultivars compared to small-leaf cultivars (Seker et al 2003), causing N to diverted from roots (the immediate source of available N for transfer) to shoots. It is important to note that a few studies have shown a lack of variation between cultivars for belowground N transfer, including the following systems: white clover-perennial ryegrass (Ledgard 1991), red clover-orchard grass (Dactylis glomerata L.) (Farnham and George 1993), and red clover-bluegrass (Thilakarathna et al 2012b) (Table 2).…”

Section: Forage Legume Cultivarsmentioning

confidence: 99%

Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review

Thilakarathna

McElroy

Chapagain

et al. 2016

Agron. Sustain. Dev.

155

111

View full text Add to dashboard Cite

Nitrogen is the most limiting nutrient in most agroecosystems and thus critical for sustaining high yields. Conventional agricultural practices use synthetic fertilizers to ensure an adequate supply of nitrogen in soils, but fertilizers come at a significant monetary and environmental cost. A strategy to improve nitrogen supply in cropping systems is the inclusion of nitrogen-fixing legumes, which can provide nitrogen benefits to companion crops through belowground nitrogen transfer. However, a better understanding of the underlying mechanisms and factors that govern nitrogen transfer is important in order to determine potential areas for improving this association. Here, we review the mechanisms of belowground nitrogen transfer in managed herbaceous cropping systems, focusing on forage systems. We classify three major routes of nitrogen transfer from legumes to non-legumes: (1) decomposition of legume root tissues and uptake of mineralized nitrogen by neighboring plants, (2) exudation of soluble nitrogen compounds by legumes and uptake by non-legumes, and (3) transfer of nitrogen mediated by plant-associated mycorrhizae. Literature data shows that rates of nitrogen transfer range from 0 to 73 % from forage legumes to companion grasses in mixed stands, depending on the legume species and cultivar. We list the factors that affect nitrogen transfer including abiotic factors, e.g., water stress, temperature, light, soil available nitrogen, and application of nitrogen fertilizer, and biotic factors, e.g., root contact, plant density, growth stage, production year, defoliation, and root herbivores. While the rates of nitrogen transfer are often constrained by abiotic conditions, such as temperature and water availability, that are beyond the control of growers, agronomic practices, e.g., planting density and choice of species and cultivar, may help to increase nitrogen transfer. Ultimately, the selection of plant pairs with compatible traits offers the best path forward to improving nitrogen transfer in intercrops.

show abstract

Section: Forage Legume Cultivarsmentioning

confidence: 99%

Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review

Thilakarathna

McElroy

Chapagain

et al. 2016

Agron. Sustain. Dev.

155

111

View full text Add to dashboard Cite

show abstract

“…Transfer will be greater where roots of the legume and grass are in close proximity as there will be less opportunity for uptake by microorganisms competing for mineralized N (Ledgard et al 1985). Field studies estimate that 18 to 71% of the total N content of grass can be transferred from clover (Boller & Nosberger 1987;Goodman 1991;Farnham & George 1993), with up to 113 kg N ha ±1 yr ±1 transferred in clover-rich swards ®xing 545 kg N ha ±1 yr ±1 (Elgersma & Hassink 1997). In contrast, in studies where less N was ®xed, clover contributed little N to the companion grass (Morris et al 1990).…”

Section: Grass/clover Leysmentioning

confidence: 99%

Is the productivity of organic farms restricted by the supply of available nitrogen?

P.M.*¹,

Sylvester‐Bradley²,

Philipps³

et al. 2002

Soil Use and Management

248

View full text Add to dashboard Cite

This paper reviews information from the literature and case studies to investigate whether productivity in organic systems is restricted by the supply of available N during the major phases of crop growth. Organic systems have the potential to supply adequate amounts of available N to meet crop demand through the incorporation of leys, N rich cash crop residues and uncomposted manures. However, this is seldom achieved because leys are only incorporated once every few years and organically produced crop residues and manures tend to have low N contents and slow mineralization rates. N availability could be improved by delaying ley incorporation until spring, applying uncomposted manures at the start of spring growth, transferring some manure applications from the ley phase to arable crops, preventing cover crops from reaching a wide C:N ratio and better matching crop type with the dynamics of N availability.

show abstract

“…Wilson et al 1933;Masterson and Sherwood 1978;Finn and Brun 1982;Murphy 1986;Overdieck and Reining 1986a, b;Norby 1987;Ta et al 1987;Vogel and Curtis 1995;Zanetti et al 1996). In the long term, legume stimulation together with transfer of legume N to non-N 2 -®xing species via legume litter decomposition, exudation and mycorrhizal hyphal interconnections between legumes and non-legumes also increases overall plant productivity (Rao and Giller 1993;Farnham and George 1993;Seresinhe et al 1994;Laidlaw et al 1996). However, all these experiments were carried out under fertile, horticultural or agronomic conditions not representative for natural plant communities where other nutrients such as P may limit legume growth.…”

Section: Introductionmentioning

confidence: 99%

Nutrient relations in calcareous grassland under elevated CO 2

Niklaus

Leadley

Stöcklin³

et al. 1998

Oecologia

View full text Add to dashboard Cite

Plant nutrient responses to 4 years of CO 2 enrichment were investigated in situ in calcareous grassland. Beginning in year 2, plant aboveground C:N ratios were increased by 9% to 22% at elevated CO 2 (P < 0.01), depending on year. Total amounts of N removed in biomass harvests during the ®rst 4 years were not aected by elevated CO 2 (19.9 1.3 and 21.1 1.3 g N m A2 at ambient and elevated CO 2 ), indicating that the observed plant biomass increases were solely attained by dilution of nutrients. Total aboveground P and tissue N:P ratios also were not altered by CO 2 enrichment (12.5 2 g N g A1 P in both treatments). In contrast to non-legumes (>98% of community aboveground biomass), legume C/N was not reduced at elevated CO 2 and legume N:P was slightly increased. We attribute the less reduced N concentration in legumes at elevated CO 2 to the fact that virtually all legume N originated from symbiotic N 2 ®xation (%N dfa % 90%), and thus legume growth was not limited by soil N. While total plant N was not aected by elevated CO 2 , microbial N pools increased by +18% under CO 2 enrichment (P 0.04) and plant available soil N decreased. Hence, there was a net increase in the overall biotic N pool, largely due increases in the microbial N pool. In order to assess the eects of legumes for ecosystem CO 2 responses and to estimate the degree to which plant growth was P-limited, two greenhouse experiments were conducted, using ®rstly undisturbed grassland monoliths from the ®eld site, and secondly designed`microcosm' communities on natural soil. Half the microcosms were planted with legumes and half were planted without. Both monoliths and microcosms were exposed to elevated CO 2 and P fertilization in a factored design. After two seasons, plant N pools in both unfertilized monoliths and microcosm communities were unaected by CO 2 enrichment, similar to what was found in the ®eld. However, when P was added total plant N pools increased at elevated CO 2 . This community-level eect originated almost solely from legume stimulation. The results suggest a complex interaction between atmospheric CO 2 concentrations, N and P supply. Overall ecosystem productivity is N-limited, whereas CO 2 eects on legume growth and their N 2 ®xation are limited by P. Key words Dinitrogen ®xation á Plant functional types á legumes á Nutrient limitation á Phosphorus IntroductionMost studies of vascular plant responses to atmospheric CO 2 enrichment show an enhancement of growth when carried out under sucient nutrient supply. In natural environments, plant productivity is often limited by the availability of mineral nutrients such as nitrogen and phosphorus (Vitousek and Howarth 1991) which in turn may limit the stimulation of plant growth by CO 2 enrichment. This underlines the importance of considering plant nutrient status in understanding their growth responses to increased CO 2 concentrations (Woodward et al. 1991;Overdieck 1993;KoÈ rner 1995b

show abstract

Dinitrogen fixation and nitrogen transfer among red clover cultivars

Cited by 26 publications

References 1 publication

Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review

Belowground nitrogen transfer from legumes to non-legumes under managed herbaceous cropping systems. A review

Is the productivity of organic farms restricted by the supply of available nitrogen?

Nutrient relations in calcareous grassland under elevated CO 2

Contact Info

Product

Resources

About