The Impact of Grazing Animals on N2 Fixation in Legume-Based Pastures and Management Options for Improvement

Menneer, John C.; Ledgard, S. F.; McLay, C. D. A.; Silvester, Warwick B.

doi:10.1016/s0065-2113(04)83004-9

Cited by 21 publications

(19 citation statements)

References 166 publications

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“…In contrast, it appears that defoliation did not affect L. corniculatus N-fixation ability: the total shoot N content was not affected and shoot N concentrations were higher in defoliated than non-defoliated plants. It has earlier been shown that defoliation can decrease nitrogenase activity and nodule weight in legume roots (Vance et al 1979;Ryle et al 1985Ryle et al , 1986 and that recovery of these attributes can take 5 to 24 days (Menneer et al 2004). Our defoliation intensity (4-7% of shoot mass) was one degree of magnitude lower than those frequently used in defoliation experiments (often superior to 50% of the biomass), which is likely to explain why the N 2 fixing ability was not affected by defoliation in our case.…”

Section: Discussionmentioning

confidence: 99%

Legume defoliation affects rhizosphere decomposers, but not the uptake of organic matter N by a neighbouring grass

Saj

Mikola

2008

Plant Soil

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Legume-grass interactions have a great influence on grassland primary production and it was recently shown how defoliation of a legume can increase the transfer of fixed N to a neighbouring grass. It has also been shown that defoliation of a plant can increase soil microbial activity and lead to better soil N availability in the rhizosphere of the defoliated plant. We combined these two perspectives and tested whether defoliation of a legume (Lotus corniculatus) can enhance N nutrition of the neighbouring grass (Holcus lanatus) by increasing growth of soil decomposer biota and the availability of soil organic matter N for grass uptake. We grew mixtures of L. corniculatus and H. lanatus in grassland soil that included 15 N-labelled L. corniculatus litter. In half of the systems, we subjected L. corniculatus to a defoliation treatment mimicking insect larvae feeding. At destructive harvests 1, 3, 9 and 30 days after the last defoliation event, we determined how L. corniculatus defoliation affected decomposer microbes, protozoa and nematodes and whether these changes among decomposers created a feedback on the growth and 15 N uptake of the neighbouring H. lanatus. Defoliation reduced the growth and litter-N uptake, but increased shoot N concentration of L. corniculatus. Of the soil variables measured, defoliation doubled the number of bacterial-feeding protozoa, but did not affect the abundance of decomposer microbes and bacterial-and fungal-feeding nematodes. Defoliation did not have statistically significant effects on H. lanatus shoot growth, shoot N concentration or litter-N uptake. Our results demonstrate how defoliation-induced changes in legume ecophysiology can affect the growth of decomposers in soil. However, these effects did not appear to lead to a significant change in the availability of soil organic N to the neighbouring grass. It seems that when positive effects of legume defoliation on grass N nutrition are found in grassland ecosystems, these are more likely to be explained by direct transfer of fixed N rather than changes in the availability of soil organic matter N.

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Section: Discussionmentioning

confidence: 99%

Legume defoliation affects rhizosphere decomposers, but not the uptake of organic matter N by a neighbouring grass

Saj

Mikola

2008

Plant Soil

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“…However, in this case, differences between treatments might not be expected since prior grazing may have provided much more mineral N than the modest fertiliser application, and this effect may last many months (Menneer et al 2004) and, furthermore, very low legume content (9%) and thus low N 2 fixation (2-4 kg ha -1 ) would mask potential treatment effects on measured N 2 fixation.…”

Section: Mineral N Depresses N 2 Fixationmentioning

confidence: 95%

“…A detailed review of the impacts of grazing animals on legume N 2 fixation are given in Menneer et al (2004). The key element of grazed dairy systems is the excretion by cattle of at least 75% ).…”

Section: Grazing and N 2 Fixationmentioning

confidence: 99%

“…Some of the more pertinent reviews on N 2 fixation in grazed perennial pastures include Haynes and Williams (1993), Jarvis et al (1995), Ledgard and Steele (1992), Ledgard (2001), Menneer et al (2004), while the reviews of Carlsson and HussDanell (2003) and Cuttle et al (2003) are also quite useful. Eckard (1998) provides salient background to the N dynamics of dairy pastures in Australia and likely responses to N fertiliser application but does not explicitly deal with N 2 fixation.…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen fixation in Australian dairy systems: review and prospect

Unkovich¹

2012

Crop Pasture Sci.

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Abstract. Quantitative measurement of N 2 fixation has rarely been conducted in Australian dairy pastures. The available data indicate that annual N 2 fixation rates in Australian dairy pastures are generally low, due to low pasture legume content. With typical legume contents of grazed pastures less than 30% of total pasture biomass production, annual N 2 fixation in herbage is usually much less than 50 kg ha -1 year -1 . Other factors which are likely to be able to contribute to increased N 2 fixation input (rhizobia, mineral N management, soil acidity, soil water contents) will have little impact until such time as legume contents are increased. In contrast, for some hay systems, such as those using lucerne, N 2 fixation input is shown to be high (200-300 kg ha). While pasture clover contents remain low there is little value in study or measurement of N 2 fixation, nor in complex modelling, as N 2 fixation will be of little quantitative importance. However, where legume contents, and thus potential N 2 fixation are increased, there is scope for investigation into potential increases in N input from this source, which is invariably linked to fertiliser application, the management of grazing and the N returns in urine and dung. These are the major influences on sward N dynamics and legume N 2 fixation. The inoculant rhizobia used for white clover in Australia (TA1) is likely to be suboptimal. Isolated in Tasmania in 1953 it has been shown to be inferior in N 2 fixation compared with other strains on several occasions. Root pests and diseases are likely to be prevalent and impact directly on clover root growth and perhaps nodulation.Modelling is often used to describe the probable influence of management and/or climate on the operation of agricultural systems. Reliable modelling of N 2 fixation requires capacity to integrate the effects of grazing and pasture composition on soil mineral N dynamics, the influence of this mineral N on nodulation and on suppression of N 2 fixation, and environmental and management influences on soil rhizobial populations. Currently no models have demonstrated this capacity. At present, a suitably calibrated regression model is probably a good option for modelling N 2 fixation in Australian dairy pastures.Environmental benefits ensuing from increasing N 2 fixation and substituting this for fertiliser N are likely to be greater offfarm (reduced GHG emissions at site of fertiliser manufacture) than on, if current fertiliser management is optimal. Nevertheless substituting fixed N for fertiliser N would have modest environmental and feed efficiency benefits.

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“…treading, defoliation, and excreta) and their management have the potential to significantly affect clover growth and N 2 fixation (see recent review by Menneer et al, 2004). Previous studies (Brock et al, 1983;Ledgard et al, 1982;Menneer et al, 2003;Vinther, 1998) have largely focused on defoliation and excreta effects on clover growth and N 2 fixation.…”

Section: Introductionmentioning

confidence: 99%

Animal treading during wet soil conditions reduces N2 fixation in mixed clover-grass pasture

Menneer

Ledgard

McLay³

et al. 2005

Plant Soil

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A field experiment was carried out over 12 months to determine the effect of animal treading on N 2 fixation in a mixed white clover-ryegrass pasture. The experimental site was defoliated by mowing for the duration of the study. A single treading event of moderate or severe pugging intensity was initiated in plots during wet spring conditions by using dairy cows at varying stocking rates (4.5 cows 100 m )2 for 1.5 or 2.5 h, respectively). Inputs of dung and urine onto the plots was avoided by overnight housing of the cows and interception of excreta during the pugging event. Soil air-filled porosity decreased from 21% in the nonpugged control to 15À16% in pugged treatments by day 3. Bulk density of soil was not significantly affected by pugging. Soil inorganic N concentration increased in pugged treatments, and was 4-fold greater on day 28 in severely pugged plots compared to non-pugged plots. White clover plant density and plant size was markedly lower in pugged treatments (up to 85% and 72% reduction, respectively under severe pugging). White clover growth was most affected during the first 156 days after pugging (up to 90% decrease under severe pugging), leading to an annual clover dry matter production loss of 9% and 52%, respectively. The proportion of clover N derived from atmospheric N 2 (%Ndfa; estimated by 15 N dilution) was initially reduced (to a lower limit of 43%) by severe pugging (days 28À71) before recovery to control levels (90%) by day 91. Annual N 2 fixation in clover herbage decreased significantly from 76 kg N ha )1 yr )1 in the nonpugged control, to 66 and 36 kg N ha )1 yr )1 under moderate and severe pugging, respectively. Most of this difference was evident within the first 156 days after pugging. Our data indicates that the major loss in fixed N 2 input under pugging was due to reduced clover growth and production resulting from pugging damage and loss of residual white clover biomass by hoof action.

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The Impact of Grazing Animals on N2 Fixation in Legume-Based Pastures and Management Options for Improvement

Cited by 21 publications

References 166 publications

Legume defoliation affects rhizosphere decomposers, but not the uptake of organic matter N by a neighbouring grass

Legume defoliation affects rhizosphere decomposers, but not the uptake of organic matter N by a neighbouring grass

Nitrogen fixation in Australian dairy systems: review and prospect

Animal treading during wet soil conditions reduces N2 fixation in mixed clover-grass pasture

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