Tamanho da parcela para estudos de recuperação de fertilizante-15N por capim-tanzânia Plot-size for 15N-fertilizer recovery studies by tanzania-grass

O entendimento da dinâmica do N em ecossistemas de pastagens pode ser melhorado por estudos em que se utilize a técnica do traçador 15N. Nesses experimentos, deve-se assegurar que o movimento lateral do traçador não interfira nos resultados. Neste trabalho foram determinadas as exigências quanto ao tamanho da parcela para experimentos com 15N em pastagem irrigada de Panicum maximum cv. Tanzânia. Foram consideradas três intensidades de pastejo (leniente, moderada e intensa) em três épocas do ano: inverno, primavera e verão. Parcelas de 1 m², com uma touceira do capim ao centro, foram adequadas, independentemente da intensidade de desfolha ou da época do ano. O aumento na distância da área adubada com 15N influenciou negativamente a quantidade de N proveniente do fertilizante (Npfm) recuperado na forragem. As menores taxas de declínio nos valores de Npfm foram observadas para as intensidades de pastejo leniente e moderada; esse fato pode ser explicado pelas características de crescimento vigoroso dessas plantas. O aumento na intensidade de pastejo determinou a redução na massa da touceira: quanto menor a touceira, maior a sua dependência do N do fertilizante.<br>The understanding of the N dynamics in pasture ecosystems can be improved by studies using the 15N tracer technique. However, in these experiments it must be ensured that the lateral movement of the labeled fertilizer does not interfere with the results. In this study the plot-size requirements for 15N-fertilizer recovery experiments with irrigated Panicum maximum cv.Tanzania was determined. Three grazing intensities (light, moderate and intensive grazing) in the winter, spring and summer seasons were considered. A 1 m² plot-size, with a grass tussock in the center, was adequate, irrespective of the grazing intensity or season of the year. Increasing the distance from the area fertilized with 15N negatively affected the N derived from fertilizer (Npfm) recovered in herbage.The lowest decline in Npfm values were observed for moderate and light grazing intensities. This fact might be explained by the vigorous growth characteristics of these plants. Increasing the grazing intensity decreased the tussock mass and, the smaller the tussock mass, the greater was the dependence on fertilizer nitrogen

Retention times, regression coefficients, detection limits and concentration ranges of selected VOC marker substances from breath (a) and feces (b).

<p>R²—coefficient of determination;LOD—limit of detection;LOQ—limit of quantification</p><p>* potential marker substances from a former in vitro study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123980#pone.0123980.ref009" target="_blank">9</a>]</p><p>^† values lower than LOD</p><p>Retention times, regression coefficients, detection limits and concentration ranges of selected VOC marker substances from breath (a) and feces (b).</p

Experimental set up for alveolar breath sampling in goats.

<p>A—sampling mask; B—CO₂-sensor; C—Needle Trap Device (NTD); D—CO₂ triggered flow valve; E—Capnogard for time resolved CO₂-monitoring; F—sampling box; dashed arrows represent air flows; continuous arrows represent electronic signals.</p

Concentration of 1-propanol in breath gas- and room air-samples.

<p>Concentration of 1-propanol in breath gas- and room air-samples.</p

PCA-scatterplots based on VOC-analysis of breath.

<p>PCA (a) was done for all substances (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123980#pone.0123980.t002" target="_blank">Table 2</a>) having different concentrations in inoculated and non-inoculated animals. The 3D-scatterplot (b) is derived from the same PCA with respect to weeks after inoculation on the third axes. The loading plot referring to this PCA analysis is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123980#pone.0123980.s004" target="_blank">S4 Fig</a>. Blue dots represent the non-inoculated group. Red dots represent the inoculated group. PC-01 explains 31% and PC-03 explains 15% of variance.</p

PCA-scatterplots based on VOC-analysis of headspace over feces.

<p>PCA (a) was done for substances (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123980#pone.0123980.t003" target="_blank">Table 3</a>) having significantly different (p < 0.05) concentrations in inoculated and non-inoculated animals. The 3D-scatterplot (b) is derived from the same PCA with respect to weeks after inoculation on the third axis. The loading plot referring to this PCA analysis is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123980#pone.0123980.s003" target="_blank">S3 Fig</a>. Blue dots represent the non-inoculated group. Red dots represent the inoculated group. PC-01 explains 31% and PC-02 explains 16% of variance.</p

Mann-Whitney-U-tests for analyses from headspace over feces.

<p>*—p-value from t-test</p><p>Mann-Whitney-U-tests for analyses from headspace over feces.</p

VOC-concentration ranges and differences in relation to MAP-specific antibody levels and interferon-γ response after stimulation with JPPD.

<p>p-values from Mann-Whitney-U-tests</p><p>^† value lower than limit of detection</p><p>* p-values from t-tests</p><p>VOC-concentration ranges and differences in relation to MAP-specific antibody levels and interferon-γ response after stimulation with JPPD.</p

Heat-map of selected VOCs from breath (a) and feces (b) normalized onto maximum of concentrations.

<p>Heat-map of selected VOCs from breath (a) and feces (b) normalized onto maximum of concentrations.</p

Giese et al 2013_suppl_image_dung heap

image of a dung heap used for cooking and heating during winte