The aim of the project was to evaluate the potential of microbial threat to feed safety in the year 2018. Analyses of the epiphytic community of several forage species (clovers, cocksfoot, fescue, festulolium, perennial ryegrass, timothy and trefoil) in variants of fertilized and non-fertilized vegetation were performed. The hypothesis is based on the fact that microorganisms are normally present on plant material during its growth all the way from the seed to the senescence; they are influenced by a plant’s fitness, and they affect its harvest and utilization. Microflora was analyzed by cultivation on specific substrates, total microbial count and five specific microbial groups were observed and quantified. Forage species did not affect plant microflora. The highest risk factor of microbial contamination of feed was proved to be harvest date. Mycotoxin contamination of fresh feed was determined (deoxynivalenol and zearalenone) using ELISA. Zearalenone (ZEA) levels were negatively correlated to fertilization intensity, although these results were not statistically significant. Deoxynivalenol (DON) levels were the lowest in a moderate fertilization regime. Significant differences in mycotoxin content were found among botanical species.
Cette étude s’est déroulée dans une plan- tation forestière en Amérique centrale, proche de la ville de Diriamba au Nica- ragua, où des plantations de teck sur 48,9 ha, dans une zone de reboisement de 76,5 ha, sont renouvelées depuis 2006 (2006 : 7,90 ha ; 2007 : 13,63 ha ;2008 : 11,93 ha ; 2009 : 12,87 ha ; 2010 :21,70 ha). Cette plantation sort de l’ordi- naire du fait de l’espacement de 1 x 1 m des arbres et des facteurs écologiques limitants de cette zone tropicale aride. L’espacement de 1 x 1 m a été choisi pour favoriser la croissance en hauteur et obtenir ainsi des tiges de haute taille, et pour limiter les ramifications afin d’éviter la formation de houppiers importants. Cela permet de démarrer une production de poteaux de teck, adaptés à certaines constructions, dès la première coupe d’éclaircissement. Les paramètres de croissance des tecks (hauteur, circonfé- rence) ont été mesurés dans les placettes expérimentales mises en place en 2011. Des données complémentaires (morta- lité, arbres cassés ou tordus) ont égale- ment été relevées. Une méthodologie de terrain a été développée et les résultats restitués sous forme de tableaux et gra- phiques. Une évaluation statistique des paramètres de croissance a été menée à partir des mesures prises sur les placettes expérimentales délimitées dans la planta- tion. Les jeunes arbres plantés la même année ont été comparés selon leur prove- nance en termes de hauteur, de circonfé- rence, de productivité et de mortalité. Au total, 10 955 arbres sur 143 placettes ont été mesurés. Sur ces peuplements de 1 à 5 ans d’âge, le bois sur pied total est estimé à 1 287,89 m3, la masse moyenne de bois à l’hectare à 17,89 m3, la hauteur moyenne des peuplements à 3,03 m et la circonférence moyenne à hauteur de poitrine à 2,74 cm. Les arbres cassés représentent 5,64 %, les arbres tordus 5,66 % et la mortalité moyenne s’établit à 21,48 %.
Teak has been planted extensively by smallholders in Central America within reforestation programmes and has become one of the most valuable timbers. The five-year growth and mortality of teak cultivated in a plantation in central Nicaragua, representing sites at the low limit of teak ecological valence, were evaluated. From 2006 to 2010, 72 pure teak stands were established, with 48.93 ha in total. For afforestation, planting stock from five provenances was used and planted at 1 m × 1 m spacing to stimulate the height growth and reduce broad crowns formed by self-pruning. In the pure teak stands, 144 permanent sample plots of 0.01 ha in size were established in 2011. From 2011 until 2015, the tree height and stem girth of all individuals in the studied sample plots were measured, and mortality based on the stand density was assessed. Significant differences between the provenances were observed. The highest growth was noted in the Local provenance originated from the studied area, whereas the Semilla provenance from Costa Rica, characterised by the lowest growth ability, was characterized by lower radial increment and mean tree height with high mortality.
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