POSSIBILITY OF REUTILIZATION OF A COMPOSTED SUBSTRATE OF 'POSIDONIA OCEANICA' (L.) DEL. IN A TOMATO GROWTH BAG

Growth analysis of a tomato crop during the first two months after planting indicates that the substrate cultivation results in faster growth and earlier fruitset than the traditionnal cultivated crop, and this by more favourable minimum temperatures in the root zone ; differences between the substrates remained very small.

High early yields were obtained by substrate cultivation and reutilization seems to give good results. Best results are obtained in the 3rd year of utilization, while during the 4th year the early yield is even lower than this of a traditional crop.

Commercial yields 150 and 180 days after planting were also the highest for the reutilized substrates during the 2nd and the 3rd year. Highest percentage of big sized fruits and highest mean fruit weight was obtained also on the crop cultivated during the 2nd and the 3rd year, while during the 4th year of utilization the percentage of big fruits and the mean fruit weight were the lowest. Traditional cultivation and utilization of a fresh substrate results in almost similar performances.

Substrate and soil analysis indicates that the new substrate is richer in Ca, Mg, N and Fe than the soil, but poorer in K and P. Reutilization of the substrate, combined with addition of well made stable manure results in an enrichment of the substrate in major elements and in a diminution of the Ca and Mg contents. There is also an accumulation of Mn, Zn and Cu and this probably by accumulation of fungicide residues.

Foliar analysis shows that reutilization of the substrate results in lower levels of Ca, Mg and K and higher levels of N and P. The lower levels in Ca, Mg and K result probably from a deficient growth by Cu excess, and this can explain the lower yields during the 4th year of utilization.

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