MARGINAL LEAF NECROSIS BY BORON EXCESS ON A TOMATO CROP CULTIVATED IN A SUBSTRATE OF POSIDONIA OCEANICA. (L.) DEL. POSSIBILITY OF CONTROL.

Composted ‘Posidonia oceanica L.’ seagrasses are very rich in Ca, Mg and B and very poor in K. Utilization of the pure substrate results in an imbalance of the K/B relation and about 2 months after planting marginal leaf necrosis is appearing in the eldest leaves of young tomato plants.

Incorporation of well made stable manure permits to abtain higher levels of K resulting in a better K/B relation.
A minimum incorporation of 10% stable manure prevented the apparition of marginal leaf necrosis, in spite of still high B levels in the substrate and the plant, and yield response was very interesting.

Incorporation of marc of grapes has also a good effect on the potassium level and on the K/B balance, but has only small effects on the yield.
Combination of 10% marc of grapes with 10% stable manure and 80% composted seagrasses gives better results.

The volume of the growth bag seems also to have a positive effect on the element uptake and especially the K/B balance seems to be more favourable by use of growth bags of big volume.

Reutilization of the substrate and yearly incorporation of 10 to 20 % well made stable manure results also in better K/B balances.

International Symposium on Substrates in Horticulture other than Soils In Situ

H. Verlodt

https://doi.org/10.17660/ActaHortic.1984.150.46