Physical and chemical evaluation of volcanic rocks and its use for tulip production

Abstract

Physical and chemical characteristics of volcanic rocks were evaluated, using two particle sizes (3 and 5 mm) and its use in the production of tulip (Tulipa gesneriana) cv. Ille de France, taking as reference the commercial substrate ProMix®. The total porous space (67 and 67.9%), the easily water available (2.9 and 2.3%) and reserved water (1.9 and 1.1%) in the volcanic rocks (3 and 5 mm, respectively) were unsuitable for growing tulips. The pH was alkaline in the volcanic rocks and acid in ProMix®, in the latter the electrical conductivity was higher (1.46 dS m-1), but still within the limit set for substrates. N content was low in both materials (0.61% in volcanic rocks and 0.82% in ProMix®); Ca and Mg were higher in the volcanic rocks at 60 and 24.7%, respectively, on the contrary, in ProMix®, K was near three times higher than in the volcanic rocks. We found no Na in the volcanic rocks at all. In plants grown in 5 mm volcanic rocks the lowest foliar concentrations of K, Ca and Mg were found (11.08, 0.8 and 1.55 g kg-1, respectively). Foliar concentrations of N and P were not different between treatments. On the other hand, foliar concentrations of K and Ca in plants growing in 3 mm volcanic rocks were quite enough; while in the established ProMix® were excessive; and in 5 mm volcanic rocks were rather poor. Foliar concentration of Mg was low in plants established in volcanic rocks. We concluded that, the use of 3 mm volcanic rocks may be an alternative for the production of tulips, as long as the frequency of irrigation is reduced.