ISHS Acta Horticulturae 401: International Symposium on Growing Media & Plant Nutrition in Horticulture
HYDRAULIC PROPERTIES OF ROCKWOOL SLABS USED AS SUBSTRATES IN HORTICULTURE |
| Authors: | F.F. da Silva, R. Wallach, Y. Chen |
| DOI: | 10.17660/ActaHortic.1995.401.7 |
| Abstract:
Increased interest in the cultivation of horticultural crops on rockwool is expected to lead to an increase in its use as a substrate. However, rockwool provides a very restricted root environment and, consequently, a low buffering capacity for water and nutrients. In this study, the hydraulic properties of rockwool slabs (Grodan HP, 90 × 15 × 7.5 cm) were characterized with the purpose of evaluating their potential effects on water uptake. Water retention curves were measured on both drying and wetting cycles. The tested range of matric suctions (h) was 0 --10 kPa. Water content (  ) was very high at saturation (≈95% by volume) but decreased sharply with increasing suction, approaching zero at -5 kPa.
In addition, a wide hysteretic loop was observed between 0 and -5 kPa.
Secondary (h) curves were determined in this range.
Hydraulic conductivity was measured at saturation (KSAT) and a main drying K(h) curve was measured in a 0 --2.5 kPa range.
Hydraulic conductivity was shown to decrease dramatically with increasing suction.
At -2.5 kPa, for example, K < KSAT by more than two orders of magnitude.
Results showed that very small suction increments may cause sharp decreases in K thus suggesting that water flow to plant roots may be hindered, even when the water content of the slabs appears to be high.
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