Articles
DEVELOPMENT OF ORGANIC SUBSTRATES FOR HYDROPONIC CUCUMBER PRODUCTION
Long-season heated cucumber crops were propagated in rockwool and then planted onto the organic substrates in the cropping house.
All nutrients were supplied to a standard hydroponic recipe, as used for rockwool.
In 1992 coir, shredded pine wood (Hortifibre), chipboard wood-waste, peat, bark (Pinus spp) and wheat straw were compared with rockwool as a standard.
Reasonable yields were produced from all the substrates, but plants grown on Hortifibre performed particularly well in terms of yield and fruit quality.
From the first year’s trials Hortifibre, straw and wood-waste were selected for further development.
In 1993 these three substrates were compared with rockwool using two different irrigation regimes.
In both years of the trial Hortifibre was the most successful substrate.
The nutrition was easy to manage and the substrate did not lose its structure.
In the straw slabs microbial activity led to locking up of nitrogen and slab breakdown.
This was detrimental to the crop in terms of reduced leaf size and fruit production.
On initial wetting up, the slightly hydrophobic nature of some organic substrates meant that it was better to maintain a shallow reservoir for a short time by not slitting the polythene wrappers to the bottom.
Once saturated, however, the water holding capacity improved and run-off from these substrates was generally less than from rockwool.
These trials showed that long-season cucumber crops could be grown successfully in all the substrates tested.
The most successful organic substrates were those that did not break down readily.
A coarse open structure was better for maximum rooting.
Irrigation and subsequent nutrient run-off was lower from organic substrates than for standard rockwool grown crops.
Shredded pine wood (Hortifibre) gave the best fruit production.