USING BIO-DEGRADABLE MATERIAL AS A GROWING MEDIA IN HYDROPONICS IN THE REPUBLIC OF SOUTH AFRICA

When the industry vegetables under protection was initiated in South Africa in 1972, the plants were planted in soil. During late 1970 soil borne diseases forced growers to change to container growing. Initially growers used vermiculite as medium with a commercial nutrient mix called Chemicult.^c This method was found costly and research was demanded to evaluate cheaper systems. Various types of growing media were evaluated including vermiculite, rockwool, perlite and composted pine bark. Costs were unacceptable and root diseases made re-use of these products impossible. This study was conducted to evaluate low cost growing media. The system finally decided on was fresh pine sawdust mixed with shavings (70:30) or only shavings in 15 or 20 litre bags with drainage holes punched into the bag 2.5 cm from the base. Fresh coarse and fine bark was also evaluated and found usable but too scarce. A special nutrient solution the "Welgevallen" mix was developed for use with fresh pure sawdust/shavings or pine bark. This combination gave the lowest cost and the waste product is bio-degradable. Each crop is started with new bags, growing media and twine which makes using dangerous chemicals for sterilization unnecessary.