Page 38 - nov21

Agrichemist’s solutions

hydroponics

Cultivating plants without soil, the accepted definition of hydroponics, continues to gain
popularity. I have visited friends in Nyanga, Zimbabwe that have a super small system inside
a greenhouse and are producing monstrously huge lettuces. While a backyard system is
being run in Nata with equally productive results. Almost everywhere you look, hydroponic
schemes are popping up and doing really well, provided of course they follow the correct
formula.

You can do hydroponics anywhere, on a super tiny scale, indoors or outdoors. All that’s
needed is to get the correct structure, lighting, water and nutrients, plant supports and grow-
ing media in place for the plants to do well. Alternative growing media has really opened up
this type of farming as now instead of having to buy expensive coconut fibre, vermiculite,
perlite, peat or rockwool, you can also use composted bark, pea gravel, sand, expanded clay,
lava rock, fiberglass insulation, sawdust, pumice, foam chips, polyurethane grow slabs and
rice hulls.

The choice also depends on the size and type of plants you wish to grow and the type of
hydroponic system being used.
Two cheap and easy products we have in good supply in Botswana are sand and gravel:
Sand is one of the oldest known hydroponic substrates, but not widely used today, mostly
because of its low water-holding capacity and weight. It can however be mixed with other
media for a greater water-holding capacity and lighter weight.

Gravel is cheap, easy to come by but also has a problem of water retention, which means
roots can dry out quickly. If mixed with coconut fibre or peat, then the weight is lessened
and this will assist in water retention. As it doesn’t degrade quickly, gravel can also be reused
so long as it is washed and sterilized between crops.
38