Agriculture Reference
In-Depth Information
residue building up on the surface. This is probably an indication of nutrient
salts than can't be used, although you will also get it if you use tap water for top
watering in hard-water areas.
In this case, water, water, water - with no fertiliser added. The only way to
reduce the levels of salts is to flush them away, down into the subsoil, where they
will be less likely to be affect your plants.
Other additives
Sterilised bonemeal
provides a slow-release form of organic phosphate that
promotes strong root growth, and is particularly useful when planting new
shrubs and trees.
Seaweed extract
contains natural plant growth stimulants and a range of trace
elements,
and
has been shown to make plants less susceptible to pest and disease
attack. Liquid feeds are a useful way to provide a short-term boost to plants that
need it, rather than being an integral part of feeding the bed. For the long term,
you need to feed the soil itself, and the basic choice is between compost and
manure.
Human urine
is sometimes used as a liquid feed, being essentially sterile and
extremely high in nitrogen, with an NPK (nitrogen, phosphorus and potassium)
ratio of around 11:1:2. However, it can also be high in salt, which can accumulate
in the soil over time, and therefore in the polytunnel it can be recommended only
for providing a short-term boost for leafy plants. It is, however, an excellent ingre-
dient for a compost heap. Urine used for watering should be diluted 1:5 with
water, or 1:10 for seedlings.
Comfrey, the wonder plant
Weight for weight, comfrey leaves contain very similar levels of NPK to manure
and compost. A liquid feed made from 14lb of leaves rotted in 20 gallons of water
is substantially higher in N, P and K than commercially available liquid feeds.
Added to a fresh compost pile, comfrey leaves are so high in nutrients that they
help the entire pile heat up - and they are large and brittle, so very easy to chop
up with a spade.
As a general feed and mineral supplement that your plants will love, comfrey tea
is hard to beat. It's very easy to make at home, although the traditional method
of rotting chopped leaves in a barrel of water is extremely smelly. For a method
of making comfrey tea without the odour, see the box overleaf.
