Fertilizers--TOW
Roy M. Sachs (Mon, 20 Oct 2003 10:40:37 PDT)

I use slow-release fertilizer, 25% N, 4% K and 4% P at a rate that
will supply approximately 50 lbs N/acre (= 50 Kg/ha). I'm not sure
that our clay soils ever become deficient in potassium or phosphorous
so I buy the richest slow-release source of nitrogen (which just
happens to be 25/4/4).

Per 1000 sq.ft. (ca 100 sq.m) to get 50 lbs N from the slow release
granules, I apply 4.6 lbs (ca 2.1 kg) annually, 2.3 lbs in the spring
and 2.3 lbs in the fall.

Slow release is easiest for me with varied irrigation rates and
sometimes very heavy rainfall, but I have used ammonium sulfate (21%
N) successfully. The ammonium form of N tends to exchange with other
cations on the clay and compost that I use.

I have calculations on a worksheet if anyone's interested.

Roy
Davis, California; Sacramento Valley, very hot dry summers , mild
spring and fall; irrigation required (usually) from April through
October.