Composts are commonly applied to soil at high dose, e.g.
from 20 to 30 t (dry matter) per ha each year. Recently, soluble
substances from urban compost at a much lower dose of 1.55 t per ha
enhanced tomato productivity much more than the compost itself. Here, we studied the effect of soluble substances at 0–700 kg per ha on red
pepper. We measured productivity, chlorophyll, and soil chemical
composition. The most remarkable result is an observed maximum
productivity for only 140 kg per ha of compost soluble substances. The
increases amounted to 90 % for the precocious crop yield, to 66 % for
the total crop production, and to 17 % for the per fruit weight. That the highest effects occur at such low treatment dose is
very promising to enhance crop productivity in a sustainable way. No
detectable change of soil chemical composition was observed.