Soil amendments produced from peats, brown coals, and composts produced from segregated biodegradable waste or biomass from fallow lands can increase soil fertility and improve soil productivity. Due to the demand for alternative horticultural substrates in last years, the concept of compost production based on the willow biomass Salix viminalis L. has emerged¹⁾.
The aim of the study was to determine the possibility of using willow biomass composts as a substrate component in horticulture. The objects of the research were composts produced from willow chips (A), willow mixed with hay (B) and willow mixed with hay and mineral nitrogen (Nmin) fertilizer (C). Composting was carried out in a pile under aerobic conditions. To determine the biological activity and fertilizing value of the composts, a pot experiment was conducted to test the germination and growth of lettuce (Lactuca sativa L.) seedlings. Compost from various stages of maturity was added to the mineral soil in a dose of 200 t/ha respectively. Pot with mineral soil was the control object. Vegetation experiment lasted for 40 days and was conducted with lettuce seedlings. Lettuce yield was determined as well as basic properties of the compost variants used in the researches.
There were observed a significant increase in pH, total content of nitrogen, phosphorus, and a decrease in TOC in the composts with the addition of hay and Nmin. Results of the experiment showed that the highest yield was obtained from the pots with the mixture of willow, hay and Nmin. It was also observed that the test plants grew and developed better on substrates contained mature composts, compare to unmatured ones.
Based on the obtained results it can be concluded that the addition of hay and Nmin significantly increased fertilizing value of the investigated composts.

¹⁾Copyright on the bases of application to the Polish Patent Office No. P.435103