D.P. Wilson, W.R. Carlile
Produce officially labelled as 'Organic' currently commands a market premium in the UK. For such a label to be issued, guidelines for growing as set out by the UK Organic Growers Association must be adhered to. Included in these guidelines is a restriction on the use of certain inorganic fertilisers. Thus, although peat-based media by nature are almost totally organic carbon, they are generally unacceptable for organic growing due to the inorganic nutrient sources usually included.

Consequently there is increasing interest in the UK into developing organic nutrient sources suitable for inclusion in peat-based media. A likely candidate for such a nutrient source is worm-worked duck waste (wwdw). This waste is particularly rich in plant nutrients compared with wastes of, for example, porcine or bovine origin and is thus suitable as a nutrient source rather than a substrate.

In this study, tomatoes (Alicante), lettuce (Webbs Wonderful) and peppers (Capsicum sp) were raised in media containing varying levels of wwdw. All species germinated well in substrates including 2-8% wwdw by volume but at higher levels of incorporation (10-20%), where conductivity and nutrient levels were high, seedling development was retarded. This was particularly pronounced with peppers.

Seedlings transferred to pots of the substrates showed optimum development in particular concentrations of wwdw. Tomatoes for example exhibited optimum growth in 8-10% wwdw by volume, while for lettuce 8% was best and for peppers 6%. At these optimum concentrations, growth of tomatoes and lettuce was superior to that in a conventional substrate containing inorganic nutrients.

Analysis of substrate nutrient status showed that rate of uptake was correlated closely with the rate of plant growth and development. Overall the study indicates that wwdw is a highly suitable nutrient source for plants raised in peat-based media.

Wilson, D.P. and Carlile, W.R. (1989). PLANT GROWTH IN POTTING MEDIA CONTAINING WORM-WORKED DUCK WASTE. Acta Hortic. 238, 205-220
DOI: 10.17660/ActaHortic.1989.238.24

Acta Horticulturae