Salt effect of dehydrated broiler litter on organic lettuce

Abstract

This paper examined salinity changes in soil in a greenhouse over four cropping cycles of lettuce (two autumn-winter cycles followed by two spring-summer cycles), testing the effect of applying an organic fertiliser consisting of dehydrated broiler litter at variable rates from 267 to 1596 g m−2 and comparing this with two mineral fertilisers; ammonium nitrate applied at 58.5 g m−2 and Nitrofoska Stábil® applied at 100 g m−2. The electrical conductivity of the soil (ECe) increased with increased rates of the organic fertiliser. Also, the increased temperatures and evaporation in the spring-summer cropping cycles resulted in increased concentrations of the fertiliser components salts in the soil. However, ECe remained below 4 dS m−1 and, although the highest fertilisation rates led to ECe levels near the acceptable threshold for lettuce (1.3 dS m−1), the weights of the lettuce increased. This result suggested that the favourable effects of the organic fertiliser on soil properties offset its adverse effects on salinity. Long-term risks of salinization can be avoided by using dehydrated manure rates not exceeding 600 g m−2 in autumn and 1200 g m−2 in spring or 532 g m−2 at any time of the year where repeated applications are made.