Steam and fish fertilisers: a potential organic systemic herbicide?

Abstract

A number claims have been made in New Zealand that the combination of steam and foliar fish fertilisers has a systemic herbicide effect. However, these claims are not supported by robust data indicating the necessity for a comprehensive research experiment in order to prove or disprove the hypothesis. A set of experiments was conducted to determine the herbicidal effect of steam in conjunction with two fish fertilisers and two vegetable oils, one containing high levels of omega-3 and omega-6 fatty acids and the other of low chemical reactivity, on a range of pasture plant species. No evidence of a systemic weed kill was found. Similar claims exist regarding the systemic effect of the organically certified contact herbicide Interceptor® in combination with steam. No experimental evidence was found for this either. It was considered that a solid refutation of the concept would be if steam heating plants prevented a systemic herbicide from working. An experiment testing this found that when applied immediately after steaming, Roundup® (glyphosate) was still effective. It can be concluded that while the idea that steam can turn fertilisers and contact herbicides into systemic ones can not entirely be refuted, there is no concrete scientific evidence to support the concept.