Improving fertilisation and crop protection regimes for organic potato production systems in Crete

Abstract

Yields in organic production systems in Crete are significantly (up to 50%) lower than those obtained in conventional farming. This is mainly thought to be due to less efficient crop protection (especially for late blight and invertebrate pests) and fertilisation methods. However, there is limited information on the effects of alternative blight management approaches (e.g. the use of more blight resistant varieties) and different organically acceptable fertiliser inputs available in Crete/Greece on potato yields in organic production. The objectives of the study were therefore to (a) quantify the effect of different organic fertilisers available in Crete (chicken manure pellets, sheep manure and communal waste compost) on crop health, yield and quality parameters of two cultivars Spunta (the main potato cultivar grown and consumed in Greece) and Sarpo Mira (a more late blight and possibly pest resistant/tolerant cultivar), (b) identify interactions between organic fertiliser types, cultivar choice and biochar soil amendments with respect to crop health, yield and quality parameters in both spring and autumn potato crops (c) compare insect resistance in the potato cultivars Spunta and Sarpo Mira using Tuta absoluta (which is endemic in the Messara Valley of Crete where field trials were carried out) as the model pest species, and (d) compare sensory quality of the potato cultivars Spunta and Sarpo Mira using untrained taste panels composed of local consumers in Crete. The study demonstrated that chicken pellets and sheep manure produced the highest yields and that Sarpo Mira has a greater disease and pest resistance than Spunta, the main variety currently used by organic farmers in Greece. Sarpo Mira also produced higher yields that Spunta, but this was only significant in spring season 2011 and autumn 2011 when compared with chicken pellets. The finding of greater resistance to Tuta absoluta indicated greater pest resistance, but the impact of switching from Spunta to Sarpo Mira on more important potato pests (e.g. Colorado beetle) should be investigated in future studies. This indicates that Sarpo Mira and a switch to chicken pellets or sheep manure may allow organic potato yields to be increased significantly, compared to currently used production methods. However, exploratory sensory evaluations indicated that consumers show a greater acceptance/preference for Spunta compared to Sarpo Mira for a range of sensory quality parameters. This should be investigated/confirmed in future studies.