The Potato Tuber Disease Occurrence as Affected by Conventional and Organic Farming Systems

A study was conducted which aimed to investigate the effect of farming systems (FS) (four conventional with increasing mineral N fertilizer amounts 0-150 kg of N ha(-1)) vs. two organic with catch crops (CC) and cattle manure (CC + M)) under the same five crop rotation system on the occurrence of tuber diseases such as common scab (Streptomyces spp.), silver scurf (Helminthosporium solani), dry rot (Fusarium spp.), and soft rot (Pectobacterium spp.). As the average of the first rotation years 2009-2011, the FS had a significant effect on the occurrence of silver scurf, dry rot and common scab (surface cover < 30 %). The organic systems had significantly more tubers (around 39 %) infected with common scab (surface cover 4-15 %) than in conventional systems (around 25 %). However, when the surface lesion severity increased (surface cover 16-30 %) then differences occurred only between organic systems (in system Organic CC 4.1 % and in system Organic CC + M 13.1 % of tubers infected). The Organic CC system had significantly fewer tubers infected with silver scurf compared to all conventional farming systems (10.5 % vs 17.8-23.4 %). During the first and after the second disease measurement there were less tubers infected with dry rot in Organic CC (0.8-0.9 %) and conventional N high (0.5-1.4 %) systems compared to N low (1.8-3.0 % of tubers infected) system. Soft rot infections were not influenced by farming systems. Thus we conclude that it is possible to influence the occurrence of some tuber diseases with FS.