Organic production of native potato landrace “pintaboca” (Solanum stenotomumJuz. & Bukasov) in Bolivia: experimenting planting times and cultivation strategies

Abstract

In the municipality of Colomi, in the highlands of Bolivia, market pressure leads small scale farmers to substitute their native landraces with commercial potato varieties. Organic cultivation might offer a channel for selling native potatoes to an emerging industry of coloured native potato crisps. Nevertheless, as the area is endemic for late blight (Phytophthora infestans), adequate cultivation practices that allow organic production must be defined. The present experiment compared four cultivation strategies (two organic, which included the use of beneficial microoorganisms applied in the soil and through foliar spray, one conventional, which included cymoxanil and mancozeb based fungicides and a control with the same soil treatment as the organic strategies but no foliar spray) and two planting dates (early and main season planting) on a native potato landrace locally known as ‘pintabocaʼ (Solanum stenotomum). Our results showed that early planting resulted in significantly higher yields, although the area under disease progress curve (AUDPC) of late blight did not differ significantly between planting dates. The lower yields in the plot planted during the main season were mainly due to the combined incidence of early and late blight. There was no significant difference in yields and quality of the tubers cultivated with conventional, organic or control treatment, with the exception that the largest tuber size category was produced only in the conventional treatment. We conclude that farmers in Colomi who want to shift to organic cultivation of the landrace ʻpintabocaʼ at altitudes around 3,300 m a.s.l. could benefit from practicing early planting, although additional trials covering several seasons are needed to confirm our results.