Effects of mixed intercropping on the agronomic parameters of two organically grown malting barley cultivars (Hordeum vulgare) in Northwest Germany

Abstract

The market for organic malting barley (Hordeum vulgare L.) is growing. One goal of producing malting barley is to attain a defined protein content. This is challenging in organic farming because nutrient uptake is unpredictable. Since malting barley is quality sensitive to high amounts of available nitrogen (N) during the grain filling phase, artificial competition for N from a second crop within a mixed intercropping system could help to limit N uptake during these later growing stages. The objective of this study was to evaluate the effects of intercropping on the brewing quality parameters of malting barley within the framework of organic farming. In a field trial, with two spring barley cultivars (Odilia, Marthe) as sole crops and in intercropping treatments of 4 intermediate mixing ratios with camelina (Camelina sativa), linseed (Linum usitatissimum) and pea (Pisum sativum), the effects on yield and malting quality were observed. The results from three growing seasons on a study site in north-western Germany showed an opposite protein response for mixtures with linseed and pea. However, sole stands of barley mostly performed as well as the mixtures. For mixtures with camelina, neither yield nor quality aspects were affected. Comparing the two cultivars, the well-established Marthe, from traditional conventional selection, showed the better overall performance with a 13% higher grain yield, a 3% higher hectoliter weight and 5% higher proportion of size fraction > 2.5 mm than Odilia, which was released later from an organic breeding program. However, the yield component analysis showed a consistent yield determination for Odilia regardless of intercropping partner or mixing ratios which might indicate its suitability in polycultures. The observed average land equivalent ratios (LER) of mixtures with linseed (1.04) and pea (1.13) showed the potential to increase land-use efficiency but were lower compared to the mean LER found in a recent meta-analysis.