Reduction in nitrogen fertilizer application by introduction of hairy vetch cultivation in two cropping systems of spring wheat in central Hokkaido

This study examined how hairy vetch seeding affects reduction of nitrogen (N) fertilizer application to the continuous cropping of spring wheat in Central Hokkaido, in 2015 and 2016. The spring wheat cultivar, 'Haruyutaka', was cultivated using two cropping systems, namely, a conventional system wherein spring wheat was sown in early April and an early winter seeding system wherein spring wheat was sown just before snowfall. Hairy vetch was grown until just before the spring wheat seeding was completed in the conventional system. In contrast, in the early winter seeding system, hairy vetch was incorporated in late October. N fertilizer application after snow melting was reduced to half the recommended level in the cropping systems employing hairy vetch. Growth and dry matter production in spring wheat were estimated in 2015 and 2016, by comparatively evaluating these results with the conventional and the early winter seeding systems without hairy vetch application. Dry weight of hairy vetch ranged from 250.1 g /square m in the conventional system in 2014 to 50.1 g /square m in the early winter seeding system in 2015. The grain dry matter weight was higher in the early winter seeding system in only 2015, but there was no difference between hairy vetch application treatments in both systems in 2015 and 2016. N content in wheat grain ranged from 2.29% to 2.52%, which was sufficient to ensure seed quality of spring wheat. The plant length was suppressed at the late growth stage in the early winter seeding system employing hairy vetch in 2016. This results suggest that N deficiency occurred at the ripening stage of wheat in this system. The present study shows the potential to reduce spring N fertilizer to half of the recommended level by introduction of hairy vetch during the previous autumn season.