Yield, Quality and Nitrogen Use of Forage Maize under Different Nitrogen Application Rates in Two Boreal Locations

Research focusing on the nitrogen (N) application and use of forage maize (Zea mays L.) in the boreal region is either limited or non-existent. The aim of this study was to investigate the response of yield, quality and N recovery efficiency (NRE) of forage maize to an increase in the N application rate and different climatic conditions in two locations in Finland. The field experiment was conducted in southern (Helsinki; 60° N) and central (Maaninka; 63° N) Finland in 2019 and 2020. Dry matter (DM) yield, forage quality and NRE were determined for N application rates of 100, 150 and 200 N kg ha−1. The DM yield was similar to all studied N application rates. Moreover, there were no marked differences in the studied forage quality traits or the NRE following the N application rates. However, the NRE of maize was generally low at 45%. The current study recommends a N application rate of 100–150 N kg ha−1 for forage maize in the boreal region. There is no need to increase the N application from current recommendations since climate conditions seem to limit the growth, development and NRE of forage maize. The observed low NRE of forage maize warrants further research in the future