Response of forage maize yield and quality to mulch film and harvest time in Northern Europe

Forage maize (Zea mays L.) yield and nutritional quality fluctuate markedly in Northern Europe due to weather conditions. A field experiment was conducted in Southern Finland (Helsinki, 2018–2020) and in Central Finland (Maaninka, Kuopio, 2019–2020) to study the effect of harvest time and use of mulch film, in order to optimize the dry matter (DM) yield and quality. Treatments included oxo-biodegradable mulch film and no mulch, and three harvest times (the latter only in Helsinki). Mulch film increased DM yield on average by 2.3 Mg ha-1 in Helsinki and by 3.8 Mg ha-1 in Maaninka. Mulch film had a minor effect on the quality, and overall, the quality improved, although DM yield accumulation had already ceased. Nevertheless, the starch contents fluctuated and remained mostly below the target rate – 300 g kg-1 DM – especially in Central Finland. The results indicate that mulch film improves forage maize yield, but a late harvest is still required to improve forage quality. However, climate conditions still restrict starch accumulation to ears in Northern European climate conditions, especially in the important milk production area in Central Finland.