20 years of variety testing in forage maize in Switzerland

In the last 20 years, the yield of mid-early forage maize increased by 2 dt dry matter/ha/ year. Varieties with major agronomical problems such as lodging were eliminated. The improvement of quality, and more specifically the content of digestible organic matter (DOM), is more difficult to evaluate, as it is highly influenced by environmental condition. Both yield and quality vary among locations and years. Dry matter content at harvest only influences the DOM up to 30 %, when seed filling is not complete and therefore grain content too low. This is one more reason not to harvest variety trial too soon, so that the late varieties can reach the minimum DM content (30 %). Data from several locations were compared. For example, differences appeared between Changins (Nyon, VD) and Reckenholz (Zurich, ZH): in Changins, summers are warmer and dryer. Satisfying dry matter content for harvest was usually reached 2 to 4 weeks earlier than in Reckenholz. Yields were lower but with similar content of DOM. DOM was less correlated to grain content in Reckenholz (R2=0.01, ns) than in Changins (R2=0.21***), where plants are smaller and ear development seems to be able to compensate the lower digestibility of the rest of the plant. New varieties showed significant improvement compared to older ones, especially for yield and quality parameters such as DOM. Variety trials over 20 years allowed these improvement to be available for the farmers.