Adaptation of silage maize varieties under extreme northern growing condions in Finland

Abstract

Trials with maize varieties from various places in the world were started in 1975. In preliminary trials in 1975, 280 varieties were tested. Between 19 and 23 varieties were selected for ordinary variety tests in 1976—78 at the University farm in Siuntio. Weather conditions, particularly average daily temperatures in 1975 were better than the long term averages, and in 1976—78 far below the average growing conditions. Dry matter yields of the seven harvested silage varieties in 1975 varied between 5.8 and 11.5 tons/ha. In 1976—78 the variation in DM yields was 3.8—8.0 tons/ha among 19—23 varieties. In 1975, 44 varieties out of 280 produced mature seed. Only one variety matured in 1978, but none in 1976—77. The developmental stage of silage maize is primarily determined by ear percentage and secondarily by DM %. In 1975 the average ear % of seven varieties was 49.1 %, in 1978 18.1 % and in 1976—77 only 4.0—5.7 % in DM. As a result of the variety tests promising varieties from Yugoslavia, France and Germany could be found. It can be concluded from the long term temperature data that with very early hybrid varieties a mature grain yield can be harvested twice in ten years. Good quality silage material can be harvested six times in ten years and a satisfactory crop can be obtained eight times in then years. The limiting factor for the growth and development of maize in Finland is the low average temperature of the growing season. Important but less significant is the length of the vegetative period, which is determined by the first killing frost in the fall. The temperature deficit is particularly critical at the beginning of the growing season.