Browsing by Author "Alitalo, Ville"

Alfalfa (Medicago sativa L.) is an interesting plant in grass mixtures because of its high yield and nitrogen fixing potential, and also high acceptance and forage value in animals. However, it is considered challenging to cultivate in Finland because of its high pH requirement and its poor ability to stand wet soil, trampling and cold winter. By ditching, liming and good management of field traffic it is possible to improve all these difficult growth conditions except for cold winter. The aim of this study was to investigate the differences in cold hardiness and the rate of cold hardening on six alfalfa cultivars having different origin and fall dormancy class. The aim was also to examine if the observed potential differences result from dry matter, starch and soluble sugar content in plant roots and shoots. Based on these traits, it was also intended to evaluate the suitability of tested cultivars for cultivation in Finland. The study composed of a field and a growth chamber experiment. In the field experiment the alfalfa cultivars ’Alexis’, ’Nexus’, ’Live’ and ’Lavo’ were tested, and in the growth chamber experiment also cultivars ’Hunter river’ and ’Rangelander’ were included. In the field experiment the samples were taken in total four times during winter 2014-2015. Sampling was done every other month starting from October. In the growth chamber experiment the plants were cold acclimated at two different programmes; 7/3 °C at day/night for three weeks and 7/3 °C for two weeks followed 5/-2 °C for one week. The cold hardiness of plants was determined by ion leakage test, in the field experiment from roots and in growth chamber experiment from roots and leaves. The dry matter content, soluble sugar content and starch content were also determined from roots and shoots in both experiments. The results showed that alfalfa plants tolerate well short cold temperatures. The 50 percent ion leakage, when plants are regarded to be dead, was not achieved with all cultivars, although the coldest freezing temperatures used in the artificial freezing test was -18 °C for the field and -16 °C in the growth chamber experiment. Freezing temperatures strengthened the hardening of plants in growth chamber trial and significant differences in cold tolerance were observed between cultivars. Hardening increased the soluble sugar content and decreased the starch content of plant roots in both experiments, but the differences between cultivars were not significant. Significant differences in sugar content of shoots were observed only between the cultivars with best and poorest freezing tolerance. According to the results of one-year field experiment all cultivars were suitable for cultivation in Finland.