Epsilon Archive for Student Projects

Abstract

Leys are the main form of agriculture in Sweden and are especially important in the northern parts of the country. They mostly consist of perennial forage grasses and legumes and are usually grown for two to four years, but sometimes up to eight years in areas where they are the main source of economic supply. In northern climates like Sweden’s, some species are selected to reduce winter damage while maintaining good productivity. However, winter kill remains a major problem and can lead to significant yield losses. This literature study reviews scientific articles, mainly from countries with similar climates, aiming to give an overview of the current knowledge and gaps on:

– Abiotic and biotic winter stresses damaging leys
– The resistance of commonly grown species in Sweden to these stresses
– Breeding methods and goals for different species
– Methods to assess winter damage and the potential for renovation through overseeding

Due to climate change, Swedish winters are expected to have higher precipitation, reduced snow cover and warmer autumns and springs. These changes can reduce the plants' ability to harden properly, which affects their tolerance biotic and abiotic stresses. Higher CO₂ levels could also reduce plants cold acclimation level. Some species lose their hardiness after warm spells during winter and are unable to reacclimate. Waterlogging and ice encasement lead to hypoxia (low-oxygen conditions) or even anoxia (complete oxygen deprivation). Timothy is the forage species showing best resistance to these conditions. Snow mould mainly affects grasses, and resistance builds up during cold acclimation. Among legumes, red clover is particularly vulnerable to clover rot during winter and root rot, especially when weakened by other winter stresses. Diploid red clover cultivars tend to be more resistant than tetraploid ones. In order to reduce yield loss, several solutions are possible. It is important to choose species adapted to the specific weather conditions and most common winter damages. Breeding forage for winter tolerance is also possible but challenging since forages have complex genomes. Breeding programs use both field testing and artificial freezing tests. Field tests allow for the evaluation of many genotypes but are less controlled, while artificial tests offer more stable conditions but are costly and limited in scale. There is limited research on how to renovate damaged leys. However, a Swedish project called Vall-reparera will explore winter damage assessment using drones and test different seed mixtures for overseeding.