I study the relationship between root growth and nitrogen uptake. I work in horticultural systems under organic or conventional management. Here winter catch crops (cover crops) and the design of crop rotations play a major role to decrease leaching of nitrate and thereby increase the nitrogen use efficiency of the system. My research is focused on the relationship between root growth and N uptake in deep soil layers. Some crops and catch crops extend roots to 1-2.5 m depth below soil surface. These deep roots may take up nitrogen at depth and can be used to reduce the leaching of nitrate from the deep soil layers to the groundwater. The work includes subjects such as root and crop physiology in relation to nitrogen uptake. The approach is laboratory and field experiments including the use of stable isotope 15N techniques for the study of N cycling, and of minirhizotrons for measurements of plant root growth. The crops in study have been deep rooted crops like white, Chinese and curly cabbage, carrot, beetroot, squash, as well as shallow rooted crops like rucola, sweet corn, potato, celleriac and leek. The catch crops and green manures include deep rooted like fodder radish, winter rye and salad burnet as well as shallow rooted like ryegrass and birdsfoot trefoil.

In addition I study the relationships between conditions during the growth phase and the quality of horticultural products; like harvest quality, sensoric properties and the content of substances of importance for human health. The focus is on the importance of the genetic material, the availability of soil nutrients and suboptimal growth conditions for the quality of vegetables, e.g. the content of glucosinolates in cabbages, and the effect of UV-light exposure on the formation of vitamin D2 in mushrooms.