Effects of leguminous ground cover competition on red birch and soil nutrient status in the nursery

Legumes as ground cover are regularly planted to increase nitrogen economy of crops and to improve soil. In the present study various clover species w ere evaluated as vegetative ground cover in nursery field production of mic ropropagated red birch (Betula pubescens Ehrh. f. rubra Ulvinen f. nova) in two 2-year experiments. The clover species and cultivars, Trifolium praten se L. 'Bjursele', T. repens L. 'Jogeva', T. repens L. 'Sonja', T. hybridum L. 'Frida', T. incarnatum L. 'Opolska', T. resupinatum L. and T. subterrane um L. were compared to grass sod Festuca rubra L. 'Ensylva' and to a coverl ess ground (control). The last one was kept weed free by hand hoeing. Birch (leaves, stems, branches and roots) and soil nutrient concentrations (N, P , K, Ca, Mg and Fe) were analysed and nutrient ratios in birch determined. The annual clovers, T. incarnatum L., T. resupinatum L. and T. subterraneum L., provided about the same nutrient status in birch as did the control. P erennial clovers and grass were strong competitors with trees. High levels of P and Mg in birch leaves relative to N concentration were typical for po orly growing seedlings. Neither annual nor perennial clovers did generally improve soil nutrient status.