Zum Einfluß von Untersaaten zur Begrünung von Ackerbrachen auf die Vegetationsentwicklung und die Nitratdynamik

Abstract

AbstractThe influence of undersown green manure crops for fallows – set‐aside land – in view of vegetation‐development and the dynamic of nitrateIn view of the establishment of rotational fallows ‐ set‐aside land ‐ as well as the bridging of the vegetation‐free winter period the suitability of different undersown grasses and legumes m winter cereals was investigated in field trials. Festuca rubra developed well in winter barley and winter wheat. The success of the cultivation of Lolium perenne, Trifolium pratense and Trifolium repens in winter cereals is uncertain because of the risk of light and water deficiences. Dactylis glomerata caused an negative influence on the yield of the cover crop. During the fallow period only low levels of nitrate could be found in the soil. Under fallow tilled repeatedly complete fallow‐ a nitrate accumulation could be observed during the fallow period. After ploughing up the fallow vegetation, nitrate concentrations ‐ depth 0–150 cm – increased to 60 kg NO3‐N · ha‐1 after the natural fallow without seeding, between 60 and 130 kg NO3‐N · ha‐1 after Trifolium and between 160 and 210 kg NO3‐N · ha‐1 after complete fallow. Lowest nitrate levels were observed from the grass‐sites. Undersown Festuca rubra seems to be the best choice in order to compete with weeds, to form a dense sod and to prevent nitrate leaching. In general a seed rate of 8 kg · ha‐1 can be recommended.