Efficiency of Mineral Nitrogen Fertilization on Yield and Botanical Composition of Grassland VI. The effect of mineral nitrogen fertilization on dry matter yield and economical mineral nitrogen application of grassland depending on its age

무기태 질소시비가 초지의 수량과 식생구성에 미치는 영향 VI. 무기태 질소시비가 초지의 경년에 따른 수량과 경제적 질소시비수준한계에 미치는 영향

This experiment was carried out to determine the effect of pure mineral nitrogen fertilization on dry matter yield and the amounts of advisable mineral nitrogen on grassland according to its age at the "Federal Institue for Agriculture in the Alps" in Austria. The results obtained were as follows: 1. With only PK-fertilizing average dry matter yields per year were progressively declined during the period of the studies. Compared with the relatively younger grassland(1st-5th year) the DM-yields were decreased by 35% in older grassland (11th-final year). 2. Due to the less reduction of DM-yields by mineral nitrogen application according to the age of grassland. With N-fertilizing the reduction of DM-yields in relatively older grassland was less than that of younger grassland by 11-21%. 3. At 4-and 5-cut systems the nitrogen amounts for the highest marginal yield(the "most efficient" Ndressing rate) per ha and year were distinctly declined in the relatively older grassland. 4. Required efficiencies of mineral nitrogen were not influenced by the age of grassland.he age of grassland.