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Publication Date

1977

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Results of one of the grazing experiments carried out in the period 1971-1975 are dis­cussed. In the experiment two rates of N fer­tilization were applied: 60 and 120 kg per hectare under each regrowth, i.e. 360-420 and 720-840 kg N/ha per year, respectively. Rates of phosphorus and potassium fertili­zation remained unchanged: 120 kg P2O5 and 160 kg K2O per hectare. High N rates led to an increase of the Cu and Zn contents and an Fe content decrease in plants, and stimulated the Cu and Fe absorption but reduced the Zn absorption by high-yielding cows. A drop of the Cu content below 8 ppm in fodder led to Cu deficiency in the blood of cows, while pasture fertilization with CuSO4 significantly increased the Cu concentration in fodder. Va­riations due to intensive nitrogen fertilization of pastures did not cause any negative changes in the prodµctivity of cows nor in their health indices investigated.

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Effect of nitrogen fertilization of pastures on the Cu, Fe and Zn content in fodder and blood of dairy cows

Results of one of the grazing experiments carried out in the period 1971-1975 are dis­cussed. In the experiment two rates of N fer­tilization were applied: 60 and 120 kg per hectare under each regrowth, i.e. 360-420 and 720-840 kg N/ha per year, respectively. Rates of phosphorus and potassium fertili­zation remained unchanged: 120 kg P2O5 and 160 kg K2O per hectare. High N rates led to an increase of the Cu and Zn contents and an Fe content decrease in plants, and stimulated the Cu and Fe absorption but reduced the Zn absorption by high-yielding cows. A drop of the Cu content below 8 ppm in fodder led to Cu deficiency in the blood of cows, while pasture fertilization with CuSO4 significantly increased the Cu concentration in fodder. Va­riations due to intensive nitrogen fertilization of pastures did not cause any negative changes in the prodµctivity of cows nor in their health indices investigated.