Effects of liming and nitrogen application on the trace element concentrations of pastures in low mountain range

In less intensively managed grassland, the micronutrient concentrations in herbage are apparently more likely to be in levels between barely sufficient and deficient than to be excessively high. Insufficient amounts of selenium, copper, manganese, and zinc cause physiological disorders in ruminants. Three identical field trials on pastures with different soil pH and organic matter content were established to assess the effect of liming and nitrogen fertilization on the micronutrient concentrations in herbage. In the case of selenium the effect of a selenate application on the Se concentration in plants was also tested. The effect of liming on the micronutrient concentrations was not always consistent with initial hypotheses. Only Mn and – to a smaller extent – Zn concentrations changed markedly with an increasing soil pH (P < 0.01). Marked differences between concentrations in primary growths and secondary growths were evident for all trace elements. The effect of added nitrogen was negligible. Se concentrations in the plant tissue in plots without selenate application averaged 21.3 μg Se/kg dm in 2002 (standard error SE = 18.63) and 48.7 μg Se/kg dm in 2003 (SE = 38.97). Sufficient Se concentrations (> 100 μg Se/kg dm) were only found in herbage fertilized with selenate. Mn concentrations met the requirements for ruminants in most cases (mean Mn concentration in 2002 = 104.2 mg Mn/kg dm; standard error SE = 62.76; mean Mn concentration in 2003 = 67.5 mg Mn/kg dm; SE = 35.91). The average Zn concentrations were 33.5 mg Zn/kg dm in 2002 (SE = 6.46) and 34.0 mg Zn/kg dm in 2003 (SE = 7.52). The average Cu concentrations were 10.5 mg Cu/kg dm in 2002 (SE = 1.24) and 9.9 mg Cu/kg dm in 2003 (SE = 1.93). Therefore, 41.7% of the measured values for Zn and 31.3% of Cu concentrations remained under the recommended levels of > 30 mg Zn/kg dm and > 10 mg Cu/kg dm.