Long-term liming changes pasture mineral profile

Abstract

There is limited information on changes of pasture mineral concentrations over the long-term in response to liming. A long-term field experiment was conducted to assess the influence of lime application on (a) changes in pasture mineral composition over time; and (b) key pasture mineral concentrations and ratios important to animal health. Perennial and annual pastures with or without lime application were sampled annually over 12 years and analysed for macro- and micro-minerals. Mineral ratios and indices were calculated to assess the potential impact on animal health. Liming increased the concentrations of calcium, sodium and silicon, but decreased the concentrations of micro-nutrients including copper, zinc and manganese. The same trend was found in both annual and perennial pastures although there were some fluctuations between years. Liming increased the calcium:phosphorus ratio and the dietary cation-anion difference but reduced the tetany index on both annual and perennial pastures. These findings suggest a potential benefit to improve animal health outcomes for some disorders on the limed pastures. However, the reduced concentrations of some trace elements following liming potentially decreases antioxidant capacity and requires further research.

Figure 1

Annual rainfall (bars) and the average rainfall (dotted line) in 1992–2003 at the experimental site.

Figure 2

Pasture mineral concentration at anthesis for macro elements (Ca, calcium; K, potassium; Mg, magnesium; Na, sodium; P, phosphorus; S, sulphur; and Cl, chloride) over 12 years on limed () and unlimed () treatments in annual (AP) and perennial pastures (PP). The lines are spline-fitted with corresponding treatments. No plant samples were taken in 1994 due to the extreme drought condition.

Figure 3

Pasture mineral concentration at anthesis for micro elements (Al, aluminium; Mn, manganese; Cu, copper; Fe, iron; and Zn, zinc) over 12 years on limed () and unlimed () treatments in annual (AP) and perennial pastures (PP). The lines are spline-fitted with corresponding treatments. No plant samples were taken in 1994 due to the extreme drought condition.

Figure 4

Pasture mineral concentration ratios and indices [K:Na, K:(Na + Mg), Ca:P ratio, grass tetany index and dietary cation–anion difference (DCAD)] with over 12 years on limed () and unlimed () treatments in annual (AP) and perennial pastures (PP). The lines are spline-fitted with corresponding treatments. No plant samples were taken in 1994 due to the extreme drought condition.

Figure 5

Correlations between pasture macro elements (Ca, calcium; K, potassium; Mg, magnesium; Na, sodium; P, phosphorus; S, sulphur; and Cl, chloride) at anthesis. Coloured lines are fitted regression lines between each pair of plant elements under limed () and unlimed () treatments. *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 6

Correlations between pasture micro elements (Al, aluminium; Mn, manganese; Cu, copper; Fe, iron; Zn, zinc; and Si, silicon) at anthesis. Coloured lines are fitted regression lines between each pair of plant elements under limed () and unlimed () treatments. *P < 0.05; **P < 0.01; ***P < 0.001.