Effect of the rate of potassium chloride on dairy production in Taranaki

Abstract

Potassium chloride (KCl) was applied at 4 rates (0, 150, 450 and 1150 kg/ha) to pasture on closed 5 ha farmlets over 3 years, and pasture and animal production and animal health measured. Friesan, Jersey and Friesan x Jersey cows were stocked at 3.2/ha on an Egmont Allophanic soil near Hawera in South Taranaki. Average soil potassium quick test (QTK) levels were 7, 8, 10 and 12 respectively from 0, 150, 450 and 1150 kg KCl/ha. There was a small significant negative linear effect of rate of KCl application on annual pasture dry matter (DM) production averaged over three years (16864 - 18359 kg/ha). The average amount of silage conserved (1369 - 2112 kg DM/ha) was consistently greater at the highest rate of KCl. Increasing rate of KCl had no significant effect on the nutritive value of grazed pasture but resulted in increased K content of silage. There was no significant effect of KCl on milksolids (MS) production (1034 -1179 kg/ha/lactation) or reproductive performance. There was a trend for the incidence of clinical metabolic disorders (8-18%) to decrease with increasing rate of KCl but this was not significant because of the low number of cows in each herd. The results from this trial suggest that soil QTK levels above the target range for optimal pasture production of 7-10 on Allophanic soils are not associated with increased dairy production and have no adverse effect on animal health. Keywords: calcium, dairy cows, hypocalcaemia, hypomagnesaemia, magnesium, milksolids, pasture, potassium, potassium chloride