Potassium cycling and losses in grassland systems: a review

Abstract

Cycling of potassium in grassland systems has received relatively little attention in research and practice in recent years. Balanced nutrient systems require consideration of nutrients other than nitrogen (N). Potassium (K) is needed in large amounts and is closely related to N nutrition. In intensive dairy farming, surpluses of K arise from the input of concentrates and fertilizer and are returned to the grassland and may lead to increasing K content in the soil. Organic farming, on the other hand, is characterized by limitations in input of nutrient sources and quantities. Leaching of K from grassland is usually low, but high levels of available soil K, high K input from fertilizer or at urine patches lead to increasing losses. High K inputs have a negative influence on Mg and Ca uptake by plants and can cause accelerated leaching of these cations. High levels of K have been associated with inducing nutrition-related dairy cow health problems such as milk fever (hypocalcaemia) and grass tetany (hypomagnesaemia). This review gives an overview of the cycling of potassium and related cations in grassland systems especially with regard to leaching losses and identifies limitations to knowledge.

Nitrogen management in organic farming: comparison of crop rotation residual effects on yields, N leaching and soil conditions

“…Potassium is a very dynamic nutrient in sandy soils (Kayser and Isselstein 2005). In our experiments only the supply of farmyard manure kept the level of available K constant over the period of more than 3 years.…”

Spatial variability of potassium in agricultural soils of the canton of Fribourg, Switzerland

“…Such practices would allow a reduction in K applications while guaranteeing sustainable management of the K fertility status. But, this need to be further investigated, as K over-fertilized soils may induce an unbalanced composition of nutrients in grass and consequently increase the risk of Mg deficiencies and related livestock illnesses, such as hypomagnesaemia, hypocalcaemia or calving issues (Kayser and Isselstein, 2005).…”

Macronutrients in Hawaii's Coastal Wetland Pastures and Potential Phosphorus Release to Water

“…Th is fi nding for Mg may have been due in part to formation of hydroxy Al-Mg polymers (Mg fi xation) in Zones 3 and 4 in response to the high pH (Riggs et al, 1995). Greater concentrations of exchangeable K and Na in Zones 2 and 4 than 1 and 3 can be attributed to redistribution in urine and to a lesser extent dung to these shaded lounging areas where the grazing animals tend to congregate (Mathews et al, 1999;Kayser and Isselstein, 2005;Sharpley and West, 2008).…”

“…Th e lack of a hilograss K diff erence between Zones 3 and 4 may have been due to antagonism of K uptake by the high exchangeable Ca concentration in these zones (Table 2) (Kayser and Isselstein, 2005), while the lack of a Ca diff erence between Zones 1 and 2 may have been because the Waipa soil exchangeable Ca/Mg ratio was narrow (1:1 or less) for both zones (Osemwota et al, 2007). Th e North Shore pasture also sampled for Zone 2 had greater paragrass N (35.7 vs. 29.8 g kg −1 ), K (33.6 vs. 29.7 g kg −1 ), and Na (4.5 vs. 3.6 g kg −1 ) concentrations in Zone 2 than Zone 1.…”