Mid-season P & K review for grazed swards

Although silage fields have the larger P & K removal rates, slipping soil fertility on grazed swards is very common and will reduce nitrogen response from all sources of nitrogen – soil, fertiliser and manures.

The P & K maintenance rates (based on the target soil index of 2 for P and 2 for K) for grazing is 20 kg/ha for phosphate and 20 kg/ha for potash. These rates will need to be higher on intensively stocked grazing platforms as offtakes are greater – 1,000 L of milk removes 2.3 kg of P.  

Potash fertility is declining on grassland farms in general, and grazed paddocks are no exception. Even though 90% of potash consumed by livestock is excreted, the 10% (1,000 L of milk removes 1.4 kg of K) utilised by livestock does add up over the course of the season. Potash is also leached from soils, albeit in small amounts. 

A common practice with rotational grazing is taking out a paddock for silage to manage grass supply on the grazing platform. Where this happens, the P & K offtakes in this silage need to be added to the annual P & K maintenance rates. Each 800 kg bale (25% DM) of silage will remove 1.5 kg/P and 6.6 kg/K. YaraMila ExtraGrass and YaraMila SulphurCut are ideal products to balance P & K offtakes and maintain soil fertility on grazing paddocks.