Nutrient Cycling in Agroecosystems

, Volume 87, Issue 1, pp 137–149

Potassium uptake and requirement in organic grassland farming

Research Article

DOI: 10.1007/s10705-009-9320-5

Cite this article as:
Øgaard, A.F. & Hansen, S. Nutr Cycl Agroecosyst (2010) 87: 137. doi:10.1007/s10705-009-9320-5


Use of mineral fertilizers is restricted in organic farming. The aim of the present paper was therefore to study whether potassium (K) limits yields in Norwegian organic grasslands. The K status in soil and herbage on 26 organic farms was investigated, and the response to K application in six fertilization experiments was explored. Further, the relationship between soil K analyses and K release from soil was examined. K application to grassland on the investigated farms was generally low, giving negative field K balances on 23 of the farms. The soils were classified as low or intermediate in readily available K (KAL) on 23 of the farms. The mean K concentration for herbage samples from the first cut on these farms was 18.0 g K kg−1 dry matter. In fertilization experiments, K application increased the K concentration in herbage. However, there was no significant effect on yield, even when K concentration in herbage on plots without K application was low. The lack of significant yield response to K application can be explained by low amounts of crop-available nitrogen (N). There was a tendency for increased plant uptake from reserve K with increasing values of acid soluble K (K–HNO3) in soil. Separate K analyses of timothy (Phleum pratense) and red clover (Trifolium pratense) revealed that red clover showed better competitiveness for K than timothy in leys where N supply was limited.


Available potassium Organic farming Potassium application Soil analysis Red clover Timothy 

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Soil and Environment DivisionNorwegian Institute for Agricultural and Environmental ResearchAasNorway
  2. 2.Organic Food and Farming DivisionNorwegian Institute for Agricultural and Environmental ResearchTingvollNorway