Concentrations of Soil Potassium after Long-Term Organic Dairy Production

Abstract

On five long-term organic dairy farms aiming at selfsufficiency with nutrients, soil concentrations of ammonium-acetate lactate extractable potassium (K-AL) and acid-soluble K was measured twice in topsoil (0-20 cm) and subsoil (20-40 cm) over periods of 6-14 years. Organic management had occurred for Ͼ9 years at the second sampling. On average there were most probably field level K-deficits. Even so, topsoil K-AL concentrations were medium high (65-155 mg K kg ؊1 soil), and did not decrease during the study period. However, for three farms, topsoil K-AL was approaching a minimum level determined by soil texture, where further decrease is slow. Subsoil K-AL concentrations were generally low (Ͻ65). The soils were mostly light-textured, and reserves of K-releasing soil minerals (illite) were low, never exceeding 6% of the mineral particles Ͻ2 mm diameter. Topsoil acidsoluble K concentrations were low (Ͻ300 mg K kg ؊1 soil) on two farms, medium (300-800) on three farms and decreased significantly on one farm. Cationexchange capacity increased on two farms. This may indicate increased amount of expanded clay minerals caused by K-depletion. On self-sufficient organic dairy farms, purchased nutrients will be required by low soil nutrient reserves to avoid seriously decreased yields and quality of crops.

Potassium-Fixing Clay Minerals as Parameters that Define K Availability of K-Deficient Soils Assessed with a Modified Mitscherlich Equation Model

“…Møberg and Nielsen (1983) and Nielsen and Møberg (1984), studying K-deficient soils from field crops as well as from pot experiments, reported a trend of reduction in illite content through K depletion, which was accompanied with a corresponding increase in vermiculite or smectite. At the same time, they found that the above changes resulted in respective changes in CEC values, and the above findings were corroborated by Tributh et al (1987) and Løes and Øgaard (2003). Recently, Moterle et al (2016) using X-ray decomposition methods found that the removal of K from the illite interlayers transformed the clay mineral into vermiculite, a fact that had a positive effect on soil exchange capacity.…”

Agricultural sustainability: concepts, principles and evidence

“…Nonetheless, there are now some 3 Mha of agricultural land in Europe managed with certified organic practices. Some have led to lower energy use (though lower yields too), others to better nutrient retention and some greater nutrient losses (Dalgaard et al 1998(Dalgaard et al , 2002Løes & Øgaard 2003;Gosling & Shepherd 2004), and some to greater labour absorption Pretty et al 2006).…”

Identifying Potassium-Deficient Soils in Kenya by Mapping and Analysis of Selected Sites

“…Hypothetically, therefore, K losses and deficiencies are more likely to occur in wet areas than in dry areas because soil erosion, surface runoff, and leaching are greater and cropping is more intense in wet areas. Indeed, excessive mining and deficiency of nutrients like K, which are taken up in large quantities, were reported in continuous cropping systems of the world and where no external inputs had been applied (Loes and Ogaard, 2003;Smaling et al, 1993;Stoorvogel et al, 1993). Nandwa and Bekunda (1998) reported an emergence of such deficiencies in continuously cultivated highlands of east and southern Africa.…”