Importance of the subsoil for the K nutrition of crops
- H. Kuhlmann
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A K/Rb isotope dilution method was used to determine the uptake of K from undisturbed subsoils. Rb was applied to the topsoil (0–30 cm) to trace the K taken up from the topsoil by crops. The K/Rb ratio in the crops increases when roots contact the Rb-free subsoil. This change in the K/Rb ratio enables the calculation of the uptake of K from the subsoil.
Results of 34 field experiments on loess-parabrown soils in N. Germany showed that the subsoil (>30 cm) supplied, on average, 34% of the total K uptake by spring wheat (range 9–70%).
The range between the experimental sites is considered in relation to the contents of K in the top and subsoils (as extracted by 0.025 N CaCl2 solution), the proportion of the total root length in the subsoils, and competition for K between roots in the top and subsoil.
In subsoils with similar K contents, uptake from the subsoil decreased significantly from 65 to 21% of total K uptake, as K contents in the topsoils increased from 4 to 8 mg K/100 g.
On sites with the same K contents in topsoils (9 mg K/100 g), the subsoil supplied 12 to 61% of total K uptake as the K contents of the subsoil increased from 2 to 27 mg K/100 g.
The contribution of uptake of K from the subsoil increased with the development of the crop, from 8% at first node stage to 35% at ear emergence, as the proportion of total root length in the subsoil increased.
High root length densities in the topsoil (9 cm/cm3) resulted in competition for K between roots and increased uptake of K from the subsoil.
- Importance of the subsoil for the K nutrition of crops
Plant and Soil
Volume 127, Issue 1 , pp 129-136
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
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- K uptake
- spring wheat
- K/Rb ratio
- root density
- Industry Sectors
- H. Kuhlmann (1)
- Author Affiliations
- 1. Centre for Plant Nutrition and Environmental Research, Hanninghof 35, D-4408, Dülmen, FRG