Trace elements

Albrecht recognized that trace elements are significant for plants, but are present 'in such small amounts that our measures yet designed are too unreliable to warrant specifications of them for either soil or crop' (Albrecht, 1963, and in Walters, 1989). Analytical techniques have since improved sufficiently to allow such measurements, but we are unable to find recommended amounts or ratios in Albrecht's research. He did find, however, that a BCSR of 2% K was the limit for uptake by plants unless B was present at a level of

1 mg kg-1, when the limit increased to a maximum of 20% K (Albrecht, 1960, and in Walters, 1989). A lack of boron prevented the formation of nodules on lucerne, but its presence increased the content of tryptophane and lysine.

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