Studies on potassium. IV. Interspecific differences in the uptake of non-exchangeable potassium

Abstract

Five soils were cropped with four plant species in pot experiments in the glasshouse, without addition of potassium, until growth virtually ceased, after which the depleted soils were replanted with either the same species, or a different one, to test the reproducibility of the 'exhaustion' conditions imposed. Uptake of potassium by the plants exceeded the changes in exchangeable potassium in four soils; the excess amounts taken up differed markedly between species and these differences were reproducible on replanting. Uptake by setaria (Setaria anceps) and siratro (Macroptilium atropurpureum) exceeded that by Rhodes grass (Chloris gayana) and lucerne (Medicago sativa), except for one swelling clay soil from which uptake by lucerne equalled that by siratro. Most of the differences between species were attributed to the uptake of initially non-exchangeable potassium, which was removed in significant amounts from three of the soils. For these three soils, uptake from non-exchangeable sources was detected only after about 80% of the exchangeable potassium had been removed. It is postulated that the efficiency of plant removal of non-exchangeable potassium from soil is directly related to the degree to which plant roots can lower the concentration of potassium in the soil solution.

Potassium Supplying Capacity of Diverse Soils and K-Use Efficiency of Maize in South Asia

“…When assessed by plant K uptake, it can be termed as "K-supplying capacity" whereas if assessed by extracting the soil with one or more extractions, a chemical index of available K (K-releasing capacity), can be the true index of plant available K. Consequently, many investigators reported, while "plant available K" can be equated to the K-supplying capacity of the soil, it can only be related to the K-releasing capacity. Thus, both K-releasing and K-supplying capacity can be considered the measures of the ability of a soil to supply K to plants [50][51][52]. The amount of total K uptake by plants from a soil depends on the potential of K-supplying capacity.…”

Potassium removal from soil by lucerne over three years and the effect of potassium topdressing

“…Fergus & Martin (1974) discussed some of the evidence for differences among plant species in their ability to absorb initially nonexchangeable K, and also presented the results of a pot trial showing such differences among four plant species, including lucerne. They postulated that these differences may be related to the degree of tolerance shown by the plant to low K concentrations in the soil solution.…”

Soil structure and potassium supply. I. The release of potassium from soil aggregates to Ca‐resin

“…However, non-exchangeable K is often significant for crops: experience shows that it is taken up concurrently with exchangeable K (Russell, 1973). In pot experiments concurrent release has been shown by Sinclair (1979) although not by Fergus & Martin (1974). Kaufman & Bouldin (1967) measured diffusion of K to H-resin and demonstrated that slow release of non-exchangeable K occurred alongside the diffusion of exchangeable K: uptake by onion roots can (greatly) exceed that predicted from resin measurements (Bagshaw et al, 1968;Dunham & Nye, 1976).…”