Relation of Available Potassium to Soil Moisture

Abstract

Preliminary studies revealed that exchangeable K levels in Iowa soils fluctuated in response to vapor pressure changes and air drying. This phenomenon was investigated in relation to (1) K nutrition of plants in the greenhouse and (2) the problem of predicting the relative K‐fertility status in a wide range of Iowa soils. The thirteen soils employed in the greenhouse study showed variable increases in exchangeable K content upon air drying. Accompanying increases occurred in K uptake by the corn plants. Effects on K absorption by plants associated with drying of the soils often were equivalent to applying 60 to 120 lbs. K per 2 million lbs. of soil. Relative ability of the soils to supply K to plants under green‐house conditions was better correlated with exchangeable K content of undried than of air dried soils. This was true whether or not soils were air dried for cropping. Under field conditions, fluctuations in soil moisture levels in the surface one‐inch layer were accompanied by marked changes in content of exchangeable K over an 11‐week period. Below this layer, exchangeable K remained nearly constant since moisture content did not drop so low as in the surface. Results obtained in both field and laboratory showed that not much increase in exchangeable K occurred until soil moisture level had dropped to near 5 per cent or below. On the basis of overall results obtained it is concluded that for Iowa soils exchangeable K values determined after air drying may not be as reliable as those determined on moist soils, in predicting K supplying abilities of soils. Additional field studies are needed, however, to evaluate effects of alternate drying and wetting of soil on K nutrition of the crop.

Evaluation of Soil Potassium Test to Improve Fertilizer Recommendations for Corn

“…The linear trend line deviated from the 1:1 line, with the greatest difference in the high and very high K range (Figure 2). Such variation in soil K levels of moist and dried soil samples had been observed in various earlier studies in Iowa [12] [24] Since the variation between KDry and KMoist was different for different sites throughout the growing season, probable factors that might contribute to the difference in drying response were correlated to the KDry/KMoist ratio and summarized in Table 4.…”

The difference of potassium dynamics between yellowish red soil and yellow cinnamon soil under rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation

“…For example, soil moisture had important effects on soil K determination (Kuchenbuch et al 1986). The result may not necessarily reflect the actual process of soil K transformation (Luebs et al 1956). …”

Growth-Promoting Effect of Potassium-Solubilizing Microorganisms on Some Crop Species

“…However, it has long been identified that drying of soil samples can influence the amount of K extracted by the traditional extract. Some researchers have reported an increase in extractable potassium upon drying (Luebs et al 1956). Haby and Ruselle (Haby et al 1990) concluded that the impact of sample drying on K extracted by tests that estimate exchangeable K depends on the deviation from the equilibrium K concentration at sampling time and on soil mineralogy.…”

“…In field and greenhouse studies, another K extraction method, called the wet-extraction method (ammonium acetate-extraction of fieldmoist soil), was reported to yield a better correlation with crop K-uptake than methods extracting K from air-dried soil (Luebs et al 1956). A recent study by Barbagelata and Mallarino (2012) also demonstrated that moist extraction K tests had a superior capacity to predict crop responses to K fertilization, as compared to the commonly used dry extraction method.…”