Effects of long-term fertilization for cassava production on soil nutrient availability as measured by ion exchange membrane probe and by corn and canola uptake.
Nguyen, H.T., Nguyen, A.T., Lee, B.W., and Schoenau, J.J. 2002. Korean J. Crop Sci. 47: 108-115.

ABSTRACT

The effects of long-term fertilization on soil properties and nutrient availability are not well documented for cassava cultivation in Vietnam. In 1990, field research plots were established with 12 treatments to test the effect of different rates of nitrogen (N), phosphorus (P) and potassium (K) on soil properties in Acrisols at Thai Nguyen University in North Vietnam. In 1999, composite soil samples (0 to 20 cm depth) were collected from eight selected plots for measurements of nutrient supply rates by ion exchange membrane probes and for growing corn and canola in a growth chamber with and without added lime. Generally, long-term N fertilization increased available N supply rates but decreased available K and magnesium (Mg).  Long-term P applications increased canola N, calcium (Ca) and Mg uptake. Canola P uptake increased with increased P rates only when lime was added. Long-term K applications increased canola N, K, Ca, and Mg uptake but only significantly increased corn N uptake. Liming significantly increased uptake of N, P, K, Ca, Mg, and sulfur (S) for both corn and canola. However, ammonium (NH₄-N), K and Mg soil supply rates were reduced when lime was added, due to competition between Ca from the added lime and other nutrients.

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