Is air-drying of soil samples an appropriate step in determining plant available potassium for corn?

ABSTRACT

Potassium (K) fertilizer recommendations are mainly based on air -dried soil samples which can lead to over- or under-estimation of plant available soil K. Three on-farm trials were conducted in North Dakota and Minnesota to determine the variation of soil test-K between air-dried (K_Dry) and field moist (K_Moist) soil samples. The differences between K_Dry and K_Moist decreased exponentially as soil K increased, but increased linearly with increasing soil moisture. Soil drying influenced the plant available soil K-test value, producing higher K values compared to the moist soil K. It is unclear based on these initial experiments which method might produce a more predictable K critical value to aid in directing K application for corn in this region.

KEYWORDS:

• Potassium
• air-dried
• corn

Acknowledgement

The authors are thankful to Norman Cattanach and Rakesh Awale for their assistance in field operations.

Funding

This experiment was funded by North Dakota Corn Council.