Soil probe lubrication and effects on soil chemical composition

Abstract

Deep soil‐profile sampling in wet, clayey soils can be difficult. Friction against the probe surface can cause core compression and impedes extraction of intact cores from the probe tube. Lubrication of the probe tube reduces friction and improves core extraction. Two studies were conducted to determine soil‐sample contamination resulting from probe lubrication and possible interactions with probe diameter (surface‐area:volume ratio) and sampling depth. Soils were sampled following probe lubrication and analyzed for organic matter and seven common nutrients. Lubricants tested contained varying amounts of organic matter (24‐>700 g/kg), nitrate‐N (NO₃‐N, 3–205 m/kg), phosphate‐P (PO₄‐P, 244 mg/kg), potassium (K, 2–1200 mg/kg), and zinc (Zn, <0.1–460 mg/kg) but relatively small amounts of manganese (Mn, <0.1–0.2 mg/kg), iron (Fe, 0.2–2.9 mg/kg), and copper (Cu, <0.1–0.6 mg/kg). Macronutrient content of soil samples was not affected by lubrication beyond variation typical among replicated soil samples from the study site. Differences among sample NO₃‐N, PO₄‐P, and K concentration means were not significant at the 0.05 probability level in either of the studies conducted. Sample organic matter content was significantly increased by some lubricants in one study. Iron, Mn, Zn, and Cu were significantly affected in one or both studies. Lubrication reduces sampling time and frustration in wet, clayey soils and generally introduces negligible contamination when sampling for macronutrients. Lubrication may not be acceptable when testing for micronutrient metals.

Notes

University of Wyoming Agricultural Experiment Station Journal Paper No. JA‐1726.

Assistant Professor/Extension Soil Fertility Specialist

Research Associate.

Associate Professor.