Soil Degradation Under Minimum Tillage Systems.

Soil degradation is becoming increasingly common under minimum tillage cereal production systems in the inland Pacific Norwest.  We will present our observational data on two factors that affect soil health: 1) acid and nutrient stratification, and 2) soil temperatures. (1) Representative 30-cm soil profiles sampled at 2.5-cm increments were analyzed for total and plant available nutrient status, soil pH and electrical conductivity.  Our profile data clearly illustrates a common occurance of base cation eluviation, and increased acidification with exceptionally high extractable forms of Al Mn and Fe in the zone of fertilizer placement. (2) We monitored the relative effects of three crop residue cover conditions on growing season root zone soil temperatures (15 cm, 30 cm and 45 cm). The combined negative effects of these factors may be among the most relevant factors that slow the conversion of crop residues to organic matter - slowing the formation of soil humus.