THE INFLUENCE OF TILLAGE METHODS, CROPPING SEQUENCE, AND N RATES ON THE ACIDIFICATION OF A NORTHERN IDAHO SOIL

Publisher Website
Google Scholar
Abstract
Soils in northern Idaho are exhibiting a rapid decline in pH. It was sought to determine the relative effects of common northern Idaho cultural practices, tillage methods, crop rotations, and N fertilizer rates, on the acidification of a northern Idaho soil. The plots were established north of Moscow, Idaho, in 1974 and evaluated no-till, minimum tillage, and conventional tillage treatments and 3-crop rotation systems: a 2 yr winter wheat (Triticum aestivum L. cv. Nugaines)-spring pea (Pisum sativum cv. Alaska) rotation; a 3 yr winter wheat-spring wheat (T. aestivum L. cv. Fieldwin)-spring pea rotation; and a 3 yr winter wheat-alfalfa (Medicago sativa L. cv. Ladak) red clover (Trifolium pratense cv. Kenland) pea-alfalfa red clover rotation. The plots were split by N application rates and sampled by depth. When sampled by 300 mm increments, depth was the only factor that affected soil pH. Soil pH increased with increasing depth. There was a statistically unique Ca chloride pH at each sampling depth down to 1500 mm. When the surface 300 mm was sampled by 75 mm increments, the interaction of crop rotation .times. tillage .times. N rate .times. depth was significant. N rates were the major influence on pH differences. Crop rotations influenced the amount of N fertilizer required for crop production and consequently affected the magnitude of the pH decline. Tillage influenced the placement of N fertilizer and consequently the location and depth of acidification in the soil profile. The greatest acidification under no-till management occurred in the surface 75 mm, under minimum tillage at the 75-150 mm depth, and under conventional tillage in the surface 250 mm. A significant decrease in pH was observed in all treatments over the 8 yr period.