Soil Sampling Depth in No-Till Acid Soils

Abstract

ABSTRACT Ammonia-based fertilizers acidify the soil during the nitrification process. No-till and other reduced till system soils are more susceptible to stratified acidification than conventionally tilled soils as there is little soil mixing. Many long-term no-till soils have acidified in North Dakota, but there is little guidance on soil sampling depth. This project evaluated what soil depth/s should be collected to remediate acid soils. Twelve differing acidic soil types across North Dakota were sampled at the 0–5.1, 5.1–10.2, 10.2–15.2, 0–7.6, 7.6–15.2, and 0–15.2 cm depths and analyzed for pH. The comparison of means procedure determined that the 0–7.6 cm soil pH was the most acidic (p-value < .001). The 0–5.1, 0–15.2, and 5.1–10.2 cm depths were similar. The highest soil pH was observed at the 7.6–15.2 and 10.2–15.2 cm depth. Soil acidity management of no-till soils when acidification is caused by nitrification should be sampled at the 0–7.6 cm depth as that pH was the most acidic and encompasses the soil environment that surrounds relatively shallow and deeply sown North Dakota crops.