Tillage, fertilizer results surprising in greenhouse gas crop check

Curbing greenhouse gas emissions from cultivated fields may require going beyond cutting back on nitrogen fertilizer and changing crop rotation cycles, USDA research shows.

A Minnesota researcher trialed corn, soybean, wheat and alfalfa in rotation, on plots treated with and without fertilizer. She also used a less-aggressive tillage system known as strip tillage. For comparison, she replicated the cropping system adopted by many Minnesota farmers-raising corn and soybeans in a two-year cycle on fertilized plots tilled with a chisel or moldboard plow. 

She found no consistent patterns to methane releases, that overall greenhouse gas releases were largely the same under two-year and four-year rotation systems, and that applying nitrogen fertilizer had less overall impact than anticipated on nitrous oxide emissions. 

Nitrous oxide emissions peaked during spring thaws when the sun warmed the soil, regardless of which tillage or rotation system was used.

While chisel and moldboard plowing increased carbon dioxide emissions for a short time, carbon dioxide emissions were no different from plots with intensive tillage than plots without it when measured over the course of a year.

Full story: Agricultural Research Service