Nitrogen Supply from Green Manure Enhanced with Increased Tillage Frequency: A Note

Core Ideas Ion exchange membranes were tested for in situ evaluation of soil mineral N. More tillage passes increased green manure decomposition and soil mineral N. Ion exchange membrane were a good indicator of arugula N uptake. Pea–oat green manure supplied up to 20% of the N required by arugula. Tillage practices influence the decomposition of green manure and could be adjusted to synchronize the N supply from residues with crop N demand. This note evaluated ion exchange membranes (IEM) as an in situ tool for monitoring ammonium (NH4+) and nitrate (NO3−) dynamics after pea (Pisum sativum L.)–oat (Avena sativa L.) green manure was incorporated by one, two, or four passes of a rototiller. Mineral N from IEM and in 2 M KCl soil extracts was related to the cumulative N assimilated by arugula (Eruca sativa L.) during a 6‐wk period. Greater tillage intensity increased the IEM‐NO3−−N concentration on ion exchange membranes significantly, from 1.94 to 18.7 µg cm−2 wk−1, and the N supplied from green manure increased arugula N uptake significantly. The IEM‐N were as reliable as the soil chemical extractant in evaluating the mineral N released from green manure under field conditions.