Timing of Nitrogen Supply to Corn from Spring Terminated Red Clover

Published Nov 30, 2015

In a Nutshell

Cultivation of cereal rye for cover crop seed offers the possibility of frost-seeding a legume into the standing rye crop in early spring, where the legume can produce biomass and fix N following rye harvest. Farmer-cooperators Tim Sieren and Dick Sloan grew corn in rotation following cereal rye frost-seeded with red clover and compared this to corn grown using synthetic N fertilizer applications. Tim and Dick invited Iowa State University graduate student Will Osterholz on to their farms to quantify N uptake by corn as well as two measures of N release from soil organic matter: net N mineralization and gross ammonification.

Key findings

Red clover did not improve corn growth, N content or grain yield compared to synthetic N fertilizer.  Soil N mineralization rates in August tended to be higher with red clover compared to synthetic N fertilizer, but differences were not statistically different. Fertilization with supplemental N at planting could provide corn with early season N before clover decomposition can provide sufficient N to the corn crop in late summer.