15N fertilizer recovery and partitioning by cover crops under greenhouse conditions

Abstract

Cover crops have the potential to decrease residual-nitrogen (N) losses from agricultural soils by capturing and storing excess N between cash crops. This study was established to assess the effect of cover crop species and N rate on the accumulation and partitioning of biomass and 15N fertilizer by cover crops produced under controlled environmental conditions. Cereal rye (Secale cereale) and tillage radish (Raphanus sativus) cover crops were grown in monoculture and in a blend under greenhouse conditions in two soils. Urea enriched with 15N (3.0 atom %) was applied to cover crops at rates of 0, 34, and 67 kg N ha−1. Shoot dry matter production and N accumulation exceeded that of roots for both cover crops. Fertilizer-N uptake increased as application rate increased, and the greatest overall recovery by the cover crops was 38% of the applied fertilizer-N. Tillage radish shoot biomass nearly doubled that of cereal rye (1,585 kg ha−1) when grown in monoculture in the Captina soil but cover crops stored similar quantities of total N in the shoots. Cover crops grown in monoculture in the Roxanna soil accumulated similar amounts of biomass and TN in the shoots; however, cereal rye root biomass was twice that of tillage radish (568 kg ha−1) when 67 kg N ha−1 was applied. Results from this study reflect the capacity for N sequestration by cover crops, which is largely determined by biomass production and N availability, and most of the captured N is translocated and stored in the shoots.