Root and shoot biomass and nutrient composition in a winter rye cover crop

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Patel, Swetabh
Sawyer, John
Sawyer, John
Lundvall, John
Hall, Jeena
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Nitrogen loss from applied fertilizer can be a significant environmental quality issue if NO3 moves to surface or ground water. The Iowa nutrient reduction strategy science assessment identified winter cereal rye (Secale cereal L.) cover crop as a practice that can significantly reduce N and P loss (41% NO3-N and 21% P reduction) from corn (Zea mays L.) and soybean [Glycine max. (L.) Merr.] fields. Cereal rye, when used as a cover crop, through its fibrous root system is able to explore the soil and use residual NO3- N. In order to further understand the effectiveness of rye as a cover crop for scavenging and recycling N, there is a need to understand the amount of root/shoot biomass and N and carbon (C) partitioning between roots and shoots at the time of rye termination. This study was conducted at the Climate and Corn-Based Cropping Systems Coordinated Agricultural Project (CSCAP) cover crop site, located at the Ag. Engineering and Agronomy Research Farm, Iowa State University near Boone, IA. Corn was grown in rotation with soybean and winter cereal rye drilled following corn and soybean harvest (three N rates applied to corn, 0, 120, and 200 lb N/acre). Two ingrowth tubes per plot were installed between rye rows in fall of 2014 after rye seeding and the tubes were harvested the next spring at the time of rye termination. For rye following corn and soybean, shoot biomass, C, and N was significantly greater than in the root biomass, with about 30% of the total plant C and 15% of the total N in the root biomass. The C:N ratio of root material was consistently high (46-51 C:N), and at least double the shoot material (17-23 C:N). Therefore, N taken up by the rye was mainly partitioned to the shoot, and thus measurement of rye cover crop aboveground biomass provides the main N amount available for recycling from the rye cover crop. With the high C fraction and high C:N ratio of the root material, inorganic-N from the soil or degrading shoot material could be immobilized with root degradation.


This is a proceeding from 45th North Central Extension-Industry Soil Fertility Conference 31 (2015): 113. Posted with permission.