Winter Rye Cover Crop Biomass Production, Degradation, and Nitrogen Recycling

Abstract

Winter rye (Secale cereale L.) cover crop (RCC) use in corn (Zea mays L.) and soybean [Glycine max. (L.) Merr.] production can alter N dynamics compared to no RCC. The objectives of this study were to evaluate RCC biomass production (BP) and subsequent RCC degradation (BD) and N recycling in a no‐till corn–soybean (CS) rotation. Aboveground RCC was sampled at spring termination for biomass dry matter (DM), C, and N. To evaluate BD and remaining C and N, RCC biomass was put into nylon mesh bags, placed on the soil surface, and collected multiple times over 105 d. Treatments included rye cover crop following soybean (RCC‐FS) and corn (RCC‐FC), and prior‐year N applied to corn. Overall, the RCC BP and N was low due to low soil profile NO3–N. Across sites and years, the greatest BP was with RCC‐FC that received 225 kg N ha−1 (1280 kg DM ha−1), with similar N uptake as with RCC‐FS (27 kg N ha−1). The RCC biomass and N remaining decreased over time following an exponential decay. An average 62% biomass with RCC‐FS and RCC‐FC degraded after 105 d; however, N recycled was greater with RCC‐FS than RCC‐FC [22 (80%) vs. 14 (64%) kg N ha−1, respectively], and was influenced by the RCC C/N ratio. The RCC did not recycle an agronomically meaningful amount of N, which limited N that could potentially be supplied to corn. Rye cover crops can conserve soil N, and with improved management and growth, recycling of crop‐available N should increase.

Establishing the relationship of soil nitrogen immobilization to cereal rye residues in a mulched system

“…Cereal rye shoot N loss ranged from 5 to 30 kg N ha −1 , resulting in approximately 45% loss of residue N by 86 DAP, a finding consistent with other studies (Poffenbarger et al 2015;Pantoja et al 2016). Most studies examining decomposition of cover crop surface residues have considered the effects of residue quality rather than residue quantity on net N mineralization (Reberg-Horton et al 2012;Lawson et al 2012;Wells et al 2013;Parr et al 2014;Poffenbarger et al 2015).…”

Can Management Practices Enhance Corn Productivity in a Rye Cover Crop System?

“…The RCC biomass C to N ratio in our study was low (15:1), which indicates there should be net mineralization of N, although the amount would be small. In a study by Pantoja et al (2016) with RCC following soybean, the RCC had a low C to N ratio (14:1) and recycled 22 kg N ha −1 (80%) by 105 d after termination.…”

“…A net N immobilization through 7 d with incubation of aboveground rye material and at the end of 20 d of rye root incubation was reported by Woli et al (2016) and Gardner and Sarrantonio (2012), while a net release of N from the decomposition of oat ( Avena sativa L.) and rye roots over a period of 112 d was reported in an incubation study by Malpassi et al (2000). A study by Pantoja et al (2016) reported that only 25% of N present in aboveground RCC biomass was released by 21 d after termination. This suggests that the use of starter N at planting would help offset N stress on corn due to the presence of decomposing RCC biomass and associated effects on inorganic‐N availability.…”

Do cover crops improve the productivity and industrial quality of upland rice?

“…Using cover crops before the summer crop resulted in a greater accumulation of N compared to that of the fallow treatment ( Table 3). Systems that do not accumulate significant quantities of N limit its supply for the following crop (Pantoja, Woli, Sawyer, & Barker, 2016). Additionally, species that favor greater N cycling and/or fixation in the offseason enable production systems that prioritize conservation concepts and minimize production costs (Koefender, Schoffel, Manfio, & Golle, 2016).…”