Characterizing Vegetative Development and Pheno-Phases of Winter Rye Cover Crop Under Iowa Conditions.

Despite the undeniable contribution of cover crops to row cropping systems, knowledge gaps remain, and adoption of the practice in the US Midwest still faces challenges. Building knowledge about pre-flowering development of cover crops adapted to the climate conditions of this region is needed to overcome the limitations. Understanding the morpho-anatomical changes that characterize in-field development assists in the identification of key phenological stages of the cover crop, and allows for better farm schedule operation, such as timely seeding and termination of the cover crop. Our goals are: 1) Describe quantitatively the tillering habits and leaf progression of a cereal rye cover crop (Secale cereale sp.) established under Iowa conditions; and 2) Monitor in-field progression of vegetative pheno-phases of the cover crop within a typical corn-soybean rotation. We counted tiller and plant populations, and estimated green canopy cover, of  broadcast seeded rye at two different dates (September 11, and September 19, 2015), over No-till plots in 2 central Iowa locations. Cover crop development was recorded distinguishing 3 vegetative phases in the Zadoks international scale, e.g.  seedling, tillering, and jointing (Zadoks, 1981). Preliminary results show no statistical differences for rye tiller counts or final leaf stage between locations although cover crop plots with higher plant populations were associated with lower tillers per plant. Likewise, we did not find significant differences for the onset of tillering, jointing, and intermediate vegetative stages, between the two locations. Future work involves simulation of rye vegetative development via process based models accounting for site-specific responses to microenvironment (e.g. temperature, photoperiod).