By Fred Cummings, manager, Manhattan Plant Materials Center
Cereal rye, an annual small grain, is a popular cover crop among experienced producers and those who are just starting to implement cover crops into their cropping system. Cereal rye has many attributes as a cover crop such as low seed cost and availability, ease of establishment, reliable performance across a diverse range of growing conditions and climatic conditions. The Midwest Cover Crops Council rates cereal rye as an excellent nitrogen scavenger, soil builder, loosens topsoil, controls soil erosion, suppresses weeds and provides forage for livestock.
Along with these positive attributes, there are also some negatives. Cereal rye may immobilize nitrogen, causing a nitrogen deficiency in the crop following cereal rye, this may be offset by applying additional nitrogen. If a cereal rye cover crop produces seed, it may become a weed in subsequent crops. In contrast to other cover crops in the Midwest, such as oilseed radish and oats, most cereal rye cover crops require termination, either chemically with a broad-spectrum herbicide, or mechanically with a roller crimper or tillage equipment.
The Manhattan, Kansas Plant Materials Center (PMC), is one of 20 PMCs participating in the evaluation of 15 commercially available cereal rye varieties for their adaptation to different soils and climate. The cereal rye varieties are Aroostook, Bates, Brasetto, Elbon, FL401, Guardian, Hazlet, Maton, Maton II, Merced, Oklon, Wheeler, Wintergrazer 70, Wrens Abruzzi, and Rymin. The performance of these cereal rye varieties provide conservation planners and producers with the information needed to make informed decisions on varieties to plant to best address the desired resource concern.
Concerns over the ability to successfully terminate a cereal rye cover crop is a common reservation preventing its large-scale adoption. The timing of termination (i.e. roller crimping at the soft dough stage, spraying at or before the boot stage) determines the level of control achieved. Selecting a later maturing cereal rye variety may provide an opportunity to extend the window of effectively termination cereal rye.
A cereal rye variety that lacks winter hardiness will still germinate and grow well in the fall to scavenge excess nitrogen, protect the soil by intercepting raindrop impacts, and add living root mass to the soil. While a variety not winter hardy may not fully address the resource concerns, a cereal rye cover crops that produces less biomass makes it easier to plant into and easier to terminate.
Weed suppression of cereal rye is attributable to the physical effect of mulching from the large amount of biomass produced and the allelopathic action of the compound DIBOA (2, 4-dihydroxy-1, 4 (2H)-benzoxazin-3-one). Some rye varieties (the later maturing typically) produce more DIBOA than others. If weed suppression is the primary goal of the cover crop selecting varieties with higher levels of DIBOA may help to best meet the resource concern.