Managing cereal rye cover crop to improve benefits in vegetable production
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Cereal rye is among the most common cover crops used in vegetable production systems in temperate regions. Because of its ability to survive winter, cereal rye fits easily into most vegetable rotation systems. In early spring, rye grows slowly but as temperature increases, it quickly reaches its exponential growth stage in late April to early May. During the exponential growth stage, biomass accumulation increases rapidly. While biomass accumulation is desired to build soil organic matter and soil quality, it is important to remember that this may cause nutrient tie up in the cover crop residue if the cover crop is not managed adequately. Also, rye produces chemicals that have been shown to injure vegetable crops, including species established from transplants if residues are not managed properly. For no-till production systems, the objective is to maximize biomass production and to provide adequate soil cover for the entire growing season. This note deals mainly with rye cover crop management in conventional tillage systems.
Here are a few tips for rye cover crop management.
Kill rye cover crop when it is still tender
Experienced growers would tell you that it is better to kill rye before it reaches your knees. Indeed, the cover crop should be killed at the vegetative stage when the tissue is still tender. Ideal stage would be at jointing during the initial phase of stem elongation but before flag leaf stage. When rye reaches boot stage, it becomes difficult to kill, the residue breaks down much slowler due to high C/N ratio, and there is greater potential for nutrient (especially nitrogen) tie up. If for some reasons rye cover crop gets out of control, consider mowing it to speed up tissue break down.
Incorporate fresh residue into the soil
Incorporating fresh residue into the soil will enhance the population of soil microorganisms that help break down the residues and release nutrients for the following cash crop. When residue is allowed to dry on the soil surface, as is the case for most herbicide-killed cover crops, subsequent residue and break down becomes slower.
Allow enough time between incorporation crop planting
Studies with many cover crops have shown that a period of about two weeks between fresh residue incorporation and crop planting is necessary to improve nitrogen availability to the following crop. This also reduces the risk of crop injury from allelochemicals released by the decomposing residue. Due to the high C/N ratio in rye, a longer period between cover crop kill and crop planting is mandated. This period will depend on the stage when rye was killed since younger tissue breaks down faster than mature tissue. Growers should be particularly careful when they are sowing small seeded vegetable crops. Chemicals released from the decomposing rye residue may lead to poor crop stand especially when rainfall is not adequate to leach the chemicals.
In most vegetable production systems, benefits of rye cover crop are optimized when it is killed at a tender (vegetative) stage, incorporated into the soil as green manure, allowed enough time for residue breakdown before planting, and when rainfall or irrigation is adequate.