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01
Oct
2015
Cereal Rye: Cover Crop Workhorse Part 3 in a Series
Author: Trenton Roberts, Research Assistant Professor, Crop, Soil & Environmental Sciences

Overview

Cereal rye is a winter cereal crop that has garnered a lot of well-deserved attention in the cover crop world. As far as cover crops go in the Mid-south region, cereal rye is a workhorse that is hard to beat in terms of the benefits that can be gained for the relatively low input cost that is required to establish and manage it as a cover crop. In most cases the name of the game for cover crop success is biomass production. Cover crop biomass production is essential to achieve many of the benefits that are associated with cover crop use including erosion reduction, weed suppression, nutrient retention, crusting prevention and increases in soil organic matter. Cereal rye is a huge biomass producer (2,000-10,000 lb biomass per acre) with little to no input costs (mainly seed cost). In many cases large amounts of biomass can be achieved by planting cereal rye without the need for additional fertilizer N inputs. However, cereal rye is also an excellent scavenger of residual soil nutrients (N, P, K, S etc.) and unlike tillage radish is not prone to decompose quickly and release those nutrients back to the successive cash crop. This nutrient scavenging ability can be great for retaining nutrients in the field and preventing nutrient runoff to surface waters, but needs to be taken into consideration when managing fertility in the following cash crop. When rice, corn or grain sorghum is following cereal rye, consider planting the cereal rye in a blend with a winter legume such as hairy vetch or Austrian winter pea. Blending cereal rye with a winter legume will add some N to the soil and lower the C:N ratio of the cereal rye which will allow quicker decomposition of the cereal rye biomass and faster release of those nutrients back into the soil profile. Applications of P and K should also be delayed until the spring to prevent sequestering of those nutrients in the cereal rye biomass that will be slowly available to the following cash crop. Cereal rye has broad adaptability and works well on most soil textures and even on what would be considered marginal or unproductive soils. One nice thing about cereal rye that allows it to fit so well in Arkansas is its ability to withstand waterlogged soils and even some ponded water. In addition, cereal rye can germinate at very low soil temperatures (~34 ̊F) allowing it to be planted and established late in the fall after crops such as late-planted soybean have been harvested. Overall cereal rye is a great cover crop choice for the Mississippi Delta region and can provide many excellent benefits with very little input costs. One question that is often raised is “why is the seed cost for cereal rye so high?” The easiest answer is supply and demand; most cereal rye varieties are not very productive and only produce ~30 bushels per acre. Cereal rye can be purchased for $15-20 per 50 lb bag, which equates to a seeding cost of $12-$24 per acre based on your planting practices. This cost is relatively low when you consider the cost of other single seeded cover crops and cover crop blends that can cost in excess of $45 per acre to establish.

 

Crop Rotations for Cereal Rye

Considering the cash crop that will be planted the following spring is the first step in developing an effective winter cover crop management plan. Having a good understanding of what you are trying to accomplish with your winter cover crops is essential to picking the right one for your farm, your soil and your crop rotation. Cereal rye, even under poor soil and climatic conditions, can produce large amounts of biomass and therefore it is great for erosion control, nutrient retention and weed suppression. Cereal rye as a single-seeded cover crop or included in a cover crop blend is a great option for all crop rotations including corn, cotton, grain sorghum, rice and soybean. For cereal cash crops (corn, rice and grain sorghum) that require N fertilizer inputs, please consider blending cereal rye with a winter legume to aid in biomass decomposition and prevent nutrient tie-ups in the cereal rye biomass.

 

Land Preparation

Similar to other cover crops, the primary benefits of erosion control, water retention and weed suppression can only truly be realized if the majority of the cover crop biomass remains on the soil surface following termination. Therefore, in most crop rotations, the best strategy is to complete all land preparation and pull beds in the fall prior to planting cereal rye with the intent of establishing your following cash crop using no-till or strip tillage equipment. Due to the large amount of biomass that can be generated when planting a cereal rye cover crop, it is important to be prepared to deal with this residue during planting of the successive cash crop. No-till planters are ideal for planting into these high density cover crop residue situations, but almost all drills and planters can be retrofitted to deal with these high residue situations. Row cleaners are often times a simple fix that can be added to many planters to aid in the establishment of cash crops planted into high residue cover crops.

 

Planting Dates

Cereal rye is highly versatile and can be effectively established early in the fall following corn harvest (August) and very late in the fall following soybean harvest (November). Minimum soil temperature for cereal rye germination is 34 ̊ F, so it can be planted very late in the fall and still germinate and establish effectively. Unlike tillage radish, fall and winter growth of cereal rye can be quite significant and often times can put on more winter biomass than a typical winter wheat crop would. However, late planted cereal rye may not tiller as well and have more winter-kill in unusually cold winters. Ideal planting dates for cereal rye in Arkansas are as follows:

 

Northern Arkansas (north of Hwy. 64) Optimum planting window is August 15th – Nov. 1st.

Central Arkansas (south of Hwy 64 to north of Pine Bluff) August 15th –Nov. 15th

South Arkansas (south of Pine Bluff) August 15th – Nov. 15th.

Rye PD 3 closeup Oct. 2014Figure 1. Establishment of cereal rye planted Nov. 1 at the Pinetree Research Station near Colt, AR. Cereal rye can germinate at soil temperatures as low as 34 degrees F.

 

As you can see, the planting window for cereal rye in Arkansas is quite large and makes it a great cover crop choice for a variety of production situations and crop rotations. Although cereal rye is not as prone to damage from residual herbicide activity as tillage radish or small-seeded winter legumes such as clover, this is something that should be considered with all cover crops. Herbicide activity is a function of soil texture, moisture and microbial activity. If you are concerned about residual herbicide activity influencing your cereal rye establishment you can easily gather soil from the fields of interest (both on beds and in-furrow) and do a simple germination test with your cereal rye seed to determine if there is a potential problem.

Seeding rates

Precision Planter- Not recommended

Drilled on 7.5-9” row spacing- 35-45 lbs. seed/acre

Broadcast or aerial seeding- 55-65 lbs. seed/acre

 

Planting depth 3/4” -1 ½ ”

Cereal rye seed is grayish brown in color and will be thinner and more elongated than the soft red winter wheat seed that is most often sown for grain in the Mid-south. Cereal rye seed looks very different than annual ryegrass seed which should not be planted in Arkansas as a winter cover crop. The most efficient establishment technique is using drills or planters similar to the establishment of a winter wheat crop, but it can be accomplished with aerial or broadcast seeding and shallow incorporation with something similar to a Kelly Diamond Harrow.

Rye Wheat Seed ComparisonFigure 2. Comparison of seed size and appearance of Cereal Rye (L) and Soft Red Winter Wheat (R).  

Fertilization

In most of the soils in eastern Arkansas, cereal rye that is planted prior to Nov. 1 will not require N fertilizer in order for producers to get the full benefits of the cover crop. However, cereal rye planted after Nov. 1 can benefit from 30 units of N to aid in tillering and help prevent winter kill in extreme winters. For cereal rye following rice on silt loam soils somewhere around 30 units of N are needed to aid in crop establishment. We have not conducted any research on clay soils, but 45-50 units of N will probably be needed for late plantings. There is no need to fertilize cereal rye with P or K for optimal results on the majority of our soils. Land that has been recently leveled will often times benefit from the application of 1-2 tons of poultry litter per acre. Applying the litter prior to cereal rye planting could lead to the tie-up of these nutrients in the rye biomass and lower the availability to the following cash crop. Research is ongoing to determine how P and K fertilization needs to be addressed in these high residue cover crops such as cereal rye, but to be safe try and apply P and K fertilizers after cereal rye termination and prior to cash crop establishment. Banding of these nutrients during planting can help avoid any potential problems that might occur.

 

Burn down/Killing Cereal Rye

In the spring, cereal rye will break winter dormancy and begin rapid vegetative growth in mid to late February, depending on your location within the state (closer to early Feb. for the southern portion of the state). Allowing the rye cover crop to grow until the first of March will provide sufficient biomass to realize many of the cover crop benefits and still allow adequate time for burndown and desiccation prior to cash crop planting. The rye cover crop should be terminated a minimum of 14 days prior to the establishment of the following cash crop to ensure that there is no “green bridge” to harbor pests such as stink bugs and armyworms. Cereal rye is one of the easiest cover crops to terminate and can generally be accomplished with 22 fl oz/A of glyphosate applied prior to the boot stage. Earlier termination of rye cover crop (prior to the boot stage) typically leads to better results. When cereal rye is planted in a cover crop blend other herbicides may need to be added to control additional cover crops species in the blend, but the addition of 2,4-D will typically aid in the termination of any broadleaf cover crop species. Please remember that cereal rye can be a large biomass producer and earlier termination can help alleviate the large amounts of biomass at planting of the cash crop.

rice planted into standing ryeFigure 3. No-till rice planted into standing cereal rye three weeks following a burndown application of 22 fluid oz/acre of glyphosate.

 

We are continuing to work with these and other cover crops to improve row-crop performance in Arkansas. This research was supported by the Arkansas Soybean Promotion Board and special thanks to Dr. Jason Norsworthy for contributions to this article.


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