By David Hunsberger
Cover crops are being utilized on more acres here in the Northeast USA each and every year. Usage is split into two main categories, winter forage production for ruminant animals and for soil cover and improvement. Both these forks in the winter crop roadmap find the same species useful – often the combinations of species and the rates of application vary quite distinctly.
When harvesting a large crop of DM from the non main growing season of fall and winter, the execution of timing of the seeding is crucial. Both rate and early window of opportunity timing are critical for achieving full mass yield potential. We require a dense sward with lots of fall tillering and some autumnal fertility to enhance the volume of the harvested crop. Again, timing is even more critical than rate; you cannot make up for late planting by simply by adding seed to compensate for being tardy. You can, however mitigate the loss of yield with an increase in seeding rate, but not account for all the opportunity cost. To ensure a timely planting, order seed early have it on hand, make sure planters are at the ready, chase the combine or chopper with the next pass of seeding!
Rates for cereals and some cereal mixes to consider are as follows: Double Play 175 lbs/A, Wheat 5 bu/A, cereal rye and triticale 125lbs/A, CARGO 120+lbs/A. If we are including a legume like crimson, vetch , or winter peas the timing is also crucial to have enough height and plant reserves to overwinter, it is paramount that we get them in, with good seed to soil contact on time, legumes are a little slower than grasses and cereals to achieve winter hardy status. If you grow your own cereal grain crop our small and large box boosters are great at providing easy access to crop diversity without a mixing facility or tying up a large number of bags of different species to get the ratios correct. A good segue is to figure out when you will stop to fill the large box, then calibrate to drop small box booster seeds at the same time, this will lessen seeding time frustration by streamlining your process of starting to use diversity on your acres. USDA hardiness zone maps can inform on specific dates for your individual locales.
For Planting Green management or just a soil protecting/soil building cover to burn down ahead of planting we do not need, nor do we want such a heavy mat of forage top growth to deal with. We want active roots and a residual mulch but not excessive DM to plant through. A caveat to this is when using a rye or triticale as a roll down for weed control in soybeans or pumpkins or other vine crops. In these circumstances you will want to use the very heavy rates and early establishment dates as you need a thick several tons of DM/acre to provide a season long roll down mulch. Waiting until full seed head emergence and the anthers begin to drop will ensure you have maximum DM accumulation; hollow stems and the crop will remain down after you roll it.
A mix from Kings that is specifically designed for planting green is our Green N Low. This is a simple mix of the dwarf turf type LowBoy annual ryegrass and Dixie crimson clover. The crimson will fix nitrogen and the LowBoy will have aggressive fibrous roots for soil building and aggregate stability, but the top growth will be more limited allowing planter operation to move down the rows with minimal interference. Our standard seeding rates are 20-25 lbs/ acre with Green N Low.
Something else to be mindful of, southern exposure is a real thing when it comes to mitigating late season effects. Height and over wintering on southern exposure sites were far more robust than northern ones. We had more purple dead nettle and chickweed pressure on northern slopes as the covers were less prevalent. The author also attempted some lower seeding rates, 10 & 15 lbs/acre in late October. These rates all provided good cover by late spring, the soil was shaded, and was easy to plant into. I wanted to have a fibrous rooted crop component as I feel that is critical to maintain soil structure following an N fixing crop like soybeans, without some off season root exudates contributing carbohydrates as I feel the soil biome will rob the glomalin glue from aggregates to get the C: N ratio in balance.
If planting into heavy fodder, small seeded crops like Green N Low in late season with limited fall precipitation may provide unsatisfactory results. Larger seed size crops performed better in this instance, emerging, and thrusting through the heavy fodder. In late March I did seed 25lbs of spring oats as a rescue green cover plan and had 12-18 inch oats to plant into by mid May.
Another low-rate plant green crop I used in autumn 2020 was the TerrraLife Rigol DT this has a recommended rate of 18-20 lbs/acre. It is designed for soil compaction relief and nutrient sequestration. The product is designed to have about 50% to winter kill and 50% to overwinter. Very nice to plant into this spring also and easy to terminate. I am very interested to observe the corn crop in that 10 acre Rigol DT field this summer as the season progresses. It appears that moisture may well be limiting factor again this year in central Pa, several farmers have told me that they are seeing springs and “dry creeks” very low August like levels here in late May. I am trusting that my plant green acres will provide a soil moisture holding mulch summer 2021.
In summary as you plan your winter forage crop needs and acres you wish to plant green into you can adjust your seeding rates and establishment dates to achieve desired results. Even a 5 foot tall cereal rye can be planted through if you have a lower seeding rate (GPS may be helpful in 5 foot rye for nighttime planter operation!) Looking for a plentiful harvest in 2021, Consider visiting the PA NOTILL website for more information on planting green.