Good cover crops key to success of never-till

Never-till is not just a tag on the bumper of his truck, it's a way of life for New Kent, Va., farmer and Virginia Tech Extension Agent Paul Davis.

The 1,200 acre L.C. Davis and Sons family farm that he helps manage has become a showplace for innovative farming techniques, including a system Davis calls ‘never-till’.

Never-till is just that — never till the soil to plant a crop. Critical to a never-till system is finding a good cover crop — the concept being to always keep something green on the soil. To find the optimum cover crop, Davis partnered with Virginia Tech Grain Crop Specialist Wade Thomason.

Included in the on-farm tests were early (Sept. 30), mid (Oct. 20) and late (Nov. 10) planting dates. Varieties planted included barley, planted early, mid, and late; rye, planted early, mid, late and in combination with vetch early, mid and late; oats, planted early, mid and late; vetch planted early, mid and late; and crimson clover, planted early, mid and late.

Cereal rye was by far the best cover crop for the soybean, corn, pumpkin, wheat cropping system grown on the Davis farm. “We weren't surprised about that,” Davis says. “However, we were surprised by how big the difference in performance was between rye and other cover crops,” he adds.

Priming the pump for each cover crop, they added 25 or 50 pounds per acre of nitrogen, applied at growth stage 25, or mid-February. Biomass yields were bumped from an average of 2.25 tons per acre with no spring nitrogen to 3.5 tons with 25 pounds of nitrogen. No significant increase above 3.5 tons per acre was recorded by going with the 50 pounds of N per acre rate.

Nitrogen uptake, which is measured as yield times nitrogen concentration in the crop, was 120 pounds per acre with spring fertilizer in early planted rye. The next best early planted crop was barley, with 50 pounds of nitrogen uptake. Late planted rye was comparable to early planted barley.

Across all crops, with no nitrogen added, early planting produced approximately 30 pounds per acre more nitrogen uptake than late planted crops. Davis notes that planting date and species are critical when choosing a cover crop for any type of conservation-tillage system.

“The priming affect showed up when we measured the amount of N the crops took up,” Davis says. The Virginia farmer/Extension agent explains that 25 pounds of N used as a spring fertilizer produced 80 pounds of nitrogen uptake, compared to only 50 pounds of nitrogen uptake with no spring fertilizer. When the starter fertilizer was upped to 50 pounds per acre, they only saw an increase of 10 additional pounds of nitrogen uptake. “It appears for our growing conditions 25-30 pounds of N used at the 25th growth stage is optimum for top cover crop performance,” Davis contends.

Across all crops, rye had the least amount of N left in the soil, indicating this cover crop did the best job of mining available N in the soil. Oats, by contrast, had the highest amount of N left in the soil. Later planting dates also left more N in the soil than early and mid-planted cover crops.

Thomason notes that the first year or two cover crops typically are not efficient in mining nitrogen from the soil. Over a period of years, we expect cover crops will uptake more N, he says, and, we expect to see bigger gaps between nitrogen left in the soil among the various cover crops used in this test,” Thomason explains.

Though the on-farm test was run to generate data for Virginia farmers, from a personal perspective Davis says what convinced him to try different cover crops was seeing one of his neighbors produce 95 bushel per acre wheat using very little spring nitrogen. This farmer had been no-tilling for 11 years, and Davis didn't want to wait that long to benefit from reducing nitrogen on the family farm.

“I wanted to grow four crops in two years to speed up the process,” the Virginia grower says. “Our first frost date is traditionally on or about Oct. 20 and our last frost date is April 15th, plus we get on average 43 inches or so of rainfall a year, so we should be able to grow lots of biomass,” Davis says.

The idea for carbon production from cover crops was enhanced by the Davis family's experience with growing pumpkins. “For our no-till pumpkins, he says, we always planted into a rye, barley, or crimson clover cover crop that had been rolled. We noticed we never had any dirt on our pumpkins at harvest and that weed control was improved and weed control costs were reduced. We knew we wanted to start scavenging more of the residual N in the soil and get more mulch on the soil surface, and the cereal rye cover crop has done the best job for us,” he adds.

Barley, oats and even wheat are like the proverbial child born with a golden spoon in their mouth, Davis contends, noting that these crops require special handling. Redneck rye on the other hand, he says will survive most anything and do the job. With one of the coldest Decembers and one of the warmest Januarys on record and a winter-long drought to boot, rye in the 2005-2006 season was put to the test on the Davis farm.

Davis points out that the NRCS (Natural Resources Conservation Service) and State Cost-Share cover crop payments are based on results. Good faith efforts, like broadcast or flying on any cover crop seed, will not guarantee results. In some crop sequences, like going into full season beans there may be enough surface soil accessible to broadcast the cover crop seed, but if you are planting into fields that have heavy soil residue, in most never-till cropping scenarios, no-till seed may never touch the ground when applied by broadcast means of seeding.

Among the other cover crops and planting dates in the test, a bushel of rye and 10 pounds of hairy vetch produced a good cover crop, when planted in both early and mid-October. Davis points out that some wheat growers are concerned about planting vetch, since it sometimes has to be sprayed with herbicides to prevent competition with the wheat crop. Davis contends that vetch can be managed early to prevent it from going to seed and causing problems.

Crimson clover at 20 pounds per acre suffered from the warm winter and drought, but still had a possibility of producing a good volume of biomass, if the area received adequate rain in April, Davis points out.

Oats planted late was probably the biggest disappointment among the cover crops. Davis contends that if you are going to plant late, go with rye and up the rate to 2-2.5 bushels per acre. It's not as good as planting early or mid, but it's better than any other cover crop when planted late, the Virginia Extension agent says.

An additional benefit of never-till in combination with using a cover crop that produces a high volume of biomass is the ability to get into a field after a 2-3-inch rain. Water doesn't stand on these fields, Davis says, and it doesn't compact the soil — it just has the ability to hold you up better, he notes.

Despite not performing as well as rye, Davis says the most economical of the cover crops tested is barley, if the grower can save seed from a previous crop. It won't touch rye in terms of biomass produced or nitrogen uptake, but it could be more economical in some situations, the Virginia farmer points out.

Though further north than other growing areas in the Southeast, Coastal Plain soils of northeast Virginia are typical of soils found up and down the East Coast. Whether rye will hold out as the premier cover crop for no-till or never-till systems depends on cropping systems, weather patterns, availability of equipment and myriad other factors.

Despite the obvious differences from state to state and region to region, Thomason and Davis agree that cover crops are a critical part of any reduced-tillage system. And, as incentive programs are advanced by Federal and state agencies, the wise use of cover crops can make the difference in qualifying for these programs and not qualifying.

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