How to Supercharge No-Till Soils

No-till fields do have regular plow-down of organic matter. Soil pH often slips under no-till conditions, which can foul up the micronutrient profile.

How is a Holstein cow like silt loam soil? Both produce more when healthy.

There is no question that healthy soil will produce better crop yields. With the pH of a freshly plowed field in the upper 6.7 range and soil tests showing a good balance of N-P-K (nitrogen-phosphorus-potassium) and micronutrients, most producers are ready to go to town.

No-till fields are different. By their nature, no-till fields do have regular plow-down of organic matter. Soil pH often slips under no-till conditions, which can foul up the micronutrient profile. There is a special technique, however, for sampling no-till soils.

Some farmers fear there is a yield penalty with no-till. In many cases, that fear is justified by agronomic research. The key question is what causes the slightly lower yields that are found on farms and in university research plots. For instance, the University of Vermont (UV) found a slight yield drag when transitioning continuous corn fields to no-till. This effect lasted while the soil improved from the cover crop and the reduced soil disturbance.

On the other hand, there are dairy producers in the Northeast who report that they did not see a reduction in yield. Is that because they manure the fields?

UV research, along with countless farmer experiences, does not show a yield drag when starting no-till corn into hay fields that are terminated in the previous fall with a herbicide. Another bonus for no-till is that – given we are seeing extreme changes in weather conditions and more summer months with little or no rainfall – corn grown in a no-till system will perform better than that planted conventionally.

Whatever the tillage method used, soil needs to have sufficient fertility to produce a profitable crop. That applies whether the crop is soybeans, corn or something else.

Agronomists at the University of Massachusetts warn that soil pH can be more difficult to manage under a no-till system. “The transition to no-till will be best if the soil pH is already in a desirable range,” said Masoud Hashemi at University of Massachusetts. That requires planning at least a season ahead of any major switchover in tillage systems.

With a no-till system, spread manure cannot be incorporated into soil; if injection is not an option, ammonia nitrogen (potentially up to 50 percent of the total nitrogen in liquid manure) may be lost to the atmosphere. However, many researchers and farmers believe the benefits of no-till and the use of nitrogen conserving cover crops outweigh the potential nitrogen loss.

Cover crops capture nitrogen from manure and residual nitrogen from the previous season, thus helping to reduce nitrogen inputs to subsequently planted corn. Even so, most no-till experts recommend applying 30 to 50 pounds of N per acre as starter fertilizer. This would be especially necessary if rye or other winter grain cover crops were terminated at a more mature stage.

Annual applications of nitrogen fertilizer increases soil acidity. Many Northeastern operations have livestock and manure spreading further lowers soil pH. It requires 7 pounds of limestone to neutralize the acidity created by a single pound of ammonium sulfate fertilizer.

In acidic soils, the natural availability of many plant essential nutrients is reduced. According to industry sources, when pH drops to 6.0, 20 percent of the fertilizer applied is wasted – and that includes almost half of the P and 10 percent or more of the N. When pH slips to 5.5, fully one-third of the fertilizer is wasted as only about three-fourths of the N and K are available to plants and less than half of the P can be taken up.

Even worse, availability of some of the undesirable elements such as aluminum is increased under acidic conditions. Limestone has carbonates that remove acidity from the soil, pushing pH closer to the desirable neutral range. Lime also supplies other essential elements such as calcium and magnesium. Keep the soil sweet.

Cover crops

Integrating cover crops as part of a program likely will cut fertilizer costs. It will increase soil organic matter. Cover crops also can reduce leaching of potassium (K), ultimately reducing the amount of purchased fertilizers for successive crops, said Richard Kersbergen at the University of Vermont.

Before the advent of no-till, relatively few producers were using cover crops. Research from 2014 by the U.S. Geological Survey, found that cover crops, in the five-county area studied, were planted following corn on 22 to 37 percent of the available acreage. This is up enormously from previous studies that found only 10 percent of crop acres were covered by cover crops.

Satellite images from Berks, Lancaster, Lebanon and York Counties in Pennsylvania show even more acres planted to cover crops after corn harvest. Between 2009 and 2013, the acreage planted to cover crops jumped from 40 percent to 65 percent in those counties. Much of this acreage was in silage corn. With the whole plant removed for the silo, there is little crop residue to stabilize the soil. Cover crops then come to the forefront in no-till operations.

Know what your cover crop requires to thrive. For two examples, red clover requires a minimum pH 6.2 to 6.5. Alfalfa requires a more neutral soil in the pH range of 6.4-6.8.

False positives

It is fairly common for the surface pH of no-till fields to be significantly lower than the rest of the soil profile. This low pH can have an especially yield-robbing effect on plant growth, said Lancaster County, Pennsylvania Extension agronomist Leon J. Ressler. It also can reduce herbicide effectiveness.

“If your standard soil test does not call for lime but you are a no-tiller, then a separate, shallow sample (no more than two inches deep) should be taken to measure the surface pH,” Ressler said. Although samples can be sent to the lab separately, for a faster and less costly method, use a field pH kit.

If surface acidity is below 6.2, Ressler recommends applying one ton of lime (2,000 pounds of calcium carbonate equivalent). Limestone applications, especially no-till applications that, of necessity, are not incorporated into the soil, should be done several months before the crop is planted. This will allow for rainfall incorporation and activation so the soil is sweeter when the crop begins to grow.

Nutrients applied to the soil surface, including lime, may become concentrated in the topsoil, Hashemi said. He agrees that soil testing of the top two inches of soil, as well as the standard 6-inch depth, may be useful to identify a buildup.

“If the nutrient concentration test results from the 6-inch deep sample are optimum or high, then nutrient accumulation near the soil surface should not be a concern,” he said. However, if the 6-inch results indicate low or very low nutrient concentrations and or the 2-inch depth indicates high concentrations, then injecting phosphorus and potash with the planter or a separate fertilizer injector is recommended.

Whether one is fertilizing for the cover crop or for grain yield, it pays to know how much fertilizer is needed.

“It is a waste of time and money to try to establish or improve stands when the soil fertility and or pH are too low to support productive plants,” said Virginia Tech Extension Forage Specialist S. Ray Smith. Only then is it time to fertilize and lime according to those soil test recommendations.

When sod is weak due to thinning of desirable grasses and legumes and encroachment of broadleaf weeds, it often can be dramatically improved by interseeding legumes and grasses, Smith said. Before seeding, apply herbicides to the weeds, fertilize, lime, and graze or clip if more than 2 to 4 inches of growth is present. It is not recommended that alfalfa be seeded into an existing stand of alfalfa more than 1 year old.

Although clover can usually be established by broadcasting seed on the soil surface in the winter, drilling provides even greater assurance of establishment success. On the other hand, it is very difficult to establish most grasses and alfalfa by broadcasting or frost seeding, Smith said.

When thickening grass-clover sods, it is best to plant the grass and clover seed with a no-till drill. Conventional grain drills will work as long as they penetrate the soil surface and adequately cover the seed. It is extremely important to have the sod grazed closely to have adequate weed control, fertility, and soil pH, Smith added.

Every field is different and every operation has its own nuances. There is little question that no-till can save producers valuable hours in the spring when the weather window is often small and the job to be done is huge. The key to success is to plan ahead – start now to adjust soil pH, know what the contribution of earlier stands of legumes is to the no-till field and check into which hybrids or varieties produce better in fields in your end of the county.

Then you can be confident that your ground is healthy and will produce at its best.