In a previous post, we discussed how conventional no-till works, including its history, its objectives, and its methods.
The primary goal of organic no-till is essentially the same as that of conventional no-till—to protect soil from erosion.
However, in organic no-till, the methods used to achieve this result are vastly different.
Common Objections to Conventional No-Till
First off, there are some disadvantages to no-till, regardless of whether it is conventional or organic:
- Initial equipment costs.
- Need for considerable advance planning and specialized knowledge (read, “steep learning curve”).
- Cooler, wetter seedbeds, which may hinder germination and growth (no-till works better with hotter, drier climates and well-drained soils).
- Weed proliferation, which will result from any attempt to cut corners on control.
- Crop diseases harbored in residues.
But there are also difficulties that are specific to conventional no-till:
- Large amounts of herbicide used.
- Need for bioengineered seed to allow for herbicide use.
- Low amounts of residue produced, insufficient for weed control and gully prevention.
The Organic Way
Organic no-till relies heavily on cover cropping to smother weeds. Cover cropping also has many other advantages, such as building organic matter and promoting the health of the biological soil community.
Once the cover crop reaches the desired stage of maturity (at the peak of its life cycle but before it goes to seed), a roller-crimper knocks it down. The roller-crimper is a heavy water-filled cylinder, drawn either by draft animals or by machinery, but it doesn’t just squash the cover crop. The diagonal ridges on the roller also crimp the stems to ensure that the crop will remain in a thick, flat mat on the ground. This is essential to prevent unwanted volunteer plants and also to prevent weed emergence. Alternatively, the cover crop can be mowed down, but mowed residue tends to become scattered over the field in random directions, clogging implements. With a roller-crimper, the cover crop stems are all laid in the same direction. As long as the drill goes with the grain, so to speak, it should work smoothly.
Planting the organic no-till cash crop is generally similar to planting a conventional no-till cash crop. Higher seeding rates are necessary with organic no-till, as the thick cover crop mat may prevent the planter from making a clean slice in the soil for good seed-to-soil contact, thus reducing germination rates. Researchers are still working on developing planters that can more easily cope with thick residues.
Operating no-till drills with draft animals presents special challenges due to a scarcity of equipment and the need to operate the machinery at a reasonably high speed for proper functioning. A PTO forecart converts the forward motion of the animals into power to operate the drill. Horses work better in no-till systems than oxen due to their quicker pace.
After harvest, the stubble of the cash crop is disked into the soil, and a new cover crop is planted.
Drawbacks of Organic No-Till
One of the problems organic no-till faces is that it relies heavily on cover cropping for success. This implies regularly taking fields out of production. Growing the cover crop over the winter takes care of the loss of time, but there is still a monetary cost.
Careful selection of the right cover crop is necessary to avoid introducing new problems. Some plants, such as alfalfa, are resistant to the effects of the roller-crimper and therefore not great candidates for this system. Also, high levels of biomass production, at least 2.5 tons of dry matter per acre, is necessary for effective weed control. Finally, the C:N ratio of the cover crop needs to be 20:1 or higher to prevent it from decomposing too rapidly and leaving the soil exposed. The best cover crops for no-till tend to be cool-season annuals, such as winter rye and hairy vetch.
Another problem is time and labor. Crimping the cover crop and planting the cash crop simultaneously will reduce the time spent in the field. This can be achieved by mounting the roller-crimper to the front of the tractor and pulling the no-till drill behind.
Organic no-till can be difficult when persistent perennial weeds have overrun the field. In such cases, an initial till can give both cash crops and cover crops an advantage.
Probably the biggest challenge of organic no-till is the level of advanced planning required. Crop rotations must be worked out and cover crop selections made well in advance. The benefits will not be reaped in a season, and soils with damaged structure may take years to heal.