Pros and Cons of Each Approach
First, let's revisit why it is desirable to move the soil at all. Conventional wisdom was soil is tilled is to loosen it so oxygen and water can reach the area where roots will grow. However, many passes over a field with equipment and even heavy animals such as oxen or horses, much less heavy equipment, further compacts the layer of soil just beneath that of which was tilled. Additionally, the broken-up soil is very prone to being compacted by rainfall. its ability to create a more natural soil that retains nutrients and water, prevents soil erosion, and compacts less.
Plowing, it is claimed, incorporates fertilizers and crop residues into the soil, making nutrients readily available to the roots of the plants. Turning organic matter under also has the benefit of preventing planters from becoming fouled with surface trash. In no-till farming, crop residues are left on the surface, where the nutrients that result from their decay can leach into the soil. This leaching process is far more thorough than you might imagine. Fertilizers—including anhydrous ammonia, phosphorus, and potassium—are at least as effective on the no-till fields where they've been dispersed as on the plowed plots. These ingredients can be placed directly into the planting trench, where they're most needed, during seeding. As for the potential problem of the planter fouling with residues, it is recommended to cut a slot through surface trash.
Though the soil does stay cooler until a little later in the spring because of the insulating layer of residue, the day/night soil temperature fluctuations are smaller. A no-till field rapidly makes up its deficit in growth rate as the weather turns warm. And if the summer should be really hot and dry, no-till yields will nearly always exceed those of plowed ground. Since soil moisture levels can be more than 10% higher in late July in an unplowed piece of ground, it's not surprising that plants are happier in a field covered with mulch.
One of the significant downsides of plowing is it tills the entire area, where doing so by hand will only create the trench needed for seeding. Both plowing and tilling can be done in a way to help minimize the amount or water runoff, but a big benefit is that no-till soils stay more moist than those in tilled fields. The surface residues trap water and protect the earth below from the evaporative effect of the wind. In areas, where adequate spring moisture depends largely on spring rains and/or snowmelt, the vegetative cover helps keep the snow from blowing away and water runoff. (For more on permaculture practice click here). The advantages don't end there, though. If you grimaced when you read "anhydrous ammonia", consider this: One of the main problems with conventional agriculture's heavy use of nitrogen fertilizers is the leaching of these compounds into surface water during runoff. By retaining rainfall, the untilled field also better holds the chemicals that have been applied to it, thereby decreasing their pollution potential.
Our Findings in the Backyard Garden
When the climate is drier, we strongly prefer a minimal till approach as described on the Building Soil page. This might involve taking a spade and lifting up the soil where the plant will go and perhaps 12 inches of space on all sides. Then as the plant grows, we will hand pick the weeds that grow up around it. This is very desirable and doable during periods of low rain fall because a minimal amount of soil is turned over to release carbon and dust in the to atmosphere, the bacteria and beneficial creatures in the slow are minimally disturbed and the weeds - with some regular diligence, and especially when a drip irrigation system are used - are easily kept under control.
However, we've also found that in optimally rainy conditions, no till seemed like a futile attempt to do the right thing for the environment. Weeds quickly out-paced our ability to pull and pests arrived in droves, often taking advantage of the long stems and leaves of the weeds around the crops to hide themselves and gain advantageous access. Our attempt at minimal tillage in a year like this left us breathless, exhausted and with a minimal yield of crops. One of our take-aways was we needed to over-turn more of the soil around the plants and we needed to weed more often. Unfortunately, tiime is not in endless supply, so here are some other things we learned:
- Mulch, mulch, mulch
- Mulching not only helps with keeping moisture in the ground and stabilizing soil temperatures, but also offers huge help relative to keep weeds under control. However, it is important to also keep an eye on the condition of the mulch. If gets warm and has yummy things to eat, you may also be attracting slugs, snails and other undesirables. If you're mulch starts harboring these critters, a refresh may be in order.
- Selecting the wrong seed variety
No-till seedlings may experience cooler and wetter seedbeds. Planting varieties that tolerate these conditions is important. Also, selecting the right kind of crop for no-till is important. Pole beans, peas, corn, okra, potatoes and many gourds do fine with no-till. So will mature crops such as rhubarb. Crops such as broccoli are easy to weed around. Crops such as radishes and tomatoes seem to fall in between. Tomatoes and peppers will need more care and plants are starting out definitely need more assistance. Shrub and vine-based crops such as blueberries, raspberries, dew berries and blackberries, once established, will also easily hold their own against weeks.
- Lack of crop rotation
Crop rotation is important to break up disease, insect and weed cycles. Double cropping the same crops every year is not a crop rotation. A field or garden space must grow a different crop at the same time of year in consecutive years to be in a rotation.
- Lack of equipment
The main equipment for a small space is a spade, hoe and gloves for a lot of weeding. For a larger space, a no-till planter and a sprayer is needed which is not practical for many backyards and small-scale farmers. If you do decide to invest in equipment and go with "conventional" no-till, the technology of both of these has improved significantly in the past decade. Using old equipment may be of as little benefit as using the wrong equipment.
- Trying to reduce inputs and expense
Often, producers try to use lower rates of herbicide or fewer herbicide applications than needed. It is wise to plan on spending at least as much on herbicide as would have been spent on tillage. Time, labor, soil moisture, and wear and tear on equipment may all be saved, but not pesticide dollars.
- Failure to correct nutrient deficiencies before starting
Fertilizer and lime can be surface-applied, but they don't move much below the top 1 inch of soil without some type of tillage. Ideally, soil nutrient levels should be adequate throughout the rooting depth and not just in the top inch of soil; yields may suffer if the levels aren't sufficient.
- Failure to leave enough residue
Residue serves many functions, such as catching precipitation, feeding beneficial soil microorganisms, preventing topsoil and nutrients from eroding, covering bare soil so weeds have difficulty germinating and preventing soil crusting. Here we've had some good luck with covering the gardening area with tarps for a few weeks prior to planting.
- Not having equipment properly adjusted
Other than spades, rakes and other hand-held tools, we have not used much else in the garden areas. Pesticides are heavily relied upon in no-till, and therefore sprayers must be properly equipped, calibrated and operated. Likewise, pressure on disk openers and closing wheels on planters and drills must also be properly adjusted. Because we want to avoid the use of pesticides, we've instead opted for weed pulling, clipping down invasive plants, covering the ground around the crop with either a ground cover or fine gravel. This is especially helpful if slugs are a problem and will significantly improve the yield in gourd patches.
- Lack of knowledge
No-till farming is not the same as conventional farming. It involves much more than simply not plowing. It requires different skill sets to optimize all the required inputs.
- Lack of attention to detail
To illustrate this point, consider this example: a plow controls all small weeds equally well, but pesticides are more selective - and again - not desirable. Conventional no-till wisdom promotes spraying at the right time and right rate with the best equipment does no good if the wrong pesticide is used for the target weed or other pest. Everything must be done correctly. We simply found getting out a hoe and gently hoeing around the plants a couple of times a weeks sufficed well.
- A failure to commit to making it work
This is the reason for most no-till failures. If a producer doesn't think no-till will work and doesn't want to make it work, it probably won't. No-till farming is a commitment to a long- term process of soil management. The production benefits of no-till are greater in year 20 than in year two. This means no-tilling for three years and then plowing every fourth year isn't really no-till, it's just not plowing for three years.
A no-till or minimal till policy does the utmost in terms of maintain the earth's precious top soil. Diligent growing practices and time in the garden managing pests and weeds will help maximize the return in the garden. Also, plant what grows well in your area, keep an eye out for pests and make sure the soil moisture is sufficient. A hardy and healthy plant is one of your best defenses against weeds and pests.