Soil Improvement

Till or No Till: The Great Debate In Gardens


Till or no till

Till or no till, that is the question! This topic is constantly in debate, and there are certainly benefits to utilizing both of these methods. The usefulness of each method also changes with each varying application, such as container, in-ground, and raised bed gardening. 

A good place to start is by defining tillage. Tillage is the process of disturbing soil frequently used to prepare the soil for planting. There is a variety of equipment for tillage and no-tillage at small and large production levels. Equipment varies in purpose, intensity, and depth. 

As someone who has spent time studying tillage and the various impacts of it on soil, environment, and productivity, I can say that this topic gets complicated. Many states on the east coast are a part of the Chesapeake Bay watershed, and agricultural runoff into the watershed represents a large part of the pollution in the water body. This article will outline till and no-till methods and what their overall impacts are. 

What Is Conventional Tillage?

Disc plow
A disc plow in a field. Source: Evelyn Simak

Conventional tillage practices are a widely used process used by home and commercial growers. These conventional practices are any that require soil disturbance. The tools vary in depth and intensity. 

In larger farm operations, moldboard plows are used for reaching 8-12 inches deep into the ground and turning it over. This is also called primary tillage as it is the first step in a multistep process. Disc plows are used in secondary and tertiary tillage passes. Those plows loosen soil closer to the surface at depths of 5-8 inches. Deep rippers and subsoilers are other varieties of tillage equipment that aim to alleviate compaction at greater depths.  Many of these plows would not be used for the home gardener considering the size and scope of production. 

For home gardeners with smaller areas of land, rototillers are common forms of rotational tillage equipment. These devices can be hooked up to small tractors or be pushed. They till 4-6 inches deep. Generally, gardeners will do several passes with the rototiller to loosen soil for planting. While preparing the soil for planting is one reason, there are several other reasons to till the soil. 

What Is No-Tillage And Conservation Tillage?

No-Till Planting
A no-till planter in the field planting seed. Source: United Soybean Board

As the name implies, no-till involves not disturbing the soil at all. In an ideal system, it includes cover crops so that the soil is never left bare. No-till goes along with a larger umbrella of tillage methods called conservation tillage. As a whole, these methods aim to disturb the soil as little as possible. Strip and chisel tillage are two of the other prominent types of conservation tillage. Strip tillage involves disc plowing in small bands where crops are grown. In between these areas is ideally crop residue. Chisel tillage roughs up the surface and leaves 50-70% of the crop residue on the surface.

There is equipment that is made specifically for this system of farming. Farmers use no-till practices like a no-till planter or seeder that cuts through the plant residue and plants or seeds. It is a real benefit to the farmer as they only need to do equipment maintenance on much less machinery. They won’t need to worry about upkeep and buying tillage equipment. It also saves time and labor costs since the farmer only needs to use the no-till seeder or planter and not tillage equipment plus a seeder. 

Cover Crops

A critical component of any farming system is cover crops. Cover crops are any crops used to cover the soil, providing benefits for overall soil and environmental health. These crops are grown in fields not in use during the season or in fields during off-seasons (fall/winter). In a general, a good rule of thumb is to always keep the soil green. This means always growing something in the field. There are a variety of soil cover plant types that all serve different purposes. Some common crops include winter rye, oats, winter peas, hair vetch, clover, forage radish, oilseed, buckwheat, sudangrass, and sunflowers. There are many others, but those are just a few of them. 

Crops like winter rye and oats produce higher amounts of biomass and have fibrous roots, it helps add more carbon to the soil. Legume cover crops (hairy vetch, winter peas, and clovers) produce less biomass but have relationships with bacteria in the soil that help convert nitrogen in the atmosphere into usable forms for plants. They provide some nitrogen for the soil and crops following them. Some of the brassicas like forage radish and oilseed help alleviate compaction. They have big, strong taproots that can help loosen compaction and provide avenues for other crops to find water and nutrients. These crops also scavenge nutrients from lower in the soil profile, bringing them closer to the soil surface. Sunflowers are a more unique cover crop that’s gaining traction for this purpose. 

Inter-row cover crop in vineyard
An inter-row cover crop in a vineyard. Source: Cortes de Cima

While growing a soil cover in the summer may seem like a wasted time because you could be growing a vegetable or fruit, it is not. For one the flowers entice many beneficial pollinators, which helps build the ecological community. A more unique thing that sunflowers do is build mycorrhizal connections in the soil, as seen in this study looking at gene expression in sunflowers found in Nature. Sunflowers also have strong root systems which help add carbon to the soil and scavenge nutrients. Sudangrass is another warm-weather cover crop that can produce high amounts of biomass. 

Cover crop mixes are the best, especially integrating legumes and grass cover crops together. This is because of having too much carbon in the form of high biomass crops like rye. These have a lot more carbon compared to nitrogen. This becomes problematic as microbes will use up the nitrogen and make it unavailable to plants. Adding legumes into the organic material mix ensures the eventual soil carbon to nitrogen ratio is better. 

Including cover crops also helps reduce weed pressure because of more residue on the ground and having more competitive plants in the ground throughout the year. 

Comparing No-Till And Conventional Tillage Systems

Comparing, these two systems get complicated when considering all aspects of the growing process like soil health, productivity, environmental benefit. These comparisons will be based on larger growing operations, but many of these concepts can be scaled down for home gardener purposes. 

Weed Control

Controlling weeds is a constant issue amongst small and large growers. Weeds themselves are unwanted plants that find their way into the field. In large-scale organic options, weed control is incredibly challenging without the use of tillage. This is because of the limited options of chemical controls of weeds. Understanding what weed you are attempting to manage is critical in understanding what management tool to use. While many weeds are managed well through tillage, others are made worse because of tillage. Choosing tillage is problematic when trying to suppress weeds like bermudagrass that propagate in ways outside of the seed. It will end up making the infestation much worse. 

Managing weeds at critical points is most important. For home gardeners, preventing weeds early is critical to getting small plants going. This is where tillage before planting comes into play as weeds will be gone initially. This allows plants to get a good start. Once the plants are established, weeds play a smaller role in productivity. In large-scale operations, weeds are problematic at harvesting time since harvesting machines would be messed up by the weeds. Home gardeners are harvesting by hand mostly making a continuous no-till method of weed management less of a concern. 

Compaction

Hardpan soil
Hardpan caused by soil compaction. Source: University of Minnesota Extension

One of the common purposes of tillage is to alleviate compaction. While there may be less compaction in the depth that was tilled, consistent tillage leaves an extremely compacted layer beneath. This is more problematic for large-scale farms where heavy machinery is used. Bare earth and wet conditions exacerbate this problem. The photo above depicts this. As you can see there is a difference in layers. The bottom portion is extremely compacted. This is problematic for water infiltration as the lack of channels and pores prevents water movement. Roots are unable to move past this layer and will be limited to the top 8-12 inches or however deep the tillage was. This limits access to water and nutrients as well. No-till systems have a reduction in this compaction. Including a forage radish or oilseed in either a till or no-till system can reduce this soil compaction.

Erosion and Nutrient Loss

Soil erosion is one of the most important factors when considering which tillage system to use. In conventional tillage, there are two parts where erosion takes place. The first is during the tillage itself, soil loss due to wind erosion occurs because of the soil being disturbed. Some tools cause less than others. Soil particles will be airborne and then get blown away. This is especially prevalent in dry conditions. 

After fields are tilled, the soil is susceptible to soil erosion caused by water. Raindrops gain a lot of energy falling. Think of the impact of a raindrop. As you can imagine, bits of dirt get thrown potentially feet away from the raindrop. With millions of raindrops falling, this can be destructive. This is combined with less infiltration of water because tillage leads to runoff pollution. Both your soils and their nutrients can be washed away, leading to worse soil health and polluting waterways.

In no-till systems, frequently crop residues remain. These residues act as a barrier between the raindrops and the soil. It reduces the disturbance of the rain and since the soil structure is preserved the infiltration is improved. More water will infiltrate the soil versus running off the surface. Including a cover crop increases the effectiveness of the protection. 

Raindrop splashing on soil
A raindrop splashing on soil. Source: Iowa State University Extension

Soil Organic Matter and Soil Organic Carbon 

Organic matter in soils is something to consider when talking about tillage. Before getting into organic matter in tillage versus untilled soils, it must be considered what organic matter is and how it accumulates. For one thing, some soils have a higher capacity for organic matter than others. This is based on the soil type. Soils with higher percentages of clay can have higher organic matter percentages compared to sandy soils. Many practices can be done to improve the amount of organic matter in sandy soil but will be ultimately be limited in what percent can be achieved. Other environmental factors impact the organic matter and carbon in the soil outside of cultivation techniques. 

Looking at soil organic carbon and carbon sequestration is important when thinking about climate change and greenhouse gases like carbon dioxide. Organic matter and soil organic carbon are critical parts of soil that are complicated topics. 

The goal for sequestering carbon is to get stable carbon into the soil. Stable carbon is organic matter broken down into molecules that remain in the soil for a long time. While there is stable carbon, there is also carbon that turns over quickly. Some quickly broken carbon is released into the atmosphere. The key to carbon sequestration and helping climate change lies in the roots of plants and decreasing decomposition. Decreased decomposition reduces the greenhouse gas, carbon dioxide. Roots ultimately make up a greater percentage of the stable carbon. 

Tillage leads to a decrease in the amount of stable organic carbon. Often, stable carbon is found in aggregation with soil particles. Tillage disrupts these stable aggregations and increases the rate of decomposition for plant material into less stable forms. This study showcases some of the differences in aggregation and stable carbon in tilled and untilled soil. Organic matter and carbon are critical for healthy soil, tillage decreases these two things. In this way, the environmental benefits of the no-till method are an improvement over conventional till methods. 

Soil Structure

The first thing to think about with soil structure and its importance is understanding how roots grow. As plants grow, their roots will want to take the path of least resistance. Plants use channels created by organisms and other plant roots to find nutrients and water. Mixes of air, water, soil, minerals, and organic matter are intertwined with the structure of the soil.  Organic matter is specifically important for creating stable aggregates which help with pore space. Tillage destroys the structure. Tillage breaks up the soil entirely so all of the channels, pores, and aggregates are reduced. The problem only gets worse as tillage usage increases. No-till practices limit soi disturbance, so the structure is preserved much better. The improved soil structure benefits root growth and water infiltration. 

Fungi and Bacteria

Soil mycelium
A network of mycelium in soil. Source: Bushman.K

Soil biological activity including soil microorganisms and fungi represents an important factor in healthy soil.  Mycorrhizal fungi create networks of extremely small filaments called hyphae throughout the soil and build relationships with most plants. Brassicas are a group of plants that do not establish these relationships. Plants give the fungi sugars in exchange for water and nutrients like phosphorus that plants struggle to obtain normally. Imagine these networks as spiderwebs connecting trees and plants. 

When tilled, these connections are broken and take time to rebuild. Constant tillage prevents these connections from forming. We find a similar occurrence with microbial communities. This study from NCBI looked at microorganism communities and nutrient cycling. The study found that the improved microorganism communities also improved nutrient cycling. This makes it even more important to keep the soil untilled.

Soil Temperature and Moisture

One reason for tilling is to warm up soils to plant. Some areas of the United States that have longer winters find that soils are too cold to plant and need to till so that the soil warms up faster and plants can be grown. The regions have much shorter growing seasons making it that much more important to get crops growing so they get a good harvest. Untilled soils remain colder and therefore take longer to get ready for planting. 

Reducing soil moisture is also a common reason for tilling, as it will tend to dry the soil out. Ultimately, attempting to increase organic matter will help with this more than a conventional till, which is a short-term solution. In addition, tilling on big farms requires large, heavy equipment. That combined with already wet soil will lead to greater compaction. 

For home gardeners, pulling back crop residue can reduce soil moisture. If you’re trying to manage weeds, that may be a perk. However, if you’re in one of the many drought-prone areas, a no-till method can also be used to produce green manure that helps retain moisture in the ground. No-tillage methods like chop-and-drop are great for this, and by planting crops that you’ll chop-and-drop later, you’re reducing the likelihood of weed problems at the same time.

What Does This Mean For The Home Gardener?

Till or no till
Deciding whether to do till or no-till gardening (shown here) is tricky. Source: innatvalleyfarms

Most of what has been discussed in this article is in terms of large or medium-scale farmers on multiple acres of land. Many of these things are scalable to home gardeners growing in-ground and raised beds.

Container gardeners don’t have to worry about what’s discussed here because most of those growing media aren’t truly soil and are instead a potting mix, and therefore do not have the same properties. In raised beds, the space is small enough that one can control weeds manually. In situations where doing that is not possible, then utilizing tillage may be the best option. Reducing the amount of tillage by adopting no-till practices in any capacity is a good thing for the soil and the planet, but not everyone is set up for continuous no-till methods. 

Planting cover crops in a crop rotation with other crops in raised and in-ground beds can be very beneficial. One thing to consider is to plant seeds early enough (depending on the climate) so that plants can get good growth before the winter chill. 

Overall, the choice is up to the gardener. Exercising patience may allow the full benefit of a no-till system. On the other hand, there are several situations where tillage is required based on the limited options of herbicides for organic production. 

Frequently Asked Questions

Q: Is till or no-till farming better?

A:  No-till farming is better than till farming systems for the planet, but can be just as productive or more productive, especially compared to frequently tilled soil. 

Q: What is the purpose of no-till?

A: No-till is a system that’s much better for the system as a whole including the soil and the environment. No-till does not use any tillage, it benefits many soil properties, limits erosion, and nutrient cycling. As a whole, it promotes healthier soil. 

Q: Why don’t more farmers use no-till?

A: In many cases tillage has been used in many different generations of farmers. While there are plenty of extremely successful farmers using no-till, conventional tillage is dominant in the United States.  Switching to no-till acres of farmland does not necessarily show the benefits immediately which makes seeing the benefit of adopting no-till farming hard. It takes multiple years generally of continuous no-till practices to maximize benefits.

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