To till or not to till? Part 2

Question: I understand that no-till farming is beneficial, but how can I control weeds if I don’t use herbicide and don’t till the soil? Hand-weeding is laborious and I can’t do it on a big plantation.

Answer: That is a very good question. The answer depends on many factors, including equipment, money, labor, pest control decisions, and management skill.

crop-rotation-mexico

A wheat rotation alongside a conventionally tilled maize field in Mexico. Photo: CIMMYT.

The bottom line is that it’s difficult to produce organic crops with no-till, unless labor for mechanical control (e.g., hand-weeding) is abundant and inexpensive. Besides herbicides and tillage, other pest control options include cultural practices, such as crop rotations.

Rotate crops

Because insects favor certain crops, crop rotations are particularly effective at limiting insect pests and disease pressure. Rotating crops helps to break pest cycles. Options include alternating cool-season and warm-season crops, as well as grass and broad-leaf crops.

When combined with limited, targeted tillage, crop rotations can also be quite effective at controlling weed populations after several years. There are also natural, biological control methods for some weed and insect pests.

Use mulches

For control of most weeds, the primary goal is to limit or prevent weed seed production. So, when possible, create less favorable conditions for weed seed germination. In the case of perennial weeds, another goal is to decrease the vigor of the plant to limit regrowth after the dormant season.

Sometimes mulches are effective at decreasing weed emergence. Plastic, paper, and crop residue mulches have all been used successfully. Disposal of plastic mulch after use creates its own set of environmental concerns, however. The decomposition of paper mulch may also induce a nitrogen deficiency. So instead of using mulch, farmers in climates with sufficient precipitation will sometimes plant understory crops to shade the soil and decrease competition from weeds.

In some climates and environments, no-till fields will also develop a sufficient residue mat on the soil surface after a few years that limits weed emergence. Tillage removes the residue mat.

intercropping-bangladesh

Maize intercropped with red amaranth, a leaf vegetable widely used in Bangladesh. Red amaranth is usually harvested within 40 days of seeding, so it doesn’t affect maize yield but helps to control weeds and conserve soil moisture. Photo: D.B. Pandit/CIMMYT

Another cultural practice is the use of prescribed fire, which decreases the number of viable weed seeds and removes the overwintering habitat of certain insect pests.

Till less

If circumstances do not allow strict no-till, use tillage as little as possible. For example:

  • If weeds occur only in patches, till only the areas with weeds rather than the entire field.
  • Use less intensive tillage methods. For example, use a sweep or blade plow. These implements disturb less soil than disk or inversion (moldboard) plows or rototillers.
  • Leave as much crop residue on the soil surface as possible.

Adding compost or manure is a good practice when using tillage, as these materials return carbon to the soil. Compost, though, does not need to be incorporated.

So, if you have a large plantation, a small labor force, and an aversion to herbicides, perhaps a carefully designed crop rotation combined with targeted, limited tillage would accomplish your weed control needs, possibly combined with other cultural practices.

–Answered by Clay Robinson, a.k.a., Dr. Dirt

Have a question for Soils Matter? Post it to the comments section below or email us at soils-matter@soils.org

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One response to “To till or not to till? Part 2

  1. I remember reading an article about an older woman with an abundant garden and flower beds. When asked what she used for mulch she replied, ” weeds”. According to her, as she pulls weeds which haven’t gone to seed, she just piles them around her plants and that they have been effective in keeping her beds and areas around trees and shrubs weed free. I’m giving this a try in my orchard this year. Theoretically it should work – 4-6″ layer will block light to inhibit new growth, as weeds decompose and compact, earthworms should begin to congregate, some nutrition will be added to soil and at end of year the matter can be turned into soil to increase aeration.

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