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.
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.
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.
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.
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.
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
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