Large-scale vegetable farms, such as those in the Salinas Valley of California, perform a substantial amount of field preparation before each crop growing cycle. Before planting broccoli, the work could include two passes of subsoiling, four passes of discing and rolling, laser leveling, four passes of chiseling, two more rounds of discing and rolling, and a pass of bed shaping. This requires hours of tractor work per acre, with substantial costs for labor, tractor maintenance, and equipment capital.
This soil work also damages the soil, which reduces its ability to support crops. Healthy soil absorbs and stores more water and reduces the need for fertilizer and pesticides. These advantages, combined with the savings in tractor work, have caused no-till farming to become widespread for commodity crops, but it is still rare on major vegetable farms.
Large-scale vegetable farms perform all of this soil work in part because they need a flat, smooth, uniform surface for mechanized seeding, transplanting, irrigation, thinning, cultivating, and harvesting. Baby greens, for example, are harvested with a blade passing just above the soil surface; uneven ground can result in soil getting mixed with the crops during harvest.
Another reason for this heavy field work is incorporating crop residue. After harvesting broccoli heads, thick stems and leaves are left in the field. Chopping them and plowing them under allows them to be incorporated into the soil organic matter and reduces the pest pressure that could arise from leaving so much plant material on the surface. In addition to handling vegetable crop residues, farmers would like ways to terminate and incorporate cover crops, which can be challenging in friendly climates like those of California.
Attempts have been made at reducing soil disruption in vegetable farming. Farmers have been experimenting with new approaches, including creative use of custom machinery, but still have not yet found a good recipe for substantially reducing tilling across a variety of vegetable crops. One approach that has shown some success is covering fields in plastic sheeting, which can improve incorporation of crop residues and cover crops, but involves the cumbersome and expensive use of large amounts of plastic (which can also be challenging to recycle).
We are exploring alternative methods to reducing tilling in large-scale vegetable growing. One possibility is to build smarter machinery that can handle seeding, weeding, and harvesting on uneven ground. Another possibility is to use high-speed electric blades to finely chop crop residue so that it can be more easily incorporated into the top level of the soil (without leaving large chunks that need to be plowed deeper into the soil). Precise monitoring and control of pests (e.g. identifying small pest issues with cameras and releasing beneficial insects targeted to those sites before they spread) could reduce the need to fully bury all the crop residue before planting, allowing some crop residue to act as mulch for the subsequent crop.
Working with farmers, we will explore these issues and potential solutions. Improving soil health provides benefits for crop health, farm economics, and soil carbon sequestration. The solutions will likely include traditional practices that have been effective on small-scale (market garden) vegetable farms; we would like to make it easier to use good soil practices at all scales of food production.