Our winter workshops seem to generate a lot of interest in bioextensive market gardening among young growers. However, we sense an undercurrent of frustration because many of the participants do not have access to enough land to fallow half of the market garden. We hope that the following list of speculative suggestions will provide some encouragement to new vegetable farmers who cannot afford to take land out of production but want to take advantage of the bioextensive principles of rotational cover cropping, minimum-depth tillage, and bare fallowing.
Cultivating Questions: No-till, No-herbicide Planting of Spring Vegetables Using Low Residue Winter-killed Cover Crops
from issue: 38-3
Ray Weil and Natalie Lounsbury’s pioneering work with forage radishes at the University of Maryland could provide a solution to the vegetable grower’s winter cover crop dilemma. When planted in August, forage radishes suppress winter weeds and scavenge left-over nitrogen keeping nutrients out of groundwater. Succulent radish tissue melts away quickly when the ground thaws leaving dark soil to absorb spring warmth and little residue to interfere with planting equipment. Quickly decomposing radishes might also release nitrogen when early vegetables need it.
We plowed up a narrow contour strip wrapping around the south side of the market garden with the idea of eventually expanding production. Since the east end of this field seemed too steep and stony for vegetables, we decided that this site would be more suitable for a small orchard. Although we had no experience managing fruit trees, we were inspired to plant enough apples to meet our own needs after seeing Soil Conservation photos from the 1930’s which indicated a well established orchard on this same sidehill site.
Cane fruit are among the most moisture demanding crops in the market garden. So, if irrigation is not available, it is essential that the cover crops grown between the rows do not compete with the berries for moisture. For example, a cover crop of oats and Canadian field peas planted right after the harvest of summer bearing raspberries would not compete with the cane fruit during the main growth and fruiting period.
Many sustainable growers subscribe to the philosophy of “feed the soil, not the plant.” Our whole farm approach to weed management follows the same line of thinking – we call it, “weed the soil, not the crop.” Instead of relying on the cultivator or the hoe to save the crop from the weeds, we use cultural practices, including cover cropping, bare fallow periods, rotation and shallow tillage, to reduce the overall weed pressure in the soil. One result of this proactive strategy is we no longer depend on the cultivator or the hoe to grow certified organic produce. “Weeding the soil” has also enabled us to use reduced tillage and living mulches without compromising weed management.
Our mild climate makes it too easy to overwinter cover crops. Then the typically wet springs (and, on our farm, wet soils) let the cover put on loads of topgrowth before getting on the soil. Buckwheat is the only crop that I can be certain will winterkill. Field peas, oats, annual rye and crimson clover have all overwintered here. Any suggestions?
Finding just the right cover crop-tillage combination for crops planted the last half of June has always been a real challenge in our location. While surface-tilling mature rye and vetch in May works well for fall crops established in July and August, this cover crop-tillage combo does not allow enough time for decomposition and moisture accumulation for end-of-June plantings.
Our cover crops have to provide the benefits of smothering weeds, improving soil structure, and replenishing organic matter. They also have to produce some income. For these purposes, we use turnips, mustard and lettuce within our plant successions. I broadcast these seeds thickly on areas where cover crops are necessary and let them do their work.
We have a double standard for planting density in the bio-extensive market garden. We plant all the vegetables in widely spaced rows to insure plenty of moisture, fertility and air circulation for each plant. For the cover crops in the fallow lands, we take just the opposite approach, seeding at a high density to quickly provide ground cover, weed suppression, and biomass. One reason we have been slow to adopt cover crop cocktails is the very low recommended seeding rate — sometimes as little as 30 lbs per acre — in order to give all of the different species in these diverse mixes lots of room to grow. The mental shift to planting cover crops at a density comparable to our widely spaced vegetables has not come easily.