If the farm does not need forages, the transition cropping sequence will probably rely on cover crops to build soil quality. Stale seedbeds (see table 3.6) and other fallow periods may be needed to reduce weed density.
In vegetables, rely on transplanted crops and large-seeded crops like sweet corn and snap beans the first few years. These are more competitive and easier to cultivate and hoe than direct-seeded crops with small seeds. Short-season crops like transplanted lettuce are useful early in transition because they can be harvested before weeds have a chance to go to seed. They also allow time for a fallow period for weed control or an additional cover crop to build soil quality. Early in the transition, winter cover crops are especially important to build soil quality. Accordingly, avoid crops that are harvested too late to plant a winter cover, or overseed a cover crop into the cash crop. Establishment will be better if the cover crop seed is covered by hoeing or cultivation.
“The extensive fine root system of the grain will help build soil quality.”
On cash grain farms, avoid starting the transition with corn, even if this would be the logical next crop for the field (see table 6.1 for potential sequences). Corn is likely to suffer from nitrogen deficiency early in the transition process (58, 119) unless large amounts of manure, compost, or expensive organic fertilizer are applied. In contrast, soybean supplies its own N. If possible, plant a winter grain like wheat or spelt after soybean is harvested. This may require using a short-season soybean. A winter grain has multiple benefits early in the transition and represents an alternative to soybean as a starting point. Since the soil does not yet have good N supplying power, however, compost or some other source of N may be required to reach full yield potential. The extensive fine root system of the grain will help build soil quality. Also, a densely sown winter grain will suppress weeds well, and it will be harvested before most spring-germinating weeds can go to seed.
|Table 6.1 Some cropping sequences for transition on a cash grain farm|
|Year||Sequence 1||Sequence 2|
|1||Soybean (short-season) followed by winter grain||Winter grain with frost-seeded red clover|
|2||Winter grain with frost-seeded red clover||Corn with interseeded annual ryegrass at last cultivation|
|3||Corn with interseeded red clover or annual ryegrass at last cultivation||Soybean|
|4||Spring grain or soybean||Winter or spring grain|
Many organic grain growers in the northeastern US overseed winter grains with clover in late winter, when frost can work the seed into the soil. The clover establishes slowly but will be ready for rapid growth by the time the grain is harvested. If weeds have started to go to seed, set the combine head low at grain harvest to cut off the seed-producing parts of the weeds. If the weeds have not yet flowered at harvest, set the combine head high, and then return and mow the field at a height of about five inches before weed seeds set. The clover will compete heavily with weed regrowth if the weeds are cut after they have flowered.
The full year’s growth of clover will supply enough N for a corn crop the following year. If the growing season is long enough, sow a winter cover crop after harvest. Otherwise, interseed a cover crop at last cultivation to ensure continued soil building. Small seeds like clover will fall into the broken soil after cultivation, but large-seeded species should be sown before cultivation. Interseeding into corn at last cultivation usually produces good stands but may occasionally fail due to drought during cover crop establishment (see chapter 7) for more on interseeding cover crops).