Brassicas are a category of plants within the mustard family, which includes common food plot options such as turnips, radishes, and forage rape. These annual forages are highly favored by wildlife managers because they offer an exceptional combination of high forage yield and cold tolerance. The appeal of brassicas is largely due to their nutritional profile, providing a substantial amount of protein, which is especially important for deer during the late fall and winter months.
Understanding the Critical Planting Window
The best time to plant brassicas is determined by calculating backward from the average first frost date in your region. Brassicas are a cool-season crop intended for consumption after the first hard frost, which causes chemical changes that make the forage more palatable. To ensure the plants have enough time to mature and produce maximum tonnage, planting should occur 60 to 90 days before this expected frost date.
A planting window of 90 days before the first frost allows for the largest root and bulb growth, such as with turnips and radishes. Conversely, a 60-day window produces good leafy tops, but with smaller root development. In Northern climates, this translates to a planting period between mid-July and early August, while Southern locations may wait until late August or early to mid-September.
Planting too early can cause the plants to mature and flower prematurely due to summer heat, which reduces their attractiveness to deer. Planting too late is a common error, resulting in stunted growth and a significantly lower yield of forage. Monitoring local weather patterns is more reliable than fixed calendar dates, especially since rainfall immediately following planting is beneficial for germination.
Preparing the Soil for Success
Successful brassica growth begins with a properly prepared seedbed, requiring a soil test to determine nutrient levels and soil pH. Brassicas perform best in a slightly acidic to neutral pH range, ideally between 6.0 and 7.0. If the soil pH is too low (acidic), applied fertilizer will be wasted because the nutrients are not available for the plants to absorb.
The next step is eliminating existing weeds and vegetation, accomplished through herbicide application or mechanical tillage. Weed control is important because brassica seedlings are small and cannot compete well against established weeds. After vegetation is cleared, the ground must be worked with a disc harrow or tiller to create a firm, fine seedbed.
Avoid over-tilling, as this can cause excessive moisture loss, which is detrimental to the tiny seeds. Brassica seeds must be planted very shallowly, ideally at a depth of no more than one-quarter inch, due to their small size. Following broadcasting, the plot should be rolled with a cultipacker or heavy roller to ensure the necessary seed-to-soil contact for optimal germination.
Post-Planting Care and Management
The most important management step after planting is the post-emergence application of nitrogen fertilizer. Brassicas are heavy nitrogen feeders and will not reach maximum tonnage potential without this nutrient boost. Application is timed for two to three weeks after germination, or once the seedlings have developed true leaves and reached a height of four to eight inches.
Urea (46-0-0) is a common high-nitrogen fertilizer used for this purpose, applied at a rate of 75 to 100 pounds per acre. This nitrogen application should be broadcast immediately before a significant rain event. If the urea granules sit on the soil surface in warm conditions without rain, a large percentage of the nitrogen can be lost to the atmosphere through volatilization.
Moisture is a factor immediately following planting to ensure the seeds germinate quickly. Adequate soil moisture is important for the initial growth of the fragile seedlings. Management also includes monitoring for early browsing pressure, as deer may begin to graze on the new forage before the plants are fully mature.