Radish Cover Crop Growth and Compaction Alleviation: Effects of Cultivar and Planting Date.

Soil compaction in the form of hardpans often restricts cash crop root growth in the Southeastern U.S., reducing plant vigor and yield potential for crops with deep taproots such as cotton. Planting forage radish (Raphanus sativus) as a cover crop has been introduced as a method to alleviate hardpans, preserve soil structure by reducing the need for deep tillage, and aid in subsoil nutrient cycling. Research is needed to assess the effectiveness of forage radish to alleviate compaction in Coastal Plain soils. In addition, basic information on radish management is needed for producers to determine appropriate planting dates and cultivars for their production systems. Five radish cultivars (i.e., ‘Lunch, ‘Sodbuster’, ‘Nitro’, ‘Tillage’, and ‘CCS779’) were planted at two locations in the Southern Coastal Plain region of Alabama to test the effect of cultivar and planting date on radish growth and soil compaction in strip-till cotton. Each cultivar was evaluated at three planting dates (i.e., mid-September, mid-October, and mid-November) and replicated three times. Plant canopy height and width, root length and diameter, and total biomass were measured at five sampling times during the growing season. Following cover crop termination and subsequent cotton planting, plots were evaluated for soil compaction using a five-probe tractor-mounted penetrometer. No statistically significant differences were found between cultivars for most growth parameters, however, the differences between planting dates were often significant. This suggests that the date of planting is much more important than cultivar selection for optimal growth. Penetrometer data shows no significant differences between cultivar treatments or planting dates. While some roots may reach deeper, the fleshy portion of the radish taproot reached consistent depths at each location, likely coinciding with a root-limiting layer. Further research is being conducted to determine the ability of fleshy radish taproots to penetrate soils at various bulk densities.