Introduction

Radish (Raphanus raphanistrum subsp. Sativus) are root crops related to other cool season crops in the Brassica family. Although not a popular or a heavily consumed crop, radishes in small portions can be found in salads and used as food decoration. Radish are also used in cocktails, relishes, and pasta, meat, yogurt and rice dishes. Radish are most often consumed raw but can be cooked. Radish are packed with nutrition, containing vitamins E, A, C, B6, and K. They also contain fiber, zinc, potassium, calcium and iron. Maybe we should start consuming them in larger quantities?

Because they are not a popular crop, variety trials are seldom conducted. However there are many choices of radish varieties available with interesting colors, shapes and sizes. A variety trial was conducted in both north Louisiana at the Northeast Research Station in Tensas Parish and south Louisiana at the LSU Botanical Gardens in East Baton Rouge Parish to determine which 16 varieties of radish perform best in the Louisiana climate and soils.

Materials and Methods

All radish seed were sown directly into the field. The soil at both locations was disked, tilled, hipped and shaped. Irrigation was not used as the entire trial would last no longer than 2 months. If rain did not occur, radishes were watered weekly so that 1 inch of water was applied. The weather was extremely rainy during this period. Treflan herbicide was applied as a pre-emergent herbicide. Fertilizer was applied at a rate of (50lbs of actual N and 100 actual lbs. of P and K) per acre preplant. Because this crop is so short lived, we side dressed once using Peter’s 20-20-20 at a rate of 200ppm.

The south Louisiana trial site was planted on February 6, 2018 and harvested on March 20, 2018. The north Louisiana trial site was planted on March 6, 2018 and harvested on April 24, 2018. The later planting date for the northern site was to avoid cooler temperatures that may have decreased germination. Radish are a cool season crop but do not tolerate freezes well nor hot temperatures. Producers generally begin planting radish about 3 weeks prior to the last frost. The LSU AgCenter recommends planting radish from January 1^st through the end of March. This is based on planting date recommendations from the Louisiana Vegetable Planting Guide.

Each radish variety was planted in a 5ft plot triple drilled. Drills were spaced 8 inches apart and 12 seed /ft. were planted. The middle 2 feet of each plot were harvested for data (all 3 drills were harvested). Data was collected on visual stand counts (% germination) and harvested roots (within the 2 ft. center of each plot) were graded using USDA standards. A USDA #1 radish must not be less than 5/8^th inch in diameter, smaller radishes were culled. For more information about grading standards, see this link https://www.ams.usda.gov/grades-standards/radish-grades-and-standards . We used a Staedtler Mars 977 102 professional general purpose template and dropped individual radishes into the 5/8^th inch opening. Radishes that went through the opening were culled because the size was less than 5/8^th inch diameter. Radishes that had growth cracks covering over 50% of the radish were also culled.

Results

Conclusions

Weight data was only collected at the north Louisiana location. The radishes did not perform as well as expected. USDA #1 size radishes were hard to achieve. We think this may be due to the excessive rainfall during the trial. Many of the radishes produced a good number of roots. However the root quality was limited. Roots in almost every variety were pithed or too small to be deemed a USDA #1 root. Based on this trial, we would not recommend ‘Watermelon’ radish to either commercial or hobby gardeners. ‘Watermelon’ is not recommended because of poor germination and lack of roots produced. ‘Ping Pong’ produced good quality roots. It had a creamy white interior and exterior and a nice round shape without pithing. This variety warrants future research. Germination of ‘Ping Pong’ seemed low, but probably because it did not produce as many tops as other varieties. ‘Sparkler’ and ‘Pink Beauty’ produced higher total number of roots as compared to the other varieties. With better timing on planting these may be good contenders for Louisiana. ‘Amethyst’ also warrants further research as they had higher number of total roots developed as well. ‘Sparkler’, ‘Pink Beauty’, and ‘Amethyst’ were of higher quality than the other tested varieties. ‘Red Head’ is not being recommended for Louisiana at this time because the interior portion of the root had cavities, which may be an indication that this variety needs more boron than other varieties.

Radish should be planted with irrigation, especially if a dry season is predicted. While we experienced growth cracks from excessive rains, lack of irrigation can also reduce root quality. Boron may also need to be applied on soils with low boron. Boron deficiencies in radish appear as hollow roots. ‘Sparkler’ and ‘Red Head’ may need extra boron applications.