Cover Crop Mixture Considerations for 2017


Mixture of sunn hemp and monster forage sorghum as a cover crop in Escambia County. Photo: Libbie Johnson
Mixture of sunn hemp and monster forage sorghum as a cover crop in Escambia County. Photo: Libbie Johnson

As dry as this Fall has been, planting cover crops has not been a priority or an option for many producers in the Florida Panhandle. One Escambia County grower planted an interesting cover crop mixture that has garnered a lot of attention locally this summer. Following his corn crop, he planted a mixture of sunn hemp and monster forage sorghum. Sunn hemp is a good option for those that plant corn or a fruit crop like watermelon or cantaloupe because it germinates and grows very quickly during the heat of late summer. This leguminous plant can grow to over 6 ft tall, providing a quantity of organic matter and nitrogen for our soils. The UF/IFAS Sunn hemp publication states that “Via atmospheric nitrogen fixation, sunn hemp may accumulate more than 200 pounds of nitrogen per acre. This crop also adds 2.5 to 4 tons of organic matter when incorporated into the soil.” Sunn hemp has also been touted for its ability to draw down nematode populations. Who wouldn’t benefit from growing this cover crop?

The Escambia County farmer likes to plant mixes. This year, he added Monster Forage Sorghum with the sunn hemp. In some parts of the country, forage sorghum is grown for silage instead of corn. Penn State’s publication, “Forage Sorghum” states “forage sorghum is closely related to grain sorghum, broomcorn, sorghum-sudangrass, and sudangrass. Forage sorghum is best adapted to warm regions and is particularly noted for its drought tolerance compared to corn.” There could’ve been no better year to plant this crop. When it was coming up, it looked like volunteer corn, but it kept growing and has put on seedheads despite this Fall drought. The publication goes on to say that this fast growing crop shades out weeds and has few pests. Co-planting the forage sorghum with the sunn hemp is an ideal mixture, and the drought hasn’t seemed to slow down the growth. You can’t tell by the photos, but the sunn hemp is at least 5 foot tall, and the forage sorghum is more than 6 foot tall.

Why should you consider planting cover crops?

According to the UF/IFAS publication Cover Crops, there are at least eight reasons:

  1. To control weeds since cover crops compete for light, water and nutrients
  2. To prevent soil losses associated with heavy rainfall (soil water erosion)
  3. To reduce soil losses due to strong winds (e.g. prevent soil wind erosion and a potential “dust bowl”) and to protect more sensitive crops such as watermelon from sand blasting damage
  4. To scavenge and retain nutrients that otherwise might be lost in water runoff or by leaching during the off-season. This helps reduce fertilizer costs for future crops and also protects the environment from problems caused by excess nutrient loading in our water sheds
  5. To reduce populations of certain soil pathogenic nematodes
  6. To generate supplemental income (e.g. via hay production)
  7. To form a suitable mulch cover for row middles and/or mulched beds
  8. To provide habitat for beneficial birds and insects.

Fall 2016 has been a bust for those who wanted to planted cover crops, but growers shouldn’t limit themselves to just winter plantings. There are options year round. Review the table below and think about what you might work best as a cover crop mixture for your fields in 2017.


Crop Yield – Biomass1 (lbs/acre) Yield – N1


Seeding Rate(lbs/acre) Seeding Date
Leguminous Crops
Aeschynomene 2000 – 4000 50-100 6-82 Mar. 1 – June 30
Alyce clover 1500-3500 20-65 15-20 Mid April to late June
Cowpeas 4000 – 6000 50-90 6-82 April to August
Hairy Indigo 7 to 10 tons of


80-150 6 – 10 Middle of March to


Sesbania 2000-8000 35-80 25-30 Mar. 1 – July 15
Sunhemp 4500-10,000 90-180 30 – 50 Mar. 1 – June 30
Velvetbeans 2200 – 4000 50-85 30-50 Mar. 1 – June 30
Grain Crops
Pearlmillet 6000-8000 55-70 12 to 15 lb/acre in rows,

of 30 to 40 lbs/acre if broadcast

Mid March to June

in North Florida, earliest planting is April 1st.

Sorghum-sudan 6500-9500 55-80 24-30 Mar. 1 – June 30
Leguminous Cropos
Crimson Clover 1500-5000 35-120 20-25 Oct. 1 – Nov. 15
Hairy Vetch 2000-4000 35-150 20-30 Oct. 1 – Nov. 15
Lupine 2000-4500 45-120 30-45 Oct. 1 – Nov. 15
Grain crops
Black oats 1500-3500 20-40 80-100 Oct. 1 – Nov. 15
Winter rye 3000-6000 30-50 80-100 Oct. 15 – Nov. 15
Leguminous Crops
Rhizoma Peanut (living mulch) 2000-10000


50-130 80-100bu of rhizomes/acre3

(1 bu=1.25 cubic ft.)

Dec. to March
Perennial Grasses
Bahiagrass 3000-8000 55-140 15-20 Junt to August

(if rainfed)

Pangola digitgrass 4000-9000 60-135 500-10003 Mar. 1 – Aug. 15
1Lower productivity reflects poor growing conditions (water stress, poor inherent soil poor inherent soil fertility/inoculation) while higher values are indicative of crop performance under optimal conditions.

2Dehulled seed (naked).

3Planted vegetatively.



Posted: November 18, 2016

Category: Agriculture
Tags: Best Management Practices (BMPs), Conservation, Cover Crop, Cover Crops, Field Crops, Panhandle-agriculture, Sorghum

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