Quick Guide: Sorghum For Forage
A Sorghum plant is an annual grass that can either be grown for grain production or as livestock forage. Sorghum originated in Africa and came to the United States in the 17th Century. Sorghum for forage is generally grown when production of corn silage is difficult due to limited water. Sorghum is grown in the United States in the Mid-West region; states to include Texas, Arkansas, Colorado, Oklahoma and Kansas. California is also becoming a large producer of Sorghum due to drought conditions and our extensive dairy production.
Wisconsin – No longer the dairy state
Currently California is estimated to have 1.78 million dairy cattle in production; Wisconsin is second with 1.2 million. Forage sorghum can yield as much corn grown for silage (25 Tons/Ac); the trade-off comes as dairy nutritionists try to balance the digestibility of Total Mixed Rations. Sorghum grain has a lower digestibility rating than corn grain and results in nutritionists recommending that less than 50% of Total Mixed Rations contain Sorghum forage. To help digestibility, seed companies have developed BMR (Brown-midrib) Sorghum varieties just as in corn. BMR lowers the lignin structures in the plant which increases digestibility. Again another trade-off occurs because lignin is a key component in the plant structure and holds the plant upright. If you are growing Sorghum in an area where lodging is an issue either regionally or site-specific, BMR sorghum varieties may not be a good choice.
Sorghum a good choice for drought
Estimates for California have current planted acreage somewhere around 100,000 acres in 2015; up from 20,000 in 2014. This is directly related to the drought as corn for silage has a total ET 25-30 inches of water in the Central Valley; Sorghum for silage can be grown viably on just 16 inches of water.
- Spacing: Forage Sorghum is generally grown in 30 or 40 inch rows. This makes it an ideal rotational crop with corn and cotton as both are grown on similar spacing.
- Irrigation: Forage Sorghum is a replacement crop for corn in areas where there is limited water availability or an ongoing drought as California is currently experiencing. Sorghum that is irrigated is usually done so by flood/surface methods. These types of irrigation method combined with the Sorghum’s 90 day crop life, results in about 4-5 irrigations being applied in a season.
As more SDI (Sub-surface Drip Irrigation) systems are being designed and installed on crops such as Corn, Cotton, and Alfalfa, there is reason to believe that drip-irrigated Sorghum is a possibility in the near future. Sorghum can have a daily ET as high as .33 inches in very hot and dry climates, .3 inches is an acceptable value in the Central Valley.
A drip irrigation example for sorghum would look like this:
- Sorghum planted in 30 inch rows has one line of tape “scratched” into the surface of the soil, providing water for two rows. Cascade, .13GPH emitter spaced at 12 inches results in an application rate of .042”/Hr. With an assumed daily ET of .3 inches, a 7.19 hour irrigation set would be required to match ET for the day. This system would require 18.88 GPM/Ac. to operate.
- Jain Irrigation products most likely to be used:
- Cascade—7/8”, 6-13 MIL, 12 & 14 inch sp .13 & .17 GPH – One line per two rows
- Chapin – 7/8” 5 & 6 MIL, 12 inch sp, .25 GPM/100’ – One line per two rows