Arizona grain sorghum was run through the ethanol plant last November through this February and worked well, Wilkey noted.
Grain sorghum is not equivalent to corn in the ethanol conversion process. Sorghum requires additional enzymes to produce ethanol, but yields the same amount of ethanol.
Two byproducts of the ethanol process are CO2 and distiller's grain. Most of the wet distiller's grain is sold within a 60-mile radius as a livestock feed ingredient. A small amount is dried, also for livestock use.
The minimum quality requirement for grain sorghum in ethanol production is No. 2 grade and 14 percent moisture or less, Wilkey said. Arizona Grain pays a 5-cent premium per hundredweight if the planting seed is purchased from the company.
The vast majority of the grain sorghum purchased is within a 100-mile radius of the ethanol plant. Some grain sorghum is also grown in the Willcox and Yuma areas.
In Arizona two planting windows exist for grain sorghum — late February to March 15 and July 1-20. Average yields are like what Clark gathered, 2.5 tons per acre, Wilkey said.
According to Tim Knudsen, Arizona Grain's marketing manager, the Golden Acres 737 variety is the most popular sorghum seed planted in Arizona. “737 is a medium to early maturity variety which produces large berries on the head that are excellent for ethanol production.” Other good grain sorghum varieties for ethanol conversion include Golden Acres 3552, 3694, 3827, plus Pioneer's 84G62 and 85G01.
Barkley Seeds Inc. also sells grain sorghum planting seed. General manager Michael Edgar said grain sorghum plantings could increase in Yuma County. “I know there are people talking about it,” Edgar said. “How many will turn words into action? That's what I don't know.”
Cattle feed yards are reportedly paying good money for the stubble coming off harvested grain sorghum fields which helps the grower in his return per acre. Most sorghum grown in Yuma County is grown on the east side due to its closer proximity to Maricopa and related lower freight charges.
Barkley Seed offers the Garrison & Townsend Inc. variety GS125. According to Alan Rubida, Barkley's field seed division manager, the variety is excellent for green chop for livestock and for grain for ethanol. Yields range from 3.5 to 4 tons per acre.
University of Arizona Extension Agronomist Mike Ottman released a guide called “Growing Grain Sorghum in Arizona” last spring. Ottman points out that grain sorghum is more resistant to salt, drought, and heat stress than many other crops.
Hybrids are classified as early, medium, and late-maturing. Hybrids usually stand at four-feet tall, but dual purpose hybrids for forage and grain are taller. Grain colors include red, bronze, tan, purple, white, yellow, or cream-colored. Sorghum seed germinates at 50 degrees F but 60 degrees creates faster germination and improved stand establishment.
Suggested planting dates based on elevation, single crop, and double crop for Arizona are as follows:
0 - 1,000 feet elevation: March 15 - April 15, single crop and July-August double crop;
1,000 - 2,000: April 15-30, single crop and July for double crop;
2,000 - 4,500: May 1-15, single crop only; and
Above 4,500: May 15-30, single crop only.
Grain sorghum can be planted in row spacing ranging from 6 to 40 inches apart or in twin rows in a variety of configurations. Bed or flat ground plantings work fine.
The optimum seeding rate for grain sorghum is about 10 pounds of seed per acre assuming a seed size of 14,000 seeds per pound and 70 percent emergence. Seed size varies depending on the hybrid, so the seeding rate on a pound-per-acre basis should be decreased for smaller seed and increased for larger seed. The goal is achieving a 100,000-plant density per acre.
The optimum seeding depth is 1-2 inches. Seed deeper on lighter than heavier soils or if seeding into moisture rather than irrigating up.
Grain sorghum usually requires about 150 pounds of nitrogen per acre with about a quarter to half applied at planting time. The actual nitrogen requirement depends on grain yield, residual nitrogen in the soil and irrigation water, plus other factors. Phosphorus fertilizer is generally not required, unless the soil phosphorus level is very low and planting occurs in the cooler part of the spring.
Sorghum requires adequate soil water for maximum yields even though the crop is drought resistant. The amount of water used by sorghum in a late June planting in Mesa, Ariz. was measured at 25 inches. Assuming an irrigation efficiency of 70 percent, the actual amount of irrigation water needed to meet this water use is 36 inches.
Weeds in grain sorghum reduce grain yield, harbor insects and diseases, and create problems at harvest. Weeds are controlled by tillage or herbicides.
Many insects can feed on sorghum, but chemical treatment may not be warranted unless severe damage occurs. Severe insect damage is most common when sorghum is planted late or following a corn or sorghum crop. Some insects that may infest sorghum are the Southwestern corn borer, lesser stalk borer, corn leaf aphid, greenbug, sorghum midge, corn earworm, fall armyworm, stink bugs, cutworms, flea beetles, and spider mites.
Grain sorghum grown in Arizona usually is not significantly damaged by diseases. However, a head smut, maize dwarf mosaic, and Yuma root rot disease are a few diseases that can be damaging. Fungicide applications usually are not economical for grain sorghum diseases. The most effective control measures are hybrid resistance and allowing at least three years between sorghum crops.
When to harvest sorghum can be a difficult decision due to uneven maturity. Also, depending on the hybrid, the stalks and leaves may still be green when the grain is ready for harvest. Sorghum can be harvested when grain moisture content is 15 percent to 20 percent, but the grain cannot be stored safely above a moisture content of 13 percent to 14 percent. Sorghum grain readily absorbs moisture from the atmosphere, and grain moisture content can change a few percentage points during the day. Sorghum grain is brittle and more easily cracked than grain of wheat or barley so care must be taken when adjusting the combine.