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WAUPACA – Over the past couple years researchers have been studying the effectiveness of sorghum as livestock forage for Wisconsin farmers.

Research has been conducted on test plots at various locations in the central and southern areas of the state. 

The study has been led by University of Wisconsin Dairy Management Specialist Matt Akins, with Extension agents Greg Blonde, Nick Baker and Abby Grisham involved in gathering data.

During  a recent meeting of Waupaca County forage growers, Akins shared results gleaned from the test plots in 2016 and 2017.

Test protocols

He noted that sorghum hybrids are becoming increasingly popular as a source of moderate quality forage in areas that experience drought stress regularly.

“Our objective was to evaluate the yield and nutrient composition of photoperiod sensitive and non photoperiod sensitive forage sorghum and sorghum-sudangrass, during 2016, at two research stations in Marshfield and Hancock in central Wisconsin,” he related.

Akins reported that treatments were arranged in randomized complete block design with four replicates. 

“Results were analyzed as a split-split plot design planting date (early or mid-June) designated as main plot harvest strategy (single or multi-cut) designated as sub-plot eight forage cultivars designated as sub-sub-plot. Plots harvested using multi-cut strategy were harvested in late August and early October,” he said.

Yields

Forage yields were greater at the Hancock site compared to Marshfield, according to Akins. “At Hancock, DM (dry matter) yields were greater for the early compared to late planting date,” he said. “Yields of plots harvested using a single-cut strategy were 2-3 times greater than the combined forage yields of plots harvested with a multi-cut strategy.”

Akins said there was a harvest strategy by variety interaction for all nutrients and locations. “The single-cut strategy decreased NDF (neutral detergent fiber) levels, and differences between NDF levels by harvest strategy were most pronounced in varieties that developed a large seed head.”

He also reported that crude protein was reduced for plots harvested using a single-cut strategy. Crude protein levels at the Hancock site were lower than at Marshfield, and plots harvested using the multi-cut strategy had greater in vitro digestibility than single-cut plots.

NDF digestibility was increased for plots harvested using the multi-cut system.

Total Digestible Nutrients (TDN) were increased in plots harvested using the multi-cut system owing to increased fiber digestibility. “Sorghum varieties with the highest yields generally had the lowest TDN values,” Akins said.

2017 plots

The 2016 study at Hancock and Marshfield continued in 2017, and was expanded to include test plots in Waupaca and Rock counties. The Waupaca County plots compared single and multiple harvests, while the Rock County plot had only a single harvest.

Production fields encompassed 12 acres, where conventional and photosensitive sorghum-suda grass were planted on July 4, (at Hancock and Marshfield) with a no-till drill with 15-inch row spacing and a seeding rate of 40 pounds per acre, which was twice the rate seeded in 2016. 

Prior to planting, the ground was fertilized with 8,800 gallons per acre of liquid manure, and 25 tons per acres of solid manure.

The Waupaca County plots, near Manawa, were planted on June 7, two weeks after rye forage was harvested. “There were 125 total units of nitrogen applied per acre, 50 on June 12 and 75 on Aug. 2,” Akins reported.

Conventional sorghum-sudangrass yielded the most tons of dry matter in the multi-harvested plots, and PPS sorghum-sudangrass had the highest in the single-harvest plot.

Harvesting on one plot took place on Aug. 7 and Nov. 1, while the crop on the single-harvest plot occurred on Nov. 1. “The first killing frost occurred on Oct. 30,” he said.

The Rock County plots were on a farm near Janesville. Planting occurred on June 13, on a field that had a previous soybean crop. “No additional nutrients were applied,” said Akins, “and moderate weed pressure was seen throughout the season.”

There was a killing frost on Oct. 30, and the single harvest took place the following day. PPS sorghum produced the highest yield.

Lessons learned

Analyzing the data from the test plots, Akins says planting and seeding rate calibration are important to high-yield production. 

“Earlier planting allows ample time for the crop to reach maturity, and dry down,” he advised. “If you’re planting later, and have concerns about the crop reaching maturity, I would recommend cutting and letting it wilt at an opportune time.”

Akins said the study shows that a single harvest maximizes yield for sorghum and PS varieties. “Frost-drying does work if maturity occurs by frost,” he added.

If planning multiple harvests, he suggests the first one should occur by late July to get a full fall cut.

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