Final report for ONC19-054
Grain sorghum is a drought-tolerant crop known for its efficient water use. However, adoption has been limited on the High Plains because farmers believe grain sorghum is not a suitable crop due to cool night temperatures which limit heat unit accumulation and delay physiological maturity. However, researchers have demonstrated in the High Plains of Nebraska and Colorado that grain sorghum production is possible in most years. In environments with less than 21 inches of plant available water, research suggests grain sorghum to be a superior choice compared to corn for both yield and profitability. Recently, a group of interested Nebraska farmers have come together with desires to incorporate grain sorghum into their dryland cropping systems. They have made arrangements with a local elevator to receive the grain. However, they do not have experience with grain sorghum and worry about successfully growing the crop. This research and educational partnership with these growers will also benefit others across the region as we identify preferred methods to produce grain sorghum for the High Plains and other regions that are limited by short growing seasons or utilize double crops. Results will be shared with growers at field days, workshops, and through publications.
Our objectives to be conducted on-farm with farmer cooperators will be: (1) to evaluate commercially available grain sorghum hybrids and experimental lines being developed in breeding programs for performance and adaptability to the High Plains region; (2) to determine the optimal planting date, row spacing, and population that will enable the crop to reach physiological maturity while also maximizing yield; (3) develop fertility recommendations for grain sorghum; (4) Disseminate research results through field days, extension and peer-reviewed publications, media outlets, and winter research updates to provide farmers with the knowledge and resources necessary to be successful growing dryland grain sorghum.
With increasing input costs, it can be difficult for producers to decide which crops should receive what amount of inputs each year. Knowing how much of what nutrient will help to maximize yields while keeping costs down is a valuable tool for producers. The objective of this study is to rate how grain sorghum performs under varying amounts of nutrients, both macro and micro.
The study was planted at two different locations in 2019 and 2020 near Sidney, NE and Rushville, NE. Planting dates in 2019 were on June 11th and June 13th, and in 2020 were May 27th and 28th, respectively. Field sites used had low fertility levels and applied rates were based on existing university recommendations to determine the 100% rate treatment. Dekalb 28E was used because it is well adapted to the area and the most commonly used. Rates of fertilizer included: 0, 50, and 100 percent of Nitrogen and Phosphorus and 0 and 100 percent of Zinc, Sulfur, and Potassium.
Row Spacing and Populations
Row spacing and planting populations for grain sorghum in the High Plains region is an area of interest as the crop is being investigated as a corn alternative. Finding the optimum row spacing and plant population can help producers determine how to plant the grain sorghum to maximize their yield while getting a boost in weed control and nutrient management. The objectives of this study were to determine what population and row spacing performed the best in our climate.
The same planting dates and locations as described in the fertility section above were used. The hybrids used at both locations were DK28E (DeKalb) and NK2212 (S&W Seeds). Row spacings of 11, 15, 22, and 30 inches were used. Within each row spacing five different populations were planted that ranged from 20 thousand to 100 thousand seeds per acre on 20k increments.
With the search for a new alternative crop in the High Plains region producers are looking at grain sorghum, or milo, as a good alternative crop in years when conditions are less favorable for growing corn. With our more temperate climate, not all varieties of grain sorghum will perform the same as they would in hotter climates. The objective of this variety trial was to examine which varieties would perform best in our region.
The study was planted on the same dates and at the same locations as the in the other experiments. There were 25 hybrids planted each year at a population of 45 thousand seeds per acre. Each plot was two rows with 30-inch spacings and 30 ft long.
Yields overall were very low for all grain sorghum experiments due to the cooler spring and summer in 2019. In 2020 severe drought limited yields. In 2019, we estimate that about half of the plants did not finish due to insufficient growing degree days to reach maturity. The residual fertility of the fields at HPAL limited the differences seen among treatments in 2019. Unsurprisingly, nitrogen had the greatest impact on grain yield in the Nitrogen/Phosphorus study. Both the 75 and 150 lb N/acre rates produced the highest yields at about 15 bushels per acre. For the micronutrient study, there were treatment differences among the eight combinations of N, P, S, Zn, and K. Those treatments that had N and P applied performed the best, and the two best yielding treatments were those that had 100% recommended rates of Zn applied. Potassium did not generate a significant response. Of the micronutrients evaluated, zinc had the greatest increase in grain yield followed by sulfur.
Row Spacing and Populations
In 2019 at the trial in Rushville, there were significant differences between different populations as well as for the interaction between row spacing and variety. In contrast, at HPAL, the interaction between row spacing and population had significant differences with variety alone having a significant effect. Thus, there are not clear trends that are similar between the sites and like the other sorghum trials, there were not logistically enough GDUs accumulated for the crop to reach physiological maturity.
In 2020, row spacing had a greater impact than population on grain yield. Narrow row spacing increased grain yield significantly. Populations below 40,000 seeds per acre decreased yield.
Across the Panhandle, grain sorghum yields were extremely low for these trials. In evaluating literature from Texas A&M Extension, most early maturing grain sorghum varieties require nearly 2700 cumulative growing degree units (GDUs) to reach black layer (physiological/harvestable maturity). We found that for most of the trials we have had the past two years, sites in the Panhandle rarely come close to that threshold. In contrast, a similar study in Grant in 2019 did very well and had adequate GDUs. However, we did see differences in yield between the varieties and among the sites tested.
In 2020, yield was suppressed by drought conditions. Overall, rainfall was nearly half of what is normally is.
Yield results have been published and are available at https://cropwatch.unl.edu/2020-CW-News/documents/variety-results/2020-Cheyenne-County-Rainfed-Sorghum-SVT.pdf
Educational & Outreach Activities
On-farm demonstration/research locations were established with two growers. Field days were hosted in September of each year (including 2020 despite COVID) for area producers to view the research and ask questions. Many reported stopping by the plots throughout the summer to check on the progress. As the field days, each experiment was discussed. Producers had the chance to walk through the plots and ask questions. A member of the Nebraska Sorghum Board was also present to discuss production practices on his farm and the efforts the sorghum board is undertaking to promote sorghum production and markets. Research was also presented at the Crop Production Clinics hosted by Nebraska Extension and at the High Plains Ag Lab spring research update and advisory board meeting.
This work was shared at field days, in person meetings, and through online print material. During this project and after, there has been renewed interest in grain sorghum. Particularly as grain prices have increased. I have talked with grain merchandisers about increasing storage capacity for grain sorghum in the Nebraska Panhandle and also to others about beginning to take the grain. Furthermore, overall interest among farmers has increased noticeably and acres across Nebraska were expected to increase over 100,000 acres in 2021 over the previous year. Grain sorghum is also gaining traction for its lower input requirements and water use compared to corn making it a more sustainable option for many farmers.