Grain Sorghum Hybrid Evaluation
Grain sorghum acreage has increased in Arizona from a few thousand acres in the early 1990's to about 50,000 acres presently. Grain sorghum performance has been documented in the past by University of Arizona personnel. However, crop varieties in general need to be evaluated over multiple years and locations before meaningful conclusions can be drawn, and grain sorghum is no exception. Arizona farmers are at a disadvantage as far as grain sorghum hybrid selection is concerned since testing is not as intense here as in major sorghum producing areas. Therefore, sorghum hybrids are occasionally grown which are not adapted to this area, usually due to lack of adaptation to water, heat, or salt stress. This report is an attempt to provide farmers with information on grain sorghum performance in Arizona.
Sorghum hybrids were evaluated at RaynerĂs Enterprise Ranch near Gila Bend and at the Marana and Maricopa Agricultural Centers. Sorghum hybrids were planted in 5 row plots with 24 inches between rows 25 feet in length. The seed was planted with a cone planter on flat ground into dry soil at a rate of 1000 seeds per plot or about 1 inch between seeds in the row for a desired plant population of near 120,000 plants per acre. The experimental design was a randomized complete block with 20 to 24 entries and 4 replications. The middle three rows of each plot were harvested with a small plot combine. Grain yields were adjusted to 12% moisture.
At the Gila Bend location, the germination irrigation was applied on July 8 and the plots were harvested on November 20. The previous crop was wheat and the soil type is a sandy loam. A total of 144 pounds of nitrogen was applied split between the first and third irrigation after emergence. Nine irrigations of 4 inches each were applied on July 8, July 14, July 24, Aug. 4, Aug. 16, Aug. 26, Sept. 5, Sept. 16, and Oct. 2. The experimental area was fairly uniform except for a salty spot where yields were not included in the final analysis. We were not able to detect bird damage.
The soil at the Marana Agricultural center is a Pima clay loam and the previous crop was barley. The plots were planted on June 19 and an irrigation was applied the same day to germinate the seed. The fertilizer applied consisted of 100 pounds of nitrogen per acre as urea at planting time. A total of 27.6 inches of water was applied in seven irrigations of 3.9 inches each except for the first irrigation which totaled 4.2 inches. The irrigation dates were: June 19, June 25, Aug. 1, Aug. 15, Aug. 28, Sept. 12, and Sept. 26. Some feeding by corn earworm was observed but determined not to be at yield damaging levels. The plots were harvested on Oct. 24. Our estimates of bird damage at this location ranged from 0 to 85%, although we appear to have overestimated bird damage based on yields obtained.
The soil at the Maricopa Agricultural center is a Casa Grande sandy loam and the previous crop was barley. The plots were planted on July 1 and an irrigation was applied July 2 to germinate the seed. The fertilizer applied consisted of 52 pounds of nitrogen per acre as ammonium sulfate at planting time plus 105 pounds of nitrogen per acre as UN32 applied in the irrigation water split among the first three post-emergence irrigations for a total of 157 pounds of nitrogen per acre. A total of eight irrigations of about 6 inches each were applied on the following dates: July 2, July 25, Aug. 5, Aug. 14, Aug. 25, Sept. 4, Sept. 15, and Sept. 26. The plots were not harvested at this location due to bird damage close to 100%. Anthesis dates representing mid-bloom and physiological maturity date from black layer formation were recorded.
Yields and other characteristics of the grain sorghum hybrids are presented in Table 1. Yields at the Gila Bend location are a fair representation of hybrid performance, but bird damage must be accounted for at the Marana location. We did not harvest at Maricopa due to extreme bird damage. The earlier varieties tended to attract birds first and had more bird damage than later varieties. Yield at Gila Bend was correlated with test weight, plant height, and anthesis and maturity date measured at Maricopa. Yield at Marana was correlated with plant height and anthesis at Maricopa but not with test weight or maturity at Maricopa. The later varieties not only tended to yield higher than the earlier varieties, but were also taller. The relationship between maturity group and yield is general and many exceptions exist in our results.
Financial support for this project was provided by Mycogen, Cargill, Richardson Seeds, DeKalb, Asgrow, and Novartis.
This is a part of publication AZ1059:
"1998 Forage and Grain Agriculture Report," College of Agriculture, The
University of Arizona, Tucson, Arizona, 85721.