Evaluating the Effect of Soil Acidity On Grain Sorghum (Sorghum bicolor) and Sunflower (Helianthus annuus L.) Production.

Evaluating the Effect of Soil Acidity on Grain Sorghum (Sorghum bicolor) and Sunflower (Helianthus annuus L.) Production

K. Butchee, B. Arnall., J. May, H. Zhang, C. Godsey   Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK

 Grain sorghum and sunflower have traditionally been grown on calcareous soils with a soil pH of >6.5 (Mask et al., 1988).  Many conventional till monoculture winter wheat producers are converting to no-till production and integrating crop rotations, such as grain sorghum and sunflower, to break weed, disease and insect cycles.  Acid tolerant winter wheat varieties are available; therefore, many producers are not accustomed to liming acid soils where continuous winter wheat has been produced.

 This study focuses on determining the effects of soil acidity on grain sorghum and sunflower production.  Experiment sites were established at Lahoma, OK (site 1), Haskell, OK (site 2) and Perkins, OK (site 3) in 2009.  The experiment utilizes a randomized complete block design replicated three times consisting of 6 soil pH treatments ranging from 4.0 to 7.0 and 2 crops, grain sorghum and sunflower.  Aluminum sulfate and hydrated lime were used to alter soil pH.  Relative yield values will be developed post harvest to assess the effect of soil pH on yield.  Plant count, plant height, and NDVI readings were collected as additional measurements of crop performance.  Non-linear regression was used to determine if linear plateaus existed.

 In 2009, grain sorghum stand was significantly impacted by soil pH; however, no clear plateau could be identified.  Sunflower at one location reached optimal stand at soil pH 5.1, yet no plateau was identified at the second location.  In 2010, timely early season rainfall aided the crop in stand establishment at all three sites for both crops.  Mid season height measurements demonstrated a plateau in grain sorghum at one location at soil pH 5.39, while the other locations showed a linear response.  Linear plateaus occurred with sunflower height measurements at soil pH 5.67 and 4.52 at site 1 and 2, respectively.  Current results demonstrate that low soil pH can negatively affect crop yield and performance; however, final yield will be used to determine the relative yield for both crops when grown in acidic soil conditions.

 Keywords: sunflower, grain sorghum, soil pH