Modeled El Nino-Southern oscillation effects on grain sorghum under varying irrigation strategies and cultural practices

Authors: Baumhardt, Roland - Louis; Schwartz, Robert; Marek, Gary; Moorhead, Jerry

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2019
Publication Date: 6/23/2019
Citation: Baumhardt, R.L., Schwartz, R.C., Marek, G.W., Moorhead, J.E. 2019. Modeled El Nino-Southern oscillation effects on grain sorghum under varying irrigation strategies and cultural practices. Agronomy Journal. 111(4):1913-1922. https://doi.org/10.2134/agronj2018.09.0616.
DOI: https://doi.org/10.2134/agronj2018.09.0616

Interpretive Summary: The longevity of the Ogallala Aquifer as a source of irrigation water is declining because withdrawals exceed recharge. Deficit irrigation which spreads limited water over crops is one option for extending the life of the aquifer. Grain sorghum is a good dryland crop that grows well with deficit irrigation and good climate conditions. However, management practices for deficit irrigation of sorghum have not been defined for the weather phenomenon commonly known as El Niño southern oscillation (ENSO). Therefore, ARS scientists from Bushland, Texas related ENSO phases to growing season rain and irrigated grain sorghum yields. La Niña phase years had 2 inches less rain for growing and made 15% less grain than Neutral or El Niño years. Compared with spreading water on an area at a 0.7 inches per week, splitting the area into 2:1 or 1:1 parts getting 1.0 or 1.4 inches per week and dryland increased grain sorghum yields 30%. These results show farmers and crop consultants that ENSO climate informed management and 2:1 or 1:1 split pivot irrigation strategies can increase dryland and deficit irrigated grain sorghum yields.

Technical Abstract: Equatorial sea surface temperatures vary systematically to cause the El Niño southern oscillation (ENSO) that produces predictable weather patterns in North America and may permit innovative crop management to better utilize irrigation resources. Declining Ogallala aquifer and well capacities in the Southern High Plains, as exacerbated by competition for water resources, challenge producers to adapt cropping practices for use with irrigation that falls short of meeting crop water demand. Our objective was to evaluate sorghum [Sorghum bicolor (L.) Moench] grain yield response to ENSO climate informed management of varying cultural practices and irrigation allocation strategies on a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll). We used the simulation model SORKAM and long-term (1961-2000) weather records from Bushland, TX, classified by ENSO phase to calculate sorghum grain yields for all combinations of irrigation levels (0.0, 2.5, 3.75, or 5.0 mm/d), planting date (DOY = 135, 156, 176), and cultivar maturity (early, 95 d; medium, 105 d; late, 120 d). Using the September-November (SON) Niño oscillation index (NOI) to identify ENSO phase, we observed 50 mm less precipitation during La Niña years and a corresponding 14.5% reduction in grain yield to 4550 kg/h for sorghum planted at 16 plants per square meter population. Although yields consistently increased with irrigation, we conclude that spreading water to uniformly irrigate an area with 2.5 mm/d produced ~24% less grain than concentrating that water to irrigate the area partitioned 2:1 or 1:1 at rates of 3.75 or 5.0 mm/d with complementary dryland areas.