Location: Soil Management ResearchTitle: Yield and Water Use Response of Cuphea to Irrigation in the Northern Corn Belt) Author
Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/3/2009
Publication Date: 8/7/2009
Publication URL: hdl.handle.net/10113/34934
Citation: Gesch, R.W., Sharratt, B.S., Kim, K. 2009. Yield and Water Use Response of Cuphea to Irrigation in the Northern Corn Belt. Crop Science. 49:1867-1875. Interpretive Summary: Cuphea is a new oilseed crop being developed for the northern U.S. Our past research shows that cuphea has a shallow root system and uses a large amount of water to produce seed. This tells us that cuphea might be prone to drought stress at various times during its growing season. In our study we used drip irrigation throughout the growing season in 2002 and 2003 to make sure cuphea had plenty of water for plant growth and seed production and then compared these plants to ones that did not get irrigated. We measured seed yield and the amount of water used by cuphea in both irrigated and non-irrigated (control) plots to determine the amount of water needed by cuphea to maximize its seed yield. Conditions were wet in 2002 and yields were not much different between irrigated and control plants. However, during late summer of 2003 when cuphea was flowering it was very dry and hot. We discovered that during this time the plants that were not irrigated suffered drought stress. In 2003, plants that were irrigated produced almost three times more seed than those that were not irrigated. Our results will help farmers decide whether they should use irrigation when growing cuphea. It will also help our industry partners who manage cuphea production, as well as farmers, to decide where to grow cuphea to get good yields without irrigation and thus, maximize economic returns.
Technical Abstract: Cuphea (C. viscosissima Jacq. X C. lanceolata W.T. Aiton, PSR23) is a new oilseed crop being developed as a source of medium-chain triglycerides. Cuphea has a sparse, shallow root system and low water use efficiency (WUE) making it potentially susceptible to water stress. Little is known about the yield response of cuphea to irrigation. A field study was conducted in west central Minnesota on a Barnes loam soil in 2002 and 2003 to compare yield and water use of irrigated and non-irrigated cuphea using a randomized complete block experimental design. Non-irrigated cuphea received only natural precipitation while irrigated cuphea received supplemental watering to maintain soil water content near field capacity throughout the growing season. Crop water stress was assessed by measuring photosynthesis, stomatal conductance, leaf water potential, and d13C. In 2002, water content within the top 0.6 m of soil was similar for irrigated and non-irrigated treatments throughout the growing season due to timely precipitation. Seed yield was similar between treatments (873 kg ha-1), but WUE was greater for non-irrigated (2.3 kg ha-1 mm-1) than irrigated cuphea (1.7 kg ha-1 mm-1). Irrigation resulted in a 2.7-fold increase in seed yield during 2003 and a greater harvest index, while WUE for both irrigated and non-irrigated cuphea was similar (2.4 kg ha-1 mm-1). Dry and hot conditions prevailed late in the growing season in 2003; by mid August, leaf photosynthesis and water potential of non-irrigated plants was 83% and 56% less, respectively, than for irrigated cuphea. Moreover, d13C of non-irrigated seed (-26.5%) was greater than that of irrigated seed (-31.2%), further confirming that non-irrigated cuphea suffered significant water stress. Our results indicate that cuphea is highly susceptible to water stress and that regions or soils prone to water stress will likely require supplemental irrigation to maximize cuphea seed yield.