Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/18/2006
Publication Date: 12/1/2007
Citation: Berti, M., Johnson, B., Gesch, R.W., Forcella, F. 2007. Cuphea plant nitrate content and seed yield response to nitrogen fertilizer. In: Janick, J., Whipkey, A., editors. Issues in New Crops and New Uses. Alexandria, VA: ASHS Press. p. 111-119. Interpretive Summary: Cuphea is a new oilseed crop being developed for agricultural production in the Midwest Corn Belt. Although we have been successful in developing many best management practices for cuphea production such as planting, weed control, and harvesting, we still do not know what cuphea’s nitrogen fertilizer requirement is for optimizing seed yield. A field study was conducted at three different locations, one in North Dakota (Casselton) and two in Minnesota (Glyndon and Morris), to determine the seed yield and plant growth responses of cuphea to nitrogen fertilizer. The plants themselves were quite responsive to taking up nitrogen from the soil. Nitrogen accumulated in the plants up to a soil fertilizer rate of about 124 pounds per acre, but it was not necessarily converted to significantly greater seed and biomass yield at the North Dakota site or the Glyndon, Minnesota, site. However, cuphea grown in Morris, Minnesota, did show an increase in seed yield when nitrogen fertilizer was added to the soil at a rate of up to 80 pounds per acre. Overall, based on two years of field experiments at the sites in North Dakota and Minnesota, it is recommended that farmers apply about 90 to 125 pounds of nitrogen fertilizer to ensure optimum seed yields of cuphea. These results will be valuable to farmers growing cuphea as well as state extension personnel and consultants serving to help farmers manage cuphea production.
Technical Abstract: Cuphea (Cuphea viscosissima Jacq. x C. lanceolata W.T. Aiton, PSR23) is a new oilseed crop being developed in North Dakota and Minnesota as a source of medium-chain fatty acids. Progress has been made on improving cuphea agronomically, but little is known about nitrogen fertility requirements for Cuphea production. The objective of this study was to determine the optimum nitrogen rate for maximizing seed yield and oil content. The experiment was conducted at Casselton, ND, and Glyndon and Morris, MN, in 2005 and 2006. Treatments (soil + fertilizer N) were a check (only soil N), as well as 60, 80, 100, 150, and 200 kg N ha-1 at Casselton and Glyndon; and a check (only soil N), as well as 171, 216 and 260 kg N ha-1 at Morris. Plant nitrate levels showed the greatest response to nitrogen fertility treatments. As nitrogen fertility was incremented, NO3-N increased in plant tissue at vegetative, bloom, and harvest maturity. At later phenological stages NO3-N decreased due to a dilution effect from dry matter accumulation. Maximum total nitrogen uptake at harvest occurred at the 139 kg N ha-1 nitrogen fertilizer level. Seed yield was enhanced with nitrogen fertility only at the Morris environments, where maximum seed yield was obtained with 216 kg N ha-1. Soil residual NO3-N accumulated as nitrogen fertility increased only in the top 60 cm. According to the average nitrogen uptake and residual soil nitrate accumulation, the general nitrogen fertility recommendation would be 100 to 140 kg N ha-1 to optimize seed yield.