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Agriculture 2018, 8(3), 40; https://doi.org/10.3390/agriculture8030040

Limited Seed and Seed Yield Response of Calendula to Applied Nitrogen Does Not Justify Risk of Environmental Damage from High Urea Application Rates

USDA-Agricultural Research Service-North Central Soil Conservation Research Laboratory, Morris, MN 56267, USA
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Received: 20 February 2018 / Revised: 2 March 2018 / Accepted: 9 March 2018 / Published: 13 March 2018
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Abstract

Calendula (Calendula officinalis L.) seed, due to its high calendic acid content, is recognized as a potential environmentally safe substitute for volatile organic compounds. Agronomic guidelines for nitrogen (N) management to produce calendula seed oil on a commercial scale are limited. Post-harvest soil N has the potential to move off-farm and contribute to water quality degradation (e.g., hypoxia in the Gulf of Mexico). Establishing N management guidelines should consider agronomic response and potential environmental risk. Calendula seed and oil yield, oil content, harvest index, N use, seed N use efficiency, oil N use efficiency, agronomic efficiency, vegetative growth, and the amount of residual soil-N following harvest response to five urea N rates (0, 34, 67, 134, and 202 kg N ha−1) were assessed in a replicated field study repeated for two growing seasons. Seed yield increased with N rate, but because of the low N conversion efficiency, there appeared to be minimal yield gains in applying N beyond 34 kg ha−1. The lowest amount of soil-N left underutilized in the soil was predicted to occur at 39 kg N ha−1 and was adequate for seed and seed oil commercial calendula production on a Mollisol in the Northern Midwest United States. View Full-Text
Keywords: industrial seed-oil; nitrogen use efficiency; agronomic efficiency; soil nitrogen; pot marigold industrial seed-oil; nitrogen use efficiency; agronomic efficiency; soil nitrogen; pot marigold
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Johnson, J.M.F.; Gesch, R.W.; Barbour, N.W. Limited Seed and Seed Yield Response of Calendula to Applied Nitrogen Does Not Justify Risk of Environmental Damage from High Urea Application Rates. Agriculture 2018, 8, 40.

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