Abstract
AbstractPearl millet [Pennisetum americanum (L.) Leeke] forage, which had been previously reported to become unpalatable under drought stress conditions, also contained high levels of nitrate and total alkaloids. This study was conducted to determine the effect of irrigation, drought stress, and drought stress elimination, as well as fertilization with 0 and 56 kg S ha−1, and 112, 224, and 336 kg N ha−1, on alkaloid and nitrate levels in pearl millet. ‘Millex 24’ hybrid millet was grown in the field during a hot, dry summer on a Darco soil (loamy, siliceous, thermic Grossarenic Paleudult) in East Texas. Chemical analyses for nitrate and total alkaloid levels were conducted on leaf blades and stems plus sheaths of vegetative plants. Alkaloid levels increased in pearl millet after extended drought and with increasing N fertilization rate. Total alkaloid concentration was higher in leaf blades (46 mg kg−1) than in stems plus sheaths (16 mg kg−1). Nitrate levels increased with improving plant water status and with increasing N fertilization. At the lowest N fertilization rate, nitrate concentrations were similar in irrigated and nonirrigated millet. At the highest N fertilization rate, nitrate was nearly two times higher in irrigated than in nonirrigated millet due to accumulation in stem portions. Nitrate concentration was higher in stems plus sheaths (14 g kg−1) than in leaf blades (5.1 g kg−1), but nitrate levels were highly correlated (r=0.90**; n=48) among plant parts. Sulfur application had no effect on either alkaloid or nitrate levels. A significant interaction between S and N rate occurred in stem plus sheath nitrate concentration (P<0.01). Whole plant alkaloid and nitrate levels were significantly correlated under N fertilization and irrigation but were not correlated under moderate drought stress or under drought stress elimination.
Published Version
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