N Fertilization for Pearl Millet Grain in the Southern Coastal Plain

Pearl millet (Pennisetum glaucum |R.| Br.) has potential as a grain crop in the U.S. Southeast because it is particularly adapted to acid, sandy Coastal Plain soils. Information is needed, though, on the effect of N fertilization on pearl millet grain and protein yields in the region. We conducted field studies for 2 years at three locations in the Coastal Plain of Georgia to observe pearl millet response to varying rates and times of N fertilizer application. The N-rate studies included 0, 50, 100, 150, 200, and 250 lb N/acre, applied 20 d after planting. Nitrogen time-of-application studies were also conducted as randomized complete blocks arranged in split-plots with N fertilizer rates of 0, 50, 100, and 200 lb/acre as the main plots. Subplots were time of N application, with treatments of 100% at planting, 33% at planting plus 67% at 20 d after planting, and 33% at planting plus 33% at 20 d after planting plus 34% at 40 d after planting. We found that pearl millet grain and protein yields increased in response to N rates as great as 100 lb/acre in experiments that had adequate rainfall and inadequate residual mineral-N in the soil profile. Grain yields decreased with increasing N fertilization, though, in experiments that were affected by drought, were planted late, and had greater amounts of mineral-N in the soil profile. However, in two of these experiments, the increase in seed protein content with N fertilization resulted in increased protein yields in spite of the grain yield reduction with greater N fertilization. Splitting the application of N fertilizer to apply one third at planting and two thirds 20 d after planting increased grain and protein yields in comparison to application of all the N at planting. Research QuestionThere is need for more information on the effect of N fertilization on pearl millet grain and protein yields in the Southern Coastal Plain, as earlier studies showed variable results. This study was conducted to determine the effects of both rate and time of N application on pearl millet grain and protein yields. By conducting the experiments for 2 years and in different locations, we expected to observe pearl millet response under varying environmental conditions and soil types. Literature SummaryPearl millet has potential as a high quality grain crop for the southeastern United States. This grain crop has many attributes that make it a good choice as a cereal grain crop for this region, especially for the nonirrigated sandy, low fertility, acid soils in the southern Coastal Plain. The excellent amino acid composition of pearl millet grain and its high levels of crude protein, make pearl millet a valuable protein source for animal and poultry feed. Pearl millet is more tolerant of drought, soil acidity, and high levels of Al than corn and sorghum. Genetic resistance to rust and leafspot, the two major pearl millet diseases in North America, is available. In addition, pearl millet can be planted from April through the third week of July in south Georgia, matures in about 90 d, and provides good flexibility for double-cropping after wheat or canola. These characteristics allow the production of acceptable pearl millet grain yields with limited inputs. Study DescriptionWe conducted field studies for two years at three locations in the Coastal Plain of Georgia: Tifton, Plains, and Baxley. Soils: Tifton loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudult), Norfolk loamy sand (Typic Kandiudult), Alapaha deep sand (arenic Plinthic Paleaquult), and Faceville sandy loam (Typic Kandiudult). Experimental design: The N-rate studies included N rates of 0, 50, 100, 150, 200, and 250 lb N/acre, applied 20 d after planting (DAP). The studies which included time of N application were designed as randomized complete block split-plots, with N fertilizer rates (0, 50, 100, and 200 lb/acre) as the main plots and time of N application (100% at planting; 33% at planting plus 67% at 20 DAP; and 33% at planting plus 33% at 20 DAP plus 34% at 40 DAP) as the subplots. Traits evaluated: Leaf N, seed N, grain yield, and protein yield. Applied QuestionsWhat N fertilizer rate and timing of fertilization should be used for grain pearl millet production? In three experiments with inadequate mineral-N in soil profiles that received adequate rainfall, pearl millet grain and protein yields responded to N rates of up to 100 lb/acre, providing up to 3800 and 530 lb/acre of grain and protein, respectively. Splitting the application of N fertilizer to apply one third at planting and two thirds 20 DAP increased grain and protein yields. Our results are consistent with the current fertilizer recommendation from the Extension Service of the University of Georgia for pearl millet grain production, which is 15 to 25 lb/acre at planting plus 80 to 120 lb/acre 3 to 4 wk after planting. Did environmental conditions have a significant effect on pearl millet grain and protein yields response to N fertilization? In four of the seven experiments, grain yields decreased with N fertilization when plants were affected by drought or were planted late. However, in two of these studies, the increase in seed protein content with N fertilization increased protein yields and compensated for the decrease in grain yield. Since the high quality protein of pearl millet is one of the most attractive traits of this crop, the potential for increase in protein yields under adverse environmental conditions is a valuable characteristic for the farmers that adopt pearl millet as a grain crop.