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CROP ECOLOGY, MANAGEMENT & QUALITY

Nitrogen Application and Critical Shoot Nitrogen Concentration for Optimum Grain and Seed Protein Yield of Pearl Millet

^a Dep. of Agronomy, LSU Ag Center, Baton Rouge, LA 70803
^b Dep. of Agronomy, LSU Ag Center, Baton Rouge, LA 70803
^c Red River Research Station, LSU Ag Center, Bossier City, LA 71113
^d Rice Research Station, LSU Ag Center, Crowley, LA 70527
^e Red River Research Station, LSU Ag Center, Bossier City, LA 71113
^f Macon Ridge Branch, Northeast Research Station, LSU Ag Center, Winnsboro, LA 71295

* Corresponding author (ckennedy{at}agctr.lsu.edu)

Pearl millet [Pennisetum glaucum (R) Br.] is a promising alternative grain crop for the Southeast and mid-South regions of the USA, but additional N fertility information is needed to optimize its production. Identification of a critical tissue N level at early growth stages is necessary to determine the need for subsequent applications of N. Field experiments were conducted to determine the response of hybrid ‘HGM 100’ grain yield, protein yield, and shoot N concentration to N application rate and to determine the relationship of grain yield and protein yield with shoot N concentration at different growth stages. Grain yield response to N fertilizer applications from 0 to 168 kg ha^-1, in 34-kg increments, varied among five field environments ranging from sandy loam to silty clay loam soils and resulted in a moderately low correlation (r² = 0.36). Relative total protein yield was more consistent (r² = 0.67). Tissue N concentration of shoots harvested 44 ± 4 d after seeding [early boot(EB)] was related to relative grain yield (r² = 0.65). A critical N concentration of 31 g kg^-1 dry matter (dm), determined by regression and "old" Cate–Nelson procedures, resulted in optimum grain yield. On a per hectare basis, total relative protein yield also correlated moderately high with shoot tissue N concentration at EB (r² = 0.70). The use of Cate–Nelson procedures determined a critical N concentration in shoot tissue at EB of 32 g kg^-1 dm. Determination of a critical N level at an earlier growth stage resulted in low correlations with yield parameters. On the basis of critical values at the EB stage, N amendments could possibly be applied in time to enhance some yield components, although the effective application window is narrow.

Abbreviations: PI, panicle initiation • EB, early boot • dm, dry matter