Chemical dwarfing and the response of cool-season grass seed crops to spring-applied nitrogen

• Published in: Agronomy journal Vol. 91; no. 2; pp. 344 - 350
• Main Authors: Young, W.C. III, Chilcote, D.O, Youngberg, H.W
• Format: Journal Article
• Language: English
• Published: Madison, WI American Society of Agronomy 01-03-1999
• Subjects: Agronomy. Soil science and plant productions; application rate; application timing; Biological and medical sciences; Cropping systems. Cultivation. Soil tillage; Dactylis glomerata; diammonium phosphate; dwarfing; establishment; Festuca arundinacea; Festuca rubra; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; harvest index; height; inflorescences; lodging; Nitrogen fertilization; Nitrogen, phosphorus, potassium fertilizations; paclobutrazol; plant characteristics; seed production; seed productivity; seed weight; seeds; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Tending. Growth control; Tillage. Tending. Growth control; tillers; yield components; yield response functions; Oregon; United States; North America; America; Nitrogen fertilization; Monocotyledones; Intervention day; Interspecific comparison; Treatment efficiency; Mollisols; Dose activity relation; Dwarfism; Paclobutrazol; Seed yield; Gramineae; Angiospermae; Triazole derivatives; Plant growth substance; Spermatophyta; Fodder crop; Yield component; Festuca rubra; Dactylis glomerata; Festuca arundinacea
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj1999.00021962009100020027x

Seed yield response of cool-season grasses to spring-applied N is usually limited because of lodging. This study investigated whether chemical dwarfing of these crops improves their seed yield response to spring-applied N. Chewing's fescue [Festuca rubra L. subsp. fallax (Thuill.) Nyman; syn. F. rubra var. commutata Gaudin], tall fescue (Festuca arundinacea Schreb.), and orchardgrass (Dactylis glomerata L.) were established in September 1983 near Corvallis, OR. Treatments were all combinations of 90, 120, 150, 180, and 210 kg N ha(-1) applied at the double-ridge stage of development, followed by paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)-4,4- dimethyl-2-(1H-1,2,4- triazol-1-yl)-pentan-3-ol] at 0, 0.25, 0.5, and 1 kg a.i. ha(-1) applied at floret initiation stage in 1985 and 1986. Averaged across years and N rates, the 1 kg ha(-1) rate reduced Chewing's fescue height by 23% and tall fescue and orchardgrass heights by 30%. In the absence of paclobutrazol, Chewing's fescue and tall fescue seed yields were the greatest at 90 kg N ha(-1). Paclobutrazol did not affect seed yield response of Chewing's fescue to N rates, but tall fescue seed yield in 1986 was the greatest at 150 kg N ha(-1) when only 0.25 kg a.i. paclobutrazol ha(-1) was applied. Averaged across N rates, the 0.5 kg ha(-1) rate increased Chewing's fescue seed yield by 32% in 1985 and 18% in 1986, and also increased tall fescue seed yield by 32% in 1985 and 23% in 1986. Orchardgrass seed yield was the greatest at 180 kg N ha(-1) in both years. Paclobutrazol did not affect orchardgrass seed yield in 1985, and the 1 kg ha(-1) rate decreased seed yield in 1986. We concluded that in western Oregon paclobutrazol application at floret initiation does not improve seed yield response of these crops to spring-applied N, but it would significantly improve Chewing's fescue and all fescue seed yield, regardless of the N rate applied. Results did not indicate any advantage for applying paclobutrazol on orchardgrass seed crop.