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Logistic Response of Bermudagrass and Bunchgrass Cultivars to Applied Nitrogen
Author(s) -
Overman A. R.,
Sanderson M. A.,
Jones R. M.
Publication year - 1993
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1993.00021962008500030004x
Subject(s) - cynodon dactylon , agronomy , cenchrus ciliaris , dry matter , tussock , forage , panicum , eragrostis , andropogon , biology , cultivar , logistic function , environmental science , mathematics , statistics
Models provide a quantitative means to evaluate yield response of forage grasses to applied N and water availability. The objective of this analysis was to estimate model parameters ( A , b , c ) for bermudagrasses and bunchgrasses grown at the same location and during the same time period. The logistic equation was used to relate annual dry matter production to applied N for three bermudagrasses [ Cynodon dactylon L., ‘Coastal’, ‘Alicia’, and ‘Coastcross‐1’] and four bunchgrasses [ Eragrostis curvula (Schrad.) Nees, ‘Morpa’ and ‘Renner’ lovegrass; Panicum coloratum L., ‘Selection‐75’ kleingrass, and Cenchrus ciliaris L., ‘Strain 18‐35’ buffelgrass]. Data were from 4 yr of field experiments at Stephenville, TX. Analysis of variance was used to show that the N coefficients b and c were independent of year and climate for each grass, in agreement with recently published results. Applied N required to provide one‐half of maximum yield was approximately 150 kg ha −1 for bermudagrass and 50 kg ha −1 for lovegrass. Variation among years was accounted for in the linear coefficient A , which was then related to rainfall. Bunchgrasses typically had lower A and b , but similar c values compared with bermudagrasses. The logistic model allows estimates of yields in terms of applied N and rainfall, and quantifies the interaction between these two factors. Bermudagrass yielded approximately 45% more dry matter than lovegrass for the same rainfall. Correlation coefficients exceeded 0.95 throughout the analysis.