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Nitrate Dynamics Following Brush Control in a Post Oak‐Blackjack Oak Forest
Author(s) -
Gay David L.,
Allen Earl R.,
Engle David M.,
Stritzke Jimmy F.
Publication year - 1996
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/agronj1996.00021962008800040006x
Subject(s) - festuca arundinacea , agronomy , growing season , environmental science , zoology , biology , botany , poaceae
Converting marginal hardwood forests to grass may increase economic output from livestock production. Nitrogen dynamics during conversion need to be evaluated to determine if conversion releases excessive quantities of NO 3 ‐N, with potential adverse effects on the environment. This study was conducted to determine the amount of NO 3 ‐N present during conversion of a mature post oak‐blackjack oak ( Quercus stellata Wangenh.‐ Q. marilandica Muenchh .) forest and to identify optimum time periods for grass uptake of available mineralized N after herbicide treatment. Four treatments were evaluated: (i) no brush kill with no grass overseeding, (ii) brush kill with no grass overseeding, (iii) brush kill with cool‐season grass overseeding, and (iv) brush kill with warm‐season grass overseeding. The cool‐ ‘K‐31’ tall fescue ( Festuca arundinacea Schreb.); ‘Plains’ Old World bluestem [ Bothriochloa ischaemum var. ischaemum (L.) Keng] was the warm‐season(C 4 ) grass. Soil profile NO 3 ‐N to a depth of 60 cm and NO 3 ‐N concentrations in soil leachate at 60 cm were measured in 15‐ by 25‐m plots during a 22‐mo period (June 1993 to March 1995). Soil NO 3 ‐N increased from ì5 kg ha −1 initially to >50 kg ha −1 when brush was killed with tebuthiuron [ N ‐[5‐(1,1‐dimethylethyl)‐1,3,4‐thiadiazoi‐2‐yl]‐ N, , N ′‐dimethylurea] application. Soil and leachate NO 3 ‐N in tall fescue overseeded plots returned to near pretreatment levels by the end of the first rapid growth phase of tall fescue in June 1994. Soil NO 3 ‐N in Old World bluestem overseeded and unseeded brush kill plots remained elevated throughout the experiment, and leachate NO 3 ‐N concentrations rose from 0 to more than 70 mg L −1 The risk of NO 3 ‐N leaching after brush control is reduced by overseeding with tall fescue.