Field studies were conducted over 3 yr to evaluate imazapic, applied either alone or combined with other commonly used herbicides for peanut weed control. Imazapic applied early postemergence alone at 71 g/ha provided excellent weed control, maximum yields, and optimum economic returns. Variations of this treat ment-such as half rate of imazapic applied alone, tank mixed with other herbicides, or supplemented with other herbicides-frequently had equivalent weed con trol and yield. However, these variations did not im prove economic return. Greenhouse studies evaluated Florida beggarweed control as influenced by weed age, imazapic rate, and application type. The three applica tion types were foliage only, soil only, and soil plus foliage. Control was independent of application type when Florida beggarweed seedlings were less than 20 d old. The soil-only application did not adequately control older seedlings. Foliage-only and foliage plus soil appli cation were equally effective. Averaged across all other factors, imazapic was less effective controlling seedlings older than 20 d. At this age, seedlings produced trifoliate rather than unifoliate leaves. Absorption of 14 C-imazapic by unifoliate and trifoliate leaves was equivalent. How ever, translocation was greater in unifoliate leaves. Re duced translocation by trifoliate foliage contributes to imazapic tolerance of older Florida beggarweed seed lings.

Peanut yield, quality, and net return to irrigation were analyzed from commercial peanut fields in the south eastern U.S. during the 1987 through 1994 crop years. The average amount of irrigation water applied ranged from 2.51 to 28.22 cm/ha. Yields in the irrigated peanut fields averaged 569 kg/ha higher than in the nonirrigated fields. Means for farmer stock grade, jumbo shelling outturn, and seed germination also were significantly higher in the irrigated fields. Conversely, aflatoxin contamination was 140 ppb lower in the nonedible oil stock category from the irrigated fields. Yearly compari sons were made to examine significant differences in irrigation associated peanut yield and quality changes in individual crop years as well as across year comparisons for nonirrigated and irrigated practices. The net return for irrigation was examined at the quota support price, weighted average farmer stock price, and contract addi tional price. Average net return over total irrigation cost were $236.99, $149.22, and -$22.64 per ha, respectively.

Research was conducted from 1978 through 1980 at Headland, AL, to evaluate the use of herbicides, mechanical cultivation, and hand-hoeing as components of a total weed control system for peanuts (Arachis hypogaeaL.). Herbicides or two cultivations alone failed to provide acceptable weed control, peanut yields, or net returns for the 3-yr period. However, adding two cultivations to the herbicide treatments produced acceptable weed control, peanut yields, and net returns for the 3-yr period. Average peanut yield for herbicide(s) plus two cultivations was 3200 kg/ha with an average net return of $260/ha. Two cultivations plus two hoeings without herbicide(s) produced good results with an average 3-yr yield of 3380 kg/ha and a net return of $280/ha. Herbicide(s) plus two cultivation treatments that had net returns equal to two cultivations plus two hoeing treatments were: dinoseb (2-sec-butyl-4,6-dinitrophenol) at 5.0 kg ai/ha applied at ground-cracking ($300/ha); dinoseb + alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 1.7 + 3.4 kg ai/ha applied at ground-cracking ($310/ha); and alachlor at 4.5 kg/ha applied preemergence ($320/ha). Treatments containing herbicide(s) plus two cultivations plus two hoeings did not substantially improve weed control, peanut yields, or net returns over herbicide(s) plus two cultivations.

Field experiments were conducted over two growing seasons (1995 and 1996) and at two locations (Jay, FL, and Headland, AL) to identify the most effective herbi cide program for Florida beggarweed [Desmodium tortuosum (SW) D. C. ] control in peanut (Arachis hypogaea L.). The most common herbicides used for Florida beg garweed control-including preemergence (PRE), earlypostemergence (EPOST), mid-postemergence(MPOST) andlate-postemergence (LPOST) applied treatmentswere evaluated in a factorial treatment arrangement. All treatments had merit and could be assembled into pro grams that resulted in maximum weed control, crop yield, and net returns. However, at least two of the four treatment timings were required to reach this level. Four systems were consistently associated with the maximum statistical grouping for both yield and net returns, as well as acceptable Florida beggarweed control (> 81%). These systems were (a) paraquat + bentazon applied EPOST, followed by pyridate + 2,4-DB MPOST; (b) same as (a) onlyprecededby norflurazon applied PRE; (c) imazapic applied EPOST followed by pyridate + 2,4-DB MPOST; and (d) norflurazon applied PRE, followed by imazapic EPOST.