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Weed Population Dynamics and Weed Control in the Peruvian Amazon
Author(s) -
Mt. Pleasant Jane,
McCollum R. E.,
Coble H. D.
Publication year - 1990
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/agronj1990.00021962008200010024x
Subject(s) - digitaria sanguinalis , weed , eleusine indica , agronomy , biology , weed control , echinochloa , population , metolachlor , digitaria , propanil , atrazine , pesticide , demography , sociology
In traditional slush‐and‐burn agriculture, forest fallow is a primary agent in weed control. Stable continuous‐cropping systems could be expected to require a comprehensive program of weed management, probably including the use of herbicides. Weed control measures in a sequence of rice ( Oryza sativa L.)‐corn ( Zea mays L.)‐soybean ( Glycine max L.)‐rice‐corn‐soybean were studied for 2 yr in Yurimaguas, Peru, with the following objectives to: (i) identify weed species resistant to the herbicide program in a continuous cropping system, and (ii) develop effective weed management practices for intensively managed cropping systems in the humid tropics. First‐crop weeds were 60% grass, 25% sedges, and 15% broadleaf weeds. The grass was composed of two species: large crabgrass [ Digitaria sanguinalis (L.) Scop.] and goosegrass ( Eleusine indica (L.) Gaertn]. Sixth‐crop weed population was 80% grass, 13% broadleafs and 7% spreading dayflower ( Commelina diffusa Burm. f.); and itchgrass ( Rottboelia exaltata L.f.) comprised 85% of the grasses. Metolachlor [2‐chloro‐ N ‐(2‐ethyl‐6‐methylphenyl)‐ N ‐(2‐methoxy‐l‐methylethyl) acetamide] controlled crabgrass, goosegrass, and most broadleafs in corn and soybean; but it did not control itchgrass. Metolachlor alone resulted in a weed population that was 97% itchgrass in the sixth crop. Sethoxydim {2‐[(1‐ethoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one}‐plus bentazon [3‐(1‐methylethyl)‐(1. H )‐2,1,3‐benzothiadiazin‐4(3 H )‐one 2.2‐dioxide] on soybean controlled grasses including itchgrass, but broadleaf weeds and dayflower increased. Propanil [ N ‐(3,4‐dichlorophenyl) propanamide]‐plus‐oxadiazon {3‐[2,4‐dichloro‐5‐(1‐methylethoxy)phenyl]‐5‐(1,1‐dimethyl)‐1,3,4‐oxadiazol‐2‐(3 H )‐one} on rice resulted in a mixed grass population. Rice was more vulnerable to weed pressure than either corn or soybean and appears inappropriate for this high‐input rotation because of the high cost of weed control.