Narrow row spacing does not affect lima bean yield or management of weeds and other pests

Potential increases in the yield of agronomic crops through enhanced light interception have led many growers to consider using narrow rows in lima be an (Phaseolus lunatus L.). However, no information is available on how narr ow row spacing affects weed management or fits into an integrated pest mana gement strategy. To address this, field studies were conducted in Delaware and Maryland in 1996 and 1997 to evaluate the effects of row spacing (38 vs . 76 cm) on weed control, and on yield and quality of lima bean. Weed manag ement inputs were also evaluated with labeled or reduced pre-emergence rate s of metolachlor plus imazethapyr applied broadcast or banded. Only 76-cm r ows were cultivated according to the standard practice for this production system. In general, row spacing, herbicide rate, and herbicide application method had no effect on lima bean biomass or yield, on weed density, contro l, or biomass production, or on economic return. However, weed control cons istency was improved when wide rows were used, even with reduced herbicide rates, possibly because of cultivation. Using reduced herbicide rates and b and applications resulted in 84% less herbicide applied without affecting w eed control. Chemical names used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiadia zin-4(3H)-one 2,2-dioxide (bentazon); 2-[4,5-dihydro-4-methyl-4-(1-methylet hyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-y1]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-meth ylethyl)acetamide (metolachlor); 2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)pr opyl]-3-hydroxy- 2-cyclohexen-1-one(sethoxydim).