Composted manure produced in deep-bedded hoop structures constitutes a source of nutrients and organic materials that can influence crop and weed emergence, growth, competitive interactions, and soil physical properties. The impact of composted swine manure on corn, soybean, winter wheat, velvetleaf, giant foxtail, and common waterhemp emergence and early growth were compared at compost rates of 0, 8, 16, or 24 Mg C/ha. Compost amendment had no effect on crop emergence but did reduce weed emergence. Inhibition of seedling emergence ranged between 15 and 57% for giant foxtail, 0 and 23% for velvetleaf, and 16 and 76% for common waterhemp. Soil amendment enhanced weed growth but not crop growth. A response surface regression analysis indicated that, while large-seeded crops have constant relative growth rates, small-seeded weed species increase their relative growth rates with compost amendment (P < 0.0001, r2 = 0.5252).
Nomenclature: Common waterhemp, Amaranthus rudis Sauer #3 AMATA; corn, Zea mays L. ‘Pioneer 3563’; giant foxtail, Setaria faberi SETFA Herm.; soybean, Glycine max (L.) Merr. ‘Pioneer 92B84’; velvetleaf, Abutilon theophrasti ABUTH Medicus; winter wheat, Triticum aestivum L. ‘Arapahoe’.
Additional index words: Compost amendment, relative growth rate, germination inhibition, organic amendment, seedling emergence, soil quality.
Abbreviations: EI%, percentage emergence inhibition; MTE, mean time of emergence; RGR, relative growth rate; VOA, volatile organic acids.