Effects of organic and inorganic amendments on weed management in sweet maize

Field experiments were conducted to determine the effects of organic and inorganic amendments on weed suppression in sweet maize cultivation (Zea mays L.). A randomized complete block design was employed with four replicates per treatment with each organic amendment used at half (x/2), single (x=10 t ha(-1)) and double (2x) rates (organic fertilization: cow manure, poultry manure and barley mulch; synthetic fertilizer (240 kg N ha(-1): 21-0-0); and control). The highest number and dry weight of weeds were recorded for double cow manure and chemical fertilizer treatments. The cow manure treatments promoted weed emergence and growth proportionally to the rate of application (x/2<x<2x). In the presence of barley residues, weed biomass or density was reduced for the species: redroot pigweed (Amaranthus retroflexus L.), common purslane (Portulaca oleracea L.) and prostrate knotweed (Polygonum aviculare L.). Weed suppressive effect of barley residues decreased with time following residue decomposition. The barley mulch plots presented the highest values of Shannon-Weiner and Simpson indices. These results indicate that green manure of barley are effective for the suppression of some weeds in sweet maize.