Effect of Residue Management and Conventional and Organic Soil Management Systems on Crop Yields and Weed Biomass

Crop residue management (RM) plays an important role in maintaining soil organic carbon (SOC) in horticulture, especially where annual crop rotations rely on frequent tillage. A trial investigating the short-term effects of sweet corn (Zea mays L. var. rugosa) residue incorporation on crop yields in a corn-cabbage (Brassica oleracea L.) rotation using organic (Org) and conventional (Conv) soil management systems (SMS) was established on 14 December 2009 in two contrasting soil types (Vertosol and Chromosol). The effect of mulched corn residue incorporation on weed biomass production was also studied. Corn was grown under the two SMS and residue was retained (+RES) or removed (-RES) after harvest on 23 April 2010. Cabbage was then grown from 4 May to 14 October 2010, under the same SMS in a three-way factorial design (SMS x RM x soil type). In both systems, equal quantities of macro-nutrients were supplied. Crop yields and weed biomass and apparent electrical conductivity (ECa) of soil were measured. There was no significant difference in total corn biomass for SMS or soil type. However, cabbage yield was significantly greater at the Chromosol site. The SMS x RM x soil type interaction was significant for weed biomass in cabbage, with Org having less weed biomass at the Vertosol site, especially in -RES. The +RES treatment had reduced weed biomass by 20 and 64% in conventional and organic SMS, respectively, in comparison to -RES in Chromosol. Soil ECa was significantly different for soil type only. The reduction of weed biomass in +RES treatment could be attributed to the mulching effect of the incorporated corn residue, the differences in weed seed bank and drainage between two sites. In conclusion, crop yields and soil ECa were not influenced by SMS or RM in short-term, but incorporation of residue in soil reduced weed biomass.