Short-term effect of corn residue incorporation on soil organic carbon in conventional and organic soil management systems

Abstract

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' var. 'rugosa' L.) residue incorporation on SOC and corn-cabbage ('Brassica oleracea' L.) yields using organic (ORG) and conventional (CON) soil management systems (SMS) was established on 14 December 2009 in two contrasting soil types (black Vertosol and brown Chromosol) in the Northern Tablelands of New South Wales, Australia. Corn was grown under the two soil management systems and residue was added (+RES) or removed (-RES) after harvest on 23 April 2010 in a two-way factorial design (SMS x RM). All +RES plots were incorporated with 14.8 t/ha mulched residue on dry weight basis with an average C:N ratio of 42.8. Cabbage was then grown from 4 May to 14 October 2010, under the two SMS. In both systems, equal quantities of macro-nutrients were supplied. Crop yields and weed biomass were recorded. Soil samples (0-10 cm) were depth collected prior to sowing sweet corn in mid-December 2009 and after harvesting cabbage in mid-November 2010. Changes in SOC, total N (TN), electrical conductivity (EC) and pH were monitored. There was no significant difference in total corn biomass for SMS or soil type, but cabbage yield was significantly greater in the Chromosol. The soil type x SMS had significant differences resulting in the increase of SOC by 7 % in ORG in the Chromosol only. The year x soil type interaction showed a significant difference due to increase of 8% SOC between years in the Vertosol only. The +RES treatment had an average ~4% higher SOC than -RES across SMS and soil types.