Influence of conservation tillage and rotation length on potato productivity, tuber disease and soil quality parameters on a fine sandy loam in eastern Canada

Potato (Solanum tuberosum L.) farming systems generally use excess tillage and produce low levels of crop residue in the potato year, both of which are detrimental to soil quality. In eastern Canada the major form of primary tillage is autumn (September-October) mouldboard ploughing (20 cm depth). which leaves the soil bare and unprotected over the winter period prior to planting potato in the following spring (May). A study (split-plot randomized block with six replicates) was initiated in 1994 on a fine sandy loam (Orthic Podzol) in Prince Edward Island to evaluate the use of conservation tillage in both 2-year [barley (Hordeum vulgare L.)-potato] and 3-year [barley-red clover (Trifolium pratense L.)-potato] potato rotations. The main conservation tillage strategy was to shift the primary tillage event from the autumn to spring, by replacing the autumn e mouldboard ploughing with a herbicide treatment, and use of a relatively shallow (15 cm depth) one-pass reduced tillage (chisel plough) just prior to potato planting. Mulches were used on all plots after potato harvest to provide soil cover over the cool season. Potato Yield and quality, incidence of tuber disease, surface residue levels after potato planting, soil organic carbon and carbon fractions, and soil structure were evaluated from 1994 to 1999, over three and two cycles of the 2- and 3-year rotation, respectively. Results for the 2-year rotation indicated that neither conventional nor conservation tillage were sustainable, due to Rhizoctonia disease pressure and decline in tuber quality, in comparison to the 3-year rotation. Potato yields and tuber quality were similar between tillage systems in the 3-year rotation. Conservation tillage significantly increased the concentration of organic carbon and macro-organic carbon at the soil 0-8 cm depth, compared to conventional tillage, and significantly improved soil structural stability. Use of conservation tillage in 3-year potato systems has the potential to maintain crop productivity, protect the soil resource, and improve soil quality. (C) 2001 Elsevier Science B.V. All rights reserved.