Author(s): Adrien N’Dayegamiye, Judith Nyiraneza, Michèle Grenier, Marie Bipfubusa and Anne Drapeau
Soil quality decline is a common concern in potato production systems. Including cereals and green manures (GMs) in potato rotation could improve soil productivity and sustain potato (Solanum tuberosum L.) yields and quality. This experiment initiated in Québec, eastern Canada, assessed the effects of two cycles of 2-yr potato rotations with cereals and GMs on soil properties and potato yield and quality, and on disease incidence from 2008 to 2011. Three cereals [corn (Zea mays), barley (Hordeum vulgare), and oat (Avena sativa)] seeded in spring, three summer GMs [mustard (Sinapsis alba), japanese millet (Setaria italica), and pearl millet (Pennisetum glaucum)], four fall GM crops [oat, mustard, wheat (Triticum aestivum), and rye (Secale cereale)], and continuous potato (Solanum tuberosum L.) were grown on main plots in 2008 and 2010. In following years (2009 and 2011), each main plot was split, and five N fertilizer rates (0, 50, 100, 150 and 200 kg N ha-1) were applied to potato. After two rotation cycles in 2011, soils under cereals and summer and fall GMs had higher soil water-extractable organic C and N contents, nitrate levels, soil respiration, urease and dehydrogenase activities, and a larger proportion of soil macro aggregates (0.25 to 2 mm), compared with the continuous potato. Cereals and summer GMs increased marketable potato yield and specific gravity, whereas fall GMs increased tuber yield but reduced tuber quality. In addition, fall GMs favored the incidence of common scab and black scurf. Summer GMs had higher potato N uptake and N efficiency compared to cereals and fall GMs. Although fall GMs produced higher net returns than cereals and summer GMs, they may not represent a viable long term option to sustain potato production and to enhance soil quality. Results indicated that growing cereals or summer GMs in rotation with potato is an interesting alternative to improve soil properties while sustaining potato yield and quality. A fall GM with a better growth during the fall season may sustain potato yield and quality, if included in longer potato rotation, but this remains to be determined.
