Crop Residue Cover on Irrigated Rotations for Potato, Dry Bean, Sugar Beet, and Soft White Wheat in Southern Alberta.

Maintenance of crop residue cover on the soil surface is an important tenet of sustainable agriculture to preclude erosion and enhance soil water conservation. This study compared conservation (CONS) and conventional (CONV) management systems in 3- to 6-yr rotations dry bean, potato, and sugar beet in southern Alberta. Conservation management included reduced tillage, cover crops, feedlot manure compost addition, and solid-seeded narrow-row dry bean production. Beginning in the third year of the study (2002), surface residue cover was estimated each spring on all rotations, using the marked rope method, prior to any tillage or seeding. Over the 10 yr (2002-11), average surface residue cover on the continuous wheat rotation was significantly higher (40%) than 4-CONS (potato-wheat-sugar beet-dry bean, 12%), or 3-CONV (potato-dry bean-wheat) and 4-CONV (potato-wheat-sugar beet-dry bean) [both 8%] rotations. A longer 5-CONS rotation (with two phases of wheat, interspersed with the three row crops) had average residue cover of 19% with 6-CONS (which included 2 yr of timothy) at 20%. Averaging all crops across rotations, wheat produced the greatest amount of surface residue (35%), significantly higher than narrow-row bean (11%), which was in turn greater than sugar beet and potato (both 8%), which were greater than wide-row dry bean (5%). The presence of wheat in rotation was the main driver of increasing surface residue cover, although few treatments were above the recommended 30% threshold required to minimize wind erosion. A fall-seeded cover crop added up to 2 Mg ha^-1 of spring biomass which helped increase surface cover on some CONS treatments.