EFFECTS OF DIFFERENT SEEDING MACHINES ON SPRING WHEAT PRODUCTION UNDER VARIOUS CONDITIONS OF STUBBLE RESIDUE AND SOIL COMPACTION IN NO-TILL ROTATIONS

Abstract

The effectiveness of several commercial seeders and an experimental triple-disc press drill was assessed on a silt loam soil at Lethbridge over a 7-yr period on fields receiving chemical weed control instead of tillage between crops. The double- and triple-disc press drills generally failed to penetrate untilled surfaces adequately when soil bulk density in the upper 5 cm exceeded about 1.2 g/cm³ or when the quantity of surface residue exceeded about 3,700 kg/ha. Hoe openers penetrated the soil but failed to clear heavy residues when stubble and straw lengths were excessive (> 25 cm). In 2 of the 7 yr, yields of spring wheat (Triticum aestivum L.) on small plots seeded with the double- and triple-disc drills were superior to those seeded with the wide-spaced hoe drill (1,159 vs. 721 kg/ha in 1969, and 667 vs. 573 kg/ha in 1973). Yield differences were primarily due to wild oats (Avena fatua L.), which germinated because of the tillage action of hoe openers, in ridge areas between rows and which, despite the use of herbicides, seriously reduced yields from wide-spaced rows (23 and 36 cm). In the other years, yields were similar for all seeding methods. On 0.4-ha chemical fallow fields, yields were up to 51% lower within sprayer wheel traffic areas (bulk densities of 1.2 g/cm³ or greater in the 0- to 5-cm soil layer) because of shallow seed placement when double-disc drills were used but not when hoe drills were used.