Performance comparison of residue management units of no-tillage sowing systems: A review

Appropriate residue management is a key factor underlying successful crop establishment in no-tillage systems. Satisfactory opening and closing of furrows, and uniform seeding depth and seed-spacing are achieved when the design of the residue management unit of the seeder, and machinery settings are correctly selected for the soil type, soil condition, and soil surface residue characteristics. Improper selection of such units or settings can result in blockage of tine furrow openers, with accumulated residues and hairpinning when disc openers are used. This can affect seed-soil contact and result in uneven seedling emergence or sub-optimal plant stand, and reduce crop yield potential. This article critically examines the effectiveness of residue management units of no-tillage sowing equipment in maintaining appropriate levels (e.g., ≥30%) of residue cover on sown rows, preventing the interference of such residue with opening and closing of furrows (blockage), enabling the seed to be correctly placed (depth control, seed-spacing), and by discussing the influence of unit's design on fuel consumption and power (draft) requirements. This review confirmed that smooth disc coulters, finger row cleaners, and their combinations can retain more than the minimum residue cover recommended for no-tillage systems. Power-assisted units can operate with surface residue up to about 9000 kg ha⁻¹ without blockage, but their adoption in developing countries is restricted by relatively high fuel consumption. Future evaluations of residue management units need to be conducted under controlled conditions. Such work will enable parametrization of suitable models (DEM) and will advance the understanding of soil-machine-residue interactions to further assist the design of no-tillage equipment. Priority research areas are presented and discussed.