Crop residue accumulation and nutrient stratification near the soil surface in tilled and direct-seeded sugarbeet cropping systems.

Abstract

Rising tillage costs have increased interest in reduced tillage among sugarbeet (Beta vulgaris L.) growers. No-tillage (NT) sugarbeet planting offers cost and soil conservation benefits but also nutrient management challenges. Growers transitioning from tillage to NT who do not have the equipment to sub-surface band fertilizer often resort to broadcast applications without incorporation. This will likely lead to nutrients being concentrated near the soil surface but sugarbeet harvest causes some soil disturbance and may ameliorate stratification. Similarly, NT allows crop residue to accumulate on the soil surface providing protection against soil erosion and a reservoir of slow-release nutrients. A field study was conducted in North Dakota, USA from 2013 to 2019 to evaluate the effect of NT on nutrient stratification in 2-year (barley [Hordeum vulgare L.]/sugarbeet) and 4-yr (corn [Zea mays L.]/soybean [Glycine max L.]/barley/sugarbeet) rotations under sprinkler irrigation. A corn-soybean rotation was included to provide a comparison with a rotation that doesn’t include sugarbeet. Tillage (30 cm deep) was performed on subplots in each of the rotations as a control. Tillage treatments were applied consistently from year to year to all rotation crops on a given plot. Soil samples were collected following barley (fall 2019) and corn (spring 2020). Soil cores were divided into depths of 0-5, 5-10, 10-15 and 15-20 cm and analyzed for extractable P, exchangeable K and organic matter. Residue samples were collected after the 8-year study was completed and residue biomass, total N and total C were determined. Stratification was greater with NT than with tillage in all rotations; however, the concentration of nutrients in the top 5 cm of soil was somewhat less in NT rotations that included sugarbeet than in the corn-soybean rotation. Stratification was greater for the largely immobile P and OM than for the somewhat mobile K. Greatest accumulation of OM in the top 5 cm of soil occurred in the NT corn-soybean plots, likely as a result of the large amount of corn residue returned to the soil every other year in this system.