The Relationship of Between Crop Production and Sustainability
This page was adapted from the article, "Relationship of crop production and sustainability, is it really ‘Us vs Them’?," which appeared in Crop & Pest Report on August 25, 2022.
Dave Franzen. NDSU Extension Soil Specialist
Most people know what ‘crop production’ is, but the meaning of the term ‘sustainability’ is fuzzier. In my perspective as a soil scientist, sustainability is the ability of a soil to minimize adverse weather effects on crop production and minimize the crop nutrient inputs required to produce yield. The major driver of sustainability in this definition is keeping topsoil in place.
Although huge amounts of topsoil have been lost in North Dakota, amounting from 2 to 3 feet in most areas, some remnants remain. In some areas of the world that have been cultivated for thousands of years, no topsoil remains. An example is the central loess plateau of China. If fertilized, this region can be incredibly productive. However, it requires half again more fertilizer than what we would dream of applying here. To produce 200 bu/acre corn requires 300 pounds N per acre in this region of China, vs about 180 pounds N per acre here. In Kazakhstan, to produce 25 ton sugar beets with 18% sugar, farmers have to apply at least 200 pound N per acre, vs about 120 pounds per acre here. Part of the reason for greater fertilizer inputs per unit yield where no topsoil is present and organic matter is less than 1 percent of soil weight is the inability of the soil to supply the nutrient. The other part of the reason for higher inputs is the lower resilience of within year and between year weather changes and the lower efficiency of nutrient uptake due to greater stress from poor soil aggregation, water infiltration and water availability through the season.
In terms of nutrients lost when wind blows North Dakota soil away, if the beginning soil organic matter is 3%, each inch of topsoil lost equals a fertilizer equivalent loss of about $800 per acre at 2021 prices. This loss is not reflected directly on a farmer annual balance sheet, but reveals itself in lower yield potential and the need for greater fertilizer input into the future.
North Dakota N fertilizer calculators for spring wheat/durum, corn and sunflower contain a direct N credit for 6 years or more continuous no-till/strip-till/one-pass seeding, amounting to about 50 pounds N per acre. The savings over 20 years of farming in N costs alone would amount to about $600 per acre if N costs were 60 cents per pound N. The long-term credit is due to greater efficiency of N use, and the greater activity of natural asymbiotic N-fixing soil organisms.
Movement to no-till/strip-till/one-pass seeding requires a change not only in planting, but it starts at the combine at harvest, the fall before seeding. Especially at the onset, minimizing residue through baling straw, harvesting corn by not using a chopper-head, leaving sunflower/corn/wheat straw as high as possible, so that the residue managers on the spring planter/seeder have as little residue covering the surface as possible. This results in faster soil drying, faster soil warm-up and it minimizes planter skips.
Crop production and sustainability in terms of soil conservation are excellent partners. Paying closer attention to soil retention including reducing tillage, use of cover crops where helpful, and better residue management will pay dividends in future crop productivity and lower fertilizer input costs.