The Economic Feasibility of Subsoiling Solonetzic Soils in Saskatchewan

The feasibility of deep tillage of soils depends on agronomic and economic considerations. The objective of this research was to determine the economic feasibility of subsoiling in Saskatchewan. The economic analysis examined the net present values associated with the cost of subsoiling and the revenues generated by the increases in crop yields using five crop prices and discount rates of 5%, 7.5%, and 10%. Subsoiling of Solonetzic soils in the “wetterl” regions of the Canadian prairies was found to be economically feasible, except under very low crop prices. Under irrigation agriculture, subsoiling of Solonetzic soils was economically feasible over the entire range of crop prices. The subsoiling costs were recovered by revenues from increased crop production by the second or third year after subsoiling. The higher discount rates reduced the magnitude of the economic returns, but did not affect the relative feasibility of subsoiling. Continuous cropping for at least 3 yr after subsoiling, and the selection of higher‐revenue crops in the second and third crop years facilitates recovering the cost of subsoiling. Research Question Subsoiling increases crop production on Solonetzic soils in the Canadian prairies. The costs associated with subsoiling are substantial, and the benefits in terms of increased crop production diminish over time. The economic feasibility of subsoiling depends on its initial cost, on the magnitude and longevity of increased crop production, and on expected crop prices. The objective of this study was to determine the economic merits of subsoiling a range of Solonetzic soil types differing in textures and weather conditions. Literature Summary There are over 15 million acres of Solonetzic soils in the Canadian prairies. In Solonetzic soils, clay translocation under high sodium levels results in the development of a Solonetzic B horizon, or hard‐pan layer, which is extremely hard when dry and impermeable to water when wet. Subsoiling has been shown to increase crop production on Solonetzic soils in the Canadian prairies. Earlier work by the senior author showed that the effect of subsoiling on increased crop production diminishes with time, lasting for up to 5 yr, with the largest yield increases apparent in the second year. Study Description Deep ripping was carried out on 11 farm cooperator fields in Saskatchewan. Three of the soils were under irrigation, and the remainder were farmed under dryland, but in the more humid part of the prairies. Soils: Seven Solonetzic soils (two Natric Mollisolls and five Natric Borolls) and four Chernozemic soils (one Typic Boroll and three Boralfic Borolls) Tillage: Deep tillage consisted of ripping the soils to 24 to 30 in. depth. Subsequent secondary tillage operations included tandem disks, heavy duty cultivars, and field cultivators to depths ranging from 4 to 8 in. Design: Two treatments (ripped and control) randomized in three replicates, with individual sub‐plots 50 to 100 ft wide by 0.5 mi long. Crop production: Crop yields were determined by means of square yard samples. The value of the crop was determined using a range of five crop prices representing grain prices in the 1980s. Economic analysis: The following discount rates were used to calculate the benefits in crop production in terms in the time value of money: 5%, 7.5%, and 10%. Applied Questions What was the cost of deep ripping? The cost of subsoiling and the additional secondary tillage operations that were required varied with soil type and soil zone from $35 to $64/acre. The selection of the different types of secondary tillage implements for smoothing down the rough soil surface left by the subsoiler made a difference of $7 to $l l/acre. Was deep ripping of Solonetzic soils economically feasible under any of the crop price scenarios? Subsoiling the dryland soils was not economically feasible at “very lowl” crop prices, but it was feasible when prices were “lowl” or higher. Subsoiling Solonetzic soils in the irrigation areas was economically feasible at all crop prices. The subsoiling costs were recovered by revenues from increased crop production by the second or third year after subsoiling. What was the effect of using different discount rates? The economic returns assuming discount rates of 7.5% and 10% were similar to those for the 5% discount rates, although smaller. The higher discount rates also required three crop years to offset subsoiling costs for dryland Solonetzic soils under “lowl” prices compared with two crop years at a 5% discount rate. What was the effect of crop selection and crop rotations on the economic returns to deep ripping? Crop rotations and crop selections that include continuous cropping for at least 3 yr after subsoiling, and the selection of higher‐revenue crops in the second and third crop year maximize the economic returns to deep ripping. Recommendations Deep ripping of Solonetzic soils is economically feasible in the more humid areas of Saskatchewan, except for dryland Solonetzic soils at very low crop prices. In Saskatchewan, secondary tillage operations following deep ripping should include using a tandem disk and not only a field cultivator. Furthermore, high valued crops should be grown, if feasible, in the second and third years following deep tillage.