Responses of spring wheat and soybean to subsurface drainage in northwest Minnesota

The advantages and adoption of subsurface drainage are well documented in many parts of the Upper Midwest. The adoption of subsurface drainage in the northern half of Minnesota, in particular the Red River of the North Basin (RRB), has been relatively small compared with other intensively drained regions of the Upper Midwest. The objectives of this research were to measure the effect of subsurface drainage on grain yield and grain quality of spring wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] in the RRB. Experimental sites were established near Brooks and Crookston, MN. At each site subsurface drainage was installed based on drainage coefficients of 6.3, 12.7, and 19 mm d^-1 of excess soil water. The grain yield of both wheat and soybean did not improve with subsurface drainage. In contrast to grain yield, grain protein in both wheat and soybean increased. The grain protein increased linearly in spring wheat as the drainage coefficient increased. In soybean, grain protein showed a quadratic response to the increase in the drainage coefficient. A correlated response to the increase in grain protein was detected with the quadratic decrease in oil content in soybean. These results suggest that subsurface drainage as a means to supplement the predominant system of land leveling and surface drainage may have limited applicability in the RRB as subsurface drainage did not improve grain yield of spring wheat or soybean, greatly limiting the economic feasibility of subsurface drainage.