Potato Yield and Quality Response to Subsoil Tillage and Compaction

Compacted soils have been found in intensively cultivated vegetable crop regions of Central Wisconsin, resulting in the wide scale use of subsoil tillage by growers. The goal of this project was to assess potato (Solanum tuberosum L.) yield and quality response to soil compaction and subsoil tillage. Potato quality factors evaluated were marketable yield, tuber size distribution, internal quality, and sugar concentration. A controlled small plot experiment and several field scale experiments located in collaborating grower fields were conducted to assess potato and soil responses to subsoil tillage. Cone index profiles showed the potential for limited root growth below the compacted soil layer with values > 2.0 MPa. Subsoil tillage reduced cone index values to < 1.0 MPa below 33 cm in 2 of 3 yr. Total and U.S. no. 1 yields were not influenced by subsoil tillage. Likewise, no consistent differences were seen in the size distributions of U.S. no. 1 tubers across treatments, but subsoil tillage tended to decrease proportion of tubers 113 to 170 g. Subsoil tillage did not affect tuber glucose or sucrose concentrations at harvest or following storage for 120d. Internal tuber defects were not affected by either compaction or subsoil tillage. The lack of consistent effects of subsoil tillage on potato yield raises questions regarding the validity of this practice. The recommendation that potato growers use subsoil tillage may be linked to increased tuber size distribution or factors other than yield such as water, nutrient, or disease management.