Reducing Pesticides and Increasing Potato Yield by Increasing Time Between Potato Crops.

In response to economic pressure in recent decades, growers have been reducing the number of years between potato crops. These short rotations may increase short-term profits, however, shorter rotations lead to higher pesticide, fertilizer, and tillage costs, as well as reduced tuber quality and yield. This multi-state project brings together growers, scientists, and consultants to examine the long-term economic, agronomic, and environmental sustainability of both short (potatoes grown at least 6 times in 12 years) and long (no more than 3 times in 12 years) potato rotations. Over a period of three years, soil, plant, and pest parameters were measured in 108 paired fields, with each pair consisting of a both a long- and a short-rotation fields. Soils from each field were used in a glasshouse trial to evaluate the impact of rotation on vegetative and tuber growth. Results show that shorter rotations lead to earlier onset of plant senescence (16 days), with complete senescence occurring earlier as well (5 days). As a result, tuber numbers increased by 10.0% and average tuber weight by 11.1%. – producing an increase of 11.9 and 20.0% for U.S. No. 1 and total yield. The reason for the differences are attributed to a combination of Verticillium dahliae and nematode infections. Results of the glasshouse trial approximately correspond with grower yields in these fields (average of 8.9 Mg ha^-1 increase for long over short rotation). As a result, growers having short rotations applied an average of 1.5 more fungicide applications. Additionally, a majority of the short rotation fields (39 of 54) required fumigation, whereas only a small percentage of long rotation fields were fumigated (14 of 54). These results show that, although short rotations may seem profitable, they result in significant increases in pesticide applications and reductions in yields.