Reducing Erosion and Phosphorus Movement in Potato Systems.
Timothy Griffin1, Gordon Starr1, C. Wayne Honeycutt1, and Matt Williams2. (1) USDA-ARS, New England Plant Soil and Water Lab, Orono, ME 04469-5753, (2) Univ of Maine, Central Bldg, Houlton, ME 04730
Soil erosion and phosphorus (P) runoff can be severe in potato production systems in the Northeast U.S., which are characterized by intensive tillage, minimal ground cover, low crop residue return, and steep slopes. We used rainfall simulators in the greenhouse and field to assess sediment and P movement associated with three conservation practices: straw mulching, interseeding barley before potato harvest, and application of polyacrylamide (PAM). In the greenhouse, a sandy loam soil was packed into 0.2 by 1.0 m boxes, and subjected to multiple rainfall events at intensity of 70 mm per hr. Runoff amount, sediment concentration, and inorganic and sediment-bound P were measured. Linear increases in straw mulch biomass (up to 3000 kg/ha) resulted in exponential decreases in sediment and P loss. Mulch applied at rates as low as 750 kg/ha provided nearly 50% ground cover and reduced sediment movement by more than 50%. Higher application rates reduced sediment loss by up to 95%. Linear increases in PAM application rate (to 20 kg/ha) also reduced sediment loss. The efficacy of this practice decreases slightly with successive rainfall events, but still had significant benefit through four simulated rainfalls. Live barley biomass was also effective at reducing sediment and P movement, although high seeding rates are needed to overcome the lack of tillering in fall-planted barley. In general, runoff volume was not strongly influenced by any of these practices and most of the P loss was comprised of sediment-bound P. All three conservation practices are effective at reducing soil and nutrient loss in intensive potato systems.