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TECHNICAL REPORTS

Surface Water Quality

Effectiveness and Efficacy of Conservation Options after Potato Harvest

^a Friedman School of Nutrition Science and Policy, Tufts Univ., Boston MA 02111
^b USDA-ARS, New England Plant Soil and Water Lab., Orono ME 04469. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture

^* Corresponding author (timothy.griffin{at}tufts.edu).

Received for publication June 16, 2008. Soil erosion and phosphorus (P) runoff can be severe in potato production systems in the Northeast USA, 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 two conservation practices: straw mulching and application of polyacrylamide (PAM). In the greenhouse, a Nokomis sandy loam soil (fine-loamy, mixed, frigid Typic Haplorthods) was packed into 0.2 by 1.0 m boxes and subjected to four rainfall events at an intensity of 70 mm h^–1. Runoff amount, sediment concentration, and inorganic and sediment-bound P were measured for 30 min after initiation of runoff. Linear increases in straw mulch biomass (up to equivalent of 3000 kg ha^–1) resulted in exponential decreases in sediment and P loss. Mulch applied at rates as low as 600 kg ha^–1 provided nearly 50% ground cover and reduced sediment movement and sediment-bound P concentration and loss by >50%. Higher application rates reduced sediment loss by up to 95% but contributed dissolved reactive P (DRP) to runoff water. Field observations using simulated rainfall on mulch-covered and bare soil were consistent with greenhouse results. Linear increases in PAM application rate (to 20 kg ha^–1) also reduced sediment loss. The efficacy of this practice decreases slightly with successive rainfall events but still had significant benefit through four simulated rainfalls on soil packed into boxes. This was not the case in the field where the effect of PAM was limited to the first two rainfall events. 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. Both conservation practices are effective at reducing soil and nutrient loss in intensive potato systems.

Abbreviations: DRP, dissolved reactive phosphorus • PAM, polyacrylamide