Effectiveness and Efficacy of Conservation Options After Potato Harvest

Authors: Griffin, Timothy; Honeycutt, Charles

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2009
Publication Date: 6/29/2009
Citation: Griffin, T.S., Honeycutt, C.W. 2009. Effectiveness and Efficacy of Conservation Options After Potato Harvest. Journal of Environmental Quality. 38:1627-1635.

Interpretive Summary: Soil conservation can be challenging in potato production systems in the Northeast U.S.. These systems have frequent soil disturbance and do not return much residue to protect the soil. We used a rainfall simulator to look at straw mulching and the application of polyacrylamide (PAM) to reduce the movement of soil and phosphorus (P) during heavy rainfall. Increasing the amount of straw mulch dramatically reduced the amount of soil and P in runoff water. Mulch applied at rates as low as 500 lb/acre covered nearly 50% of the soil surface and reduced soil loss by more than 50%, and higher application rates reduced soil loss by up to 95%. Applying PAM at rates up to 20 lb/acre also reduced soil loss, but this practice became less effective with successive rainfall events. Potato growers and other farmers could use both of these conservation practices to reducing soil and nutrient losses, resulting in improved water quality.

Technical Abstract: 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 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 intensity of 70 mm per hr. Runoff amount, sediment concentration, and inorganic and sediment-bound P were measured for a 30 min period 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 more than 50%. Higher application rates reduced sediment loss by up to 95%, but contributed dissolved reactive P (DRP) to runoff water. Simulated rainfall to mulch-covered and bare soil under field conditions 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.