Modeling Alternatives to Reduce Dairy Farm and Watershed Nonpoint Source Pollution

Abstract

Management practices are available that may reduce sediment or phosphorus (P) loading to streams draining agricultural land. An evaluation of the long term effects of implementing one or more of these practices is needed. We used the Erosion Productivity Impact Calculator (EPIC) and Agricultural Non‐Point Source (AGNPS) models to evaluate 20 management practices for sediment and P yields from 4 ha fields in a 1272 ha watershed of dairy farms. Five crop sequences [continuous corn (Zea mays L.) CC(OA)AAA, CC(OA)AAAA, CCC(OA)AAA, and CCCAAA; 0, oat (Avena sativa L.); A, alfalfa (medicago sativa L.)] combined with either fall moldboard plowing (mFMP), chisel plow (mFCP), no‐till (mNT), or no‐till substituting anhydrous ammonia for manure (aNT), were imposed on a toposequence of three Alfisols. The normal sequence, 2 yr of corn, oat/alfalfa seeding, 3 yr of alfalfa with fall application of solid manure followed by moldboard plowing, CC(OA)AAA‐mFMP, served as reference. Scenarios were subjected to 42 yr of simulated local climate. Scenarios with 43% or less row crop and mNT on a 4% sloping soil reduced sediment yield from 24 to 47%, at edge of field, but increased total P yield from 158 to 338%, mostly as soluble P. The EPIC output parameters (soil loss ratio [C] for June, erodibility [K], Manning's n, and SCS curve number [CN]) served as inputs to the (AGNPS) model, a cell based single rainfall event model that simulates runoff, sediment, and P yields from a watershed. Crop sequences not exceeding 43% corn and mFCP or aNT reduced watershed sediment yield 13 to 41%, but increased total P yield by 44 to 113% as compared with CC(OA)AAA‐mFMP. Average annual costs were $11 ha−1 less for these sequences when compared with CC(OA)AAA‐mFMP.

Modelling Changes in Stream Water Quality Due to Climate Change in a Southern Ontario Watershed

“…Validation of the model for sediment and runoff was shown by Koelliker and Humber (1989) for fi ve watersheds in Kansas. Sugiharto et al (1994) applied the AGNPS model to evaluate 20 management practices dealing with sediment and phosphorus yields from four ha fi elds in a watershed dominated by dairy farms. Best management practices were evaluated for watersheds in southern Iowa (Tim et al, 1994) and coastal watersheds in South Carolina (Choi and Blood, 1999).…”

Evaluation of Epic for Assessing Crop Yield, Runoff, Sediment and Nutrient Losses From Watersheds With Poultry Litter Fertilization

“…EPIC has been applied throughout the U.S. and many other countries (Bernardo et al, 1993;Sugiharto et al, 1994;King et al, 1996;Potter et al, 1998;Brown and Rosenberg, 1999;Pierson et al, 2001;Bernardos et al, 2001;Rinaldi, 2001;Chung et al, 2002;Apezteguía et al, 2002). The model has been integrated into the Resources and Agricultural Policy System (RAPS) designed to evaluate the economic and environmental impacts of agricultural polices for the north central U.S. (Babcock et al, 1997).…”

Trade-off between water pollution prevention, agriculture profit, and farmer practice—an optimization methodology for discussion on land-use adjustment in China

“…Like other conventional methods, a number of best management practices (BMPs) have to be planned and their effectiveness has to be tested (Stewart et al 1975;US-NRC 1993;Sugiharto et al 1994;Correll 1996). Since this approach of NPS pollution prevention is based on studies on the watersheds in several developed countries, it mainly emphasizes the effectiveness of pollution control.…”