Impact of crop rotations on optimal selection of conservation practices for water quality protection

Abstract

This research integrates modern multiobjective optimization tools, water quality modeling capability, and data on costs of implementing conservation practices to develop a tradeoff frontier of cost-efficient nonpoint source pollution reduction solutions, which can be used to derive the watershed-level pollution abatement cost curve. Farmers' decisions, both on the intensive and the extensive margin, are likely to affect the shape of the tradeoff frontier as well as the mix of conservation practices selected for achievement of given nutrient reduction goals. In this paper, we wish to explore the consequences of changes in the cropping practices on the intensive margin and changes in the amount of cropland on the extensive margin on the baseline water quality as well as the shape of the tradeoff frontier and the mix of conservation practices. An empirical application focuses on a typical Midwestern agricultural watershed, Squaw Creek watershed in central Iowa. Using detailed crop production budgets, we follow Secchi and Babcock (2007) to demonstrate an alternative land-use scenario, which could arise from recently observed changes in crop prices and production costs. We find that the change in cropping practices effects direct changes in the shape of the tradeoff frontier and the mix and location of conservation practices selected to achieve particular nutrient loading reductions. In particular, we find that a potential shift to more corn (Zea mays L.)-intensive crop rotations and an increase in the amount of cropland in the watershed may lead to increased loadings of both nitrate and phosphorus and that additional conservation investments are required to maintain water quality gains achieved under the baseline (historic) cropping practices. In terms of conservation practices selected, the optimal placement of terraces appears robust to the changes in crop rotations and amount of cropland in the alternative land-use scenario.

A Multi-Objective Approach to Evaluate the Economic and Environmental Impacts of Alternative Water and Nutrient Management Strategies in Africa

“…This type of approach has great potential for addressing problems in managing conflicting objectives (Ines et al, 2006;Bryan and Crossman, 2008;Higgins et al, 2008;Sadeghi et al, 2009;Meyer et al, 2009;Whittaker et al, 2009;Latinopoulos, 2009). Several authors have combined the use of biophysical and multi-objective programming models (Fernandez-Santos et al, 1993;Rabotyagov et al, 2010;Panagopoulos et al, 2012;Panagopoulos et al, 2013). Pandey and Hardaker (1995) provide an overview of the usefulness of bio-economic modelling for studying the interaction between farm management practices and economic criteria to analyse sustainability of farming systems.…”

USDA water quality projects and the National Institute of Food and Agriculture Conservation Effects Assessment Project watershed studies

“…In the paper "Impact of crop rotations on optimalselection of conservation practices for water quality protection" Rabotyagov et al (2010) explore the relationship between conservation practice costs and effectiveness, with land use practices and changes. Researchers used detailed crop production budgets, water quality models, and optimization tools (evolutionary algorithms-a class of stochastic optimization methods) to determine a watershed-level pollution abatement cost curves with land use changes.…”

Spatial Multiobjective Optimization of Agricultural Conservation Practices using a SWAT Model and an Evolutionary Algorithm

“…The optimization objectives in this case are to minimize nonpoint-source pollution in the watershed, simultaneously minimizing the cost of conservation practices. A recent and expanding set of research is attempting to use similar methods and integrates water quality models with broadly defined evolutionary optimization methods 3,4,9,10,[13][14][15][17][18][19]22,23,25 . In this application, we demonstrate a program which follows Rabotyagov et al's approach and integrates a modern and commonly used SWAT water quality model 7 with a multiobjective evolutionary algorithm SPEA2 26 , and user-specified set of conservation practices and their costs to search for the complete tradeoff frontiers between costs of conservation practices and userspecified water quality objectives.…”