Environmental Benefits of Improved Water and Nitrogen Management in Irrigated Sugar Cane: A Combined Crop Modelling and Life Cycle Assessment Approach

Abstract

AbstractThe application of irrigation water and nitrogen (N) fertilizer in excess of crop demand reduces profitability and has multiple detrimental impacts on the environment. N dynamics in agro‐ecosystems are extremely complex, and mechanistic crop models are most often required to quantify the impact of improved management practices on reducing fertilizer N losses. In this study, life cycle assessment (LCA) methodology and mechanistic modelling were used to quantify the environmental benefits of improved management of water and fertilizer N by sugar cane farmers in a case study in Pongola, South Africa. A baseline scenario, representing farmer intuition‐based irrigation scheduling management, and two additional scenarios in which water, and water and N were more rationally managed, were compared. Results show that improved water and N management can lead to a 20% reduction in non‐renewable energy consumption per functional unit (FU), with sustained or even increased yields. Total greenhouse gas (GHG) emissions can potentially be reduced by 25% through more efficient water and N management. Limiting the rates of fertilizer N applied, made possible by decreasing N leaching through improved irrigation scheduling, resulted in the highest reductions for both impact categories. While total water consumption was very similar between the scenarios, more efficient use of rainfall was achieved through accurate scheduling, reducing blue water requirements. Through the simultaneous consideration of multiple environmental impacts, combining mechanistic crop modelling and LCA shows potential to identify improved management practices as well as to establish environmental stewardship incentives. Copyright © 2015 John Wiley & Sons, Ltd.