Low-input cropping systems to reduce input dependency and environmental impacts in maize production: A multi-criteria assessment
Résumé
Intensification of cropping systems in recent decades has increased their productivity but affected air, soil and water quality. These harmful environmental impacts are exacerbated in Maize Monoculture (MM) and hasten the need for solutions to overcome the trade off between crop yield and environmental impacts. In a three-year cropping systems experiment, a conventional intensive maize monoculture (MMconv), with a winter bare fallow, deep soil tillage, non-limiting irrigation was compared to three Low Input Cropping Systems (LI-CS) designed as alternatives to the conventional system. They were managed with decision-rules implemented to reach specific objectives of input reduction. The LI-CS designed with Integrated Weed Management (IWM) techniques and other sustainable cropping practices, were:(i) MMLI-an IWM Low Input MM; (ii) MMCT-a Conservation Tillage combined with cover crop MM; and (iii) Maize-MSW-an IWM maize grown in rotation with soybean and wheat. A comprehensive multi criteria assessment was carried out to quantify the agronomic, economic, social, and environmental performances of each system. A canonical discriminant analysis of performance metrics revealed large differences between the four systems. Yields were significantly higher in MMconv (11.0 Mg ha(-1)) and MMLI (10.3 Mg ha(-1)) than in Maize-MSW (8.6 Mg ha(-1)) and MMCT (7.8 Mg ha(-1)). MMCT had the largest weed infestation (density and biomass) despite the greatest use of herbicides. The Herbicide Treatment Frequency Index (HTFI), used to indicate differences in herbicide use, revealed that the MMLI (HTFI = 1.0) and Maize-MSW (1.1) halved the herbicide use as compared to the MMconv (2.1), despite having similar weed abundance levels. The LI-CS, especially MMCT, produced high biomass winter cover crops and then less nitrogen fertilization was required as compared to MMconv. Gross margins in the MMLI (1254 (sic) ha(-1)) and MMconv (1252 (sic) ha(-1)) were higher than the MMCT (637 (sic) ha(-1)) and Maize-MSW (928 (sic) ha(-1)). MMLI and MMconv had similar labour requirements. Water drainage, pesticide leaching, energy use, and estimated greenhouse gas emissions were higher in MMconv than in the LI-CS in most years. Results from this research show good potential for the MMLI to reduce the environmental impacts of MMconv while maintaining its economic and social performance.