Sustainable alternative to irrigated maize monoculture in a maize-dominated cropped area: Lessons learned from a system experiment

Abstract

Maize is the most-produced food crop in the world and is grown in intensive rotations or in monoculture (continuous maize) systems. As maize production has expanded massively across the world, many concerns have emerged about its local environmental and other global impacts. Agronomists have designed innovative cropping systems and assessed them using system experiments to make arable systems more sustainable. However, knowledge is still lacking on the sustainability of innovative cropping systems compared to highly intensive systems such as irrigated maize-based monoculture. Here, we present the assessment results of a nine-year system experiment in Alsace, France, developed to compare an innovative system based on a diversified rotation and innovative management practices (three-year rotation of maize/soybean/winter wheat (plus a cover crop) combined with reduced tillage) with a continuous maize reference system. The results cover a six-year assessment period following an initial three-year design period. Classic criteria, such as profitability, workload, pesticide use, fossil energy consumption and nitrate leaching, were assessed along with other less studied criteria, such as pesticide leaching risk, soil structure, soil chemical quality and soil biological activity. Sustainability - which includes environmental, social and economic dimensions - was assessed with the MASC 2.0 method. Overall sustainability was substantially enhanced in the innovative system (5 out of 7 sustainability classes) in comparison with the low level of the reference system (2 out of 7). This was due to a clear improvement in the environmental performance (from 2 out of 5 to 5 out of 5) while social performance was high in both systems (4 out of 5) and economic performance was low (2 out of 5) due to very low contribution to economic development. Nevertheless, the innovative system had a major drawback: lower profitability, especially when scenarios included high maize prices. Furthermore, herbicide use on maize was higher in the innovative system than in the reference one. Avenues for progress, such as encouraging stakeholder participation at the assessment stage or additional innovations such as multiple cropping, are suggested.

Keywords: Continuous maize; Indicators; Innovative cropping system; Pesticide; Reduced tillage; Sustainability.

Graphical abstract

Fig. 1

Overview of the innovative cropping system. False seed bed consists in preparing soil by one or more tillage in order to favor weed emergence to eliminate them at a young stage by another tillage.

Fig. 2

Main sustainability performance indicators of the reference (REF) and innovative (INN) cropping systems with detailed results by crop for the innovative system: (a) semi-net margin (euros/ha) for profitability, (b) workload (h/ha/y) for quality of life, (c) treatment frequency index for pesticide use, (d) pesticide transfer to groundwater indicator (0 = high risk, 10 = low risk) for water quality (pesticide), (e) nitrate leaching indicator (kg N–NO₃/ha) and f) energy consumption indicator (GJ/ha) for energy use. For (a) and (d), the higher the result, the better the assessment. For (b), (c), (e) and (f), the higher the result, the worse the assessment. The bars represent the range of variation of the INN system within a year for a given indicator. Results were analyzed in terms of the frequency with which the REF system was exceeded by the INN system.

Fig. 3

Description of soil structure for the reference and innovative systems. The method is detailed in Supplementary Material 4 and the colour code in Table S4. Green: (very) favorable, yellow: rather favorable, pale orange: slightly favorable, dark orange or red: unfavorable, brown: very unfavorable, blue: very unfavorable (hydromorphy). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Average semi-net margin (SMN) of the two systems, reference (REF) and innovative (INN) in function of price scenarios (Table S8).

Fig. 5

Synoptic presentation of the results from a multicriteria sustainability assessment with the MASC 2.0 model; (a) depicts the reference system and b) the innovative system.