Sustainability assessment of cropping systems: A field-based approach on family farms. Application to maize cultivation in Southeast Asia.

Maize cropping has often become the only way for many family farmers in Southeast Asia to rapidly obtain a cash income. However, the intensification of maize-based cropping systems is raising concerns about its environmental sustainability. This study contributed to field-based approaches for ex post sustainability assessment of current cropping systems on farms and for the design of more sustainable prototypes, in conditions where the information required for estimating sustainability indicators are not readily available. A 3-year regional agronomic diagnosis was combined with a multicriteria assessment and a prototyping procedure. The latter aimed to increase the performances on the indicators that showed critical levels on current systems. A local diversity of maize fields in Laos was used to test the approach. We defined and used indicators representing farmers' socio-economic objectives and risks for the environment. Sustainability indicators were calculated using data extracted from farm surveys, direct measurements in fields managed by the farmers and crop modelling. Our analysis showed that the most frequent weaknesses in all current maize-based cropping systems were (i) low land and labour productivity, (ii) high susceptibility to weed infestation, (iii) high risk of herbicide leaching, (iv) risk of soil fertility depletion, (v) risk of soil erosion. None of the current cropping systems performed well simultaneously on both indicators of land/labour productivity and control of herbicide leaching. These sustainability issues mainly resulted from difficulties in mastering mechanised crop establishment. Taking the current cropping system as a starting point, prototypes with successful crop establishment thanks to well mastered mechanisation would significantly improve the following sustainability indicators: control of herbicide leaching (improved by 130–340%), yield (multiplied by 1.3–2.3), gross margin (multiplied by 1.3–2.2), weed control (improved by 180–430%) and labour productivity (multiplied by 1.4–3.4). However, it would increase erosion (erosion control divided by 1.6–7) and seasonal cash outflow would increase (multiplied by 1.1–2). Overall, improving crop establishment would increase sustainability (overall sustainability score multiplied by 1.1–1.6). Our results suggest that providing farmers with enhanced capacity to master crop establishment would not solve all sustainability issues of maize cultivation, but at least help avoid a catastrophic overuse of herbicides in that context. • A method to assess sustainability of cropping systems in data-scarce environments is proposed. • Our method is based on measurements in a network of farmers' fields. • We enlarged the focus of agronomic diagnosis paving the way to sustainability diagnosis. • In our case-study, sustainability increase seems within reach with only changes in crop establishment. [ABSTRACT FROM AUTHOR]