Conservation agriculture (CA) is one of the agroecological practices aiming at improving and sustaining agricultural productivity, profits and food security while preserving and enhancing the resource base and environment (Castella & Kibler, 2015). CA is characterized by three main principles: (1) minimum or no soil tillage, (2) permanent organic soil cover (crop residues or cover crops), and (3) crop species diversification (intercropping, crop rotation, etc.). These principles trigger ecological processes, a continuous flow of fresh organic matter, driving soil biota diversity and functionality, soil structure and soil organic C and N accumulation contributing to the resilience of the system (Séguy et al., 2006). Based on these principles, CA presents an innovative practice in agricultural production systems, contributing to enhancing biodiversity, land resources management and soil resource conservation, and leading to greater ability and livelihood of farmers and communities to be resilient to climate change impacts and economic shocks. Practical evidences have shown that CA-based cropping practices have improved land and labor productivity when appropriate-scale mechanization is available, and have had positive impacts on soil biological functioning, soil organic accumulation, water infiltration rate and nutrient cycling (Hok et al., 2015; Pheap, Lefèvre et al., 2019). 

CA covers approximately 180 million hectares (11% of the worldwide arable land) with the following area per continent: South America million hectares, North America 63 million hectares, Africa 1.5 million hectares, Europe 3.6 million hectares, Russia and Ukraine 5.7 million hectares, Asia 14 million hectares, Australia and New Zealand 23 million hectares. Major increases in the adoption of CA cropping systems are expected across Asia in the coming decades. In many Asian countries, CA is being mainstreamed in national agricultural development programs or backed by suitable policies and institutional support (Kassam et al., 2019).

On the other hand, sustainable intensification (SI) is an approach widely known as a “combination of agricultural processes in which production is maintained or increased while environmental outcomes are enhanced” (Pretty, 2018). The main goal of SI is to make better use of natural and human resources such as land, water, biodiversity, knowledge and technologies, so that cultivation of more land and loss of natural capital could be avoided. SI is based on three non-linear stages in transition towards sustainability: (1) Efficiency making better use of on-farm and imported resources, (2) Substitution focusing on the replacement of technologies and practices and (3) Redesign (transformative) harnessing ecological processes and connecting scales (field to markets). There has been evidence that farmers who adopt various SI approaches could increase productivity by either applying new and improved varieties with changes of agronomic-agroecological management, or diversifying farms into a range of crops, livestock or fish in addition to the existing cropping. In other words, SI systems should generate more food, fiber and fodder, on a sustainable basis with minimal use of additional land while protecting biodiversity and ecological systems, which is central to the global efforts in improving food security. 

Agroecology is a holistic approach that aims at addressing complex and interrelated challenges of poverty, malnutrition, environmental degradation and climate change (Altieri, 2002). Agroecology intends to move towards integrated sustainable development in its three dimensions – environmental, social and economic – and places the co-generation and sharing of knowledge as the cornerstone of the intervention, combining science, traditional and practical knowledge of smallholder farmers and others stakeholders (FAO, 2018). Agroecology is based on territorial approach combining ecological, economic and social dimensions. Agroecology values biological diversity and natural processes (i.e. the cycles of nitrogen, carbon, and water), seeking to improve food yields for balanced nutrition, strengthen fair markets for their produce, enhance healthy ecosystems, and build on local and science-based knowledge. Agroecology relies on five main principles: (1) recycling (organic matter and nutrient cycling), (2) minimizing losses of energy, water, nutrients and genetic resources, (3) diversity of species and genetic resources (over time and space at the field and landscape level), (4) regulation, and (5) synergies promoting key ecological processes and services). 

These three approaches are considered to share common biophysical principles and allow combining a diversity of scales from soil, field, farm, landscape, territory (including value-chain), the engagement of farmer communities, agricultural cooperatives, local private sector, agri-business and consumers to deliver both productivity improvements and benefits to ecosystem services. Therefore, the redesign of agroecosystems is a continuing effort of transformation and improvement. Conducive policies to sustainably manage soil fertility while maintaining productivity and to produce safe and nutritive-density food is of paramount importance to reach these goals.

Table 1: Summary of CA, SI and Agroecological Approaches