Since 2008/2009, conservation agriculture (CA) cropland area has been expanding globally at an annual rate of more than 10 M ha per year. In 2015/2016, the total CA cropland area was 180.4 M ha, corresponding to 12.5% of global cropland area. In 2018/2019, the total cropland area was 205.4 M ha, corresponding to 14.7% of global cropland area. The spread of CA has been expanding in Asia, Africa, and Europe in recent years because farmers are becoming better organized in working together and networking. More attention and resources are being allocated by stakeholders towards supporting farmers to adopt CA and in generating new knowledge to improve their performance. Globally, expansion of CA remains largely farmer-driven and has become a multi-stakeholder movement comprising formal and informal CA networks at national and international levels involving individuals and institutions in the public, private, and civil sectors. Several lessons from the global spread of CA are elaborated responding to the questions: (i) Why are the three interlinked CA principles universally applicable? (ii) Why does CA work sustainably and optimally? (iii) Why does CA deliver ecosystem services? (iv) Why is CA a valid alternative agricultural paradigm for sustainable development? (v) What are the sufficient conditions for scaling and mainstreaming CA?

Land degradation and soil fertility deterioration are two of the main causes of agricultural production stagnation and decline in many parts of the world. The model of crop production based on mechanical soil tillage and exposed soils is typically accompanied by negative effects on the natural resource base of the farming environment, which can be so serious that they jeopardize agricultural productive potential in the future. This form of agriculture is destructive to soil health and accelerates the loss of soil by increasing its mineralization and erosion rates. Conservation agriculture, a system avoiding or minimizing soil mechanical disturbance (no-tillage) combined with soil cover and crop diversification, is considered a sustainable agro-ecological approach to resource-conserving agricultural production. A major objective of tillage is supposed to be weed control, and it does not require very specific knowledge because soil inversion controls (at least temporarily) most weeds mechanically (i.e., by way of burying them). However, repeated ploughing only changes the weed population, but does not control weeds in the long term. The same applies to the mechanical uprooting of weeds. While in the short term some tillage operations can control weeds on farms, tillage systems can increase and propagate weeds off-farm. The absence of tillage, under conservation agriculture, requires other measures of weed control. One of the ways in which this is realized is through herbicide application. However, environmental concerns, herbicide resistance and access to appropriate agro-chemicals on the part of resource-poor farmers, highlight the need for alternative weed control strategies that are effective and accessible for smallholders adopting conservation agriculture. Farmers in semi-arid regions contend with the additional challenge of low biomass production and, often, competition with livestock enterprises, which limit the potential weed-suppressing benefits of mulch and living cover crops. This paper reviews the applicability and efficacy of various mechanical, biological and integrated weed management strategies for the effective and sustainable management of weeds in smallholder conservation agriculture systems, including the role of appropriate equipment and prerequisites for smallholders within a sustainable intensification scenario.

The challenge to eradicate hunger and establish food security across all its four pillars (availability, accessibility, health and safety, and continuity) is ongoing. The actual situation in global food production leads most of the attention to improving accessibility and safety of food, particularly to vulnerable populations. However, in view of the growth in demand, which includes changes in preferences for example towards food of animal origin, availability and continuity will play larger roles in future. Food production needs to increase over the coming decades at challenging rates, while facing problems of degradation and reduced availability of natural resources for production such as soil and water, and facing increasing challenges from climate change. The actual trends in yield development suggest that a simple gradual improvement of production within the existing concepts will not provide a sustainable or feasible solution, and that more fundamental changes in the agricultural production paradigm are required to face these future challenges. The Sustainable Intensification represents such a change in paradigm in which high production levels are combined with sustainability. The concept of sustainable intensification, the rationale for it and its functional elements, represented by Conservation Agriculture, are presented in this paper.

Conservation Agriculture (CA) and the System of Rice Intensification (SRI) are both agroecologically-oriented production systems that support more productive, sustainable, and resource-conserving farming, with synergies arising from their respective assemblages of reinforcing agronomic methods. This review article examines the compatibility between CA and SRI, considering examples of their being utilized in complementary ways. The application of CA principles enhances the growth, yield, and performance of the crops grown under the cropping system as well as the health and resilience of the whole ecosystem. SRI practices create more favorable conditions for the development of crop plants below- and above-ground, including conditions that can be enhanced by CA management. SRI practices such as reduced plant density m⁻² can elicit a better phenotypic expression of the genetic potentials of crops grown with CA. For these two agronomic systems to converge at the field level, some of their respective practices for plant, soil, water, and nutrient management need to be modified or aligned. One such adaptation is to practice SRI in CA systems on permanent, no-till, mulch-covered raised beds, with rainfall or irrigation water in the furrows between the beds furnishing and controlling water and providing weed suppression and improved nutrient recycling. SRI rice cropping can benefit from the CA practices of no-tillage, mulch soil cover, and diversified cropping, both in paddies and on raised beds. Several examples have shown that this convergence of cropping systems is feasible for smallholding farmers as well as for larger-scale producers and also that SRI practices within a CA system are amenable to considerable mechanization. Further research and experimentation are needed to identify and assess appropriate practices for capitalizing upon their synergies.

Conservation Agriculture (CA) and the System of Rice Intensification (SRI) are both agroecologically-oriented production systems that support more productive, sustainable, and resource-conserving farming, with synergies arising from their respective assemblages of reinforcing agronomic methods. Application of CA principles enhances the growth, yield, and performance of the crops grown under the cropping system as well as the health and resilience of the whole ecosystem. SRI practices create more favorable conditions for the development of crop plants below- and above-ground, conditions that can be enhanced by CA management. SRI practices such as reduced plant density m-2 can elicit better phenotypic expression of the genetic potentials of crops grown with CA.. For these two agronomic systems to converge at field level, some of their respective practices for plant, soil, water, and nutrient management need to be modified or aligned. One such adaptation is to practice SRI in CA systems on permanent, no-till, mulch covered raised beds, with rainfall or irrigation water in the furrows between the beds furnishing and controlling water; and providing weed suppression and improved nutrient recycling. SRI rice cropping can benefit from the CA practices of no-tillage, soil mulch cover, and diversified cropping, both in paddies and on raised beds. Several examples have shown that this convergence of cropping systems is feasible for smallholding farmers as well as for larger-scale producers, and also that SRI practices within a CA system are amenable to considerable mechanization. This review article examines the compatibility between CA and SRI, considering examples of their being utilized in complementary ways. Further research and experimentation are needed to identify and assess appropriate practices for capitalizing upon their synergies.