The Ability of Conservation Agriculture to Conserve Soil Organic Carbon and the Subsequent Impact on Soil Physical, Chemical, and Biological Properties and Yield

Abstract

Increases in human populations and the emerging challenges of climate change mean that the world's agricultural systems will need to produce more food in an environment that is increasingly variable and where the quality of our natural resource base is declining. One central measure of an agricultural system's capacity to do this is its ability to preserve soil organic carbon (SOC), due to the pivotal role that this plays in maintaining soil physical, chemical, and biological properties and ultimately yield. This narrative review examines the literature published worldwide over the last 30 years to assess the impact of one widely applied agricultural management system, conservation agriculture (CA), on its ability to maintain SOC and the subsequent impacts on soil physical, chemical and biological properties, and yield. While the effects of CA on SOC worldwide are variable, with both increases and decreases observed, in regions where soil and climatic conditions are favorable for biomass production and where the system does not negatively impact yield, then CA can lead to higher amounts of SOC relative to conventionally managed systems, particularly in the surface of the soil profile. Where greater SOC occurs, these are also often accompanied by improvements in soil structure, water infiltration and soil water storage, plant nutrient availability, microbial biomass and diversity, and yield. However, where CA is used in certain environments (e.g., cold, wet environments with poorly drained soils) or where the CA system has not been well-adapted to local conditions, taking into account the specific agronomic, social, and environmental challenges present, then it may not be a successful system of management. Farmers require access to a range of tools and resources to allow them to identify if the principles of CA are likely to lead be appropriate for their situation and well-designed, locally adapted systems to successfully overcome the agronomic, social and economic challenges that can be associated with its use.

High probability of yield gain through conservation agriculture in dry regions for major staple crops

“…In some other conditions, such as winter crop in cold region, we did notice that not covering the soil increased the chance of yield gain compared to continuous soil cover. We showed that winter wheat in northeast of China, NT has better performance than CA, this might be because the soil cover reduced the mean soil temperature 37 , which delayed the crop establishment and growth 4,38,39 . However, it is also reported that residue cover could decrease the rate of soil temperature change 37 , increase the minimum soil temperature in extreme cold conditions [40][41][42] , and provide a buffer layer that can increase the crop resistance to the increasing climate variability and the occurrence of extreme events 4 .…”

Effects of Long-Term (7 Years) Adoption of Conservation Agriculture and Nutrient Management Practices on the Soil Properties, System Crop and Water Productivity and Farm Economics of a Maize–Chickpea Rotation 

“…After seven years', the ZTFB and PNB with residues improved the OC content by 18-20% and total OC stock by 15-16% (0.0-0.10 m depth) than the CT. This would be associated with a better physical protection of particulate organic matter, greater amount of C-residues remain on the soil surface coupled with lesser turnover of macro-aggregates as well as minimal contact between residue and soil 48 . Perhaps, extensive tillage reduces OC, as it breaks open the previously protected SOM leading to the increased microbial decay 49,50 , as observed under the CT system.…”

The impact of climate change on the productivity of conservation agriculture

“…We also show that there is higher chance of yield gain from CA under dryer conditions, compared to wetter environments [5][6][7]18 . This is likely due to CA improving soil aggregate stability via crop residue returns to soils, which reduces soil evaporation and surface runoff, and maintains a higher level of soil moisture content compared to CT [19][20][21][22][23][24][25][26][27] . This competitive advantage of CA comes into play for dryer climate conditions [28][29][30][31][32][33] , but does not apply in wetter and cooler environment (S2a-c, S2f-i) where the soil evaporation is less intense.…”