1. Introduction
According to the Synthesis Report of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, the combined land and ocean globally averaged surface temperature increased by 0.85° over the period of 1880 to 2012 [
1]. Moreover, the increase in temperature has resulted in a robust increase in extreme weather event indices and a series of detrimental effects on natural systems [
2]. Climate change has a particularly significant impact on agricultural cultivation, due to its dependence on environmental factors. Weather and climate conditions such as droughts, flash floods, untimely rains, frosts, hail, and storms may cause a drop in agricultural production [
3]. Because of intensive farming using conventional tillage practices, food production has shown a significant growth, which has decreased the proportion of human suffering from hunger [
4]. Moreover, to this day, plowing and rotary tillage for land preparation is still commonly practiced by farmers. Such conventional tillage exacerbates soil disturbance and not only has a negative impact on soil health, but is also a bad option for increasing agricultural climate resilience.
2. Definitions of Climate Resilience and Conservation Tillage
Agriculture is one of the most sensitive sectors in response to climate change, and crop production is highly dependent on environmental factors. Therefore, the impact of climate change is particularly pronounced on crop production. Over recent years, climate change, mainly characterized by global warming, has changed the former environment of agricultural cultivation, coupled with the impact of extreme weather such as droughts, floods, and wind storms, which has brought about many impacts on crop production. Agriculture, as the foundation of human survival, has a significant influence on food security, industrial development, and social stability, and has received extensive attention due to its significant status. In response to the impact of climate change on agriculture, the concept of “climate resilience” has been introduced to help improve agriculture’s ability to cope with climate change.
Resilience is an umbrella term widely used in the academic community (
Table 1). The term resilience was first used in physics or engineering to refer to the ability of a material or building to resist stress and disruption and its ability to recover after deformation [
6]. The use of the term then gradually expanded to other disciplines. Holling [
7] introduced the concept of resilience to the ecosystem and proposed that resilience determines the persistence of relationships within a system. It is an indicator to measure the ability of these systems to absorb changes in state variables, driving variables, and parameters, and still persist, thus enriching the connotation of resilience. Walker [
8], from a social-ecological perspective, uses resilience to refer to the capacity of a system to absorb disturbances and reorganize when undergoing change in order to still retain essentially the same function, structure, identity, and feedbacks. When it comes to climate change, IPCC [
9] defined resilience as the “ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner.” Furthermore, especially in agriculture, Daniel EI Chami believes that resilience refers to the capacity of agricultural systems to respond to social, economic, and environmental changes via structural reorganization, in order to offset the impacts of future changes, and to engage in new opportunities, to ensure the continuity of agrosystems [
10].
In the context of climate challenges faced by agriculture, “climate resilience” refers to the ability to maintain agriculture’s core functions, including food security, soil and water conservation, and economic growth, while mitigating the impacts of climate change.
Conservation tillage is considered a potential way to improve the climate resilience of agriculture, so it is necessary to clarify exactly what conservation tillage entails. One of the most widely accepted definitions, from the Conservation Technology Information Centre (CTIC) [
11], is “any tillage and planting system that covers 30% or more of the soil surface with crop residue, after planting, to reduce soil erosion by water.” Based on specific circumstances, different countries and regions have developed their own definitions of conservation tillage. In accordance with the relevant documents issued by the Ministry of Agriculture and Rural Affairs of the People’s Republic of China, conservation tillage is a modern farming technology system that mainly involves residue incorporation and no/reduced tillage [
12]. The definition of conservation tillage by the United States Department of Agriculture is the same as that of the CTIC [
13]. In the United Kingdom (UK), conservation tillage is commonly called non-inversion tillage [
14]. The Department for Environment, Food, and Rural Affairs of the UK defines no-till farming by advising, “do not use cultivation machinery when you prepare the land for crops” [
15]. According to Eurostat, conservation tillage refers to arable land treated by conservation (low) tillage, which is a tillage practice or practice system which leaves plant residues (at least 30%) on the soil surface for erosion control and moisture conservation, normally by not inverting the soil [
16]. In Sub-Saharan Africa, soil nutrient depletion is an important constraint to sustainable agriculture development [
17]. As a potential way to mitigate climate change and achieve sustainable agricultural development, Sasakawa Global 2000, an international non-governmental organization, introduced conservation tillage to Sub-Saharan Africa, and the main technical points advocated by Sasakawa Global 2000 are the non-interference with the soil and the retention of mulch through the non-reversing of the soil [
18].
Above all, it is not difficult to see that crop residue and no-tillage are the core technologies of conservation tillage practice (Table 1). Therefore, it can be concluded here that conservation tillage should refer to the agricultural production system with more than 30% crop residue and no-tillage as the basic operations that can improve the ability of agriculture to maintain its core functions and mitigate the impacts of climate change.
Table 1. Technical points of conservation tillage practice in different countries and regions.
3. Conservation Tillage Can Improve Climate Resilience for Agriculture
Climate change is manifested by climate warming, abnormal precipitation, floods, droughts, wind storms, and other extreme weather, which cause a number of problems to agriculture, including disturbance to soil structure, loss of soil nutrients, decrease in biodiversity, plant diseases and pest outbreak, and low crop yield. The following subsections will explain how conservation tillage can function to enhance climate resilience by improving soil health from the aspect of water dynamics, soil physicochemical properties, and the eco-environment and by reducing greenhouse gases to mitigate the negative impact of climate change (Figure 1).
Figure 1. How Conservation Tillage Enhances Climate Resilience in Agriculture.
3.1. Conservation Tillage Can Improve the Hydrologic Function of Soil
Abnormal precipitation caused by climate change poses many problems for agriculture. Long-term precipitation or short-term but heavy precipitation often make it difficult for water to infiltrate, causing surface runoff, which eventually leads to flooding. Likewise, a long-term drought easily causes water shortages during the growing seasons of crops, leading to yield reduction. However, there are some cases to support the idea that conservation tillage has positive effects on soil hydrologic function. Xuan Yang [
19], using APSIM (Agricultural Production Systems sIMulator)-based simulation modelling and data collected in Xifeng, Gansu, China, found that conservation tillage has better performance for soil water storage, reducing soil evaporation and reducing evapotranspiration, while only plant transpiration is greater compared with conventional tillage. Qi Zhang [
20] conducted a long-term experiment in Ganjing, Heyang County, Shaanxi Province, China. This study showed that no-tillage reduced water consumption by 10.6% compared with conventional tillage over the entire growing season, and no-tillage could increase the water use efficiency as well. In particular, the water use efficiency of maize showed a significant improvement under a certain rainfall distribution showing poor rainfall in the jointing-tasseling stage and adequate rainfall in the grain filling-maturity stage. In addition, Juan li [
21] (Li et al. 2020) also found that conservation tillage can increase water use efficiency in comparison to traditional rotary tillage in an experiment that was carried out in Fuping County, Shaanxi Province. Ziyou Su [
22] found, in a six-year field experiment in Mengjin County, Luoyang City, Henan Province, China, that winter wheat with no tillage mulch had a greater amount of available water storage and higher water use efficiency. Conservation tillage is able to enhance water infiltration and reduce water evaporation, thus increasing soil water storage and improving water use efficiency, which gives agriculture higher resilience to cope with climate change.
3.2. Conservation Tillage Can Improve Soil Structure and Increase Soil Nutrients
Extreme weather is one of the manifestations of climate change, which has a negative impact on food production. Wind storms and heavy rain, for instance, tend to erode topsoil and rob soil of nutrients, thereby reducing crop yield. Fortunately, there is some evidence demonstrating that conservation tillage can mitigate the impact of climate change. Zhe Liu [
23] conducted the study in Shaanxi Province, China, and the results indicated that conservation tillage can promote the increase in soil organic matter and total nitrogen content, and can improve soil structure as well. In a five-year experiment conducted in Weinan City, Shaanxi Province, China, Juan Li [
21] observed that no-tillage was able to decrease soil bulk density. Rafiq Islam [
24] had a similar finding at the David Brandt farm, Carroll, Ohio. The findings confirmed that soil bulk density decreased significantly at a 0 to 30-cm depth under long-term no tillage. Furthermore, no-tillage can increase soil aggregate stability. In addition, conservation tillage can increase soil nutrients. Besides soil bulk density, the research of Juan Li [
21] also showed that continuous no-tillage increased soil organic carbon remarkably. R. Islam [
24] found that no-tillage not only increases soil total carbon, but also increases soil total nitrogen and particulate organic matter. V. Kushwa [
25] initiated a long-term experiment on a soybean-wheat cropping system and found that no tillage can increase soil organic carbon content and available phosphorus concentration. As for potassium, A. D. Karathanasis [
26] observed that exchangeable and soluble K increased by two or three times after long-term no-tillage in western and central Kentucky, USA. Conservation tillage is beneficial for improving the soil’s physical and chemical properties. No-tillage reduces soil disturbance so that the soil structure can be improved and soil aggregate stability can be enhanced as well. Conservation tillage can increase soil nutrients through stubble mulching. In this way, conservation tillage mitigates the impact of climate change on agriculture and increases climate resilience.
3.3. Conservation Tillage Can Reduce Greenhouse Gases to Mitigate Climate Change
The IPCC [
27] reported that 23% of total greenhouse gas emissions are derived from agriculture, forestry, and other land uses. The soil organic carbon pool is the largest organic carbon pool in terrestrial ecosystems [
28]. Conservation tillage is considered one of the most promising potential methods to achieve soil carbon sequestration and reduce greenhouse gas emissions. One method of carbon sequestration by conservation tillage is to enhance soil aggregate stability, and the other method is to place soil organic carbon in the sub-soil horizons and incorporate it with biomass. The cementation of primary particles, clay domains, and micro-aggregates is based on the formation of organo-mineral complexes. These complexes bind clay into aggregates, thereby immobilizing and sequestering the carbon [
29]. In terms of greenhouse gases emissions, numerous studies have shown that conservation tillage can reduce greenhouse gas emissions. Guo Zhang and Xiaoke Zhang [
30] reviewed some new publications that report the impact of conservation tillage on the emission of greenhouse gas, carbon sequestration, and the global warming potential of greenhouse gas in China. The results indicated that conservation tillage can reduce greenhouse gas emission by considering carbon sequestration. Jinfei Feng [
31] carried out a global meta-analysis based on 49 papers published before December 2016. The results showed that no-tillage significantly reduced the overall global warming potential of CH
4 and N
2O emissions by 6.6%, in comparison with conventional tillage. Yawen Huang [
32] used the data from 90 publications between 1900 and 2017 to obtain similar results showing that no-tillage can reduce 15.5% of CH
4 emissions, which can reduce the global warming potential, under specific conditions.
3.4. Conservation Tillage Can Improve the Soil’s Eco-Envirnment to Achieve Weed and Pest Control
Climate change caused a rise in land-based temperature, which has a considerable impact on weeds and soil organisms. Climate change greatly affects the abundance of soil organisms, including fungi and nematodes, and created a suitable environment for weed growth and favorable conditions for pest diseases. Conservation tillage has a positive impact on soil health, providing a good living environment for soil organisms and increasing the abundance and species diversity in soil organisms. Ziting Wang [
33] performed trials in Yangling, Shaanxi, China. The richness and diversity of soil bacteria were observed by the Shannon index and Simpson index. The results showed that conservation tillage increased the abundance of profitable functional bacteria species. Lijun Cai [
34] also found that conservation tillage can improve soil bacterial richness and diversity after conducting a long-term experiment in Jiamusi, Heilongjiang, China. In addition, the results demonstrated that conservation tillage has the best performance in increasing soil bacterial richness and diversity under 60% residue mulching. In Dehui County, Jilin Province, China, Shixiu Zhang [
35] compared the response of microflora and microfauna under different treatments. The results indicated that conservation tillage has a positive impact on the richness and abundance of bacteria.
The increase in the abundance and diversity of soil organisms, especially the natural enemies of pests, can achieve pests control. Meanwhile, conservation tillage can affect pathogens and predators to eliminate pests. The study that Shixiu Zhang [
35] conducted in Jilin Province, China, confirmed that conservation tillage can build a more functionally stable food web. According to the assessment of Robert P. Jaques [
36], entomopathogens have the potential to control pests. Ronald B. Hammond [
37] proposed that conservation tillage is a useful practice for soybean growers to prevent soil pests due to its direct impact on arthropods, and cover crops have the same use as well. Giovanni Tamburini [
38] conducted an experiment in Udine Province, northeast Italy. The study showed that conservation tillage is able to increase the abundance of predator communities and support higher aphid predation (rate). Compared with conventional tillage, conservation tillage can provide better biological pest control and can easily derive benefits from the practices.
Conservation tillage is sufficient to restrict the growth and propagation space of weeds to achieve their suppression. In an experiment on the Loess Plateau of China, YangMei [
39] found that no-tillage with stubble retention is an effective way to achieve weed control. Furthermore, conservation tillage can increase the population of predators of weed seed. R.H. Field [
40] conducted a trial in western Hungary, and the results suggested that conservation tillage might attract seed-eating birds. N.F. Quinn [
41] conducted a field experiment in Benton Harbor, Michigan, USA, and came to the conclusion that conservation tillage increases the number of predators of weed seeds, in particular spiders and ground beetles. No-tillage causes seeds accumulate on the surface and can reduce soil disturbance so there will be more predators, such as insects, rodents, and birds, and they could access seeds easier to increase the removal rates of weeds to realize weed control [
42]. Moreover, using crop rotation along with conservation tillage is encouraged, as crop rotation can increase biodiversity to achieve weed control [
43].
3.5. Conservation Tillage Can Stabilize and Increase Yield
A slight change in the climate will have a huge impact on food production and an adverse impact on crop yield. Conservation improves farming conditions from the aspect of hydrologic function, soil physicochemical properties, and the eco-environment, which stabilize and increase crop yield, enhance agriculture’s resistance to climate change, and maintain its core functions. Hongwen Li [
44] collected data from the Conservation Tillage Research Center, Chinese Ministry of Agriculture, and analyzed four regions: the northeast ridge tillage areas, the north dryland areas (the Loess Plateau and North China along the Great Wall), the northwest China region, and the north China plain region. The results showed that conservation tillage has a positive effect on crop yield in China. Juan Li [
21] conducted a test in Weinan City, Shaanxi Province. The results showed that crop yields had a significant improvement under conservation tillage. Rafiq Islam [
24] made a similar finding in Carroll, OH, USA. With long-term no-tillage, crop yields are increased or at least maintained. This finding is not isolated. Yawen Huang [
32] used meta-analysis to reveal that no-tillage is able to increase crop yields as well. The stable and increased crop yields ensure food security, provide raw materials for the industry, and help improve the economy. Thus, it is not hard to see that conservation tillage is able to help agriculture to maintain core functions.
This entry is adapted from the peer-reviewed paper 10.3390/agronomy12071575