This is Chapter 8 in a new 2024 CRC Press book on soil and drought edited by Rattan Lal. The author suggests CA is increasingly endorsed as a type of Climate Smart Agriculture, contributing to both climate change adaptation and mitigation. The objective of this chapter is to describe and review the benefits of CA increasing water use efficiency in dryland agriculture where water is the most limiting factor and the impacts of SOM on soil hydrological properties and crop yields. Management of soil carbon is also central to maintaining soil health and ensuring global food security. The organic carbon content of soil is a key indicator of soil health that indicates the efficient functioning of many ecosystem processes.

This research from China divided the soil into three aggregate size classes (mega-aggregates), macro-aggregates, and micro-aggregates and evaluated the response of aggregate stability, SOC and microbial communities within aggregates to long-term conservation tillage, which consisted of two tillage methods (conventional tillage and no-tillage) and three nitrogen application rates (105, 180, and 210 kg N ha(-1). Under the NT treatment, the high nitrogen rate increased SOC within mega- and macro-aggregates but reduced the total amount of phospholipid fatty acids (PLFAs) within all aggregates. The paper describes the results for CT and NT with nitrogen rates. They conclude that overall, high nitrogen application under longterm no-tillage protects SOC within mega-aggregates by altering aggregate formation through the microbial communities, providing information that may be useful in developing management strategies to enhance carbon sequestration in agricultural soils.

This research used 16 S rRNA amplicon sequencing to investigate the diversity and composition of bacteria associated with two Collembola species of different life forms under four different tillage practices: (1) conventional moldboard plow tillage with no straw mulch (CT), (2) moldboard plow tillage with straw mulch (MT), (3) no-tillage with straw cover (NT) and (4) no-tillage with straw cover and crop rotation (NTR). Results showed that the NT treatments increased Collembola abundance and associated bacterial diversity but little affect on soil bacteria. MT and NTR significantly affected the composition and network structure of Collembola-associated bacteria. The authors recommend the no-tillage with straw mulch and rotation (NTR) as the most optimal strategy for conserving soil biodiversity.

The paper evaluates various methods of tillage, residue management and nitrogen application on wheat yield, water use efficiency (WUE) and nitrogen use efficiency NUE). Tillage consisted of CT and NT, with (R+) and without (R0) maize residue, and 3 N levels, 60,120 and 180 kgN/ha.Tillage and residue management influenced the grain and biomass yield of wheat. Over the two years, NT exhibited a 7% higher WUE compared to CT, but the change was insignificant. However, in years with lower rainfall, crop residue mulching had a significant positive impact on WUE, while in years with higher rainfall its effect on WUE was insignificant.

This article assesses the impact of different tillage types and fertilizer application on soil and plant nitrogen using a N15 isotope technique. NT was compared with CT with 3 nitrogen doses in Durum wheat. Results showed that  there was no significant difference between tillage types and nitrogen doses for grain and straw yields and grain total nitrogen. In contrast, the effect of both factors and their interaction were significant for straw total nitrogen. They also found that NUE in grain and straw under no-tillage was higher than under conventional tillage in all three nitrogen doses. These results show that soil conservation techniques such as no-tillage and the integrated application of nitrogen fertilizer can be a good strategy for reducing soil nitrogen losses.

This paper from Uzbekistan looked at soil productivity and yield of a legume based rotation comparing CT with NT in a saline soil in an arid area. CA consistently out yielded CT for wheat, millet, chickpea and maize over two years. The increased residue retention under NT facilitated soil porosity, structural stability, and water retention, thereby improving soil quality and organic matter content. Soil salinity decreased under NT compared  to CT, reducing salinity buildup. They concluded that the NT method with legume-based intensive cropping helps maintain soil health and crop yield leading to more sustainable land management of drylands.

This paper is based on two long-term experiments started in 2013 in Zimbabwe. There were 6 treatments: Conventional tillage (CT); CT plus rotation (CTR); No-tillage (NT); NT+ mulch (NTM); NT+ rotation (NTR); NT + mulch+rotation (NTMR). Maize was the main crop with treatments using rotation growing cowpea. SOC and soil bulk density (SBD) were taken from 9 depths from 0-100cm. Results show that SOC stocks were higher in NTM, NTR and NTMR treatments compared to NT and CT in the upper soil samples (0-5 and 0-10cm). NT alone had a small negative impact on upper SOC stocks. Cumulative SOC stocks were not significantly different between treatments in the whole 100cm soil profile. NTM enhances SOC stocks but only in the topsoil and showed the highest cumulative organic carbon inputs. Last, results showed thatat least 2 CA principles were needed to increase SOC stocks in these low-nitrogen-input cropping systems.

This article reports the results of evaluation of new wheat cultivars in on-farm conditions using different tillage systems. There were 7 wheat cultivars (3 bread wheat and 4 durum) and 3 tillage systems; conventional (CT), reduced (RT), and No-Till (NT) in two locations for 3 cropping seasons. Overall the CT treatment had the highest yield and NT the lowest. But maybe that was because there was no residue mulch or there were problems with the NT equipment or soil moisture at planting. NT needs a higher soil moisture at seeding that a CT soil. However, there were differences in yield between the different cultivars by tillage. Some cultivars had better yield under CT and others under NT. The experiment needs to look at cultivars by tillage with and without residue and plant the NT when the moisture is higher and not wait for the CT plots to be planted.

This article looks at humic acid (HA) quality and the clay-humus complex to provide information regarding soil carbon (C) and recalcitrant C under CA in a field experiment. No-till with and without residue was compared with conventional tillage without residue (CT) in a maize-wheat-pigeonpea system. Results showed that the NT+R treatment had more positive results than NT-R or CT in terms of humic acid quality and the clay-humus complex. NT+R also had higher yields than CT in both the cropping systems except in wheat crops in the M-W system. They conclude that ZT+R has the potential to enrich the organic carbon (C) quality in soil and increase the aromaticity of HA, leading to carbon stabilization in soils.

This a second paper from India that addresses the problem of surface residues by developing and using an attachment for the combine harvester. They developed a seeding attachment with a concave disc furrow opener that is attached to the combine that allows sowing of wheat at the same time rice is harvested. They evaluate the performance with 3 forward speeds, and three stubble heights in terms of wheat emergence, effective tillers, grain yield, fuel consumption, and the field capacity of the combine. The results showed that the total energy used for wheat crop establishment using the new seeding attachment was about 63% of the average energy demand from other methods.

This is another study of the impacts of CA but on permanent broad beds (PBB), narrow beds (PNB) and NT flat beds with residue retention on SOC protection within soil aggregates compared to conventionally tilled plots (CT). CA plots had a higher total SOC content than CT ones and improved soil physical properties. Plots under PBB + R, PNB + R and ZT + R had only ~11, 3% and 23% more SOC within silt + clay fraction, respectively, than CT plots (5.85 Mg ha−1). Thus, SOC stabilization within microaggregates inside macroaggregates was the major mechanism, and not the chemical stabilization within silt + clay, of C sequestration under CA. They conclude In this maize/cotton-wheat system that CA on beds or flat are viable options for carbon sequestration, water holding capacity and resistance to erosion.

This paper used a comprehensive database on the three main conservation agriculture practices (cover crops, diversified crop rotations, and no-till and/or reduced tillage (NT/RT)) to elucidate the effect of CA on N2O emissions and also identify the most important predictors of soil N20 emissions. Their analysis showed that NT/RT decreased soil N20 emissions compared to CT. The N20 reductions were w more common in humid climates and where the C level was less than 20g kg(-1). N20 emissions were variable using cover crops and different rotations. Cover crops were more likely to reduce soil N20 emissions in neutral soil pH and the lower C content listed above for tillage and N levels around 3g kg(-1). Diversified rotations tended in increase N20 emissions in temperate regions and neutral pH. They are able to describe the conditions where CA can contribute to mitigation of climate change.

This South Dakota study assessed the impact of tillage CT and NT); crop rotation: 2-year corn-soybean, 3-year corn-soybean-oat and 4-year corn-soybean-oat-wheat; cover crops (cover crop [CC] and no cover crop [NC]); and drainage (tile drainage [TD] and without drainage [ND]) on soil organic matter (SOM), bulk density, wet aggregate stability (WAS), and field-saturated hydraulic conductivity (Kfs). Soil samples were collected over 2 years from five depths and analyzed for SOM, bulk density, and WAS. NT increased soil bulk density, soil organic matter, and wet aggregate stability (WAS) for the 0- to 10-cm depth but decreased Kfs within the soil profile compared to CT. CC and tile drainage(TD) had minimal impact on SOM, bulk density, WAS, and Kfs.

This article uses a 5 year rice experiment in China using No-till (NT), Reduced till (RT) and conventional till (CT) to assess soil microbial necromass C (MC, including fungal and bacterial necromass C, FC, and BC) as well as soil bacterial and fungal community composition. At 0-10 cm, NT increased FC, BC, and MC but did not significantly alter the FC/BC and MC/SOC ratios. The increase rate of MC (NT vs. CT and RT) was higher than that of total SOC. The authors suggest that the composition of the microbial community may play a pivotal role in driving the accumulation of MC. Short-term NT in rice paddies resulted in increased levels of both MC and SOC. Notably, the rate of increase in MC exceeded that of SOC, suggesting the potential for SOC stabilization.

This paper from Nepal looks at the issue of crop field fragmentation  that farmers use to ensure irrigation and rainwater in rice and wheat growing areas. This requires lots of labor and reduces the area for planting crops. The paper looks at the possible use of laser land leveling (LLL) to overcome these problems. Obviously, smallholder farmers cannot own a laser leveler so the paper looks at using service providers to allow these smallholders to benefit from this technology. They found that farmers were willing to pay for LLL services. The paper goes on to discuss LLL in relation to farmers with higher land acreages and farmers with low irrigation access.

This article from Brazil looked at soil biological activity response to soil management and conservation practices. Large plots were used for 3 treatments: a) Non-Terraced catchment (NTC), cultivated using no-till (NTS) used by most farmers of the region, in which the agricultural operations are carried out in the direction of the slope and without terraces used; b) Best Management Practices (BMPs) were adopted in NTS with additional autumnal cultivation of cover crops, and also the direction of machine traffic was transverse to the slope direction; and c) Terraced catchment (TC), cultivated in NTS was associated with erosion control, using wide base, level terraces. Soil microbial properties were sampled in the top 10cm layer shortly after the summer crop harvest. Natural inoculum potential of arbuscular mycorrhizal fungi (AMF), respirometry, metabolic coefficient, acid phosphatase activity, and organic carbon and nitrogen in the microbial biomass were assessed. The results showed a greater potential for AMF inoculum in BMPs (b) and TC (c) systems.

This paper evaluated the impact of tillage on agronomic, physiological, and biochemical traits in canola in Morocco. There were 4 tillage systems; deep (DP) and chisel (CP) plowing, minimum tillage (MT) and no-till (NT). Results showed that NT consistently exhibited superior performance with the highest seed yield and oil content. In contrast, DP faced challenges during a severe drought in that resulted in no production. They concluded that no-till can be recommended for canola cultivation in Morocco as well as in other North-African and Mediterranean countries with similar climate and soil conditions.

This field experiment from India looked at the effects of nitrogen (N) and residual sulphur (S) on maize in the 11th year of a long term CA maize-mustard system. CA (3) was NT maize with mustard residue + brown manuring (not described in the paper) and NT mustard with maize residue had the highest maize height and dry weight than other CA and CT treatments except CA (4) that had mungbean residue for the NT maize that had similar height and dry weight. The 100% and 75% recommended dose of N gave comparable grain yield under all CA-based treatments, indicating a saving of 25% N compared to CT. The sulphur applied to mustard did not show any residual effect on maize grain. They conclude that the CA framework enhances yield and incomein a maize-mustard system.

This interesting paper looks at Agriculture as both the main cause of anthropogenic global warming and at the same time impacted by climate change. It is also a solution for climate change through sequestration of soil organic carbon (SOC) facilitated by CA. This paper assesses the actual capabilities of CA to mitigate climate change but also be a profitable management system for farmers. The paper elicits the economic profitability and environmental performance of CA from a field experiment in Northern Italy.

This article reviews the question "Can farmers in sub-Saharan Africa (SSA) increase yields and make food more available without using mineral fertilizer?" Supporters that say yes suggest that the principles of agroecology that rely on recycling, better efficiency and practices such as use of legumes and manure will mean more chemical fertilizer is not needed to raise yields. But this paper after extensive literature review suggests that more mineral fertilizer is needed in SSA. They put forward 5 reasons for this conclusion and can be found in this paper. They conclude there is a critical need for more mineral fertilizer in combination with the use of agroecological practices backed up by adequate policy support.

With the residue not being burnt and left as a mulch, there is a need for equipment to plant into this residue. This paper This paper describes a automatic control strip-till piece of equipment to overcome this problem in maize in China. The equipment has an air spring and electric linear actuator that controls the plowing depth straw width control that improves the stability of the equipment. Field tests showed that the straw clearing and soil crushing rates, tillage depth and breadth stability were above 90%. They conclude that the designed equipment would allow conservation tillage  for maize farmers.

This article conducted a systematic review to compare crop yield from cropland with conventional management versus different CA practices, specifically reduced- or no-tillage, agroforestry, organic farming and cover crops. The data was first analyzed for different climate regions, soil textures, and cash crop types followed by how yield responses correlated with soil properties change under different CA practices. Their results showed that CA practices provided a mean increase of yield of 12% primarily with maize that had a 41% yield increase. Agroforestry increased crop yield by 66% and cover cropping by 11%, likely due to increases in soil water content and nutrient availability and decreases in erosion and surface runoff. However, other agricultural systems showed no significant increase after CA compared with conventional row cropping practices.