Soil carbon declined from 55 to 19% and microbial biomass by up to 50% for the different treatments over the 4-year period. Microbial biomass was also strongly correlated with SOC. Hence, this study provided a unique opportunity to evaluate if different microbial taxa were more sensitive to this major carbon resource shift and to determine if crop and/or management practice altered the microbial community over the relatively short time period. We used pyrosequencing of the SSU rRNA gene to determine community structure as it provides sufficient information depth so that community responses could be quantified under the contrasting soil management schemes.After four years, microbial communities in Ghanaian soil responded to the different managements with detectable changes in their diversity and composition. The overall microbial community diversity was higher for all agricultural managements than in the elephant grass eshrub dominated unmanaged plot . Bacterial groups that were responsive to particular treatments were additions to the endogenous community found in Eu. These groups are likely part of the “rare biosphere” in the Eu community but respond to the new selection provided by the new managements. Physical disturbance of the soil under these managements due to plowing, planting, and burning of fallow plants may induce more community dynamics, including resource competition. In terms of species richness, the lowest diversity was found in BF, which was likely due to very low carbon inputs. Even though fertilizer application led to the highest carbon input due to organic residue deposition , microbial diversity was relatively lower in the EfM plot, both in terms of richness and evenness. This is likely due to the higher nutrient availability, driving a less metabolically diverse r-selected community. Conversely, the PM management sequestered some carbon as woody biomass derived from high lignin content in pigeon pea. providing more aromatic residues and slower nutrient release, as well as added N from its N2-fixation capabilities. Based on these results,black plastic planting pots and supported by previous T-RFLP analysis , pigeon pea appears to be an appropriate cover crop for the fallow period in tropical agricultural systems by fostering a diverse microbial community while also maintaining SOC and supplying nitrogen. Soil microbial community structure and specific taxa distributions were found to be most affected by SOC. Sequestered carbon appeared to largely influence Actinobacteria and Acidobacteria abundance in soil.

The low-SOC BF treatment consistently exhibited the highest abundance of Actinobacteria, mostly of the subclass Rubrobacteridae. Previously isolated bacteria within this subclass, Rubrobacter and Thermoleophilum , are resistant to radiation and are found primarily in arid soil, which is consistent with the harsh exposed soil condition due to the meager summer maize crops in last two experimental years . It does not appear that all Acidobacteria groups uniformly respond to the same environmental variables, especially SOC. This is not unexpected for this very large, diverse and understudied phylum. Acidobacteria Gp4 and Gp6 were present in higher abundances in the nutrient-enriched plots than Acidobacteria Gp1 and Gp7 , even though Acidobacteria are thought to be oligotrophs. Network analysis also supported a positive correlation between SOC and modules containing Acidobacteria Gp4 and Gp6. Previously, the abundance of Acidobacteria groups was correlated to soil pH , with Acidobacteria Gp1 and Gp3 abundance largely positively correlated to acidity while Gp4, Gp5, Gp6, and Gp7 correlated to alkalinity when soils within the ranges of 4.5e8.3 were tested . Also, wheate soybean rotation was associated with the higher Acidobacteria Gp4 abundance than continuous wheat management while Gp1 abundance was the opposite . This is also explained by a difference in soil pH of different crop rotations: wheate soybean rotation and continuous wheat management . However, our soils were within pH 6e6.9 ; as such, pH does not appear to be a significant factor in this study. Our soil exhibits lower SOC than the general range of global SOC, a narrower pH range and no cold or freezing stresses. Thus, the abundance of Acidobacteria groups in our study can provide insight into understanding the ecophysiology of the Acidobacteria phylum in low SOC and near neutral pH environments. Burning of residues produces measured soil temperatures in topical soils of 200e800 ” C at 0.5 cm and 100e200 ” C at 2.5 cm depths . Soil temperatures of 120 ” C and 250 ” C have been shown to be lethal to 34e80% and 85e99%, respectively, of the microbial biomass . Although temperature was not measured in this study, the higher proportion of Bacillales, especially genera Bacillus and Sporosarcina, in the burned plots was notable. It may be due to the heat resistance of these spore-forming bacteria. Sporosarcina spp. not only tolerates high temperature, but also grows at 50 ” C .

Our core samples were taken over the top 18.5 cm so the effect of burning was probably muted by the populations at the lower depths unaffected by temperature. The fact that we could see any effect, however, suggests that burning was selective on the resulting community. Carbon is the key resource supporting most terrestrial microbial communities. Its decline due to cultivated agriculture in temperate region soils is much slower. In tropical systems, however, the continuously warmer temperatures and where moisture is suffi- cient and perhaps cultivation occurs, there is a faster loss of organic carbon. In this study the soil carbon declined by up to 55% in only 4 years. This loss plus the lack of significant annual resupply of available carbon by plants especially in years 3 and 4 of the bare fallow treatment would be expected to be a major perturbation to the microbial community, and did show a loss of 50% of the microbial biomass . We found a significant but not dramatic change in the microbial community structure, suggesting that the community as a whole is rather resistant to this even more extreme decline in its food sources.Because of the employment opportunities and economic multipliers it creates, especially during the early stages of development, agriculture has long been at the center of discussions about poverty reduction and economic development . Increasingly, so are its related up- and down-stream activities in input supply, food logistics, food processing, retail, and food services, which, together with agriculture, make up the broader agri-food system . The AFS remains a major employer, particularly in poorer countries and for the poorer segments of society . Much hope is vested in the AFS to create badly needed jobs for youth in Africa, as well as for vulnerable populations and people in lagging regions elsewhere in the world . In contrast, employment in the AFS has dropped to only 10 percent of the labor force in high income countries, where the majority of AFS jobs are now off-farm in food processing and services. There, the domestic workforce has shifted out of the AFS. New digital technologies are enabling the automation of some historically labor-intensive agricultural tasks and providing an alternative to domestic labor substitution through international migration. COVID-19 will likely reinforce these trends. Given these developments, what role will the AFS play in the future of inclusive job creation across different countries worldwide? At the early stages of development, employment in the AFS largely coincides with employment in farming.

A large share of the population lives in rural areas and engages in subsistence production. Food supply chains are short and, for the most part, local. As countries develop, however, populations urbanize and food supply chains become longer. The income elasticity of demand for food declines, agriculture’s role as employer diminishes ,drainage pot and the farm workforce becomes older, more wage-oriented, and more immigrant.1 Urban consumers, and those with rising incomes, demand foods that are more protein- and nutrient-rich, processed, and convenient to consume. This change in demand provides some scope for agriculture related job creation beyond the farm, particularly in food processing and services. While these changes occur, jobs on the farm typically become more remunerative and competitive with jobs off the farm even though they dramatically shrink in terms of share and number.2 These dynamics, driven importantly by food demand behavior, have been observed across countries throughout history. They are broadly known as the structural transformation and the agricultural/dietary transformation . Often, these transformations are accompanied by deeply wrought societal change in response to growing rural-urban income divides and ineffective policy responses, including agricultural protectionism, especially when investment in rural public goods and inclusive food value chain development lags behind . Technological revolutions further shape these dynamics . Examples include steam power, railways and tractors in the 19th century, and electricity and cold storage in the 20th century. The current century is witnessing a rapidly unfolding digital revolution , with another revolution in energy just around the corner . These technological advancements of the 21st century and the associated business and product innovations are affecting structural and agricultural transformations across the globe. They have the potential to profoundly alter the global organization of the food system, as well as labor and skill demands. They dramatically reduce transaction costs in input and output markets, change economies of scale, and modify the optimal capital/labor mix in agricultural production, processing, and marketing. Because some agricultural tasks are arguably more automatable than those in industry and services , automation could accelerate the exit of labor out of agriculture in developing countries and transform farms and food processing firms in the developed world. A future with robots in the fields and packing plants, together with technology-savvy farm workers to complement new technological solutions in specific commodities and tasks, already is taking shape. Solar driven water pumps , cold storage, and agro-processing equipment are also beginning to spread in rural India and East Africa, accelerating the transition away from subsistence production . Historically, during this process of structural and agricultural transformation, societies typically evolved from having a surplus to a shortage of domestic farm labor. Inefficient land markets and sluggish food value chain development slowed farm consolidation and diversification, and social protection for the self employed remained limited.

As a result, farm incomes have struggled to keep up with more secure and faster-growing incomes off the farm. Domestic workers shifted from the primary sector to the secondary and tertiary. More often than not, in developed countries farm labor shortages have been filled largely by foreign agricultural wage workers, especially for difficult-to-automate tasks like harvesting fresh fruits and vegetables. Migrant-sending households in low-income countries benefited through remittances. However, with anti-immigration sentiments flying high in migrant-destination countries, the structural transformation unfolding in migrant-source countries, and technology increasingly offering alternatives to hired labor everywhere, opportunities to close income gaps across countries through legal farm labor migration may be narrowing . The shift in policy dialogue away from immigration solutions to farm labor problems coexists with a bifurcating global demographic. Many developing countries, especially in Sub-Saharan Africa, struggle to provide employment for their young, rapidly-expanding populations, presenting a missed opportunity for development from the so-called “demographic dividend” , including through international migration. Agricultural trade is similarly challenged in its role to help address global imbalances in farm labor, partly because of its purported contribution to global warming. The domestic and global forces of structural transformation and food demand behavior, the new technological revolution and associated business innovation, and the deceleration of agricultural trade and labor migration provide much of the socioeconomic backdrop against which the future of work in the AFS unfolds across countries. These transformations are further affected by the recent COVID-19 pandemic. It already has set back income growth . In the long run, the pandemic will reinforce existing trends in AFS automation and digitization and decrease reliance upon agricultural labor migration and trade, especially in the developed world. The pandemic has also exposed vulnerabilities in supply chains, as some countries experienced difficulty securing supplies of strategic goods and risks ushering in a new wave of protectionism .How countries address these, and related, challenges will shape the extent to which the AFS can continue its historically crucial role in reducing poverty and fostering shared prosperity by raising smallholder incomes and creating employment opportunities for young, expanding work forces. We argue that a policy and business environment supportive of inclusive agricultural value chain development will be a critical component of the solution. Adequate competition policies to address the challenge of rising power concentration within the AFS need to be part of the solution, as does the provision of broad access to digital infrastructure.