The Microbiome in Agroecosystems
To feed human populations worldwide, agricultural production has been tremendously increased in the last decades. The global population has increased from 3 to 7 billion people in the last 50 years and is assumed to increase further before leveling off at about 10 to 11 billion people. This immense population growth may at least require a doubling of global food production. To date, higher agricultural productivity has been obtained by modification of crops and their genetics, improvements of fertilization and irrigation regimes, and enhanced pest regulation. These strategies have led to substantial changes in land use with associated loss of biodiversity and soil erosion, as well as to pollution of aquatic and terrestrial habitats through leaching of nutrients and bio-accumulation of persistent pesticides. The impact of these strategies on ecosystem health are tremendous and sustainable production is becoming indispensable.￼Little is known about the effective sustainability of organic farming practices. Conservative use of fertilizer and pesticides in organic systems may lead to a decrease in yield that in turn may lead to an increased demand for agricultural land and the conversion of natural ecosystems into agriculture areas to maintain productivity. Thus, benefits emerging from organic farming with regards to reduced fertilizer and pesticide application, reduced energy input, and increased soil organic carbon, are confronted with the detrimental effect of yield loss and increase demands for land use. Increasing the efficiency in nutrient use, water use and pest control may be the only way to decrease the environmental impact of agricultural land use. Among those strategies, breeding of high-efficiency crops, use of cover crops and crop rotations, reduction of soil tillage, improved timing of fertilizer application, enhanced irrigation regimes, and investments in research and education may reduce fertilizer losses by leaching and decrease the amount of fertilizers required for high crop yields. However, the optimal balance of all these forces to obtain sustainable agricultural areas is not entirely understood yet.Proper stewardship of soil is the cornerstone of sustainable land use in agricultural systems. Soil serves as reservoir for many essential nutrients, provides structure essential for plant growth, efficiently detoxifies waste and filters water. At the system level, microbial metabolism drives the biogeochemical processes essential for soil fertility and plant growth. Thus, intact and functional soil microbial communities are key for the long-term sustainability and productivity of farming systems. However, our inadequate understanding of soil microbial communities and their metabolic activities limits our ability to manage agricultural systems for sustainability. Fertilization and pesticide regimes can substantially alter the microbial communities with potentially significant consequences for soil fertility and ecosystem health. I study the influence of different farming systems on the agricultural soil microbiome in order to elucidate how fertilization treatments, plant protection regimes and crop rotations select for specific microbial populations.