Evaluation of Soil Ecosystem Services and Carbon Balance for Different Agroecosystems in Khorasan

Soil is the basic element for all ecosystem services which enhances different functions of ecosystems. It  provides  and  regulates  a  large  number  of  ecosystem  services and functions, and  plays  an  important  role  in  human health. Results of some experiments indicate a positive correlation between ecologically-based soil management with qualitative soil indices. Increase in soil organic matter enhances 10 different functions in agricultural ecosystems including biogeochemical cycle, nutrient returns, formation, and stability of soil aggregate, water purification and holding capacity, pH regulation, decreasing of erosion and finally crop growth improvement. In agricultural ecosystems, crop yield is notably dependent on soil properties. It has been stated that maintaining function and services of ecosystems could only be achieved by proper soil management. As a  consequence  of  land use, global warming, climate  change  and  conventional management,  soil  ecosystem services  are  being  drastically  degraded,  endangering food safety for coming generations. This  decreases  soil  ecosystem  services  and functions regulation  capacity  and  affects  the  sustainability  of  the  communities. It has been observed that no-tillage system which results in less soil disturbance and more accumulated crop residue has physical, chemical, and biological properties.

In order to evaluate soil ecosystem services based on different low and high input management in Khorasan province, the samples were taken from 10 sites by completely randomized design with four replications in 2014. The soil samples were collected from the depth of 0-30 cm in low input fields of saffron and orchards, high input wheat and corn fields, and annual research field (Agricultural Research Station, Ferdowsi University of Mashhad). Physical and chemical soil properties such as bulk density, organic carbon, total nitrogen, available P and K, pH, electrical conductivity (EC), and also biological criteria including microbial biomass carbon, dehydrogenase, and phosphatase enzyme activity were measured. Inputs used including chemical fertilizer, herbicide, insecticide, fungicide and also the acreage for wheat, tomato, alfalfa, corn, potato, sugar beet and canola were determined during the growing season of 2013-2014. After calculating greenhouse gases emission including CO2, N2O and CH4 based on emission indices, global warming potential was computed.

Results showed that type of ecosystem management affected all soil properties except the acidity (p ≤ 0.01). Management of high input and annual field crops (experimental) and also farmers’ fields caused reduction of organic carbon content, total nitrogen, available P, available K, EC, microbial biomass carbon, dehydrogenase and phosphatase enzyme activity and carbon sequestration in comparison with perennial field of saffron. However, bulk density was reduced. The highest and the lowest carbon contents were observed for orchard and annual experimental fields with 0.104 and 0.036 percent, respectively. The highest and the lowest sequestered carbon were observed for orchard and annual field crops (experimental) with 335.31 and 182.48 kg carbon per ha, respectively. Management of perennial fields (saffron), annual corn field and annual wheat field caused reduction of 12, 35 and 41 percent, respectively, in sequestered carbon compared with that for orchard fields. The highest global warming potential (GWP) was recorded for corn and potato with 3.69 ton CO2 equivalent per ha which was 53, 37, 16 and 12 percent higher than those for wheat, sugar beet, tomato and corn, respectively. The lowest GWP was recorded for canola with 1.35 ton CO2 equivalent per ha.

It can be concluded that reduction of chemical fertilizer and applying more organic inputs seem to be rational ecological approaches for sustainable management of the cropping ecosystem with a consequence of reduction in greenhouse gases and climate change mitigation. These sustainable practices are crucial to improve soil biodiversity. Using pesticides and herbicides has, however, a negative impact on biodiversity.