Changes in Soil organic carbon and total nitrogen following long-term grazing exclusion in Saral grasslands, Kurdistan (Iran)

Abstract

Abstract Background and aims: Land use change favouring agriculture is considered a global threat as it interrupts ecosystem services of grasslands. However, exclosure from grazing has been widely known as effective in maintaining or even restoring grasslands. This study examined the impacts of long-term (45 years) exclosure, heavy grazing and rainfed wheat farming on soil organic carbon (SOC) and total nitrogen (TN) in the cold semi-arid grasslands of Saral Agricultural and Natural Resources Research Station, Kurdistan, Iran. Methods: In this investigation, 90 soil samples were taken from 0-20 cm depth within an area of 0.5 hectare for each land use (exclosure, heavy grazing, wheat farming). Samples were collected in the four non-consecutive years of 2009, 2013, 2017 and 2021. The Walkley-Black and Kjeldahl methods were used to measure SOC and TN respectively. Results: Results showed that value of SOC differed significantly among different land uses (P<0.01). In the studied years, SOC in the excluded site in 2021 had the highest level with 34,787 kg/ha, while the grazed site recorded the lowest SOC with 26,342 kg/ha in the same year. TN was also the highest at 0.130 percent in the excluded area in 2021, while TN was lower at 0.102 and 0.103 percent in the grazed and wheat-farming areas respectively in 2021. Conclusion: This suggests that in grasslands with the same ecological conditions, managers can choose appropriate grazing intensity as an alternative to either heavy grazing or rainfed wheat farming, though more investigations on the efficiency of different grazing intensities are needed.