Soil conservation in an abandoned agricultural rain-fed land through inoculation of cyanobacteria

Abstract

Newly abandoned rain-fed lands, due to soil quality decline, are the main sources for soil erosion in semi-dry lands agricultural hill-slopes. However, adopting compatible environmentally friend measures have not been adequately implemented. Following various resultful laboratory studies, in this paper, we assessed the effect of field inoculation of cyanobacteria in an abandoned rain-fed land on controlling the natural rainfall-induced soil loss and improving the biological soil crust (BSC) quality mixture of two cyanobacteria (viz. Nostoc sp. and Oscilatoria sp.). The cyanobacteria were inoculated on 22.1 m × 1.83 m-sized plots located on the study hill-slope. The experiment was carried out for a rainfall period of 6 months under natural conditions. Measurements of 7 erosive rainfalls showed a considerable soil loss (i.e., 0.88 ± 0.10 to 9.79 ± 1.60 g m−2) from the un-inoculated plots (control), while cyanobacteria decreased the soil loss by 36 to 57% in comparison with those recorded for the control. Soil losses in the inoculated plots were 2.39 ± 0.24, 4.8 ± 0.58, 3.32 ± 0.33, 1.49 ± 0.12, 0.87 ± 0.12, 0.52 ± 0.05, and 0.56 ± 0.08 g m−2, from the first to last rainstorms, respectively. Our results, therefore, showed a poor linear relationship between soil loss (from both treatments) and rainfall properties. Cyanobacteria also improved organic carbon and nitrogen contents as two important BSC quality indicators to the tunes of 32 and 56%, respectively, in comparison to the control, during the study period. In winter, when environmental conditions were inappropriate for growing vegetation, the effect of cyanobacteria on soil loss reduction was found to be more tangible in comparison with spring. On the whole, our field soil inoculation under uncontrolled conditions, as pioneering research, facilitated to promising results for large-scale use of cyanobacteria to rapidly restore abandoned rain-fed lands.