Zeolite amendments in silty loam soils: Impacts on infiltration, runoff and soil erosion

This study evaluates the effects of natural zeolite and nanozeolite on runoff generation, soil loss (sediment yield) and infiltration under controlled rainfall in a silty loam soil near Shiraz, Fars Province, Iran. Zeolite was mixed and incorporated in the top 5 cm of the soil at the rates of 0, 4, 8 and 12 g kg −1 soil. Nanozeolite was sprayed and soil surface‐applied at the rates of 1.5, 3.0 and 4.5 g m −2 equivalent to 22.4, 44.8 and 67.2 mg kg −1 , respectively. The different application methods and rates (3D incorporation of bulk zeolite in soil matrix versus 2D surface layer spraying), however, led to inconsistent units for zeolite and nanozeolite. Laboratory experiments were conducted under a FEL3 rainfall simulator at an intensity of 30.3 mm h −1 on soil‐filled trays with 5% slope for 60 min. Runoff, cumulative infiltration, time to runoff, final infiltration rate, sediment concentration (g l −1 ) and sediment yield (kg ha −1 ) were measured. Statistical analysis was performed using a completely randomised design with three replicates at α = 0.05. Results showed that zeolite and nanozeolite significantly reduced runoff while increasing cumulative infiltration and final infiltration rate. The largest significant improvements were observed for 12 g kg −1 zeolite and 4.5 g m −2 (equivalent to 67.2 mg kg −1 ) nanozeolite. Zeolite at 12 g kg −1 reduced sediment yield by 28.6%, runoff volume by 8.2% and runoff coefficient by 10% compared to the control. Nanozeolite at 4.5 g m −2 achieved similar reductions of 13, 7.8 and 12%, respectively, despite much lower applied mass. However, a key finding was the mass efficiency of nanozeolite. While 12 g kg −1 bulk zeolite equals roughly 16–20 t ha −1 (assuming a 10–15 cm plough layer), 4.5 g m −2 nanozeolite (67.2 mg kg −1 ) corresponds to just 45 kg ha −1 , yet both achieved statistically identical runoff reduction. Moreover, time to runoff generation increased by 16% and 14% compared to the control in the 12 and 4.5 g m −2 treatments, respectively. Experimental evidences revealed that nanozeolite was more effective (i.e. per unit increase of mass of nanozeolite) in reducing runoff volume and final infiltration rate compared to zeolite. However, sediment concentrations and yields were significantly reduced under zeolite application rates compared to nanozeolite. The possible reason might be that zeolite is more durable in soil profile, while nanozeolite was easily washed and lost. The possible mechanisms driving improvements are discussed in light of literature on zeolite and nanozeolite. This study provides new insights on comparison between the zeolite and nanozeolite and suggests practical recommendations for using zeolite amendments to mitigate soil erosion and improved soil and water conservation in semi‐arid agricultural landscapes.