Enhancing soil resilience in Iranian Haploxeralfs: A study on the impact of two organic matters on aggregate stability and mechanical resistance

Abstract

In arid regions around the world, erosion is a frequent occurrence due to low annual rainfall weakening plants, which in turn affects the concentration of soil organic matter (SOM). When the soil is exposed, sudden and heavy rainfall can lead to soil degradation, particularly in soil with high sodicity where unstable aggregates are easily ruptured, initiating the first phase of soil erosion. To investigate this phenomenon, soil samples were collected from an erosion‐prone area near Maharloo Salt Lake, specifically Chah‐angiri (soil 1) and Kamal-abad (soil 2), which are loam and silty clay loam soils with low SOM.<strong> </strong>To evaluate the effect of organic matter sources on soil stability, cow manure (animal source) and wheat straw (plant source) were applied to both soil samples at four different rates (0.0, 10.0, 20.0, and 40.0 g kg<sup>−1</sup>) and incubated for four months. The soil’s aggregate stability and mechanical resistance were then assessed using two different methods: mechanical resistance, which was measured as the module of rupture and penetration resistance, and aggregate stability, which was evaluated using the conventional and Le Bissonnais methods.<strong> </strong>The application of organic matter resulted in a linear increase in aggregate stability in both soils, with the increase in Chah‐angiri (with lower sodicity) being greater than Kamal‐abad (with higher ESP). Both linear and exponential equations showed that organic matter treatment reduced soil mechanical resistance exponentially, with wheat straw proving more effective than cow dung at stabilizing aggregates against slaking and lowering soil mechanical resistance in both soils.<strong> </strong>Furthermore, the stability of aggregates changed by mechanical breakdown (MWD<sub>stir</sub>) was found to have the strongest relationship among three Le Bissonnais treatments (MWD<sub>slow</sub>, MWD<sub>fast</sub>, and MWD<sub>stir</sub>) and the aggregate stability test using the usual technique (Kemper and Rosenau). The organic matter rate had a significant effect (<em>P </em>< 0.001) on MWD<sub>stir</sub>, which increased with rate in a linear relationship (<em>r</em><sup>2</sup> = 0.957, <em>P </em>= 0.022). Finally, the stability of soil aggregates in water was also investigated.