Soil Mulching – A Resilience Strategy to Improve Drought Conditions in Drylands

Abstract

The aim of the present investigation was to evaluate the effect of regulated deficit irrigation (RDI) strategies with soil surface mulching (SSM) on maize grain yield, water use efficiency (WUE) and some soil physical properties. The field experiment was conducted at Soil and Water Resources Research Station in Baghdad with the latitude of 33°14′ N, Longitude of 44°04′ E under the autumn growth of 2015. A randomized complete block design (RCBD) was used with three replications. The irrigation treatments included full crop water requirements (I₁) and deficit irrigation (30% below the full water requirements, I₂), both with and without mulching (M₀ and M₁, respectively). Volumetric soil moisture measurements were taken with a capacitance probe (Diviner-2000) to schedule irrigation and water amounts. Water applications were measured for each irrigation season; actual evapotranspiration (ETₐ) was determined as differences of soil water storage between consecutive irrigations. The measured response variables were grain yield, water use efficiency (WUE), actual water requirement, saturated hydraulic conductivity (Kₛₐₕ), mean weight diameter of water-stable aggregates (MWD), soil organic carbon (SOC) and bulk density (ρb). The results showed that the total seasonal water application reduced by 1,600 m³ ha⁻¹ (26%) under the deficit irrigation (I₂) compared to the full irrigation (I₁; 6,200 m³ ha⁻¹) and no statistically significant decrease in grain yield (≈14% numerical decrease). (ii) Full irrigation (I₁) resulted in 14.1% greater yield of grain compared to deficit irrigation (I₂). (iii) The mulched plots (M₁) gave better results than bare soil plots (M₀) and increased grain yield by 22.5% and WUE by 21.8% respectively. The maximum grain production (7,710 kg ha⁻¹) was achieved in I₁M₁ while the minimum (5,420 kg ha⁻¹) was obtained in I₂M₀. Compared with deficit irrigation, the full irrigation treatments resulted in increased Kₛₐₕ, aggregate stability, and SOC of 24.1%, 19.4% and 9.5%, respectively. The mulching resulted in the increase of the SOC (30.3%), aggregate stability (57.1%) and Kₛₐₕ (61.5%) when compared to non-mulched treatments. On the other hand mulching reduced bulk density by 7.8% as compared with bare soil (vii). (viii) Peak values for Kₛₐₜ (27.6 mm h⁻¹), aggregate stability (28.7%), and SOC (2.75 g kg⁻¹) were observed under I₁M₁, while minimum values (13.2 mm h⁻¹, 14.9%, and 1.91 g kg⁻¹, respectively) were recorded under I₂M₀. (ix) The maximum bulk density (1.42 Mg m⁻³) was measured under I₂M₀, and the minimum (1.27 Mg m⁻³) under I₁M₁.