Long-term effects of barley residue managements on soil hydrophysical properties in north-western Iran

The cold semi-arid cropping system is facing soil degradation, climate variability, and drought. For this reason, crop residue management is critical to soil and water conservation and the sustainability of farmers' livelihood. This study was conducted to test the hypothesis that in a cold semi-arid climate, the hydraulic properties of soil can be significantly affected by long-term crop residue management. To test this hypothesis, we investigated the changes in soil hydraulic properties (saturated hydraulic conductivity (Ks), soil water retention (SWR), cumulative infiltration (CI), parameters of van Genuchten SWR (theta s, theta r, alpha, and n), and Philip's equation indices (sorptivity and A) following long-term (five years) crop residue management. There were three treatments: (i) complete removal of crop residue from the soil surface (T1), (ii) incorporation of crop residue into the soil after harvest (T2), and (iii) burning of crop residue on the field (T3). The results showed that the Ks value was higher (p <= 0.05) in T2 (incorporation, 0.36 cm min-1) than in T1 (removal, 0.30 cm min-1) or T3 (burning, 0.26 cm min-1). Also, the alpha value was lower (p <= 0.05) in incorporation treatment (0.032 cm-1) than in removal treatment (0.042 cm-1) or burning treatment (0.048 cm-1). The value of S (1.72 cm min-0.5) in incorporation treatment differed significantly (p <= 0.05) from that of removal (1.09 cm min-0.5) and burning (1.31 cm min-0.5) treatments. Noticeable differences in soil water retention were greater at low soil water suction heads in the SWR. The differences between the SWR of treatments at low suction heads grew over time. A little difference was observed between the SWR of treatments in high suction heads. The cumulative infiltration curve for incorporation treatment differed from that obtained for removal and burning treatments, with no sizable differences observed between removal and burning over five years. The results of this study indicated that the increase in soil organic matter (SOM) for burning reduced the negative effects of burned barley residue on soil hydraulic properties to some extent. Thus, burning residues may have a little negative impact on a sustainable cropping system. The results revealed that the incorporated barley residue increased the infiltration of water into the soil more than other residue management practices in the cold semi-arid region.