Surface crusting as a constraint to sustainable management on a tropical alfisol: II. Strength characteristics during crust development

Abstract

Crust strength impacts agronomic production through its effect on tillage and planting, seedling emergence and establishment, as well as, runoff and erosion. Therefore, a field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India, to evaluate surface crust strength characteristics under six cropping and management systems. Penetration resistance (PR) and shear strength (VS) of surface soil was 50 to 300% higher prior to tillage, under dry and crusted conditions than at 21 and 60 days after tillage (DAT). Cohesion and unconfined compressive strength (UCS) followed similar trends to those of PR and VS with 30 to 65% higher values by 109 DAT compared to 0 and 50 DAT. These results reflected the effect of moisture content as welt as crust development from compaction and consolidation of the surface (5–10 mm) soil layer. During the post-harvest period PR, VS and needle penetration resistance (NPR) exhibited sharp increases at soil moisture contents less than about 0.10gg−1, suggesting possible hardsetting tendency of the soil. Highest NPR (ranging from 1.6–7.2 MPa) occurred at 78 and 156 DAT when visible crusting was apparent. Lower NPR at 156 DAT than at 78 DAT for some treatments was attributed to soil surface micro-variability due to crust cracking, soil faunal activity and excessive drying. Adequate soil cover from crop residue or deep-rooted, prolific perennials such as Cenchrus and Stylosanthes may effectively reduce and ameliorate surface crusting on Alfisols in the semi-arid tropics.