Long-term rice-based cropping system effects on near-surface soil compaction

Irrigated rice (Oryza sativa L.) production is associated with frequent cycling between anaerobic and aerobic conditions, which can lead to a greater rate of soil organic matter (SOM) decomposition, thus potentially increasing soil bulk density (BD) over time. A study was conducted in the Mississippi River Delta region of eastern Arkansas, USA to evaluate the long-term effects of rice-based crop rotations, tillage [conventional tillage (CT) and no-tillage (NT)], soil fertility regime (optimal and sub-optimal), and soil depth (0-10 and 10-20 cm) after 10 years of consistent management on near-surface soil compaction, as measured by BD. Soil BD was greater under NT than CT in the top 10 cm, but was similar between NT and CT in the 10to 20-cm depth interval. Soil BD differed among common ricebased cropping systems with corn, soybean, and winter wheat, but few consistent trends were evident. It appears that, even after 10 years of continuous CT or NT rice production on a siltloam soil, substantially increased near-surface soil BD has not occurred to the point where soil compaction would be a likely culprit responsible for a reduced early season stand establishment or crop yield differences among ricebased copping systems.