Long-term rice rotation, tillage, and fertility effects on near-surface chemical properties in a silt-loam soil

A majority of the rice (Oryza sativa L.) produced in the United States occurs on alluvial soils in the lower Mississippi River Valley, lower coastal plains of Louisiana and Texas, and in the Sacramento River Valley of California. Rice is a staple grain of global importance, so ensuring the sustainability of rice production systems is vital to feeding the world's population and protecting economic livelihoods. Therefore, a study was conducted at the Rice Research and Extension Center near Stuttgart, Arkansas to evaluate the long-term effects of rice-based crop rotations [with corn (Zea mays L.), soybean (Glycine max L.), and winter wheat (Triticum aestivum L.)], tillage (conventional and no-tillage), and soil fertility treatments (optimal and sub-optimal) after 11 years (1999-2010) on soil organic matter (SOM) content, soil pH, and Mehlich-3 extractable nutrient contents in the top 10 cm of a Dewitt silt loam (fine, smectitic, thermic, Typic Albaqualf). Results revealed increases in SOM (9-14 %) and extractable Mn (68-220 %), Fe (82 %), and Na (37-76 %) contents in most tillage-fertility-rotation treatments over time. Soil P (fourfold to eightfold) and K (twofold to threefold) contents increased in rotations with wheat and soil pH (9 %) increased under sub-optimal fertility. In contrast, extractable Ca (22 %), S (30 %), and Cu (27 %) contents decreased over time in all treatment combinations and Zn (twofold) contents decreased under continuous rice. Understanding the decadal effects field management practices have on soil chemical properties will provide insight into the longer-term economic and environmental sustainability of rice-based cropping systems.