Long-Term Rice Rotation, Tillage, and Fertility Effects On Extractable Soil Nutrients in a Silt-Loam Soil.

Of the roughly 1.1 million ha of rice (Oryza sativa L.) planted and 8.5 million Mg of rice grain produced in the United States annually, over 44% of the total rice area (454,000 ha) and over 42% of the total grain production (3.5 million Mg) occurs in the Mississippi River Delta region of eastern Arkansas. Rice is considered the number one cash-crop in Arkansas and is an important agricultural crop in Louisiana, Mississippi, Missouri, Texas, and California. Therefore, ensuring the sustainability of rice production systems is vital to protecting the economic livelihood of Arkansas and other rice production areas of the United States. One of the key factors to accomplishing viable food-production systems is through the continual management and maintenance of proper soil fertility. Therefore, a study was conducted 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-tillage and no-tillage (NT)], and fertility (optimal and sub-optimal) treatments after 11 years (1999-2010) of consistent management on extractable soil nutrients (Mehlich-3 extractable) in the top 10 cm of a silt-loam soil. The field study was conducted at the Rice Research and Extension Center near Stuttgart, Arkansas. Results showed that phosphorous and potassium contents increased over time in rotations with wheat and where generally greater under NT. Extractable manganese, iron, and sodium contents increased over time in most tillage-fertility-rotation treatments. However, decreases were observed in extractable sulfur, calcium, and copper contents over time in all treatment combinations, and zinc concentrations decreased over time in continuous rice. Understanding the decadal effects of rice-based crop rotations and the associated management practices have on soil fertility will give insight to the longer-term sustainability of these systems so that they remain highly productive without detrimental effects to the environment and the soil resource.