Macro-Scale Nutrient Budgets in Mississippi Delta Agronomic Crop Production.

About 80% of annual seeded agronomic crops grown in Mississippi are in the 18,130 km² lowland region of the Yazoo River Basin which comprise all or part of 18 counties in the northwestern part of the state. The region is comprised of flat alluvial plains formed in ancient floodplains of the Mississippi River,  and is commonly called the “Delta” where the level or gently undulating landforms, abundant water resources, and fertile soils facilitate large scale mechanized crop production practices. Soils are very deep, and often are poorly drained, or moderately poorly drained and been characterized as fertile, with little need for macro-nutrient fertilization other than crop specific nitrogen applications. Major crops are corn (Zea mays L.), wheat (Triticum aestivum L.), sorghum for grain (Sorghum bicolor L.), rice (Oriza sativa L.), soybeans (Glycine max L.), and cotton (Gossypium hirsutum L.). The Yazoo River Basin is within the larger Mississippi River Basin which has been linked with seasonal hypoxia in the northern Gulf of Mexico through nitrogen (N) and (P) enrichment of surface waters. The 2008 draft Gulf Hypoxia Action Plan attributed about two percent of the N load and ten percent of the P load to the Gulf of Mexico to the Lower Mississippi Basin. Recent interagency efforts have targeted Best Management Practice implementation in various smaller watersheds within the Yazoo River Basin to reduce nutrient transport to surface water. More accurate information concerning nutrient use rates and trends, soil fertility needs, and production systems is needed to provide baseline information. The objectives of this study are to characterize annually seeded crop production, native soil fertility, and collate macronutrient fertilizer application adoption and rates for the alluvial region.