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Although cotton is the number one row crop in Alabama, Georgia, Mississippi, and Arkansas in terms of

Poultry broiler litter (BL) is widely used as an alternative source of N, P, and K for crops and forages and is often applied at excessive rates of both N and P. Soil samples were periodically collected from experiments with BL at two locations in Alabama, a Coastal Plain site and a Tennessee Valley site, from 1991 though 2000. The objective was to determine the accumulation and movement of plant nutrients and metals in soil profiles when BL is compared with ammonium nitrate (AN) as a source of N for cotton (Gossypium hirsutum L.) and corn (Zea mays L.). The Tennessee Valley site was fertilized and cropped for 3 yr, and the Coastal Plain site was fertilized and cropped for 12 yr. The two N sources were applied at rates from 0 to 269 kg N ha−1 based on total N in the material. Incremental soil samples to a depth of 1 m were taken periodically from 1990 through 2000. Broiler litter maintained surface soil pH on the coarse‐textured soil at the Coastal Plain site whereas AN resulted in a decline in pH. There were no significant differences in surface soil pH due to source on the finer textured Tennessee Valley site. Application of BL resulted in increasing accumulations of total soil organic C, total N, and Mehlich‐1 extractable Ca, Mg, P, K, B, Zn, and Cu as the rates increased from 134 to 269 kg N ha−1 as BL (approximately 4.48–8.96 Mg ha−1 yr−1) over a 10‐yr period. While differences in NH4–N and NO3–N were observed to a 1‐m depth due to treatment, soil concentrations were very low compared with standards used in the presidedress soil nitrate test for corn (PSNT). No significant accumulations of heavy metals were observed during the experiments.

The pulp and paper industry in the southeastern USA produces ≈ 6500 t of boiler ash and lime by‐products (waste lime, grit, and dregs) daily. A survey of 88 pulp and paper mills indicated that most of these by‐products are placed in landfills, with only 10% being land‐applied. Seventeen boiler ash samples and 14 lime by‐products from 12 Alabama pulp and paper mills were analyzed and evaluated for their potential as soil liming materials. Most boiler ash resulted from the burning of wood or wood in combination with other materials and averaged 37% calcium carbonate equivalent (CCE), while 14 lime by‐products averaged 99% CCE. In an 84‐d incubation study, boiler ash and lime by‐products applied to an acid (pH = 5.2) Marvyn loamy sand (fine‐loamy, siliceous, thermic, Typic Kanhapludults) at equivalent rates based on CCE resulted in mean pH values significantly higher than values achieved with agricultural lime. All materials increased Mehlich‐1 extractable P, K, and Mg. In a field study conducted on an acid (pH = 5.1) Vaiden clay (very‐fine, montmorillonitic, thermic Vertic Hapludalfs), dallisgrass‐fescue (Paspalum dilatatum Poir.‐Festuca arundinacea Schreb.) herbage yield increased 62% the second year and 49% the third year after surface application of boiler ash, lime by‐products, and agricultural lime.

Renewed interest in low‐input and sustainable crop production has rekindled interest in long‐term agronomic research. Research plots that have been monitored continuously since the late 19th Century exist in several states. Twenty‐five experiments have been identified that have been monitored for over 25 yr; 12 of these are more than 50 yr old. Yield and treatment records provide valuable information on the effects of cropping systems, tillage, manuring, and fertilization practices on yields and on soil physical and chemical properties, Most of these very early tests were non‐replicated studies using large plots and crop rotation systems. Four of America's oldest, continuous agronomic research tests were reviewed in more detail: (i) Illinois' “Morrow Plots” (c. 1876), (ii) Missouri's “Sanborn Field” (c. 1888), (iii) Oklahoma's “Magruder Plots” (c. 1892) and (iv) Alabama's “Old Rotation” (c. 1896). All of these are listed on the National Register of Historical Places. These studies document that long‐term crop production can be sustained and improved in different regions and on different soils of the USA. Long‐term studies have shown that crop rotations and attention to recognized and established soil fertility practices, which may or may not include legumes and manuring, are essential to maintaining high, sustained production.