Understanding long-term effects of agricultural management influences on soil organic carbon (SOC) dynamics and aggregate stability is essential for crop production sustainability. In this study, effects of crop rotation, cover crop and nitrogen (N) fertilization on SOC physical and molecular fractions and water-stable aggregate stability were evaluated by characterizing soils of the world’s oldest, century-long (> 120 years) continuous cotton experiment located in the southern USA. Field treatments include: 1) Continuous cotton with no winter legume/no N (CK), 2) Continuous cotton with winter legume (CWL), 3) Corn-cotton rotation with winter legume (CCWL), 4) Corn-cotton rotation with winter legume plus mineral fertilizer N (CCWLN), and 5) Continuous cotton only with mineral N fertilizer (CN). Total organic C (TOC), total nitrogen (TN) as well as acid-hydrolysis C (AHC) and water extractable organic C (WEOC) from both bulk soil and different aggregate fractions were determined. Soil organic matter (SOM) composition was characterized using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results showed that CCWL and CCWLN increased bulk soil TOC, AHC and TN by 150-165%, 300-315%, and 198-223%, respectively, as well as aggregates-associated C by 180-246% over CK. The CWL and CN treatments also increased TOC, AHC, and TN but at a less degree. The CCWL increased macroaggregates (250-2000 µm) by 92% followed by CCWLN by 46%, whereas CWL and CN had only limited effects by 1-7% compared to CK. Moreover, CCWL and CCWLN soil samples had more and diversified compounds of polysaccharides, aliphatic, aromatic, lignin, and phenols followed by CWL, CN and CK samples. Across different treatments, aggregate stability indices, mean weighted diameter (MWD) and geometric mean diameter (GMD), were positively related to TOC and TN (R2=0.57-0.65), N-containing compounds and phenols (R2 = 0.71-0.89) as well as polysaccharides and aliphatics (R2=0.53-0.71). It was concluded that the diversified inputs of SOM composition brought by synergistic interactions between corn rotation and winter legume inclusion were mainly responsible for the observed TOC accumulation and aggregate formation and stability in these subtropical cotton production systems.

Methods used to compare the effectiveness of liming materials (e.g., relative neutralizing value, RNV; effective calcium carbonate equivalent, ECCE) were developed for ground limestone. This method is relatively untested on industrial byproducts that could be used when limestone is expensive or unavailable. The objective was to determine if RNV applies to both ground limestones and industrial byproducts. A 42-d incubation study was performed on three acid soils with 11 ground limestones and 9 different byproducts at four rates based on titration and the modified Adams-Evans buffer method. Overall effectiveness, assessed as RNV compared to Ca(OH)(2), averaged 101.5 +/- 0.9% for all the evaluated liming materials, except the paper sludge and dolomitic marble. Thus, RNV was a good estimate of neutralizing ability when particle size was accurate. Addition of RNV to packaging would facilitate the commercial use of byproducts as liming materials allowing consumers to compare products by price and properties.

This chapter describes case studies of individual forest products companies who have developed successful ash application programs. For each case study, it also describes the practical aspects of setting up a program in cooperation with local landowners, university extension scientists, and state regulators. The chapter summarizes results from program research trials and demonstration plots on the effects of ash on soil properties and crop growth. These examples support the contention that wood ash is well suited as an agricultural soil amendment and demonstrate the importance of developing partnerships early on between generators of the ash, local landowners, extension scientists, and regulators. The chapter provides information on wood ash, although substantial quantities of boiler ash also are derived from other fuels such as coal and paper mill wastewater treatment plant residuals. These other types of ash also can have beneficial effects when land-applied, although their composition is more variable.

Phosphorus (P) Indices in the southern United States frequently produce different recommendations for similar conditions. We compared risk ratings from 12 southern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas) using data collected from benchmark sites in the South (Arkansas, Georgia, Mississippi, North Carolina, Oklahoma, and Texas). Phosphorus Index ratings were developed using both measured erosion losses from each benchmark site and Revised Universal Soil Loss Equation 2 predictions; mostly, there was no difference in P Index outcome. The derived loss ratings were then compared with measured P loads at the benchmark sites by using equivalent USDA-NRCS P Index ratings and three water quality models (Annual P Loss Estimator [APLE], Agricultural Policy Environmental eXtender [APEX], and Texas Best Management Practice Evaluation Tool [TBET]). Phosphorus indices were finally compared against each other using USDA-NRCS loss ratings model estimate correspondence with USDA-NRCS loss ratings. Correspondence was 61% for APEX, 48% for APLE, and 52% for TBET, with overall P index correspondence at 55%. Additive P Indices (Alabama and Texas) had the lowest USDA-NRCS loss rating correspondence (31%), while the multiplicative (Arkansas, Florida, Louisiana, Mississippi, South Carolina, and Tennessee) and component (Georgia, Kentucky, and North Carolina) indices had similar USDA-NRCS loss rating correspondence-60 and 64%, respectively. Analysis using Kendall's modified Tau suggested that correlations between measured and calculated P-loss ratings were similar or better for most P Indices than the models.

Potassium (K) deficiency in crops in southern US Coastal Plain soils has been documented since the l880s. Long-term soil fertility studies such as Alabama's Cullars Rotation experiment (circa 1911) have been conducted with K since 1911. Other Alabama long-term experiments on several Coastal Plain and related Hapludults, Paleudults, and Kandiudults also contain K variable treatments which have been monitored since 1929. Soil test data from these long-term experiments have allowed us to answer some practical questions regarding K dynamics in Coastal Plain soils. Potassium movement through the soil profile is dependent on the soil's cation exchange capacity (CEC) but relative accumulation is greater in the plow layer regardless of soil CEC. While subsoil K testing may be useful for identifying situations where subsoil K has been depleted, this extra effort and expense is not necessary for most cropping situations. A crop will remove most of its K from the plow layer if it is present in sufficient quantity based on soil test. Crop depletion of plow-layer K to the point where yield may be reduced is gradual and may take 10-15years or more depending upon soil CEC and initial soil K concentration. Depletion is most rapid in low CEC soils as would be expected. However, soil test K can vary considerably during the course of a crop season with the lowest soil test K concentrations occurring immediately after harvest.

Soil penetrometers measure penetration resistance to characterize soil strength for different management practices, primarily tillage. Our objective was to demonstrate a simple approach to quantify soil strength differences among treatments collected with a multiprobe cone penetrometer using cone index measurements to complement contour graphs and statistical analyses. The approach involves obtaining average cone index values by row position and calculating the area under the curve for cone index (AUC(C.I.)), with units of megapascal-centimeters (MPa-cm). Data were collected from a tillage and cover crop experiment in Prattville, AL (November 2009), and at the Old Rotation experiment in Auburn, AL (December 2014). Cone index values were averaged across depths for five row positions perpendicular to the center of the row (0 cm) and 22.5 and 45 cm on either side of the crop row. The approach identified that three conservation tillage implements reduced penetration resistance compared with no tillage based on AUC(C.I.) values from the Prattville experiment. Although no statistical comparisons were possible from the unreplicated Old Rotation experiment, AUC(C.I.) values were numerically lower for the 3-yr rotation compared with continuous cotton (Gossypium hirsutum L.) and the 2-yr rotation. Results from both sets of cone index measurements demonstrated that the area under the curve (AUC) approach can be used to quantitatively distinguish among treatments. Results from the AUC approach can be used to facilitate simple comparisons among treatments in field experiments and aid in the interpretation of traditional statistical analyses combined with contour graphs.

There is a potential in the southeastern US to harvest winter cover crops from cotton (Gossypium hirsutum L.) fields for biofuels or animal feed use, but this could impact yields and nitrogen (N) fertilizer response. An experiment was established to examine rye (Secale cereale L.) residue management (RM) and N rates on cotton productivity. Three RM treatments (no winter cover crop (NC), residue removed (REM) and residue retained (RET)) and four N rates for cotton were studied. Cotton population, leaf and plant N concentration, cotton biomass and N uptake at first square, and cotton biomass production between first square and cutout were higher for RET, followed by REM and NC. However, leaf N concentration at early bloom and N concentration in the cotton biomass between first square and cutout were higher for NC, followed by REM and RET. Seed cotton yield response to N interacted with year and RM, but yields were greater with RET followed by REM both years. These results indicate that a rye cover crop can be beneficial for cotton, especially during hot and dry years. Long-term studies would be required to completely understand the effect of rye residue harvest on cotton production under conservation tillage.

Caption title. June 2011. Includes bibliographical references (p. 7). Also available on the World Wide Web.

After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long-term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long-term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2-yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max. (L.) Merr.] in a 3-yr rotation produced little long-term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in-row subsoiling, high-residue, conservation tillage, and genetically modified cultivars; in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha(-1) in 2006, 14.8 Mg corn grain ha(-1) in 1999, 6.34 Mg wheat ha-1 in 2001, and 4.50 Mg soybean ha(-1) in 2004.

Astragalus membranaceus is an important traditional Chinese medicinal herb and has been used for thousands of years. Information on its cultivation in Southeastern United States is lacking. Three field experiments were planted on beds in September 2006 to test the effects of varieties, deep tillage (subsoiling vs. no subsoiling) and P and K fertilizer and lime on root yield in Auburn, Alabama on a Southern Coastal Plain soil. Each experiment consisted of a randomized complete block design with four replications. Plant mortality was most severe with small seedlings, but was observed throughout the season, and was associated with insect damage to roots and underground stems, and with root and crown rot. The fungi Pythium and Phytophthora were identified on specimens from the field. Larvae of beetles were found in or around the roots and crowns. Astragalus roots branch in compacted soils, which is not desirable for the market. Subsoiling did not prevent branching of the taproot, but branching in subsoiled plots occurred at 2–4 cm below the crown, compared to 0.5–2.8 cm from crown without subsoiling. The average root length in August 2007 were 57 cm in Subsoiler treatment and 49 cm in No Subsoiler treatment. Subsoiling did not affect root weight or diameter. Phosporus and potassium application increased root yield. Varieties differed in root weight and diameter.

The most contentious event in our nation's history, the Civil War deeply divided families, friends, and communities. Both sides fought to define the conflict on their own terms-Lincoln and his supporters struggled to preserve the Union and end slavery, while the Confederacy waged a battle for the primacy of local liberty or states' rights. But the war had its own peculiar effects on the four border slave states that remained loyal to the Union. Internal disputes and shifting allegiances injected uncertainty, apprehension, and violence into the everyday lives of their citizens. No state better exemplified the vital role of a border state than Maryland-where the passage of time has not dampened debates over issues such as the alleged right of secession and executive power versus civil liberties in wartime. In Maryland Voices of the Civil War, Charles W. Mitchell draws upon hundreds of letters, diaries, and period newspapers-many previously unpublished-to portray the passions of a wide variety of people-merchants, slaves, soldiers, politicians, freedmen, women, clergy, slave owners, civic leaders, and children-caught in the emotional vise of war. Mitchell tells the compelling story of how Maryland African Americans escaped from slavery and fought for the Union and their freedom alongside white soldiers and he reinforces the provocative notion that Maryland's Southern sympathies-while genuine-never seriously threatened to bring about a Confederate Maryland. Maryland Voices of the Civil War illuminates the human complexities of the Civil War era and the political realignment that enabled Marylanders to abolish slavery in their state before the end of the war.

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 use of site assessment indices to guide agricultural phosphorus (P) nutrient management has been widely adopted in the United States. This study compares P-index ratings from 12 southern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, and Texas) on fields representing three dominant southern agricultural systems: upland pasture, upland cornfield, and artificially drained field. The structure of each P-index varied enough to produce widely divergent ratings when applied to similar scenarios where individual factors (such as soil test P, poultry broiler litter application rate, or buffer absence or presence) were adjusted across a broad range of P-index input values. Variation in P-index ratings was the unique combination of each state's selected factors, weighting of the factors, and factor combination (added, multiplied, or a mixture of both addition and multiplication). Although the flexibility of and differences among the southern states' P-indices result in dramatically diverse P-index ratings for the same set of conditions, the diversity in P-index construction allows for indices designed to match individual state conditions and concerns. The substantial differences in P-index results identified in this survey highlight the need for close coordination between states in revising P-indices if they are to be applied across state lines.

Quicklime or burnt lime (CaO), is a highly soluble liming material recognized as an acceptable means for neutralization of acid soils in the United States. Blending CaO and MgO with agricultural lime (CaCO3) may prove an alternative to ground agricultural limestone for raising soil pH and providing fertilizer Ca and Mg for crop growth. The objectives of this study were to determine the chemical properties of several CaO. MgO, and CaCO3 liming blends compared to carbonate limestones, and analyze their respective effects on soil solution chemistry and shoot yield of a sorghum-sudangrass hybrid grown under greenhouse conditions. Three formulations of oxide liming materials (CaO, CaO + CaCO3, and CaO+MgO+CaCO3) were evaluated in the laboratory to determine their respective effectiveness as soil amendments compared to two dolomitic limestones (ground and pelletized) and reagent-grade calcium hydroxide [Ca(OH)(2)]. A 150-day incubation study was conducted to determine the effects of liming materials on soil pH and extractable nutrients, and a greenhouse study was completed to observe the effects of liming materials and rates on the herbage yield of a sorghum-sudangrass hybrid. Oxide liming materials averaged higher calcium carbonate equivalence (CCE) than ground and pelletized dolomitic limestones. An incubation study found CaO, CaO+CaCO3, and CaO+MgO+CaCO3 resulted in rapid pH adjustments (from pH 4.1 and 4.4 to 6.0+) at one day after test initiation for two soil types and gave higher mean pH values than carbonate limes when applied at equivalent rates based upon CCE. Oxide liming materials also resulted in higher concentrations of soil extractable calcium (Ca) and magnesium (Mg), and the use of all liming materials, regardless of chemical form, alleviated Al toxicity. In a nine week greenhouse bioassay, all oxide liming materials and reagent-grade Ca(OH)2 were applied at 1/2X, 1X, and 2X the recommended application rate of ground dolomitic limestone based on CCE, resulting in similar or higher shoot yields comparatively at conclusion of this study. Because oxide liming materials have higher CCE values Lind provide more water-soluble sources of fertilizer Ca and Mg compared to ground and pelletized limestone, producers have potential for obtaining a more complete neutralization of acid soil conditions and shoot yields similar to or higher than those obtained with dolomitic limestone. using less material in the process. This study did not determine if changes in current liming practices would result in reductions of total fertilizer costs per year using oxide limes in place of carbonate forms.

Nitrogen fertilization is a required production practice for cotton (Gossypium hirsutum L.) with risks arising from under‐ and over‐fertilization. Tissue testing for diagnosing N deficiencies in crops can use leaf blades and the total N concentration, but this practice has not been rigorously examined in cotton. The primary objective of these experiments was to determine the leaf‐N concentration of the uppermost, fully mature leaf blade below which yield loss could be expected. Nitrogen‐rate field experiments were conducted at 12 research station and farm sites in the Midsouth USA in Louisiana, Arkansas, Mississippi, and Alabama in 1996 and 1997. Leaf‐blade total N concentrations associated with yield loss were 4.3% N at early bloom (R2 = 0.50) and 4.1% N at mid‐bloom (3 wk after early bloom, R2 = 0.32). The likelihood of applying N when not needed could be reduced by lowering the early bloom critical value to 3.9%. Only 4% of all samples sufficient in N would have been incorrectly diagnosed N deficient at that critical value, but 44% of all deficient samples would have been misidentified as N sufficient. Reduced yields due to over application of N were evident in some samples with leaf N between 4.6 and 4.8% at early bloom. These concentrations were also common for N‐sufficient plants, making accurate diagnoses of the over application of N unlikely. Our leaf‐N critical values probably differ from previously established values because earlier values were derived via survey techniques and because faster fruiting cultivars may require higher leaf N.

When vegetables are double-cropped on polyethylene mulch, fertilizer recommendations for each crop may need to be adjusted because liming and preplant applications are done prior to laying plastic. When current fertilizer recommendations for single crops were used for cucumber following tomato, the cucumber plants looked like green, indicating a nitrogen (N) and/or potassium (K) deficiency was developing, suggesting that nutrient availability for the second crop was not adequate for producing the highest yields. Therefore, the nutritional status of both crops was diagnosed using sufficiency range data and DRIS norms to determine which nutrient(s) vas limiting crop nutrition. Regardless of N source used as a sidedress injection material (at a rate of 7 kg N ha(-1) wk(-1) as ammonium nitrate or calcium nitrate) or liming material used to adjust soil pH to 6.5 (carbonate- or oxide-based calcitic or dolomitic lime), foliar levels of N and K, and possibly phosphorus (P) were found to be limiting factors according to sufficiency range data and DRIS norms. This study suggests that current fertility recommendations for tomato and cucumber grown as single crops in Alabama need to be reevaluated for double crops.

For economical reasons, cucumber (Cucumis sativus L.) may be grown as a double crop after tomato (Lycopersicon esculentum Mill.). In this production system, plant nutrition may be limited for the second crop due to pH change or insufficient levels of calcium or magnesium. The objective of this 2-year field study was to compare the effects of selected liming materials on yield and grade distribution, and soil available nutrients of a tomato/cucumber double crop produced with plasticulture. Liming materials were compared to a control and a CaSO4 treatment based on the same neutralizing value as standard agricultural limestone. Supplemental N fertilization was provided by weekly injections at a rate of 7 kg/ha/week from ammonium nitrate (NH4NO3) or calcium nitrate [Ca(NO3)(2)]. Each year, soil samples were collected at the beginning of the study and after each crop to determine nutrient availability. All liming materials raised soil pH in 1998 and 1999 over the unlimed control, though not to the target level for tomato and cucumber production (pH 6.5). Throughout the study, agricultural limestone, a high CaO-containing blend (calcitic blend) and a CaO/MgO (dolomitic blend), resulted in greater fruit weights compared to the control and CaSO4. These materials, along with quick lime (CaO), provided higher levels of soil Ca and Mg available for plant growth. However, it was found that current recommendations for potassium (K), regardless of liming source, were not adequate for optimal soil reserves and yields in this tomato/cucumber cropping system. Ammonium nitrate as a source of N for fertilization was as effective as Ca(NO3)(2).