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Many crops in volcanic regions exhibit symptoms of B deficiency but do not respond to B fertilizer rates that solve deficiency problems in non–volcanic-influenced soils. The US recommended rates are routinely adopted in these regions without accounting for differences in soil B dynamics. Because of the paucity of investigations and the resulting lack of understanding of B adsorption/desorption dynamics in volcanic ash–derived soils over the past 40 yr, it would be incorrect to extrapolate the few data available to all volcanic ash–derived soils because they have not been analyzed as a function of andic character. This paper aims to create an understanding of what soil properties govern B availability in volcanic-influenced soils and to establish if there are low-cost testing methods that can help estimate appropriate field B application rates in these soils. Boron adsorption/desorption isotherms were constructed for a group of volcanic ash–derived and non-volcanic ash–derived soils, and the derived parameters were compared with various standard soil tests. Our results show that soil B availability in volcanic-influenced soils is governed mainly by strong and stable B complexation with short-rangeorder (SRO) minerals. Boron adsorption maxima exhibit a wide variability not directly correlated with clay content but rather with reactivity quantified by SRO mineral and organic matter contents. Organic matter is not a significant variable explaining specific surface area for the overall group of soils, but it becomes significant for soils containing <200 g clay kg-1, suggesting that a new approach to analyzing whole-soil reactivity based on mineral surface abundance is needed. The maximum adsorption capacities of volcanic-influenced soils can be as much as 18-fold higher than for non-volcanic soils, with the reversibility of adsorption reactions decreasing as andic character increases. These findings explain why standard B fertilizer rates fail to solve deficiency problems in volcanic-influenced soils. Because pH in NaF is strongly related with acid-oxalate Al (SRO minerals) and B desorption index, this low-cost test can potentially be used as a measure of soil andic character to better reflect B availability and corresponding field application rates. [ABSTRACT FROM AUTHOR]

A reliable laboratory index of N availability would be useful for making N recommendations, but no single approach has received broad acceptance across a wide range of soils. We compared several indices over a range of soil conditions to test the possibility of combining indices for predicting potentially mineralizable N (N0). Soils (0-5 and 5-15 cm) from nine tillage studies across the southern USA were used in the evaluations. Long-term incubation data were fit to a first-order exponential equation to determine N0, k (mineralization rate), and N0 (N0 estimated with a fixed k equal to 0.054 wk-1). Out of 13 indices, five [total C (TC), total N (TN), N mineralized by hot KCI (Hot N), anaerobic N (Ana_N), and N mineralized in 24 d (Nmin_24)] were strongly correlated to N0 (r > 0.85) and had linear regressions with r2 > 0.60. None of the indices were good predictors of k. Correlations between indices and N0 improved compared with N0, ranging from r = 0.90 to 0.95. Total N and flush of CO2 determined after 3 d (FLCO2) produced the best multiple regression for predicting N0 (R2 = 0.85) while the best combination for predicting N0 (R2 = 0.94) included TN, Fl_CO2 Cold_N, and NaOH_N. Combining indices appears promising for predicting potentially mineralizable N, and because TN and Fl_C02 are rapid and simple, this approach could be easily adopted by soil testing laboratories. [ABSTRACT FROM AUTHOR]

Poultry litter (PL) can supply N, P, K, and other plant nutrients; however, excessive application may cause environmental problems, depending on management and crop nutrient demand. Changes in soil test (ST) nutrient content in a Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) during a 10-yr period of PL use was evaluated at the USDA-ARSJ. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. During the cotton (Gossypium hirsutum L.) cropping phase (1995-2000), 4.4 Mg PL ha-1 yr-1 resulted in small changes in ST nutrient content in the surface 15 cm. Differences were observed between tillage treatments, with less accumulation of Ca, Mg, and Mn and greater accumulation of Zn for no-till (NT) than conventional tillage (CT). During the corn (Zea mays L.) cropping phase (2001-2005), average annual PL inputs (11.2 Mg hat) increased P and Zn contents, with changes being similar for CT and NT After 10 yr, ST nutrient contents in the surface 15 cm reflected 25, 4, 45, 26, 17, and 97% of the input from PL for P. K, Ca, Mg, Mn, and Zn, respectively. Changes in soil profile nutrient content (to a depth of 60 cm) from 1997 to 2005 were predominantly at 0 to 15 cm, where P and Zn increased >200%. Accumulation of Ca, K, P, and Zn at lower depths was also observed. Strategies for increasing nutrient removal following repeated long-term application of PL should be considered to avoid excessive levels of nutrients. [ABSTRACT FROM AUTHOR]

Analyzes the relationship between soil test phosphorus and phosphorus runoff. Value of including other soil properties in phosphorus loss prediction equations; Soil test phosphorus levels; Influence of the inclusion of site-specific information about soil aluminum and iron content on the relationship between soil test phosphorus and runoff phosphorus.