Abstract

1. Consequences of Aluminum or Ferrous Sulfate Amended Poultry Litter on Concentrations of Aluminum in Plant and Soil Sosten Lungu, Haile Tewolde and Dennis E. RoweUSDA-ARS, Waste Management and Forage Unit, Mississippi State, MS a a b b b a b a b b b b b b c c c c c c c c Abstract Amending poultry litter with aluminum sulfate (alum) reduces phosphorous (P) runoff and ammonia volatilization but its effects on soil pH are not completely researched. Greenhouse pot experiments with cotton (Gossypium hirsutum L.) and soybean (Glycine max. L. Merr) as test crops were conducted with a sandy loam (Fine-loamy, siliceous, semiactive, thermic Typic Paleudults) soil, that was adjusted to pH’s of 4.5, 5.0, 5.5 and 6.5 using fine Ca(OH)2. The objective was to determine if poultry litter amended with aluminum sulfate (alum) or ferrous sulfate at 0, 10% and 20% by weight affected soil pH, soil exchangeable aluminum and plant aluminum concentration when applied to meet N requirement of the crop. Application of non-amended litter and litter amended with 10% alum increased soil pH on all treatments. Application of litter amended with alum or ferrous sulfate at 20% reduced soil pH and increased soil exchangeable Al extracted with 0.01M CaCl2. The increase in soil exchangeable Al and reduction in soil pH were greater for soils with pH of 4.5 and 5.0 than for soils with higher pH. Amendments significantly increased shoot Al concentration for plants grown in soil with pH of 4.5 and 5.0. The application of alum or ferrous sulfate at higher rates to soils with pH less than 5.5 has detrimental effects on the soil and plant and is of environmental concern. Introduction Long-term amendments of agricultural land with poultry manure based on N requirement of the crop have resulted in P retention in soils. The sole environmental effect of P is its role in the eutrophication of surface waters (Sims and Wolf, 1994). On site poultry litter management using chemicals amendments have been evaluated to reduce P release from soil and ammonia volatilization (Moore and Miller, 1994). Aluminum sulfate (alum) has been shown to be economically viable for reducing P and ammonia volatilization. Concerns have been raised that long term application of poultry litter amended with alum may lead to more available aluminum in soils than present levels. The objectives of this research were to determine the effects of alum amended litter on soil pH, soil extractable aluminum and aluminum uptake by plants. Fig.1. Relationship between extractable aluminum and soil pH in soils consecutively fertilized with poultry litter treated with alum at 0, 10 and 20% by weight. Fig.4. Effect of soil pH and repeated application of poultry litter amended with alum sulfate at 0, 10, and 20% weight rate on plant tissue Al concentration. a a c c c Fig.5. Effect of soil pH and repeated application of poultry litter amended with iron sulfate at 0, 10, and 20% weight rate on plant tissue Al concentration. Results • Soil pH significantly increased with application of poultry litter alone. • There was a modest increase in soil pH with application of poultry litter amended with alum or ferrous sulfate at 10% by weight but was significantly lower than poultry litter alone. • There is a reduction in soil pH when fertilized with alum or ferrous sulfate treated litter at 20% by weight. • Soil extractable Al significantly increased in soils fertilized with poultry litter treated with alum or ferrous sulfate at 20% rate with initial soil pH of 4.5 and 5.0. • The lowest amounts of extractable Al was with poultry litter alone although it was not statistically different from litter amended with alum or ferrous at 10% rate. • Plant aluminum uptake was also significantly higher in soils fertilized with litter at 20% of alum or ferrous at pH below 5.0. • Litter amended with alum or ferrous sulfate at 20% had significantly lower dry weights at pH of 4.5 and 5. • These results indicate that higher amendments chemical amendments rates with poultry litter may not be desired to the plant and soil particularly at soil pH of below 5.0. • There was an increase in total aluminum with alum amended litter and this may be of concern in the longer term. Fig.2. Relationship between extractable aluminum and soil pH in soils consecutively fertilized with poultry litter treated with iron sulfate at 0, 10 and 20% by weight. Materials and Methods The research was conducted in a greenhouse at the Crop Science Research Laboratory of the USDA-ARS at Mississippi State, MS in a Ruston soil collected from Mississippi Agriculture and Forestry Experiment Station (MAFES), Newton, Mississippi. The soil was collected from the upper 0.20 m soil profile of a site that was cropped with Coastal bermudagrass (Cynodon dactylon). The soil was a fine sandy loam (Fine-loamy, siliceous, semiactive, thermic Typic Paleudults) and consist of well-drained medium acid to very strong acid soils. The site where the soil was collected has no known history of poultry litter application. The treatments included initial soil pH of 4.5, 5.0, 5.5, and 6.5 in a full factorial combination with five poultry litter treatments in a randomized complete block design replicated 7 times. The five litter treatments were (1) Poultry litter alone; (2) Poultry litter + 10% (w/w) alum; (3) Poultry litter + 20% (w/w) alum; (4) Poultry litter + 10% (w/w) Iron Sulfate, and (5) Poultry litter + 20% (w/w) Iron Sulfate. Fig.3. Effect of poultry litter treated with alum or iron sulfate at 0, 10 and 20% weight rates on soil pH. Same letters are not significantly different (p<0.05) in each cropping cycle