Lawrence J. Sikora

A biologically based indicator of soil quality

Soil quality indices are attempts to classify soil conditions and to compare these conditions to their historical use. From this information it may be possible to determine which uses of soils are better for the long-range goals of agriculture and society. With many factors involved in the profitable production of safe foodstuffs without significant degradation of the environment and soils, an indicator that represents a broad biological perspective of quality is appropriate. Among a group of biological indicators, the ratio of crop N uptake to mineralized N as determined by microbial respiration plus net mineralized N found over a growing season is an useful indicator of soil quality. An evaluation of the 12-year-old Farming Systems Trial at the Rodale Institute Research Center indicated that soils in plots that had been conventionally managed were of lower quality than soil treated with manure or planted with legume-cash grain crops.

A new growth medium for the study of siderophore-mediated interactions

SummaryA microbial growth medium, RSM, was developed to study the role of siderophores (microbial Fe-transport compounds) in the inhibition of the take-all pathogen, Gaeumannomyces graminis var. tritici, by Pseudomonas putida strain B10. The inorganic constituents of the medium were designed to mimic the rhizosphere while the organic composition was designed to promote rapid growth and siderophore production. The antibiosis experiments were highly reproducible and the antagonism appeared to be due to production of pseudobactin, the siderophore of B10. On plates amended with chrome azurol S, G. graminis did not produce siderophores while other fungi did. The growth of G. graminis on plates prepared with Fe chelate buffers was inhibited at a free ferric ion concentration of 10−24.6M, although three other fungi were not inhibited, even at 10−25.5M, presumably due to their greater production of siderophores. In liquid medium amended with Fe chelate buffers, both the doubling time and the lag phase of P. putida increased as the free ferric ion concentration was reduced. A wide variety of fungi and bacteria were found to grow on this medium. Because the inorganic composition of RSM is based on that of the rhizosphere, the development of this medium may be a first step towards the study of the chemistry and biology of the rhizosphere under well defined conditions.

Changes in Soil Phosphorus Availability with Poultry Compost Age

Composting reduces the available nitrogen (N) content of organic materials by immobilizing it and converting it to a slow release form. The effect of composting on phosphorus (P) is less clear. Adding compost to soil can increase water extractable soil P by direct addition, dissolution, displacing sorbed, or reducing sorption capacity for P. Organic acids can affect soil P and vary with compost maturity. The objective of this study was to examine the effect of poultry manure compost on available soil P levels. Compost of different maturities was studied to evaluate the effect of biological activity on extractable P levels in two contrasting soils, a loam and clay. Turkey litter was mixed with orchard grass hay at a 3:1 volume ratio and turned frequently, and temperature, carbon dioxide, and oxygen were measured regularly. Compost samples were taken at day 0 when the compost was made, and at weeks 2, 4, and 8. Compost maturity determined by the Dewar self-heating and oxygen uptake tests indicated that two-week old compost had greater biological activity than compost at 4 or 8 weeks. Compost samples were added to a loam or clay soil at 0.15 and 0.30-g total P kg soil−1 and then incubated for 8 weeks. At 1 d and at 2, 4, and 8 weeks, water-extractable and Mehlich-1 extractable P were determined. The effect of compost age was most pronounced in the loam on day 1 with water-extractable P compared to the Mehlich-1 extractable P fraction. These data suggest that water-extractable P may increase when loam soils are amended with biologically active, immature compost or when the sorption capacity of the soil is not sufficient to offset the effects of the compost addition. Because water-extractable P is implicated in runoff events, caution should be exercised in applying immature composts to critical source areas within the watershed, which are most vulnerable to P loss in surface runoff and erosion.

MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH3 volatilization, CO2 evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO2 evolution and reduced N loss. Nitrogen loss from composting dairy manu...

Mesophilic composting of arctic char manure

Manure in coldwater aquaculture production systems is typically settled in quiescent zones created within raceways to concentrate it prior to being pumped to storage in off-line settling basins. As the water passes through the off-line settling basins, the solids settle out and the excess water is discharged to surface water. Since the basins are not frequently emptied, the organic solids mineralize and nutrients flow out of the basins with the surface water discharge. A system was tested to remove solids from settling basins frequently and treat by mesophilic composting. Two carbon (C) sources (wheat straw or oak sawdust) were evaluated. Manure was applied to beds of carbon sources at a rate of about 1cm of arctic char manure (8% solids) every 10 days using a vacuum tank spreader modified for side discharge over the plots. The open and porous structure of wheat straw resulted in several advantages over the oak sawdust; there was not runoff during application even during freezing winter temperatures when the oak sawdust compost was frozen solid, aerobic conditions were maintained with lower amounts of C, and decomposition rates were higher resulting in less time needed to reach stability (about 90d vs. 140d). Inorganic nitrogen (N) increased as the organic matter decomposed with either C source. Mineralization and nitrification rates were higher with wheat straw. Water-extractable P decreased as the organic matter from both C sources decomposed. Land requirements are about 0.001 ha to compost the manure for each 1 Mg Arctic char produced annually, but could be significantly higher for the wheat straw since experimental loading rates were limited by the reduced capacity of the oak sawdust compost. A layered mesophilic compost system may be a viable manure management system to store and treat manure and replace long-term storage in off-line settling basins for fish farmers. In this system, solids would continue to be settled in the off-line settling basins but pumped onto straw nearby for storage and stabilization on land thereby minimizing discharge of nutrients to surface water.

Availability of Compost P to Fescue Under Nonlimiting N Conditions

Nutrient management plans require an accurate assessment of P fertilizer additions to soil. The fertilizer equivalents of manures and composts must be estimated in order to comply. A previous study comparing triple superphosphate(TSP) to poultry litter compost (PLC) as a source of P for fescue indicated that overall they were equal, but when N became limiting during the final harvest, PLC supplied more P to fescue than TSP at comparable rates. A subsequent study was initiated to determine if P from PLC was more available to fescue than TSP when N was not limiting. Sassafras soil was amended with PLC and TSP at rates of 0, 50, 100 and 150 kg ha−1. Nitrogen was supplied to be uniform across all treatments taking into account the N mineralization rate of PLC. Two harvests of fescue were taken and analyzed for yields and P uptake. Nitrogen was added to all treatments at the original application rate of 120 kg ha−1 and two more harvests plus roots were collected. Yields were affected by harvest date but not by P rate or source of P. P uptake was affected by date and rate but not source of P. The P uptake response to PLC and TSP was curvilinear and linear respectively, but within the range of P application rates used, the source of P was not a significant factor in P uptake by fescue. Based on the current study testing the effect of unlimited N, addition of supplemental N did not affect P supply from either source. Poultry litter compost is considered equal to TSP in supplying P to fescue and N availability did not affect these conclusions.

Dissipation of 17β-estradiol in composted poultry litter.

The excreted estrogen rate of all livestock in the United States is estimated at 134 kg d. The influence of manure treatment on the fate of estrogens is critical in deciding the recycling of over 300 million dry tons of livestock produced annually. The effects of two common manure management practices, heated composting and ambient temperature decomposition, on the fate of 17β-estradiol in poultry litter were determined. A mixture of poultry litter, wood chips, and straw was amended with [C]17β-estradiol and allowed to undergo decomposition with a laboratory-scale heated composter (HC) or room temperature incubation (RTI) for 24 d. Radiolabel in the finished products was fractionated into water-extractable, acetone-extractable, nonextractable, and mineralized fractions. Total 17β-estradiol radioactive residues in the HC and RTI ( = 2) treatments were not different ( > 0.05), except that statistically less 17β-estradiol was mineralized to CO during HC than RTI (1.1 vs. 10.0% for HC and RTI, respectively). Estrone was the major degradation product in extracts of HC and RTI treatments as determined by liquid chromatography/mass spectrometry analyses. The nonextractable residues indicated no quantitative differences among the humins between the treatments. An estimated 3% of the fortified estrogenicity remained after HC treatment, and 15% of the fortified estrogenicity remained after RTI treatment. If reduction of water-removable, biologically active 17β-estradiol is the treatment goal, then HC treatment would be slightly preferred over ambient temperature degradation. However, unmanaged, ambient temperature litter piles are less costly and time consuming for food animal producers and result in greater mineralization and similar immobilization of estradiol.

Fate of 17β-Estradiol in Anaerobic Lagoon Digesters

The fate of [C]17β-estradiol ([C]E2) was monitored for 42 d in triplicate 10-L anaerobic digesters. Total radioactive residues decreased rapidly in the liquid layer of the digesters and reached a steady-state value of 22 to 26% of the initial dose after 5 d. High-performance liquid chromatography and liquid chromatography-tandem mass spectrometry analyses of the liquid layer of the anaerobic digesters indicated a rapid degradation of E2 to estrone (E1), which readily adsorbed to the sludge layer subsequent to its formation. Estrone was the predominant steroid identified under anaerobic digestion in the liquid layer or sorbed to sludge at 42 d. Methane formation represented 11.1 ± 5.7% of the initial E2 fortification with 0.3 to 0.5% of the starting E2 mineralized to carbon dioxide. Maximum [C]methane production appeared between Days 4 and 7. An estimate of estrogenicity of the final product based on reported estrogen equivalents for E1 and E2 was 2% of the original in active digesters. Anaerobic digestion of swine waste has several management benefits; moreover, this study demonstrated that it reduces the potential of environmental release of estrogens, which are known endocrine disruptors.

In situ respiration determination as tool for classifying soils according to soil organic matter content.

Abstract Soil respiration is indicative of biological status of the soil and high respiration is correlated to high contents of available carbon (C) in soil and/or organic matter content. Because of soil respirations relationship to soil organic matter status and content, soil respiration is considered one measurement that could aid in determining the quality of soil. In the global scale, the cycling of C in soil is important because the rise in CO2 in the atmosphere is linked to global climate change. In situ measurement of CO2 using instruments that are portable and perform analyses quickly are important to obtain sufficient number of measurements in the field to overcome spatial variability. Soil respiration tests were conducted in plots amended with fertilizer or organic amendments of agricultural or municipal residues since 1994. Besides CO2, moisture and temperature were measured over a period where the moisture varied from near saturation to below wilting point. It was found that flux was curvilinearly related to moisture from 5 to 40% (v/v). Maximum flux occurred for all plots between 30 and 40% saturation. The ratio of flux normalized by temperature to the volumetric soil moisture divided soils into two categories, those with soil organic matter (SOM) content above or below 4.5%. The determinations of CO2 flux, moisture and temperature uses equipment that is portable so that several sites in a field can be analyzed to reduce spatial variation. The only limitation is that the determinations must be performed on soils with less than 40% saturation or 25% moisture (v/v) because the normalized function is no longer linear above this moisture content. More than two SOM categories might be found if studies are expanded to soils with a wider range of SOM content.

Effect of Industrial Byproducts Containing High Aluminum or Iron Levels on Plant Residue Decomposition

Abstract Excess phosphorus (P) in soils is a result of manure and fertilizer additions that exceeded crop P requirements. Reducing or eliminating future P fertilizer additions or manures is one method of remediation. Another would be to treat manures or soils with byproducts that contain iron (Fe), aluminum (Al), or calcium (Ca) that adsorb P readily. A study was conducted in which two industrial byproducts and 14C-labeled soybean leaves and stems were added to two soils and soil organic matter and residue decomposition were monitored. Water treatment residue (WTR) containing high Al content and iron-rich residue (IRR) were added to Sassafras and Matapeake soils at rates from 0.5 to 10.0 g kg−1 soil. Lime (CaO) was added as a treatment to determine the effect of increased pH. Additions of WTR to either soil did not affect decomposition of 14C-labeled soybean leaves and stems, soil organic matter decomposition recorded by total CO2 evolution or residual soil 14C. Addition of IRR affected decomposition of 14C-labeled soybean leaves and stems, soil organic matter decomposition recorded by total CO2 and residual soil 14C. Although no one factor explained the effects on decomposition, salinity may be a factor as well as pH. Lime addition corrected the low soil organic matter decomposition as a result of the 10 g kg−1 IRR amendment. Lime also reduced salinity about 20%. Remediation of high P soils or treatment of manure is beneficial, but additional tests on biological effects on industrial byproduct addition may be necessary.