Influence of biochar on nitrogen fractions in a coastal plain soil.

Interest in the use of biochar from pyrolysis of biomass to sequester C and improve soil productivity has increased; however, variability in physical and chemical characteristics raises concerns about effects on soil processes. Of particular concern is the effect of biochar on soil N dynamics. The effect of biochar on N dynamics was evaluated in a Norfolk loamy sand with and without NHNO. High-temperature (HT) (≥500°C) and low-temperature (LT) (≤400°C) biochars from peanut hull ( L.), pecan shell ( Wangenh. K. Koch), poultry litter (), and switchgrass ( L.) and a fast pyrolysis hardwood biochar (450-600°C) were evaluated. Changes in inorganic, mineralizable, resistant, and recalcitrant N fractions were determined after a 127-d incubation that included four leaching events. After 127 d, little evidence of increased inorganic N retention was found for any biochar treatments. The mineralizable N fraction did not increase, indicating that biochar addition did not stimulate microbial biomass. Decreases in the resistant N fraction were associated with the high pH and high ash biochars. Unidentified losses of N were observed with HT pecan shell, HT peanut hull, and HT and LT poultry litter biochars that had high pH and ash contents. Volatilization of N as NH in the presence of these biochars was confirmed in a separate short-term laboratory experiment. The observed responses to different biochars illustrate the need to characterize biochar quality and match it to soil type and land use.

Long-term biosolids application effects on metal concentrations in soil and bermudagrass forage.

The long-term application of biosolids that periodically contained elevated metal concentrations has raised questions about potential effects on animal health. To address these concerns, we determined metal concentrations (As, Cd, Cu, Pb, Hg, Mo, Ni, Se, and Zn) in both soil and bermudagrass [Cynodon dactylon (L.) Pers.] forage from 10 fields in the following categories of biosolids application: six or more years (>6YR), less than six years (<6YR), and no applications (NS). Soil metal concentrations in all groups were similar to values reported for mineral soils in Georgia, and well below USEPA cumulative limits. Average metal concentrations in the forage were below the maximum tolerable level (MTL) for beef cattle, although two biosolids-amended fields in the >6YR group produced forage that was at or near the MTL for Cd and Mo, and one field in the <6YR group produced forage above the MTL for Cd. The Cu to Mo ratios in forage decreased with increasing time of sludge application, with the average in the >6YR group at a proposed 5:1 Cu to Mo ratio limit to protect ruminant health. Sulfur concentrations in the forage from all three groups was near the MTL of 4 g kg(-1). The study indicated that toxic levels of metals have not accumulated in the soils due to long-term biosolids application. Overall forage quality from the biosolids-amended fields was similar to that of commercially fertilized fields; however, due to the relatively high S and potential for a low Cu to Mo ratio, Cu supplements should be used to ensure ruminant health.

Survey of food safety practices on small to medium-sized farms and in farmers markets.

As produce consumption has increased, so have foodborne disease outbreaks associated with fresh produce. Little research has addressed food safety practices used on small to medium-sized farms selling locally or in farmers markets. This study evaluated current food safety practices used by farmers on small to medium-sized farms and managers of farmers markets in Georgia, Virginia, and South Carolina based on responses to surveys. Surveys were developed, pretested, and revised before implementation with target audiences and were implemented via mail and the Web to maximize participation, with reminders sent to nonrespondents. Data were collected from 226 farmers and 45 market managers. Frequencies and percentages were calculated for all response variables. Responses from farmers indicated that more than 56% of them use manures. Of those who use manures, 34% use raw or mixtures of raw and composted manure, and over 26% wait fewer than 90 days between application of raw manure and harvest. Over 27% use water sources that have not been tested for safety for irrigation, and 16% use such water sources for washing produce. Over 43% do not sanitize surfaces that touch produce at the farm. Only 33% of farmers always clean transport containers between uses. Responses from market managers indicated that over 42% have no food safety standards in place for the market. Only 2 to 11% ask farmers specific questions about conditions on the farm that could affect product safety. Less than 25% of managers sanitize market surfaces. Only 11% always clean market containers between uses. Over 75% of markets offer no sanitation training to workers or vendors. While farmers and market managers are using many good practices, the results indicate that some practices being used may put consumers at risk of foodborne illness. Consequently, there is a need for training for both farmers and market managers.

Release of nitrogen and phosphorus from poultry litter amended with acidified biochar.

Application of poultry litter (PL) to soil may lead to nitrogen (N) losses through ammonia (NH(3)) volatilization and to potential contamination of surface runoff with PL-derived phosphorus (P). Amending litter with acidified biochar may minimize these problems by decreasing litter pH and by retaining litter-derived P, respectively. This study evaluated the effect of acidified biochars from pine chips (PC) and peanut hulls (PH) on NH(3) losses and inorganic N and P released from surface-applied or incorporated PL. Poultry litter with or without acidified biochars was surface-applied or incorporated into the soil and incubated for 21 d. Volatilized NH(3) was determined by trapping it in acid. Inorganic N and P were determined by leaching the soil with 0.01 M of CaCl(2) during the study and by extracting it with 1 M KCl after incubation. Acidified biochars reduced NH(3) losses by 58 to 63% with surface-applied PL, and by 56 to 60% with incorporated PL. Except for PH biochar, which caused a small increase in leached NH(4) (+)-N with incorporated PL, acidified biochars had no effect on leached or KCl-extractable inorganic N and P from surface-applied or incorporated PL. These results suggest that acidified biochars may decrease NH(3) losses from PL but may not reduce the potential for P loss in surface runoff from soils receiving PL.