Julia W. Gaskin

Biochars impact on soil moisture storage in an Ultisol and two Aridisols

Abstract Biochar additions to soils can improve soil-water storage capability; however, there is sparse information identifying feedstocks and pyrolysis conditions that maximize this improvement. Nine biochars were pyrolyzed from five feedstocks at two temperatures, and their physical and chemical properties were characterized. Biochars were mixed at 2% wt wt−1 into a Norfolk loamy sand (Fine-loamy, kaolinitic, thermic Typic Kandiudult), a Declo silt loam (Coarse-loamy, mixed, superactive, mesic xeric Haplocalcid), or a Warden silt loam (Coarse-silty, mixed, superactive, mesic xeric Haplocambid). Untreated soils served as controls. Soils were laboratory incubated in pots for 127 days and were leached about every 30 days with deionized water. Soil bulk densities were measured before each leaching event. For 6 days thereafter, pot-holding capacities (PHC) for water were determined gravimetrically and were used as a surrogate for soil-moisture contents. Water tension curves were also measured on the biochar-treated and untreated Norfolk soil. Biochar surface area, surface tension, ash, C, and Si contents, in general, increased when produced under higher pyrolytic temperatures (≥500°C). Both switchgrass biochars caused the most significant water PHC improvements in the Norfolk, Declo, and Warden soils compared with the controls. Norfolk soil-water tension results at 5 and 60 kPa corroborated that biochar from switchgrass caused the most significant moisture storage improvements. Significant correlation occurred between the PHC for water with soil bulk densities. In general, biochar amendments enhanced the moisture storage capacity of Ultisols and Aridisols, but the effect varied with feedstock selection and pyrolysis temperature.

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.

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 (NH3) 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 NH3 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 NH3 was determined by trapping it in acid. Inorganic N and P were determined by leaching the soil with 0.01 M of CaCl2 during the study and by extracting it with 1 M KCl after incubation. Acidified biochars reduced NH3 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 NH4 +-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 NH3 losses from PL but may not reduce the potential for P loss in surface runoff from soils receiving PL.

Characterization of Char for Agricultural Use in the Soils of the Southeastern United States

Char produced from the pyrolysis of biomass has potential as an agricultural amendment in low fertility soils. Much of the interest in its use as an agricultural amendment has been stimulated by research discussed in this book and the previous volumes on the role of charcoal in terra preta soils. Results from studies conducted in South American and African tropics on acidic, highly-weathered Oxisols with low organic carbon (C), cation exchange capacity (CEC), and base saturation indicate that addition of charcoal has significantly influenced nutrient cycling, soil biology, and crop productivity (Glaser et al. 2002; Lehmann and Rondon 2006; Oguntunde et al. 2004). Increased yields and biomass have been reported for various legumes (Iswaran et al. 1980; Lehmann et al. 2003; Topoliantz et al. 2005) and for corn (Lehmann and Rondon 2006; Oguntunde et al. 2004). Increased productivity may be related to available nutrients (Glaser et al. 2002; Lehmann et al. 2003; Steiner et al. 2007), or increases in pH (Topoliantz et al. 2005; Steiner et al. 2007), and CEC (Steiner et al. 2007; Liang et al. 2006), as well as changes in water relations and soil biology (Glaser et al. 2002; Steiner et al. 2004). Although most studies report increased plant productivity with charcoal addition, plant biomass decreases have been observed, particularly at high application rates (Glaser et al. 2002). These responses could be related to nitrogen immobilization through high C:N ratios and sorption of NH 4 and NO 3 (Lehmann and Rondon 2006). The southeastern United States is an important agricultural area. The state of Georgia alone has approximately 4.3 million hectares of corn (Zea mays), soybean (Glycine max), cotton (Gossypium hirsutum), and peanuts (Arachis hypogaea) in production and 9.6 million hectares of forestland largely in loblolly pine (Pinus taeda) production (USDA 2002; Georgia Forestry Commission 2007). The growing interest in biofuels is increasing demands on row crop production and may also increase demand on forestlands. The Ultisols of the southeastern United States are similar to tropical Oxisols with low organic C concentrations of less than 1%, low CECs of approximately 5 cmol kg, and low base saturation of usually less than

Parasitism of Megacopta cribraria (Hemiptera: Plataspidae) by Paratelenomus saccharalis (Hymenoptera: Platygastridae) in Organic Soybean Plots in Georgia, USA

Summary Megacopta cribraria (F.) (Hemiptera: Plataspidae) is a newly invasive, exotic pest of soybean (Glycine max [L.] Merr.; Fabales: Fabaceae) in the southeastern United States. In 2013, the exotic egg parasitoid Paratelenomus saccharalis (Dodd) (Hymenoptera: Platygastridae) was discovered parasitizing eggs of this pest in kudzu (Pueraria montana var. lobata [Willd.] Maesen & S. Almeida; Fabales: Fabaceae) and soybean in 3 states in this region of the United States. We evaluated parasitism of M. cribraria egg masses by P. saccharalis in conventional tillage and no-till organic soybean experimental plots in 2013. Density of M. cribraria egg masses was significantly higher in conventional tillage soybean than in no-till soybean in weeks 2 through 5 for the 7 wk period M. cribraria egg masses were detected on soybean. Percentage of parasitism of M. cribraria egg masses by P. saccharalis was significantly higher in conventional tillage soybean (58.4%) than in no-till soybean (44.9%). In general, parasitism rates of egg masses were higher in conventional tillage soybean, where M. cribraria egg mass density was higher, than in no-till soybean.

The Nitrogen Contained in Carbonized Poultry Litter is not Plant Available

Abstract Pyrolysis of biomass, reduces its volume, mass, odour, and potential pathogens, while concentrating nutrients in the resulting biochar. However, the plant availability of nutrients in particular of nitrogen remains largely unknown. Therefore, we investigated the nutrient availability of carbonized poultry litter. A nutrient poor soil was either fertilized with poultry litter or poultry litter carbonized at 500°C at the rates of 1.5, 3 and 6 t/ha. These organic amendments were compared with corresponding rates of mineral fertilizers (NH4NO3, KCl, CaHPO4, MgSO4) in a pot experiment. After four successive harvests of ryegrass (Lolium sp.) in a greenhouse we analyzed plant nutrient uptake and nutrient concentrations in the soil. While all treatments showed a linear increase in plant growth and nitrogen uptake, the plants fertilized with carbonized poultry litter did not show such a response. The carbonized poultry litter treatment produced more biomass than the unfertilized control, but the tissue concentration of nitrogen was below that of the control. Mehlich 1 extractable nutrients in the soil showed that there is more available phosphorus, potassium, calcium and magnesium in the soil fertilized with the carbonized poultry manure, but these available nutrients were not utilized due to the nitrogen limitation to plant growth. The results clearly show that nitrogen contained in carbonized poultry litter is not available for plants