Impact of switchgrass biochars with supplemental nitrogen on carbon-nitrogen mineralization in highly weathered Coastal Plain Ultisols.

Although an increase in soil fertility is the most frequently reported benefit linked to adding biochar to soils, there is still a need to pursue additional research that will improve our understanding on the impact of soil fertility enhancement because the effect could vary greatly between switchgrass (Panicum virgatum, L) residues (USG) and switchgrass biochars (SG). We hypothesized that SG with supplemental nitrogen (N) would deliver more positive effects on carbon (C) and N mineralization than USG. The objective of this study was to evaluate the effects of USG and SG, with or without supplemental inorganic N fertilizer on C and N mineralization in highly weathered Coastal Plain Ultisols. The application rate for SG and USG based on a corn yield goal of 112 kg ha(-1) was 40 Mg ha(-1). Inorganic N was added at the rate of 100 kg N ha(-1), also based on a corn yield of 7.03 tons ha(-1). Experimental treatments were: control (CONT) soil; control with N (CONT + N); switchgrass residues (USG); USG with N (USG + N); switchgrass biochars at 250 °C (250SG); SG at 250 °C with N (250SG + N); SG at 500 °C (500SG); and SG at 500 °C with N (500SG + N). Cumulative and net CO2-C evolution was increased by the additions of SG and USG especially when supplemented with N. Soils treated with 250SG (8.6 mg kg(-1)) had the least concentration of total inorganic nitrogen (TIN) while the greatest amount of TIN was observed from the CONT + N (19.0 mg kg(-1)). Our results suggest that application of SG in the short term may cause N immobilization resulting in the reduction of TIN.

Efficacies of designer biochars in improving biomass and nutrient uptake of winter wheat grown in a hard setting subsoil layer.

In the Coastal Plains region of the United States, the hard setting subsoil layer of Norfolk soils results in low water holding capacity and nutrient retention, which often limits root development. In this region, the Norfolk soils are under intensive crop production that further depletes nutrients and reduces organic carbon (C). Incorporation of pyrolyzed organic residues or "biochars" can provide an alternative recalcitrant C source. However, biochar quality and effect can be inconsistent and different biochars react differently in soils. We hypothesized that addition of different designer biochars will have variable effects on biomass and nutrient uptake of winter wheat. The objective of this study was to investigate the effects of designer biochars on biomass productivity and nutrient uptake of winter wheat (Triticum aestivum L.) in a Norfolk's hard setting subsoil layer. Biochars were added to Norfolk's hard setting subsoil layer at the rate of 40 Mg ha(-1). The different sources of biochars were: plant-based (pine chips, PC); animal-based (poultry litter, PL); 50:50 blend (50% PC:50% PL); 80:20 blend (80% PC:20% PL); and hardwood (HW). Aboveground and belowground biomass and nutrient uptake of winter wheat varied significantly (p⩽0.0001) with the different designer biochar applications. The greatest increase in the belowground biomass of winter wheat over the control was from 80:20 blend of PC:PL (81%) followed by HW (76%), PC (59%) and 50:50 blend of PC:PL (9%). However, application of PL resulted in significant reduction of belowground biomass by about 82% when compared to the control plants. The average uptake of P, K, Ca, Mg, Na, Al, Fe, Cu and Zn in both the aboveground and belowground biomass of winter wheat varied remarkably with biochar treatments. Overall, our results showed promising significance for the treatment of a Norfolk's hard setting subsoil layer since designer biochars did improve both aboveground/belowground biomass and nutrient uptake of winter wheat.

Ameliorating soil chemical properties of a hard setting subsoil layer in Coastal Plain USA with different designer biochars.

Biochar application is an emerging management option to increase soil fertility. Biochars could improve chemical properties of soils with hard setting subsoil layer. However, biochar effect can be inconsistent because different biochars react differently in soils. We hypothesized that addition of designer biochars will have variable effects on improving the chemical properties of hard setting layers. The objective of this study was to investigate the effects of biochars on soil properties in Norfolk's soil with a hard setting subsoil layer grown with winter wheat (Triticum aestivum L.). All designer biochars were added at the rate of 40 Mg ha(-1). Feedstocks used for biochars production were: plant-based (pine chips, 100% PC); animal-based (poultry litter, 100% PL); 50:50 blend (50% PC:50% PL); 80:20 blend (80% PC:20% PL); and hardwood (100% HW). Higher nutrient availability was found after additions of biochars especially additions of 100% PL and 50:50 blend of PC and PL. On the average, applications of 100% PL and 50:50 blend of PC:PL had the greatest amount of soil total nitrogen with means of 1.94±0.3% and 1.44±0.3%, respectively. When compared with the control and other biochars, 50:50 blend of PC:PL additions resulted in increase of 669% for P, 830% for K, 307% for Ca, 687% for Mg and 2315% for Na while application of 100% PL increased the concentration of extractable P, K, Ca, Mg, and Na by 363%, 1349%, 152%, 363%, and 3152%, respectively. Overall, our results showed promising significance since biochars did improve chemical properties of a Norfolk's soil.

Carbon mineralization in two ultisols amended with different sources and particle sizes of pyrolyzed biochar.

Biochar produced during pyrolysis has the potential to enhance soil fertility and reduce greenhouse gas emissions. The influence of biochar properties (e.g., particle size) on both short- and long-term carbon (C) mineralization of biochar remains unclear. There is minimal information on the potential effects of biochar particle sizes on their breakdowns by soil microorganism, so it is unknown if the particle size of biochar influences C mineralization rate and/or stability in soils. In order to evaluate the effect of different sources (BS) and particle sizes (BF) of biochar on C loss and/or stability in soils, an incubation study on C mineralization of different biochar sources and particle sizes was established using two soils (ST): Norfolk soil (fine loamy, kaolinitic, thermic, typic Kandiudults) and Coxville soil (fine loamy kaolinitic, thermic, Paleaquults). In separate incubation vessels, these soils were amended with one of two manure-based biochars (poultry litters, PL; swine solids, SS) or one of two lignocellulosic-based biochars (switchgrass, SG; pine chips, PC) which were processed into two particle sizes (dust, <0.42 mm; pellet, >2 mm). The amount of CO2 evolved varied significantly between soils (p≤0.0001); particle sizes (p≤0.0001) and the interactions of biochar source (p≤0.001) and forms of biochars (p≤0.0001) with soil types. Averaged across soils and sources of biochar, CO2-C evolved from dust-sized biochar (281 mg kg(-1)) was significantly higher than pellet-sized biochar (226 mg kg(-1)). Coxville soils with SS biochar produced the greatest average CO2-C of 428 mg kg(-1) and Norfolk soils with PC had the lowest CO2-C production (93 mg kg(-1)). Measured rates of carbon mineralization also varied with soils and sources of biochar (Norfolk: PL>SS>SG≥PC; Coxville: PC>SG>SS>PL). The average net CO2-C evolved from the Coxville soils (385 mg kg(-1)) was about threefold more than the CO2-C evolved from the Norfolk soils (123 mg kg(-1)). Our results suggest different particle sizes and sources of biochar as well as soil type influence biochar stability.

Nitrogen and phosphorus status of soils and trophic state of lakes associated with forage-based beef cattle operations in Florida.

Forage-based livestock systems have been implicated as major contributors to deteriorating water quality, particularly for phosphorus (P) from commercial fertilizers and manures affecting surface and ground water quality. Little information exists regarding possible magnitudes of nutrient losses from pastures that are managed for both grazing and hay production and how these might impact adjacent bodies of water. We examined the changes that have occurred in soil fertility levels of rhizoma peanut (Arachis glabrata Benth.)-based beef cattle pastures (n = 4) in Florida from 1988 to 2002. These pastures were managed for grazing in spring followed by haying in late summer and were fertilized annually with P (39 kg P2O5 ha(-1)) and K (68 kg K2O ha(-1)). Additionally, we investigated trends in water quality parameters and trophic state index (TSI) of lakes (n = 3) associated with beef cattle operations from 1993 to 2002. Overall, there was no spatial or temporal buildup of soil P and other crop nutrients despite the annual application of fertilizers and daily in-field loading of animal waste. In fact, soil fertility levels showed a declining trend for crop nutrient levels, especially soil P (y = 146.57 - 8.14 x year; r2= 0.75), even though the fields had a history of P fertilization and the cattle were rotated into the legume fields. Our results indicate that when nutrients are not applied in excess, cow-calf systems are slight exporters of P, K, Ca, and Mg through removal of cut hay. Water quality in lakes associated with cattle production was "good" (30-46 TSI) based on the Florida Water Quality Standard. These findings indicate that properly managed livestock operations may not be major contributors to excess loads of nutrients (especially P) in surface water.

Characterization of the pesticide chlordane in estuarine river sediments.

Sediments are increasingly recognized as both carrier and potential source of contaminants in aquatic environments. This study investigated the characteristics and spatial distribution of total chlordane and its three most abundant compounds, including alpha-chlordane, gamma-chlordane, and trans-nonachlor, in sediments from the Cedar and Ortega rivers, Florida, USA, using geographic information system (GIS)-based kriging analyses and field measurements. Kriging analysis showed that two areas, one from the Cedar River area and the other from the northern end of the Ortega River area, were contaminated. The maximum concentrations of total chlordane, gamma-chlordane, alpha-chlordane, and trans-nonachlor in the sediments were, respectively, 101.8, 20.1, 26.3, and 19.2 microg/kg. A plot of total organic carbon (TOC)-normalized chlordane concentrations showed that effects of grain size on sediment chlordane contamination were negligible. A principal axis analysis further revealed that a linear correlation existed between alpha-chlordane and total chlordane as well as between gamma-chlordane and total chlordane, whereas no correlation existed between trans-nonachlor and total chlordane. Comparison of total chlordane concentration with Florida Sediment Assessment Guidelines showed that the Cedar River and the northern end of the Ortega River had total chlordane concentrations above the probable effect level (4.79 microg/kg), which could pose a potential risk to aquatic life.