Biochar and manure effects on nitrogen nutrition in silage corn

Aluminum-based water treatment residuals (Al-WTR) have a strong affinity to sorb phosphorus. In a proof-of-concept greenhouse column study, Al-WTR was surface-applied at 0, 62, 124, and 248 Mg/ha to 15 cm of soil on top of 46 cm of sand; Al-WTR rates were estimated to capture 0, 10, 20, and 40 years of phosphorus from an urban watershed entering an engineered wetland in Boise, Idaho, USA. Creeping red fescue (Festuca rubra) was established in all columns; one set of columns received no Al-WTR or plants. After plant establishment, once per week over a 12-week period, ~1.0 pore volumes of ~0.20 mg phosphorus/L was added to each column. Infiltration rates were measured, leachate was collected and analyzed for soluble phosphorus, and fescue yield, phosphorus concentration and uptake were determined. After plant harvest the sand, soil, and the Al-WTR layer were collected and analyzed for Olsen phosphorus, amorphous aluminum, iron, and phosphorus storage capacity (PSC), and soluble+aluminum+iron-bound, occluded, and calcium-bound phosphorus phases. Infiltration rate increased only due to the presence of plants. Leached phosphorus decreased (50%) with plants present; Al-WTR further reduced soluble phosphorus leaching losses (60%). Fescue yield, phosphorus concentration and uptake increased with increasing Al-WTR rate, due to Al-WTR sorbing and potentially making phosphorus more plant available; Olsen-extractable phosphorus increased with increasing Al-WTR rate, supporting this contention. The PSC was reduced with the 62 Mg/ha Al-WTR rate but maintained with greater Al-WTR rates. The 124 and 248 Mg/ha Al-WTR rates also contained greater phosphorus associated with the soluble+aluminum+iron and occluded phases which should be stable over the long-term (e.g., decadal). It was recommended to apply Al-WTR near the 124 and 248 Mg/ha rates in the future to capture urban runoff soluble phosphorus in the Boise, Idaho engineered wetland

Biochar and manure effects on net nitrogen mineralization and greenhouse gas emissions from calcareous soil under corn

Few multiyear field studies have examined the impacts of a one-time biochar application on net N mineralization and greenhouse gas emissions in an irrigated, calcareous soil; yet such applications are hypothesized as a means of sequestering atmospheric CO2 and improving soil quality. We fall-applied four treatments, stockpiled dairy manure (42 Mg/ha dry wt.); hardwood-derived biochar (22.4 Mg/ha); combined biochar and manure; and no amendments (control). Nitrogen fertilizer was applied in all plots and years based on treatment’s pre-season soil test N and crop requirements, and accounting for estimated N mineralized from added manure. From 2009 to 2011 we measured greenhouse gas fluxes using vented chambers, net N mineralization (NNM) using buried bags, corn yield, and N uptake, and in a succeeding year, root and shoot biomass and biomass C and N concentrations. Both amendments produced soil produced persistent soil effects. Manure increased seasonal and three year cumulative NNM, root biomass, and root:shoot ratio 1.6-fold, CO2-C gas flux 1.2-fold, and reduced soil NH4:NO3 ratio 58% relative to no-manure treatments. Relative to all other treatments on average, biochar-only produced 33% less cumulative NNM, 20% less CO2-C and 50% less N2O-N gas emissions, 35% less root biomass, and increased soil NH4:NO3 ratio 1.8-fold. These long-term effects suggest that biochar slightly impaired nitrification and N immobilization processes, and are likely caused by enduring biochar porosity and surface chemistry characteristics that influence N-transform-ation processes, alter microbial populations, and sequester soil ammonium. While the biochar-only treatment demonstrated a potential to increase corn yields and minimize CO2-C and N2O-N gas emissions in these calcareous soils; biochar also caused decreased corn yields under certain soil nutrient conditions. Combining biochar with manure effectively utilizes these soil amendments as it eliminated potential yield reductions and maximized manure net N mineralization potential

The effects of biochar and manure in silage corn

Amending soil with biochar may be a means of sequestering atmospheric CO2 and improving soil quality, but few multiyear field studies have examined the impacts of a one-time biochar application in an irrigated, calcareous soil. We fall-applied four treatments: dairy manure (18.7 tons/ac dry wt.); hardwood-derived biochar (10 tons/ac dry wt.); combined biochar and manure; and no amendments (control). We measured net N-mineralization using buried soil bags and soil greenhouse gas emissions (CO2, CH4, and N2O) from late spring to fall, corn silage yields, and crop N uptake each year. The influence of biochar and manure on silage yield changed with time after application in fall 2008. Biochar increased corn yields slightly (5%) in 2009, decreased yields by 14% in 2010, and had no effect in 2011. Conversely, manure had no affect on yields in 2009, but increased yields substantially in 2010 (33%) and again slightly in 2011 (7%). When compared with a class comprising all other treatments, biochar-only produced 33% less cumulative net N mineralization, 20% less CO2-C and 50% less N2O-N gas emissions, and increased the soil NH4:NO3 ratio 1.8-fold, indicating that biochar impaired nitrification and N immobilization processes. While the biochar-only treatment demonstrated a potential to increase corn yields and minimize CO2-C and N2O-N gas emissions in these calcareous soils, biochar also caused decreased corn yields under conditions in which NH4-N dominated the soil inorganic N pool. The combined biochar-manure treatment more effectively utilized the two soil amendments as it eliminated potential yield reductions caused by biochar and maximized manure net N mineralization potential

Does turbulent-flow conditioning of irrigation water influence soil chemical processes: II. Long-term soil and crop study

Recent laboratory evidence suggests that the intrinsic behavior of molecular water in soil is altered by turbulent-flow conditioning (CTap) of mineralized irrigation water (Tap). This 9-yr (2009 to 2017), irrigated, outdoor, cropped pot study evaluated the effect of Tap and CTap irrigation water on soil leachate chemistry, nutrient availability, and aboveground crop biomass yield and nutrient uptake. CTap increased cumulative mass losses of: NO3-N 2.5-fold; Mn 2-fold; K 1.6-fold; Mg, DOC, and NH4-N an average 1.2-fold; and increased the mean EC of leachate 1.2-fold. In both the current and a previous laboratory study (see Part 1), K, NH4-N, and Mg were leachate components most consistently selected by multivariate analysis as best discriminating between water treatments. The evidence also suggests that CTap increased mean available soil: Zn 2.4-fold; Cu, K, and Olsen P an average 1.4-fold; Na and Fe 1.2-fold; and decreased soil TC (4%), TIC (8%) and Mg (9%) relative to the Tap. In addition, CTap increased average crop biomass element concentrations of: Zn, Fe, and Al an average 1.3-fold; TN, Ca, K, and S 1.1-fold; and decreased TC (2%) relative to Tap. If the capacity of this simple device to increase soil cation leaching can be confirmed in broader applications, it could potentially provide an economical means of increasing the availability of nutrients in treated soils and managing or remediating degraded, salt-affected soils

Biochar elemental composition and factors influencing nutrient retention

Biochar is the carbonaceous solid byproduct of the thermochemical conversion of a carbon-bearing organic material, commonly high in cellulose, hemicelluloses, or lignin content, for the purposes of carbon sequestration and storage. More specifically, the thermal conversion process known as pyrolysis occurs when carbon-containing substances are introduced to elevated temperatures in the absence of oxygen at varying residence times, yielding biochar. Several pyrolysis techniques employed to produce biochar differ in the temperature of reaction and residence time in the reactor. Different reactor residence times are described as slow (hours to days), fast (seconds to minutes), and flash (seconds). Fast or flash pyrolysis typically occurs around 500oC with residence times less than 500 milliseconds to 1 second and produces relatively greater gas yields with a concomitant decrease in biochar yield (~ 12%). Slow pyrolysis temperatures have ranged from 350 to 750oC but with residence times ranging from minutes to days. Slow pyrolysis yields a greater quantity of biochar (between 25 to 35%). Pyrolysis temperature and type may be varied to maximize the desired biochar end-product. In general, increasing pyrolysis temperature tends to increase biochar total carbon, potassium, and magnesium content, pH, and surface area, and decrease cation exchange capacity. Slow pyrolysis, in general, tends to produce biochars with greater nitrogen, sulfur, available phosphorus, calcium, magnesium, surface area, and cation exchange capacity as compared to fast pyrolysis. In addition to altering temperature and time, the importance of feedstock source needs to be recognized when utilizing biochar in situations such as a soil conditioner. Over the last 10 years biochar research and use has expanded exponentially and so have the feedstocks utilized. Biochars have now been created from corn, wheat, barley and rice straw, switchgrass, peanut, pecan, and hazelnut shells, sugarcane bagasse, coconut coir, food waste, hardwood and softwood species, poultry and turkey litter, swine, dairy, and cattle manure, and biosolids to name a few. Feedstock source influences end-product characteristics, and in general most plant-based biochars containing elevated carbon content and lesser quantities of necessary plant nutrients as compared to manure-based biochars. It has been demonstrated that the mineral content of the feedstock has a significant effect on product distribution, with higher amounts of chloride salts reducing the amount of the solid biochar product. In addition, chloride and other inorganic salts also impact the chemical composition of the liquid, gas, and char pyrolysis products, potentially producing products with higher economic values. Existing studies indicate that even the trace amounts of minerals present in the various biomass sources and feedstock mixtures do have an impact on the chemical compositions of the products. Furthermore, both temperature and residence time, along with feedstock source or mixtures of sources, affect end-product characteristics

Manure and fertilizer effects on carbon balance and organic and inorganic carbon losses for an irrigated corn field

Data collected from both artificially and field (naturally) weathered biochar suggest that a potentially significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Through scanning electron microscopy (SEM) we characterized this physical weathering which increased structural fractures and possessed higher numbers of liberated biochar fragments. This was hypothesized to be due to the graphitic sheet expansion accompanying water sorption coupled with comminution. These fragments can be on the micro and nano-scale, but are still carbon-rich particles with no detectable alteration in the oxygen to carbon ratio of the original biochar. However, these particles are now easily dissolved and could be moved by infiltration. There is a need to understand how to produce biochars that are resistant to physical degradation in order to maximize long-term biochar C-sequestration potential within soil systems

Biochar Usage: Pros and Cons

Soil fertility benefits of charcoal application have been reported as early as 1847 indicating that plant nutrients are sorbed within charcoal pores. The use of biomass-derived black carbon or biochar, the solid byproduct from the pyrolysis processing of any organic feedstock, has garnered recent attention as a potential vehicle for carbon sequestration and a beneficial soil conditioner. However, most of the past biochar research has focused on improving the physico-chemical properties of tropical (i.e. terra preta) and highly weathered soils, while little research has focused on improving arid or semi-arid soils of the USA. Here, we present an overview of the potential benefits and drawbacks of biochar usage in western US agro-ecosystems based on research performed at multiple USDA-Agricultural Research Service locations (Washington, Idaho, Minnesota, and South Carolina)

Physical Disintegration of Biochar: An Overlooked Process

Data collected from both artificially and field (naturally) weathered biochar suggest that a potentially significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Through scanning electron microscopy (SEM) we characterized this physical weathering which increased structural fractures and possessed higher numbers of liberated biochar fragments. This was hypothesized to be due to the graphitic sheet expansion accompanying water sorption coupled with comminution. These fragments can be on the micro and nano-scale, but are still carbon-rich particles with no detectable alteration in the oxygen to carbon ratio of the original biochar. However, these particles are now easily dissolved and could be moved by infiltration. There is a need to understand how to produce biochars that are resistant to physical degradation in order to maximize long-term biochar C-sequestration potential within soil systems

Soil health, crop productivity, microbial transport, and mine spoil response to biochars

Biochar is being evaluated by scientists from the United States Department of Agriculture (USDA) Agricultural Research Service (ARS) for its potential to sequester soil C, to improve soil health, and to increase crop yields. ARS scientists from multiple locations such as Florence, SC, Kimberly, ID, Bowling Green, KY, Corvallis, OR, and St. Paul, MN, are conducting investigations with agronomic experiments at the laboratory, greenhouse, and field plot scales. To further expand biochars utility, ARS scientists have collaborated with United States Environmental Protection Agency (US EPA) investigators to reclaim mine-impacted soils. In the agronomic investigations, both positive and negative aspects of biochar application were revealed. In some experiments, biochars were reported to have no effect on crop yields, and minimal impact on movement of microbial pathogens through soil. In other experiments, biochars were reported to improve soil fertility, increase water retention, and bind with heavy metals in solutions and in mine spoil soils. This variation in biochars influence, substantiates and encourages further work on the designer biochar concept, which states that the biochars can be crafted for targeted agronomic and environmental purposes. There is a need to broadcast the successes and failures of biochar research reported by scientists from both agencies. Consequently, the objectives of this review are: to report on biochar effectiveness as a soil amendment; to ascertain its ability to modify soil properties, to evaluate its impact on soil leaching of microbes; and its potential capacity to help reclaim mine spoil sites