H. Allen Torbert

United States Department of Agriculture | USDA · Agricultural Research Service (ARS)

Producers are looking for more sustainable methods of producing fresh vegetables. No-till systems that use cover crops to keep the soil surface covered can increase sustainability by reducing soil erosion, reducing weed pressure, and retaining soil moisture compared to bare soil cropping systems. Cover crop termination methods along with planting e...

Phosphorus (P) runoff from agricultural lands receiving poultry litter (PL) poses a major environmental challenge. Application of flue-gas-desulfurization (FGD)-gypsum produced from coal power plants in agricultural lands has shown promise to reduce P losses. However, no information is available about the effectiveness of FGD-gypsum addition in red...

Numerous studies have investigated effects of long-term manure application on total phosphorus (P) and inorganic P (Pi ), but few have evaluated soil organic P (Po ). Little is known about crop management effects on Po in soils with varying minerology. In this study, sequential fractionation was used to characterize specific P forms after 25 y of b...

Phosphorus (P) over-loading is often a central topic due to its linkage to harmful algal blooms (HABs) and its importance in wastewater treatment that has fueled immediate remediation attempts to reduce P loading from point (e.g., wastewater) and nonpoint sources (e.g., fertilizers). Conventional remediation techniques (e.g., filtration) are often...

Flue-gas desulfurization (FGD) gypsum, a byproduct of coal-fired electrical utility plants, has been shown to effectively reduce phosphorus (P) leaching in many agricultural systems. However, its applications in horticultural production systems have been insufficiently researched resulting in limited industry adoption. To evaluate the efficacy of F...

Repeated applications of poultry litter (PL) in weathered soils cause soil phosphorus (P) accumulation and is a major environmental concern. Much remains unknown about the distribution of inorganic P (Pi) and organic P (Po) forms along with their retention and release characteristics in soils that have had a history of PL application. The objective...

Multiple tagged neutrons are emitted from an associated particle imaging neutron generator. The tagged neutrons penetrate a target material and interact with the target material nucleus-which emits nucleus-specific gamma rays. A gamma ray detector detects all gamma rays including the nucleus-specific gamma rays. An alpha gamma timing spectrum is co...

This chapter describes technical aspects of neutron stimulated gamma ray analysis of soil carbon. The introduction covers general principles, different modifications of neutron gamma analysis, measurement system configurations, and advantages of this method for soil carbon analysis. Problems with neutron-gamma technology for soil carbon analysis an...

This chapter is devoted to the application of neutron-gamma methods, mainly pulsed fast thermal neutron analysis (PFTNA), for soil elemental measurement and mapping. Herein, we provide a description of general PFTNA principles, main components and configurations of a PFTNA field system, and procedures for primary data (gamma spectra) acquisition fo...

Mapping total soil potassium based on scanning gamma spectroscopy, paired with GPS technology is described. Total potassium was determined from the 1.46 MeV gamma peak area of the 40K isotope. A calibration coefficient was defined based on measuring spectra of small reference samples (dozen of cubic decimeters) and Monte-Carlo simulations (Geant4)...

In response to agriculture’s contribution to surface water quality, considerable effort is being made to develop best management practices to reduce nutrient loss. To evaluate the efficacy of gypsum as a horticultural media amendment for controlling phosphorus (P) leaching, flue gas desulfurization (FGD) gypsum was added to a standard horticultural...

Abstract Individual states in the United States have adopted different soil test P (STP) methods for agronomic and environmental purposes. Working between soil regions and state borderlines can be complicated by using multiple STP methods. For example, Alabama uses Mehlich 1 (M1) for noncalcareous soils (Appalachian Plateau [AP], Coastal Plain [CP]...

Applications of neutron-gamma analysis for chlorine determination in different materials (e.g., solids, aqueous solutions, surface contaminations) are discussed. Solid samples were measured with a Pulsed Fast/Thermal Neutron Analysis (PFTNA) system consisting of a pulsed neutron generator and sodium iodide gamma detectors and an Associated Particle...

Previous work by these authors have quantified cumulative greenhouse gas (GHG) emissions for several woody and herbaceous perennial species, in interaction with several standard best management practices (container size, fertilizer application and irrigation delivery methods, and light level). In this study, the greenhouse production of three annua...

With rising global demand of poultry products, a surge in poultry production would warrant safe disposal of waste byproducts such as poultry litter (PL). A dilemma exists over environmental phosphorus (P) loss risk and agronomic utilization of PL in highly weathered soils with high P fixation capacity. The objective of this study was to determine P...

Canola (Brassica napins L.) has the potential for being used in a double‐cropping system (two crops grown in one year) as a winter crop in the humid subtropical southeastern US climate, but little information is known about its nitrogen management when grown in this region. Thus, a field study was conducted at two locations (Shorter, AL ‐ Compass l...

Canola (Brassica napins (L.)) has the potential to be used as a winter crop in the southeastern US, but little information is known about its nitrogen management when grown in this region. Increasing fertilizer costs have also increased interest in using poultry litter (PL) as an alternative nutrient source for crops in this region. However, evalua...

Water availability is a major constraint affecting the growth and yield of crops/plants worldwide. Some studies have shown that specific strains of free-living bacteria found in the plant rhizosphere can improve the tolerance of plants during water stress. A greenhouse study was conducted to evaluate the effects of two mixtures of plant growth-prom...

Soil elemental (mainly carbon) analysis is one of the critical features in agricultural practice. The based on different physical principal methods are began applied today instead of traditional chemical analysis. One of such methods is neutron-gamma analysis. This method has a lot of advantage before traditional methods. It is nondestructive in si...

Accurate soil carbon field mapping can benefit modern agricultural practices. For creating such maps, soil carbon measurements using neutron-gamma analysis were developed and applied as a better alternative to traditional chemical analysis. Main components of a neutron-gamma analysis system are a neutron generator, gamma detectors, and special elec...

The level to which ornamental plant production impacts rising atmospheric greenhouse gas (GHG) concentrations remains unknown. Research to date has focused on developing baseline estimations of GHG emissions from plant-pot production systems and their contribution to global warming potential. To date, pot size, irrigation delivery method and fertil...

Soil elemental (mainly carbon) analysis is one of the critical features in agricultural practice. The based on different physical principal methods are began applied today instead of traditional chemical analysis. One of such methods is neutron-gamma analysis. This method has a lot of advantage before traditional methods. It is nondestructive in si...

Pastures represent a significant portion of the rural landscape in the southeastern US, yet remain understudied agro-ecosystems in terms of the effects of rising atmospheric CO 2 concentration. Therefore, in 2005 we initiated a long-term (10 yr) study of bahiagrass (Paspalum notatum Flüggé) response to elevated CO 2 using open top field chambers on...

The United States Army produces a significant amount of classified paper waste that is pulverized to a fine consistency unsuitable for recycling. However, cheap, high quality organic materials such as classified paper waste are useful as soil amendments. The objective of this research was to evaluate the utilization of pulverized classified paper w...

The possible application of Pulsed Fast/Thermal Neutron Analysis (PFTNA) for determining the carbon-to-nitrogen ratio (C/N) of compost will be discussed. This analysis method has several advantages over traditional chemical analysis, including that it is a nondestructive in situ method that does not require extensive sample collection and it analyz...

Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage. Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed. A Global Positioning System (GPS) device and softwares required to simultaneously acquire gamma signals and geographical positions duri...

Laboratory determination of carbon content in 30-50 kg soil samples is described. The method is based on the tagged neutron technique. Procedure for carbon determination in such samples was developed based on a physical model and Monte-Carlo simulations (Geant4) of neutron stimulated gamma spectra. Measurement results of samples with different dens...

Sustainable agricultural practices have been steadily increasing in the last couple of decades. These management practices frequently involve cover crops, less or no-tillage, and organic fertilization. In this study, we evaluated the effects of cropping systems, tillage and no-tillage, and the application of poultry litter (PL) on selected soil phy...

An associated particle imaging (API) experimental setup with nanosecond precision electronics was constructed and tested. This API setup has the ability to measure alpha-gamma coincidence (timing) spectra, time correlated energy gamma spectra, and energy correlated timing spectra. The speed of 14.1 MeV neutron was defined from measurement of carbon...

Gypsum has a long history as a soil amendment. Information on how flue gas desulfurization (FGD) gypsum affects soil, water, and plant properties across a range of climates and soils is lacking. We conducted a meta‐analysis using data from 10 field sites in the United States (Alabama, Arkansas, Indiana, New Mexico, North Dakota, Ohio, and Wisconsin...

Agriculture is one of the largest contributors of greenhouse gas (GHG) emissions. To date, much work on reducing GHG emissions has centered on row crops, pastures, forestry, and animal production systems, while little emphasis has been placed on specialty crop industries such as horticulture. In this horticulture container study, Japanese boxwood (...

There are concerns regarding the fate of nutrients from surface application of animal manure. One approach to reduce losses of P is to treat manure with industrial byproducts such as flue gas desulfurization (FGD) gypsum. However, concerns regarding potentially toxic elements contributed to the environment have arisen based on previous element‐rich...

A greenhouse study was conducted to evaluate the effects of plant growth-promoting rhizobacteria (PGPR) on root establishment and biomass production of corn (Zea mays L.) using three fertility sources (poultry litter (PL), biosolids, and urea). Applying PL significantly improved root morphological parameters and increased plant biomass at the V4, V...

This work is devoted to review the new scientific divisions that emerged in agrophysics in the last 10-15 years. Among them are the following: 1) soil quality assessment using a fuzzy indicator modeling, 2) zoning of an agricultural field using a fuzzy indicator modeling, 3) agrophysical and physic-technical bases of plant breeding, and 4) developm...

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra du...

Gypsum (calcium sulfate dihydrate, CaSO 4 ⋅2H 2 O) has long been used to improve soils and crop production, and its use has recently been encouraged by the USDA–NRCS for soil conservation through a new Conservation Practice Standard: Code 333. However, there is concern regarding the adverse effects of excessive direct ingestion of sulfate in gypsum...

Considerable amounts of flue gas desulfurization (FGD) gypsum are being produced as a by-product of generating electricity. As a result, beneficial reuse of this by-product is being sought to reduce landfilling and its associated cost. The use of this by-product as a low-cost soil amendment for suppling Ca and S to crops, improving soil structure,...

Microbial-based inoculants have been reported to stimulate plant growth and nutrient uptake. However, their effect may vary depending on the growth stage when evaluated or fertilizer applied. Thus, the objective of this study was to test the hypothesis that microbial-based inoculants known to promote root growth and nutrient uptake will promote pla...

Soil pore structure has a strong influence on water retention, and is itself influenced by plant and microbial dynamics such as root proliferation and microbial exudation. Although increased nitrogen (N) availability and elevated atmospheric CO2 concentrations (eCO2 ) often have interacting effects on root and microbial dynamics, it is unclear whet...

Considerable effort is being made within the scientific community to identify mechanisms to reduce nitrous oxide (N2O) emissions from agricultural soils. The objective of this study was to test the hypothesis that microbial-based inoculants known to promote root growth and nutrient uptake will reduce N2O emissions in the presence of ammonium nitrat...

Flue gas desulfurization (FGD) gypsum may be a viable low-cost alternative bedding material for broiler production. In order to evaluate FGD gypsum's viability, a study was conducted to determine its influence on live performance (body weight, feed consumption, feed efficiency, and footpad dermatitis), litter characteristics (caking, moisture perce...

Cover crops are an important part of no-till conservation agriculture, and these crops must produce optimum biomass amounts to effectively protect the soil surface from erosion and runoff, conserve soil water, and provide a physical barrier against weeds. Because of the large amount of residue produced by cover crops, the residue must be managed ap...

Nitrous oxide (N2O) emissions are increasing at an unprecedented rate owing to the increased use of nitrogen (N) fertilizers. Thus, new innovative management tools are needed to reduce emissions. One potential approach is the use of microbial inoculants in agricultural production. In a previous incubation study, we observed reductions in N2O emissi...

Current state of agricultural lands is defined under influence of processes in soil, plants and atmosphere and is described by observation data, complicated models and subjective opinion of experts. Problem-oriented indicators summarize this information in useful form for decision of the same specific problems. In this paper, three groups of proble...

Inelastic neutron scattering (INS) was applied to determine soil carbon content. Due to non-uniform soil carbon depth distribution, the correlation between INS signals with some soil carbon content parameter is not obvious; however, a proportionality between INS signals and average carbon weight percent in ~10 cm layer for any carbon depth profile...

Increased biofuel production has prompted concerns about the environmental tradeoffs of biofuels compared to petroleum-based fuels. Biofuel production in general, and feedstock production in particular, is under increased scrutiny. Water footprinting (measuring direct and indirect water use) has been proposed as one measure to evaluate water use in...

In this work, an Adaptive Neuro-Fuzzy Inference System (ANFIS) applied for study the contiguous relations between soil disturbed indicators. Several ANFIS surfaces, which described the contiguous relations between individual soil disturbed indicators (DFSs), values of soil parameters and depth, as well as the contiguous relations between DFSs and c...

Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. 'Conthery'), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.'Ruby')] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry...

Controlling the threat that pastures intensively managed with poultry litter (PL) pose to accelerating eutrophication is a major issue in the southeastern United States. Gypsum (CaSO4) has been identified as a promising management tool for ameliorating litter P losses to runoff. Thus, research was conducted to elucidate gypsum's residual effects on...

Soil disturbance can have important impacts on soil quality and productivity which impact management decisions. However, the extent of potential damage to soil due to soil disturbance is not always obvious. Methods are needed to determine the level of soil disturbance from soil testing. A methodology for this problem could be found using a tool for...

Cogongrass [Imperata cylindrica (L.) P. Beauv] is an invasive C4 perennial grass which is listed as one of the top ten worst weeds in the world and is a major problem in the Southeast US. Five cogongrass ecotypes [Florida (FL), Hybrid (HY), Louisiana (LA), Mobile (MB), and North Alabama (NA)] collected across the Southeast and a red-tip (RT) orname...

A modified low-cost method of measuring ammonia (NH3) volatilization is described for use with static chambers. This technique utilizes glass tubes coated with oxalic acid placed inside the chambers to adsorb NH3 being evolved from soil. The advantage of this procedure is that it can be used to quantify NH3 emissions from field plots used for evalu...