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Previous studies have indicated that soil properties and texture could lead to differences in N mineralization from applied organic materials. We conducted a 100-day (d) incubation study to measure net N mineralized from feather meal (14–0.1–0.1) and pellet mix (10–1–6) at 150 mg N kg soil −1 (approximately 72 kg N ha−1) incorporated into four common southeastern soils: Cecil 1, Cecil 2, Greenville, and Tifton. A second 23-d study was conducted to determine pH dynamics and the potential for ammonia volatilization from the same soils and materials. There were no differences in net N mineralized from pellet mix among soils, but net N mineralized from feather meal was lower in Greenville soil, which had the greatest clay content. Analysis of the first-order dynamics of N mineralization indicated that even in soils that differ in clay content it may be possible to describe N mineralization from feather meal and pellet mix with a single model. Our results also suggest that the effect of pH on the N mineralization dynamics of these fertilizers may be more important than the effect of clay content. No ammonia loss was observed regardless of soil texture, soil pH buffering capacity, or initial soil pH. [ABSTRACT FROM AUTHOR]

Dew deposition is often overlooked in humid regions, such as the southeastern USA, but may play an important role in nutrient cycling for surface-applied fertilizers and broiler litter. The objectives of this study were to measure dew in a pasture and to evaluate the effect of simulated dew on NH3 volatilization in a laboratory study. A microlysimeter method was used to measure dew in a tall fescue (Festuca arundinacea Schreb.) and bermudagrass (Cynodon dactylon L.) pasture over 206 d. In the 206 d measured, 119 d received dew with an average dew fall of 0.19 mm and greater events observed in the cooler spring and fall months. dew accumulated during the measurement period accounted for 6% of the precipitation measured. Under lab conditions, the effect of simulated, daily dew (0.2 mm) on NH3 volatilization from surface-applied broiler litter to air-dry soil was evaluated under diurnal fluctuations of temperature (6-27°C) and relative humidity (26-91%) for 15 d. dew application significantly increased NH3 volatilization losses (31% of the applied NH4-N and 5% of the applied total nitrogen [TN]) when compared with NH3 losses in the absence of dew (15% of the applied NH4-N and 2.4% of the applied TN). These results suggest that dew may affect NH3 losses from surface-applied broiler litter under dry field conditions. [ABSTRACT FROM AUTHOR]

Broiler litter is commonly surface applied to grasslands as fertilizer in the southeastern United States. Surface application may lead to losses of P in surface runoff and to losses of N through NH3 volatilization. Adding gypsum to broiler litter can reduce water-soluble P and, therefore, the potential for surface water contamination, but no information is currently available on the effect of gypsum on NH3 volatilization when broiler litter is applied to soil. We conducted three laboratory studies to evaluate the effect of adding flue-gas desulfurization (FGD) gypsum to broiler litter or soil on NH3 volatilized and N mineralized. In two studies, soil with or without 0.01 g FGD gypsum g-1 soil was packed into acrylic columns and broiler litter with or without 0.25 g FGD gypsum g-1 litter was applied on the soil surface and incubated at 25°C for 15 d. In a third study, litter with or without 0.25 g FGD gypsum g-1 litter was mixed with soil and incubated at 25°C for 63 d. Our results showed that the addition of FGD gypsum to broiler litter or soil did not affect net N mineralized or NH3 volatilized when litter was surface applied. Similarly, the addition of FGD gypsum to broiler litter did not affect net N mineralized when broiler litter was incorporated into soil. Thus, the addition of FGD gypsum at these rates does not change NH3 loss or N mineralized from broiler litter. [ABSTRACT FROM AUTHOR]

A tool to estimate the amount of net N mineralized under field conditions would be useful to adjust N fertilizer rates. A simulation model of soil N may be useful to develop such estimates, but must first be evaluated under the conditions in which it will be used. In this work, we implemented the N subroutine of CERES-N in Stella 6.0 modeling software to simulate net N mineralized from soil organic matter and cotton residues at three locations in a Coastal Plain field of south Georgia. The model was first calibrated with laboratory data of net N mineralized from an incubation study of cotton leaves and stems, and then used to simulate net N mineralized at three field locations. The calibrated model underestimated net N mineralized at two of the field locations by 45% and 56%, respectively. This underestimation was apparently caused by an underestimation of N mineralized from soil organic matter. To explore possible reasons for the underestimation, we collected soil samples monthly for 1 year to measure potentially mineralizable N at the three field locations, and used the data to modify the rate of soil organic matter mineralization throughout the year according to a sinusoidal wave. Simulated values of net N mineralized with this modification were within the 95% confidence interval for field-measured values. These results suggest that further research should be conducted to study the dynamics of the microbial population and microfauna present in soil, which may be partially responsible for seasonal changes in N mineralization rates. [Copyright &y& Elsevier]

Near-infrared reflectance (NIR) spectroscopy was evaluated for use in predicting the plant-available N (PAN = NH4-N + NO3-N) and mineralizable N (MN) from poultry litter (PL) samples on an "as received" water content basis. Near-infrared reflectance scans were collected on 118 PL samples of variable water content without drying. The samples were not fresh but had been stacked or otherwise stored for various lengths of time and were closely representative of the PL applied to crop and pasture soils in Georgia (United States). Average PAN for the samples studied was 6.3 g kg-1 PL (dry weight). One-hundred-day soil incubations with a loamy fine sand and a sandy clay loam were used to determine MN. An average of 19% of the organic N was mineralized after 100 d. Total PAN after 100 d (PAN100 = PANinitial + MN) averaged 33% of the total N for these samples. Near-infrared reflectance calibration models were developed with a modified partial least squares procedure. The results show that NIR calibration models can be developed on PL with variable water contents for total N (r² = 0.896, ratio of performance to deviation [RPD] = 3.5), NH4-N (r² = 0.795, RPD = 3.2), NO3-N (r² = 0.926, RPD = 2.7), uric acid N (r² = 0.909, RPD = 4.0), organic N (r² = 0.821, RPD = 3.6), water-soluble organic N (r² = 0.897, RPD = 4.0), MN (r² = 0.842, RPD = 2.6), initial PAN + MN (r² = 0.888, RPD = 2.6), total C (r² = 0.926, RPD = 3.7), and water content (r² = 0.996, RPD = 15.6). We conclude that drying is not necessary to develop highly successful NIR calibrations for N forms from PL. [ABSTRACT FROM AUTHOR]

Local effective microorganism (LEM) is an inoculant produced using leaf litter collected from forest floors near the location where it is to be utilized. While this locally-sourced inoculant is used around the world, more research is needed to fully understand the potential benefits or drawbacks of its use in agricultural systems. The objectives of this study were to observe the effects of combining LEM with composted broiler litter to fertilize edamame (Glycine max L.) on plant-available nitrogen, nematode trophic group communities, and soybean productivity. The study was carried out in a randomized, complete block design on piedmont soils in the southeastern United States comparing broiler litter composted with LEM, False-LEM or water (Control) treatments which were applied at the beginning of each growing season (June 2015, 2016, 2017). In the first year of the study, soil (0–10 cm) that received the LEM treatment mineralized greater amounts of N and mineralized N faster than CONT soils (P = 0.0665 and P = 0.0717), respectively, during one week of incubation. In year 2 (2016) plots experienced drought stress, with soil moistures as low as 2%. In LEM plots soil samples taken during the drought contained significantly greater populations of all nematodes, excluding Mononchidae when compared to the other treatments. When calculated per unit of soil N, measured after application of treatments, no differences in edamame soybean yield were observed between treatments. Combining LEM with composted broiler litter jump-started N mineralization early in growing seasons and maintained abundance of multiple nematode trophic groups during drought. This signifies LEM's potential to strengthen a soil's food web resistance to drought stress – providing more security for a functional agroecosystem under uncertain climate conditions. • Nitrogen mineralization is jump-started by addition of locally effect microorganisms. • Edamame nodulation was not influenced by bio-inoculum. • Bio-inoculant maintained free-living nematode communities under drought conditions. [ABSTRACT FROM AUTHOR]