Yuanliang Shi

Use of nitrogen process inhibitors for reducing gaseous nitrogen losses from land-applied farm effluents

Applications of dairy farm effluents to land may lead to ammonia (NH3) volatilization and nitrous oxide (N2O) emissions. Nitrogen (N) transformation process inhibitors, such as urease inhibitors (UIs) and nitrification inhibitors (NIs), have been used to reduce NH3 and N2O losses derived from agricultural N sources. The objective of this study was to examine the effects of amending dairy effluents with UI (N-(n-butyl) thiophosphoric triamide (NBTPT)) and NI (dicyandiamide (DCD)) on NH3 and N2O emissions. Treatments included either fresh or stored manure and either fresh or stored farm dairy effluent (FDE), with and without NBTPT (0.25xa0gxa0kg−1xa0N) or DCD (10xa0kgxa0ha−1), applied to a pasture on a free-draining volcanic parent material soil. The nutrient loading rate of FDE and manure, which had different dry matter contents (about 2 and 11xa0%, respectively) was 100xa0kgxa0Nxa0ha−1. Application of manure and FDE led to NH3 volatilization (15, 1, 17 and 0.4xa0% of applied N in fresh manure, fresh FDE, stored manure and stored FDE, respectively). With UI (NBTPT), NH3 volatilization from fresh manure was significantly (Pu2009<u20090.05) decreased to 8xa0% from 15xa0% of applied N, but the UI did not significantly reduce NH3 volatilization from fresh FDE. The N2O emission factors (amount of N2O–N emitted as a percentage of applied N) for fresh manure, fresh FDE and stored FDE were 0.13u2009±u20090.02, 0.14u2009±u20090.03 and 0.03u2009±u20090.01xa0%, respectively. The NI (DCD) was effective in decreasing N2O emissions from stored FDE, fresh FDE and fresh manure by 90, 51 and 46xa0% (Pu2009<u20090.05), respectively. All types of effluent increased pasture production over the first 21xa0days after application (Pu2009<u20090.05). The addition of DCD resulted in an increase in pasture production at first harvest on dayxa021 (Pu2009<u20090.05). This study illustrates that UIs and NIs can be effective in mitigating NH3 and N2O emissions from land-applied dairy effluents.

Effects of form of effluent, season and urease inhibitor on ammonia volatilization from dairy farm effluent applied to pasture

PurposeWith land application of farm effluents from cows during housing or milking as an accepted practice, there are increasing concerns over its effect on nitrogen (N) loss through ammonia (NH3) volatilization. Understanding the relative extent and seasonal variation of NH3 volatilization from dairy effluent is important for the development of management practices for reducing NH3 losses. The objectives of this study were to determine potential NH3 losses from application of different types of dairy effluent (including both liquid farm dairy effluent (FDE) and semi-solid dairy farm manure) to a pasture soil during several contrasting seasons and to evaluate the potential of the urease inhibitor (UI)—N-(n-butyl) thiophosphoric triamide (NBTPT, commercially named Agrotain®) to reduce gaseous NH3 losses.Material and methodsField plot trials were conducted in New Zealand on an established grazed pasture consisting of a mixed perennial ryegrass (Lolium perenne L.)/white clover (Trifolium repens L.) sward. An enclosure method, with continuous air flow, was used to compare the effects of treatments on potential NH3 volatilization losses from plots on a free-draining volcanic parent material soil which received either 0 (control) or 100xa0kgxa0Nxa0ha−1 as FDE or manure (about 2 and 15xa0% of dry matter (DM) contents in FDE or manure, respectively) with or without NBTPT (0.25xa0g NBTPT kg−1 effluent N). The experiment was conducted in the spring of 2012 and summer and autumn of 2013.Results and discussionResults showed that application of manure and FDE, both in fresh and stored forms, potentially led to NH3 volatilization, ranging from 0.6 to 19xa0% of applied N. Difference in NH3 losses depended on the season and effluent type. Higher NH3 volatilization was observed from both fresh and stored manure, compared to fresh and stored FDE. The difference was mainly due to solid contents. The losses of NH3 were closely related to NH4+-N content in the two types of manure. However, there was no relationship between NH3 losses and NH4+-N content in either type of FDE. There was no consistent seasonal pattern, although lower NH3 losses from fresh FDE and stored FDE applied in spring compared to summer were observed. Potential NH3 losses from application of fresh FDE or manure were significantly (Pu2009<u20090.05) reduced by 27 to 58xa0% when NBTPT was added, but the UI did not significantly reduce potential NH3 volatilization from stored FDE or manure.ConclusionsThis study demonstrated that NH3 losses from application of FDE were lower than from manure and that UIs can be effective in mitigating NH3 emissions from land application of fresh FDE and manure. Additionally, reducing the application of FDE in summer can also potentially reduce NH3 volatilization from pasture soil.

Effects of poly-γ-glutamic acid (γ-PGA) on plant growth and its distribution in a controlled plant-soil system

To demonstrate the responses of plant (Pakchoi) and soil to poly-γ-glutamic acid (γ-PGA) is essential to better understand the pathways of the promotional effect of γ-PGA on plant growth. In this study, the effects of γ-PGA on soil nutrient availability, plant nutrient uptake ability, plant metabolism and its distribution in a plant-soil system were tested using labeled γ-PGA synthesized from 13C1-15N-L-glutamic acid (L-Glu). γ-PGA significantly improved plant uptake of nitrogen (N), phosphorus (P), and potassium (K) and hence increased plant biomass. γ-PGA greatly strengthened the plant nutrient uptake capacity through enhancing both root biomass and activity. γ-PGA affected carbon (C) and N metabolism in plant which was evidenced with increased soluble sugar contents and decreased nitrate and free amino acids contents. About 26.5% of the γ-PGA-N uptake during the first 24u2009h, after γ-PGA application, was in the form of intact organic molecular. At plant harvest, 29.7% and 59.4% of γ-PGA-15N was recovered in plant and soil, respectively, with a 5.64% of plant N nutrition being derived from γ-PGA-N. The improved plant nutrient uptake capacity and soil nutrient availability by γ-PGA may partly explain the promotional effect of γ-PGA, however, the underlying reason may be closely related to L-Glu.

Effects of poly-γ-glutamic acid on soil nitrogen and carbon leaching and CO2 fluxes in a sandy clay loam soil

Abstract: Poly-γ-glutamic acid (γ-PGA) has shown a significant promotional effect on plant production. However, little is known of the environmental footprint generated from the application of γ-PGA. A laboratory trial was conducted to study the effects of γ-PGA on soil nitrogen and carbon leaching loss and carbon dioxide (CO2) emission by applying 0, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.4, and 0.8 g γ-PGA kg-1 soil to soil receiving 150 kg N ha-1 in the form of urea. Results showed that the cumulative loss of ammonium and nitrate decreased by 17.81%–29.31% and 8.27%–52.42% when the application rate of γ-PGA reached 0.1 g kg-1 soil. Cumulative total dissolved nitrogen loss was diminished by 7.16%–40.10% when the γ-PGA application rate was 0.2–0.8 g kg-1 soil. Cumulative loss of dissolved organic carbon was rarely affected by the γ-PGA, whereas cumulative CO2 flux was notably enhanced by 26.87%–180.70%. Soil total nitrogen (TN) and soil organic carbon (SOC) contents varied with the different application rates of γ-PGA; soil TN increased by 6.34%–8.04%, and SOC remained unchanged only when the γ-PGA application rate was 0.4–0.8 g kg-1 soil. In conclusion, before considering using γ-PGA in an agroecosystem, its effects on both the environment and plant production should be examined.