Excess nitrogen (N) after animal slurry application is a persistent problem of intensive agriculture, with consequences such as environmental pollution by ammonia (NH3) and nitrous oxide (N2O) emissions and nitrate (NO3−) leaching. High-carbon organic soil amendments (HCAs) with a large C:N ratio have shown the potential of mitigating unintended N losses from soil. To reduce gaseous and leaching N losses after the application of slurry, a laboratory incubation study was conducted with silt loam soil. We tested the potential of three different types of HCA—wheat straw, sawdust, and leonardite (application rate 50 g C L−1 slurry for each of the three HCAs)—to mitigate N loss after amendment of soil with pig and cattle slurry using two common application modes (slurry and HCA mixed overnight with subsequent addition to soil vs. sequential addition) at an application rate equivalent to 80 kg N ha−1. Compared to the control with only soil and slurry, the addition of leonardite reduced the NH3 emissions of both slurries by 32–64%. Leonardite also reduced the total N2O emissions by 33–58%. Wheat straw reduced N2O emissions by 40–46%, but had no effect on NH3 emission. 15 N labeling showed that the application of leonardite was associated with the highest N retention in soil (24% average slurry N recovery), followed by wheat straw (20% average slurry N recovery). The mitigation of N loss was also observed for sawdust, although the effect was less consistent compared with leonardite and wheat straw. Mixing the slurry and HCA overnight tended to reduce N losses, although the effect was not consistent across all treatments. In conclusion, leonardite improved soil N retention more effectively than wheat straw and sawdust.

Nitrogen (N) losses during fertilization with livestock slurry, mainly in the form of ammonia (NH 3 ), can cause environmental problems and reduce fertilizer efficiency.Leonardite, which is characterized by oxygen-rich functional groups and low pH, has been found to decrease losses of slurry N. However, leonardite, as a byproduct of open-cast lignite mining, is not a renewable resource. The objective of this study was to modify biochar by chemical surface oxidation in order to find a sustainable but similarly effective substitute for leonardite. Biochar was produced from spruce sawdust in a pyrolysis oven at a maximum temperature of 610 ˚C. Then the biochar was oxidized using the Fenton reaction, with a ratio of Fe 2+ /H 2 O 2 of 1:1,000, as a source of highly reactive HO• radicals to introduce oxygen-rich functional groups to the biochar surface. The ammonium (NH 4 + ) adsorption capacity of biochar, oxidized biochar, and leonardite was tested in ammonium sulfate [(NH 4 ) 2 SO 4 ] solution, pHadjusted (NH 4 ) 2 SO 4 solution, and cattle slurry. The results showed that biochar had the highest total NH 4 + adsorption of 1.4 mg N g −1 in (NH 4 ) 2 SO 4 solution, whereas oxidized biochar had the highest reversible NH 4 + adsorption of 0.8 mg N g −1 . In the pH-adjusted ammonium solution, all materials reduced NH 3 emissions by ≥90%, and oxidized biochar reduced NH 3 emissions by 99.99%. In contrast, leonardite reduced NH 3 emissions the most in cattle slurry, and oxidation of biochar increased the reduction in NH 3 emissions from 22 to 67% compared with non-oxidized biochar.In conclusion, biochar oxidized by means of the Fenton reaction greatly decreased NH 3 emissions by increased adsorption of NH 4 + in cattle slurry compared with nonoxidized biochar, indicating the great potential of oxidized biochar for reducing N losses during slurry application.

The basic principle underlying organic orchards is increased soil nutrient content, particularly organic matter content and increases soil bacterial activity and diversity. A standard organic management stratep < 0.05) soil alkaline phosphatase, urease, and sucrase activities and soil organic matter, total nitrogen, total phosphorus, and nitrate nitrogen contents. The soils of two orchards mainly ed by Proteobacteria, Acidobacteria, Actinobacteria, , and Gemmatimonadetes. Correlational analysis showed that the bacterial community was ganic matter. Catalase, urease, sucrase, and alkaline phosphatase activities and soil organic matter, total nitrogen, and nitrate-nitrogen contents promoted soil bacterial content. A comprehensive analysis showed that organic orchard management improved soil nutrients and enzyme activities and changed the soil bacterial diversity compared with those of conventionally managed soil.

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Purpose Compost has great potential for use in sustainable agriculture. Stoichiometric relationships between C, N and P play an important role in soil biogeochemical processes. The aim of this study was to quantify greenhouse gas (GHG) emissions, soil nutrient retention and leaching, aboveground biomass and crop yield at different soil C:N:P ratios. Methods The lysimeter experiment included six treatments: (1) without fertilization and seeding (bare), (2) common P fertilization (control), (3) P fertilization at twice the common level, (4) compost addition of 40 t ha-1 and common P fertilization, (5) compost addition of 40 t ha-1 and P fertilization at twice the common level, and (6) compost addition of 80 t ha-1 and common P fertilization. Treatments 2-6 were all fertilized at the same N level. Results Compost application significantly increased aboveground biomass and grain yield, particularly in the double compost treatment, where the variability between replicates was particularly low. However, the effect of compost application on GHG emissions was insignificant. Addition of 80 t ha-1 of compost increased dissolved organic carbon (DOC), compared to the control, but did not lead to a significant increase in DOC, N and P leaching losses. In contrast, bare soil resulted in significant leaching losses of DOC and nitrate (NO3–) compared to plant-covered treatments. Conclusion We conclude that combined compost and N fertilizer application is a suitable management option for increasing crop yield and reducing its variability, as it does not lead to increased GHG emissions and leaching losses of NO3– and P.