Archive for the category: Feature Presentation

Liuqing Yang^{1, 2}, Xiaotang Ju¹*,Xiaojun Zhang²*

¹ China Agricultural University, No.2 Yuanmingyuan Xilu, Haidian District, Beijing, China, 100193, yangliuqing.1224@163.com
²Shanghai Jiao Tong University, No.800 Dongchuan Road, Minhang District, Shanghai, China, 200240
*Author for correspondence juxt@cau.edu.cn;  xjzhang68@sjtu.edu.cn

Abstract

The linkage between situ N₂O emissions and abundance of functional genes ammonia monooxygenase  gene (amoA), nitrate reductase gene (narG), nitrite reductase genes (nirS and nirK), N₂O reductase gene (nosZ) is not well understood, impeding proposing methods for mitigation in agricultural management. Our work was focusing on this linkage. Combined traditional study method and molecular biological technique and four treatments were involved in: N₀ (Zero N application, straw removal), N_opt and CN_opt (Improved N_min test, straw removal and return respectively), CM (Manure supplementary, chemical fertilizer N based on N balance calculation, straw return). Soil samples were collected on 16^th April (reflect long-term N and C management effect), 9^th and 14^th August (reflect before and after short-term fertilization on 11^st August) for biological and chemical properties analysis. We found that the amoA gene responed to short-term fertilizer while denitrification genes had no response and annual N₂O emission had significant positive relationships with gene abundance mentioned above. We concluded that strong nitrification triggered by high ammonia concentration after fertilization, nitrifier denitrification or denitrification triggered by strong rainfall or irrigation in normal crop growing days without nitrogen addition were most probably responsible for N₂O emissions. It is critical to reduce amoA gene function after urea-based fertilization. Meanwhile, we need to pay attention to enhanced denitrification genes functions in their favourable conditions to produce N₂O when increased SOC due to long-term manure fertilization.

LIN Xiaolan¹, YOSHIDA Koshi², MAEDA Shigeya², KURODA Hisao²

¹ The United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, Japan, 183-8509, linxiaolan0402@gmail.com

² College of Agriculture, Ibaraki University, 3-21-1, Chuuo, Ami, Inashiki, Ibaraki, Japan, 300-0393

Abstract 

The characteristics of oxidation-reduction (redox) layers were reviewed under natural conditions. This study was carried out a field survey from 2014 to 2015. The survey was conducted in a paddy field. Soil temperatures, air temperatures, and T-N concentrations of water had been measured. The dissolved oxygen (DO) concentrations of redox layers in flooded soil were measured per 0.2 mm with a special DO concentration sensor through surface to 6 cm depths of soils. Based on the DO concentration results, the soil of the oxidized layers where the concentration was over 1 mg L^-1 was sampled, along with reduced layer of less than 0 mg L^-1. The denitrification activities of redox layers were measured by acetylene blocking technique.

The DO concentrations in paddy field soil have a seasonal change and changed in a thin layer. A positive correlation is observed between the thickness of the oxidized layer and soil surface temperature in the range of 12 ~ 24 °C. The oxidized layer denitrification activities are little, denitrification of paddy fields is dependent on the reduced layer.

Peter R. Quin^{1, 2, 3}, Lukas van Zwieten^{1, 2, 3}, Peter R. Grace⁴, Lynne M. Macdonald⁵, Annette L. Cowie^{1, 6}, Dirk V. Erler⁷, Iain M. Young⁸, Stephen W. Kimber²
1 – School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia. Email: peter.quin@internode.on.net

2 – NSW Department of Primary Industries, 1243 Bruxner Highway, Wollongbar, NSW 2477, Australia.

3 – Southern Cross Plant Science, Southern Cross University, Military Rd, East Lismore, NSW 2480, Australia.

4 – Institute for Sustainable Resources, Queensland University of Technology, 2 George St, Brisbane, QLD 4000, Australia.

5 – CSIRO Agriculture, Glen Osmond, SA 5064, Australia.

6 – NSW Department of Primary Industries, Trevenna Rd, University of New England, Armidale, NSW 2351, Australia.

7 – School of Environment, Science and Engineering, Southern Cross University, Military Rd, East Lismore, NSW 2480, Australia.

8 – School of Life and Environmental Sciences, Faculty of Science, University of Sydney, NSW 2006, Australia.

Abstract

Increasing concentrations of atmospheric nitrous oxide (N2O) are making a significant contribution to anthropogenic climate change and the depletion of stratospheric ozone. These increases are known to primarily result from the use of synthetic nitrogen fertilisers and manures. Our study aimed to answer some of the many remaining questions about the mechanisms of production and movement of N2O in soil. In a field study we injected ¹⁵N-labelled nitrate into repacked columns of Ferralsol, at a depth of either 75 mm or 200 mm. We sampled soil gas at 3 depths and surface emissions. In-soil concentrations of N2O rose by approximately two orders of magnitude when water-filled pore space increased to >80 %. This coincided with periods of high hydraulic conductivity, potentially draining dissolved ¹⁵N2O from the 75 mm injected columns at 189 µg ¹⁵N-N2O m^-2 h^-1 compared with a surface flux of 1.2 µg ¹⁵N-N2O m^-2 h^-1 and from 200 mm injected columns at 30 µg ¹⁵N-N2O m^-2 h^-1 compared with a surface flux of 0.24 µg ¹⁵N-N2O m^-2 h^-1. Data suggests that indirect emissions of N2O by leaching and surface runoff from some soils may be much greater than the default 0.225 % of N applied recognised by the IPCC. This may go some way towards reconciling the discrepancy between ‘top down’(~4 %) and ‘bottom up’ (~1.3 %, IPCC default) estimates of direct N2O emissions from applied N. We also show that deeper placement of nitrate fertiliser may decrease direct N2O surface emissions, although the effect on indirect emissions remains unclear.

Hoang Thi Thai Hoa¹, Do Dinh Thuc¹, Trinh Thi Sen¹, Tran Thi Xuan Phuong¹

¹ Hue University – Hue College of Agriculture and Forestry, 102 Phung Hung street, Hue city, Thua Thien Hue province, Vietnam, 530000, http://www.huaf.edu.vn, hoangthithaihoa@huaf.edu.vn

Abstract

Wetland rice is the largest source of CH₄ emission from cropping and also offers the most options to modify crop management for reducing these emissions. The experiment was conducted in two rice cropping systems in 2014 and 2015 to assess the influence of rates and types of nitrogen fertilizer on CH₄ emission in rice fields of Central Vietnam. Results show that high fertilizer N rates (120 kg N ha⁻¹) increased seasonal cumulative CH₄ emissions from 11.6 – 26.7 g m^-2 for urea and 6.7 – 19.5 g m^-2 for ammonium chloride in winter spring and summer cropping seasons relative to when no N fertilizer was applied. Replacing urea with ammonium chloride at the same N rate significantly reduced CH₄ emissions by 35% (winter spring cropping season) and 32% (summer cropping season) at the rate of 120 kg N ha^-1_. Average CH₄ emission was about 2.1 – 2.2 times higher in summer season as compared in winter spring season. To develop effective GHG mitigation strategies future work is needed to (i) quantify the effects on both CH₄ and N₂O emissions), (ii) investigate options for combining mitigation practices.

Baobao Pan¹, Shu Kee Lam¹, Arvin Mosier¹, Yiqi Luo², Deli Chen¹

1 Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC 3010, Australia, Email: bpan@student.unimelb.edu.au

2 Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA

Ammonia (NH₃) volatilization is a significant pathway of nitrogen (N) loss from cropping systems. A number of studies have investigated the effects of management practices on NH₃ emission, but the findings are sometimes contradictory or inconclusive. A meta-analysis was conducted to quantitatively synthesise the global literature on the strategies for mitigating NH₃ emission from agricultural systems. Unlike qualitative reviews, a meta-analysis combines results from different studies to identify patterns among study results. The mitigation strategies included in our meta-analysis were: irrigation, N application method (deep placement), fertilizer type (ammonium-based vs. urea) and the use of urease inhibitors and controlled release fertilizers. Irrigation after fertilization and deep placement of N fertilizers decreased NH₃ emission by around 35% and 55%, respectively. Ammonium-based fertilizers decreased NH₃ loss by 31-75% when compared to urea. Both urease inhibitors and controlled release fertilisers effectively decreased NH₃ volatilization by 54-68%. The findings provide critical information on how to minimize NH₃ volatilization and increase N use efficiency and productivity in cropping systems.

Mei Bai^1*, Helen Suter¹, Shu Kee Lam¹, Rohan Davies², Deli Chen¹

¹ Crop and Soil Sciences Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, VIC 3010, Australia

²BASF Australia Ltd., Southbank, VIC 3006, Australia

*Corresponding author: mei.bai@unimelb.edu.au

Abstract

Ammonia (NH₃) volatilization to the atmosphere following urea based nitrogen (N) fertilizer application not only causes nutrient loss but also detrimentally impacts on the environment, our ecosystems, and contributes to global warming (as an indirect greenhouse gas). Here, we report our studies of quantifying NH₃ emissions from dairy pasture following urea application, and the effectiveness of a urease inhibitor in mitigating NH₃ loss. Two experiments were conducted in summer at Queensland (northern site) and autumn at South Australia (southern site) where urea was surface applied to pasture. A urease inhibitor (NBPT, applied with urea as Green ureaNV^TM) was added at the northern site. Open-path NH₃ laser concentration sensors were used to measure line-averaged concentrations along an open path downwind of the treatment plots. Ammonia fluxes were calculated using the inverse-dispersion technique (WindTrax). We found NH₃ flux increased following urea application and varied temporally at the two sites. Daily average NH₃ flux from dairy pastures fertilized with urea was 4.4 ± 0.46 and 6.4 ± 1.2 mg N m^-2 h^-1 for the northern and southern sites, respectively. Nitrogen loss as volatilised NH₃ from the urea application over the course of the experiments (12-15 days) accounted for approximately 40 and 60% of total applied N for the northern and southern sites, respectively. The difference between sites is likely attributed to the differences in N input, soil properties and microbial activity. The urease inhibitor reduced NH₃ emissions by approximately 71% compared to that from the urea treatment. The results in these studies also demonstrated that inverse-dispersion technique combined with the open-path lasers is able to measure NH₃ fluxes from large-scale field sites, and the open-path NH₃ laser has adequate detection resolution.