Science

NZAGRC Science Leadership Team

The role of NZAGRC Science Leadership Team (SLT) is to play a key part in the development, implementation and monitoring of all of the Centre’s science programmes and strategies.  It consists of respected New Zealand-based researchers with excellent science credentials accompanied by strong leadership, communication, strategic and inter-personal skills with expertise in those areas of science covered in the NZAGRC Strategy and Science Plan.

Membership is agreed by the Steering Group and includes the NZAGRC Principal Investigators in addition to the NZAGRC Director and NZAGRC Operations Manager.  

Dr Graeme Attwood  AgResearch  
Dr Cecile DeKlein   AgResearch 
Professor Hong Di  Lincoln University 
Dr Robyn Dynes  AgResearch  
Dr Peter Janssen  AgResearch  
Dr David Whitehead   Manaaki Whenua

 

Science leadership & capability building 

The NZAGRC is committed to providing opportunities for researchers to be trained and work with leading experts in New Zealand.  Some students go on to continue their studies or enter a postdoctoral position under guidance from NZAGRC science leaders, other enter into industry based positions.

The NZAGRC supports more than 50 researchers and students by providing funding via its core research programme or via its student scholarships programme.

Below are profiles of our scientists and past students. 

Changes in denitrification rate and N2O/N2 ratio with varying soil moisture conditions in New Zealand pasture soils

Jha, N., Saggar, S., Tillman, R., & Giltrap, D. (2012). Changes in denitrification rate and N2O/N2 ratio with varying soil moisture conditions in New Zealand pasture soils In: Advanced Nutrient Management: Gains from the Past - Goals for the Future. (Eds L.D. Currie and C L. Christensen). 

Abstract

Denitrification is the primary process of N2O production in temperate grassland soils and accounts for 60% of the total N2O emissions globally. There are various soil and environmental factors that regulate denitrification and affect denitrification rate (DR) and N2O/ N2 ratio. Among these, soil moisture is the most important. Generally, DR increases and N2O/N2 ratio decreases with increasing soil water content. However, the effect of changing soil moisture on DR and N2O/N2 ratio may vary with the type of soil, its nutrient status and the management practices followed on the farm. The interrelationships among the various factors affecting DR are not very well quantified.

Therefore, the current study was planned to investigate the effect of soil moisture on DR and N2O/N2 ratio in five different New Zealand pasture soils with varying physical and chemical characteristics such as soil texture, total porosity, pH, NO3- and NH4+ content, total nitrogen (TN), total carbon (TC), microbial biomass carbon (MBC) and denitrification enzyme activity (DEA). The experiment involved incubation of surface (0-10cm) and subsurface (10-20cm) soil samples at field capacity (FC) and complete saturation at constant temperature (25oC). DR and N2O/N2 ratio were estimated using an acetylene inhibition (AI) technique.

Denitrification rates were higher in soils incubated at saturation than in soils incubated at FC. Similarly, the N2O/N2 ratio decreased in soils when incubated at saturation as compared to FC. The extent of these increases in DR and decreases in N2O/N2 ratio with increasing moisture content varied among the soils due to differences in NO3- and NH4+ content, MBC and DEA of the soils.

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