M.Sc Thesis

M.Sc StudentDarzi Ran
SubjectFTIR Systems for Tracking N2O and NH3 Emmission while
Testing Nitrogen Use Efficiency in Greenhouse
Experiments with Advanced Nitrogen
DepartmentDepartment of Civil and Environmental Engineering
Supervisors ASSOCIATE PROF. Yael Dubowski


Nitrogen-based fertilizers are essential to modern agriculture cropping system coping with global changes and increasing food demand. In spite of their undoubtable importance, nitrogen losses and low nitrogen recovery by the plant severely pollute the environment.

Urea ((NH2)2CO), the most widely used N-fertilizer, dissolves rapidly and decompose to (NH4 ( 2CO3 by enzymatic hydrolysis within 1-2 days. Such hydrolysis affects the soil chemical properties favoring high NH3(g) emissions and toxic NO2- accumulation. Furthermore, high N-fertilizer loads relative to plant uptake capability are affected by microbial transformations, resulting in NO3- leaching and N2O(g) emissions. Enhanced Efficiency Fertilizers (EEFs) offer slow-pace and continuous nitrogen supply throughout the growing cycle, minimizing nitrogen loss and improving Nitrogen Use Efficiency (NUE).

The objective of this work is to evaluate the NUE of urea-based EEFs in comparison to common granulated urea, at greenhouse scale with Basil speedlings planted in containers filled with sandy-loam soil. Environmental and agricultural response to each fertilizer is examined according to comprehensive multi-phase monitoring of N in plant, soil, drainage and gaseous emissions. NH3(g) and N2O(g) emissions were measured in closed-chambers combined with laboratory Fourier Transform Infrared (FTIR) spectroscopy. In addition, the present work examines on-line detection and quantification of gaseous emissions using Open-Path (OP)-FTIR remote sensing spectroscopy.

Two experiments were performed in a custom tables array, enabling application of four different fertilizer treatments in randomized blocks arrangement. Fertilizers applied in experiment 1 were: 2-months controlled release polymer coated urea (CRF-2M), 4-months controlled release polymer coated urea (CRF-4M), 4-months controlled release polymer sulfur coated urea (PSCU-4M) and regular granulated urea (UREA). In experiment 2, the following fertilizers were applied: CRF-2M, CRF-4M, UREA and urea with a mixture of NPPT and NBPT Urease Inhibitors (UI). A third experiment focused on continuous and real-time gaseous emissions monitoring using OP-FTIR. Measurements were taken in a closable plastic tunnel (11.2 meters long) placed over three basil-planted growth beds, each treated with CRF-4M, UI or UREA.

The custom greenhouse set-up allowed comprehensive multi-phase nitrogen monitoring. It clearly demonstrated the environmental and agricultural disadvantages of common urea. All EEFs tested increased crop yields, reduced nitrogen losses and consistently performed better than UREA. CRF-4M and PSCU-4M performed better than CRF-2M and UI. They increased NUE by 50%-90% relative to UREA treatment, decreased nitrogen leaching by 26%-57% relative to all other treatments and had negligible gaseous emissions.

Both the laboratory FTIR and the OP-FTIR systems successfully detected NH3(g) and N2O(g) emissions and allowed quick and simple measurements without any complicated sample preparations. The closed-chambers measurements were affected by NH3(g) dissolution and further improvement and adaptations are needed in order to achieve more accurate gaseous emissions fluxes relevant to real-field scale.

The presented experimental set-up indicates that greenhouse scale experiments are an important tool for improved and consistent evaluation of EEFs potential to reduce environmental impact along with improving agronomic and economic benefits. Moreover, it provides a powerful mass-balancing tool of N resources (inputs, outputs and losses) for evaluating various EEFs under various agronomic, environmental and climatic conditions.