Soil nitrogen supply rates during a cotton season

Coverdale, Constance (2015) Soil nitrogen supply rates during a cotton season. [USQ Project]

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Abstract

As a result of the demand for increased yield per hectare production output for cotton farms in Australia, as well as the limitations of expanding paddock areas to meet this demand, an increase of nitrogen - the primary cotton plant is required. This comes at a time when rising input costs, as well as sustainability targets are key factors in determining the type of nitrogen fertiliser applied and other components associated with fertiliser usage such as time and rate of application. By matching a cotton plant’s varied nitrogen requirements with peak soil potential nitrogen supply, soil nitrogen losses can be minimised, creating sustainable and more efficient nitrogen use for growers.

The mineral nitrogen supply patterns of Urea, the most commonly used nitrogen fertiliser, as well as ENTEC® Urea, a controlled release fertiliser were investigated. This research was specifically designed to compare the potential net soil mineral nitrogen supply over a period of 60 days for each treatment, as well as the potential greenhouse gas emissions from the soil that included nitrous oxide, carbon dioxide and methane over the same time period.

To compare soil nitrogen mineralisation and nitrogen release patterns and processes between fertiliser treatments, a pot study was conducted under laboratory conditions. The study was based on a 60 day aerobic incubation method with a constant soil temperature (25oC), fertiliser application rate (600 kg/ha N), soil moisture range (>75% field capacity) and soil type (Black Vertosol from an irrigated cotton farm Yargullen, QLD).

Soil extraction (2M KCl), colorimetric and gas chromatography laboratory methods were used to obtain sufficient data for the net soil nitrate and ammonium concentrations on days 0, 3, 7, 14, 30, 45 and 60. Concurrently, soil gaseous emissions in the form of a linear flux over 45 minute sampling periods for days 0-5, 14, 45 and 60 were achieved.

Results indicated that soil applied with ENTEC® Urea provided a delay in the peak net mineral nitrogen supply with a steady increase occurring until day 60, when compared to Urea which peaked in mineral nitrogen supply by day 14. If fertiliser was applied in September at a similar time to planting, net supply from Urea would not coincide with increased nitrogen demands from first boll fill and boll opening phase (50-100 after sowing). ENTEC® Urea however, would meet the nitrogen requirements of cotton plants with a single fertiliser application at season commencement, as well as providing a more sustainable fertiliser option with a 73.3% reduction in nitrous oxide emissions when compared to Urea.

Further investigation could include relating the results to field conditions using a degree day relationship and to compare the mineral nitrogen and gaseous emission results from field experiments.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Environmental Engineering (Honours) project
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying
Supervisors: Melland, Alice Antille, Diogenes
Date Deposited: 01 Jun 2016 02:03
Last Modified: 06 Jun 2016 01:09
Uncontrolled Keywords: Soil nitrogen potential, Mineralisation, Urea
Fields of Research : 09 Engineering > 0907 Environmental Engineering > 090799 Environmental Engineering not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/29193

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