Abstract
Current fertiliser recommendations for nitrogen are limited in their accuracy and may be improved by the use of simple on-farm soil rapid tests. This paper investigates the potential for using nitrate (NO3−) ion selective electrodes (ISEs) and dual wavelength UV spectroscopy as part of a rapid soil NO3− diagnostic test. Three soil types, representing the major soil types for agriculture in the western UK, were tested. For the three soils, the ISE rapid test procedure gave a near 1:1 response (r2 = 0.978, 0.968, 0.989) compared to the internationally-approved standard laboratory method. However, the accuracy of the ISE rapid test was reduced at low soil NO3− concentrations (<10 mg NO3− L−1). We also show that NO3− analysis of H2O soil extracts by dual wavelength UV spectroscopy was also highly correlated (r2 = 0.978, 0.983, 0.991) to the standard laboratory method. We conclude that both ISE and dual wavelength UV spectroscopy have clear potential to be used for the rapid on-farm determination of soil NO3− concentration. Barriers to use of these field-based assessment tools include, farmer perception of cost-benefit, general attitude to new technologies and the ability to generate useful fertiliser use strategies from soil NO3− measurements.
Highlights
Improving nitrogen use efficiency (NUE) is a major goal within agricultural systems [1] and is key to the success of sustainable intensification [2]
This work shows that ion selective electrodes (ISEs) can offer a reasonably accurate and rapid way of determining NO3−
This can be combined with a rapid extraction procedure using H2O where the soil is shaken by hand for 2 min
Summary
Improving nitrogen use efficiency (NUE) is a major goal within agricultural systems [1] and is key to the success of sustainable intensification [2]. In a purely economic sense, an optimum N fertiliser strategy can be defined as the point at which the cost of an additional unit of N is no longer covered by the resulting increase in crop yield. Calculating an optimum N fertilisation strategy is extremely desirable, but very difficult to achieve due to the inherent complexity of the soil-plant system, temporal and spatial variability and the importance of uncontrolled variables such as weather [5]. One theoretical method for improving NUE is to ensure synchronicity of supply and demand, both spatially and temporally, by maintaining the pool of plant available N in the soil at the minimum size required to meet crop demand [7,8].
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