Abstract
Soil testing is frequently conducted to specify nutrient supply recommendations. By adjusting fertilizer type and application rates, farmers can achieve desired crop yields with lower production costs and are thereby less likely to contribute to eutrophication of nearby waterbodies. However, traditional methods of soil testing can be costly, time-consuming and are often impractical in rural and resource-poor regions in China, where rapid population growth and consequent food demand must be balanced against potential environment risks. Smartphones are nearly ubiquitous and offer a ready capability for providing additional support for existing extension advice. In this study, we used an Android-based smartphone application, in conjunction with commercially-available Quantofix test strips, to analyze soil samples with a goal of providing specific fertilizer recommendations. The app transforms the smartphone into a portable reflectometer, relating the reaction color of the test strips to the concentration of soil nutrients available. A 6-month long field study involving two growing seasons of vegetables was conducted in a suburban area of Nanjing, Jiangsu Province of China to evaluate the accuracy and precision of smartphone-mediated soil analysis. Results obtained via the smartphone correlated well with the yield response of the common green vegetable Ipomoea aquatica (water spinach) and could be applied in calculations of necessary off-farm inputs throughout the open-field vegetable growing season. Together, the smartphone and test strip in combination were shown to offer an acceptable screening tool for soil nutrient concentration assessment with the potential to result in substantial monetary savings and reduction of nutrient loss to the environment.
Highlights
Global food production has been greatly expanding to meet the growing world population, which is expected to reach 9.8 billion people by 2050
Smartphones used in conjunction with test strips offer such a technological opportunity because they: (1) are free of human bias associated with color detection; (2) are capable of providing precise and replicable results in contrary to the standard visual method; (3) have capacity for storing and geotagging results for future use, and; (4) offer the potential for inclusion of wider extension and agronomical advice alongside the immediate results, and; (5) offer a pragmatic alternative to expensive commercial reflectometers on offer by test strip manufacturers, such as the Quantofix Relax Reflectometer utilised with Quantofix test strips
High residue nitrogen was recorded for treatments BC198 and IF198, which were equivalent to 272 kg of N per ha for Trial 1 and 334 kg of N per ha for Trial 2
Summary
Global food production has been greatly expanding to meet the growing world population, which is expected to reach 9.8 billion people by 2050. Studies have shown that plant uptake rates for N can be as low as 10–20% in horticultural systems[4] Vegetable production, both in open land and greenhouse-based, involves frequent cultivation, high fertilizer application rates (up to 900 kg per ha), low rooting density and short growing-seasons – those systems are associated with high environmental risks of nutrient leaching and greenhouse gas emissions[5]. Both in open land and greenhouse-based, involves frequent cultivation, high fertilizer application rates (up to 900 kg per ha), low rooting density and short growing-seasons – those systems are associated with high environmental risks of nutrient leaching and greenhouse gas emissions[5] This is concerning given that the need for fresh produce, vegetables, will increase alongside the awareness of the impact of poor nutrition on morbidity and mortality rates in relatively wealthy societies[6]. By employing Akvo Caddisfly, it is possible to provide farmers, who might otherwise have had limited access to conventional soil testing, with a simple decision support tool that can provide information about the quantity of plant available nitrate and phosphorus in the soil
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