Novel procedure for testing of soil field test kits involving paper strips

Abstract

The need for facilitation of access to soil information has never been greater. Growing human population, shrinking land and water resources, soil pollution, climate change and unequal distribution of agriculture-oriented technology impact negatively on global food security. There has been a longstanding interest in developing low-cost and easily accessible soil field kits to measure different properties of agricultural soils in order to improve their agronomic capacity. Test strips, in particular, have provided a favoured method of obtaining soil nutrient status information since the 1970s. Today there is renewed interest in using semi-qualitative colorimetric methods in soil assessment due to incorporation of modern technological solutions, such as smartphones, which could in turn increase the accuracy and precision of the existing methods. In this paper, we propose streamlined testing procedures based on experience gathered that may be conducted prior to a field kit development involving test strips. Results from laboratory and field experiments are presented, highlighting important factors which ought to be taken into account at the commencement of test-strip oriented studies.

An analysis of in‐field soil testing and mapping for improving fertilizer decision‐making in vegetable production in Kenya and Ghana

“…In Kenya, the difference between methods is similar to that found with the methods of soil analysis currently used for advisory purposes, that is, the difference between sub-samples analysed during a single run of segmented flow autoanalyzer was estimated at ±10 mg kg −1 (Golicz et al, 2019). Those results are consistent with other paper strip studies, where the deviation from standard method can range between 19.9 mg kg −1 and −55.7 mg kg −1 (Golicz et al, 2020). To be able to inform better decisions about soil fertility and crop growth, paper strips would only provide part of a wider range of information support that is needed in the capacity as a screening tool.…”

“…Filtrate testing was conducted using the Quantofix paper strips (manufacturer: Machery-Negel, product reference: 913 51) and Akvo Caddisfly app (Akvo, 2020;Heijstek, 2017), which acted as a portable reflectometer, that is, a test strip colour reader, following the method developed by Golicz et al (2020). Akvo Caddisfly requires a calibration card to adjust colour development in the paper strip during the reaction time (for 60 s) and then uses a phone's camera to quantify the amount of available nitrate based on the colour intensity of the reactive pad.…”

“…Soil sampling, extraction and filtration with medium speed filter paper for three W's, or 15 samples, took a few hours, limiting the number of farms that could be reached in a day for a soil testing service. Reduction in time requirement can be achieved by utilizing a coagulating soil extractant such as 0.01 M KCl, which has limited negative effect on the test strip colour development (Golicz et al, 2020) or a syringe filter.…”

“…These, in conjunction with reflectometers that quantify the reactive zone's colour, have been successfully applied in soil testing across the USA (Jemison & Fox, 1988), Germany (Schmidhalter, 2005) and Australia (Wetselaar et al, 1998). However, concerns regarding agreement between paper strips and conventional F I G U R E 1 Screenshots of Kenya Crops and Fertilizer App (Google, 2017) methods of nutrient analysis have been recently highlighted (Golicz et al, 2020). In this study, nitrate-sensitive paper strips were used alongside Akvo Caddisfly-a smartphone app that temporarily turns the phone into a portable reflectometer, to understand how useful the tool is as a method for assisting farmers in using HWDF.…”

A novel analytical approach for the simultaneous measurement of nitrate and dissolved organic carbon in soil water

“…During the last half-century, clear trends of rising nitrate concentrations in groundwater have been observed in aquifers all around the globe (Jin et al, 2012;Kourakos et al, 2012;Liao et al, 2012). The World Health Organization (WHO) has determined that nitrate levels in drinking water should not exceed 50 mg L −1 (WHO, 2011).…”