AbstractSoil analysis is a widely adopted method for the evaluation of soil fertility and, as a tool for fertilizer recommendations. In developing countries, technology transfer is restricted due to a lack of laboratory infrastructure, specialized training and essential yet time consuming supportive research. Moreover, soil testing is also costly. Consequently, poor farmers cannot usually afford to have the nutrient status (NPK) of their soils evaluated. Currently, soil testing for NPK requires nutrient-specific chemical extractants and determination methods, expensive instrumentation, and highly trained personnel. In this paper, the authors present a method for obtaining a point-of-collection and quantitative determination of primary soil nutrients like Nitrogen (N), Phosphorous (P) , Potassium (K) and pH using commercially available test strips and analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the test strip on which a colorimetric reaction of a target sample has occurred. Phones marketed by different smartphone makers were used. A software program was developed to use with the phone for recording and analyzing the LAB color of the picture. This method uses the smartphone having a Akvo Caddisfly app and a color card developed by us that provides an external environment-independent/internal light-free, imaging environment independent of the smartphone platform being used. The result can then be presented quantitatively or turned into a more consumer-friendly measurements displayed to the user, stored for later use and communicated to a location where practitioners can provide additional review. Around 50 field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Lab method and Akvo Caddisfly (Phones A, B and C),with correlation coefficient ranging between --------- and --------. In addition, there was no significant difference in the nutrient content values between Lab and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for soil analysis in the field. Objective of our research is to analyze soil properties for accurately mapping various primary nutrients in the soil.KeywordsSoil Analysis, Primary Soil Nutrients, Nitrogen, Phosphorous, Potassium, pH , Test strips, Smartphone, Color Card, Colorimetry, 1. IntroductionIn order to fulfill the growing need for food, agricultural land per unit area required to achieve maximum efficiency and highest quality product. It is known that the nutrition of the plant is the one of the most important factors to control agricultural productivity and quality. Rates of nutrients in the soil affects the quality of yield. In the permanent agricultural land, the soil will be very poor in nutrients, as a result, inefficient. Therefore, producers, fertilize the soil, combat pests, irrigation and process of agricultural activities to make more efficient to soil. Fertilization among these activities remains a priority at all times. Recent studies, however, excessive use of fertilizers is the need for additional land outside the public and environmental health of the reported adverse affects. Excessive fertilization and mindless, but there were soil salinity, heavy metal accumulation, water eutrophication and accumulation of nitrate, to consider in terms of air pollution in the air of gases containing nitrogen and sulfur, giving and can lead to problems such as the greenhouse effect.  We can determine these soil nutrients in the soil by various methods. Many researchers tried to invent the method that give the information regarding the soil nutrient contents. There are various method to determine soil nutrients such as electrochemical methods, spectroscopy methods and optical methods . These all methods are important to determine the soil nutrients like nitrogen, phosphorous, potassium, iron, magnesium, calcium, manganese, boron, minerals, soil organic matter, soil water content.Hak-Jin Kim et al.  discussed the two sensing technologies for determination of soil macronutrients like nitrogen, phosphorous and potassium. Accurate determination of soil nutrient is required for efficient crop production including site specific crop production. Twosensing approaches i.e. electrochemical method and optical diffuse reflectance sensing are the most promising methods.One of the most critical aspects of soil testing is actually obtaining representative soil samples (i.e. collected with adequate spatial density at the proper depth and during the appropriate time). Practical advice related to the collecting and handling of soil samples was given by Vitosh et al. (1995) and Gelderman and Mallarino (1998). However, the location and number of soil samples depends on the approach used to manage soil fertility (Havlin et al., 1999). Currently, random, adaptive, and grid sampling techniques are often used. In random sampling, soil cores are obtained from random locations within the field. In adaptive sampling, selected locations depend on prior information. Grid sampling, on the other hand, involves systematically collecting samples from predetermined points in the field. None of the existing soil sampling practices has been recognized as the most effective (Wollenhaupt et al., 1997).2. Materials and Methods2.1. ReagentsMehlich 1 Solution - This solution has following composition: 0.05N HCl + 0.025N H2SO4. It can be prepared by measuring 4.125 ml of Concentrated HCl (Spacific gravity of 1.18 g/ml) and 0.7 ml of Concentrated H2SO4 (Spacific gravity of 1.8 g/ml) in a beaker and diluting it to 1 L with distilled water.2.2. Test StripspH test strips - Hach-Product:2745650Nitrate & Nitrite test strips - Hach-Product:2745425Ammonia test strips - Hach-Product:2755325Phosphate test strips - Quantofix-Ref:91320Potassium test strips - Merck-Product:1179852.3. Color CardThe color card developed to automate reading the strip tests measures 167mm x 109mm. Follow is the descriptiom about the color card.Printing: The color card is printed on non-reflective card paper with a matte finish for the ink as wellQR Code: The card double up as a QR code that not only helps with focussing the camera, but also encodes the version of the cardCard Version: The card version is printed on the lower left position element of the QR code. In the picture above, the version is 2.Colour Swatches: A series of colour swatches are provided in a 13 x 5 grid on the card. These colours are chosen from across the spectrum and shades of grey.Strip Backdrop: A large, black area is provided at the bottom of the colour reader to place the strip for readingStrip Positioning Marks: Vertical stripes indicate in which direction the strip should be placed.
Abstract[TODO: Why chlorination] [TODO: Upper and lower limits. Deleterious effects on human health] [TODO: DPD. Advantage of detection with a smartphone] KeywordsChlorine, Residual Chlorine, Free Chlorine, DPD, Smartphone, ColorimetryIntroductionMaterials and MethodsResultsDiscussionConclusionReferences
AbstractpH as a measure of the H+ or OH- concentration in water is an important measure to assess its potability. Several methods exist to pH including litmus tests, universal indicators, and glass electrodes. Commercially available strip tests are easily available around the world and are fairly accurate.Strip tests work by changing color depending on the pH. Values are assigned by comparing the color developed on the strip the colors printed on the packaging. Because of the inherent variability in human color perception, there could be varying interpretations of the value.The authors present a method of reading the color developed by the strip test - Hach pH Strips, Cat No 27456-50 - automatically using a smartphone. This method removes subjective interpretation of color as a source of error in strip tests. The apparatus and software account for variables such as varying light conditions, different phone models and time taken for color.The results show a correlation of [TODO Correlation] with a pH electrode. Though readings taken in conditions of open sunlight and shade do show a variation [TODO Correlation], the authors consider this to be sufficient for a screening test.KeywordspH, Strip Test, Dipstick Test, Smartphone, Mobile Phone, ColorimetryAuthors[TODO]IntroductionThe parameter usually first tested to evaluate drinking water is its pH. This is expected to be in the range of 6 to 9 to be considered potable[citation]. Methods to test pH include litmus paper, litmus liquid, glass electrodes, indicator liquid, and strip tests.Test Type Advantages Disadvantages Litmus Paper Simple to use Poor accuracy Litmus Liquid Simple to use, good accuracy Provides semi-quantitative results Indicator Liquid Good accuracyGives semi-quantitative results in the absence of a spectrophotometerGlass Electrode Good accuracy, fairly simple to use Requires maintenance, and is not very convenient for field use Strip Test Simple to use Semi-quantitative resultsFrom the table above, it can be inferred that strip tests make for a good screening test, if the disadvantage of semi-quantitative results can be alleviated. Performing a pH strip test is fairly straightforward and can be done in the field with very little training. The authors propose a method where the human subjectivity in interpreting colour is removed in comparing the colour developed by the strip by automating the colour interpretation by the smartphone app. In screening tests a variability of +/- 0.2 is considered acceptable [cite].Materials and MethodsStrip TestsIn this study, Hach pH strips were used directly (Cat No. 27456-50). The strips have a range 4 - 9.[TODO: Images of strips and colour chart]Colour CardThe colour card developed to automate reading the strip tests measures 167mm x 109mm.