The well being of the humans including animals depend upon very much on how the soil productivity is maintained without ecosystems degradation. Most likely soil can efficiently sustain humanity with food, fibre, feed to animals and clean environmental maintenance only when it is considered and managed from the holistic and ecosystem points of view. Plants need at least 16 essential elements for their normal growth and to complete their life. The soil testing provides the status of the nutrients determined in the laboratory for the application of appropriate rate of fertilizers to eliminate the nutrients limiting for production. The soil testing along with plant analysis gives the true status of plant nutrients affected by soil properties to take the proper care for the plant growth. Our available water resources are diminishing and getting polluted with excess use of fertilizers and pesticides which are ultimately affecting the environment, food produced and water quality. The purpose of this book ‘Soil Testing and Analysis’ is (i) to provide the vital plant nutrients functions for which soil testing is to be made; (ii) to determine the nutrient status of the soil with appropriate methods, measurements and criteria for interpreting those assessments; (iii) to analyze the appropriate parts of the plant samples for nutrient elements with available methods of analysis; (iv) to analyze the important water quality parameters with interpretations; and (v) to prepare the soil, plant and water samples for the analysis of pesticide residues with the different available methods. This is a comprehensive presentation of useful information for the scientific and technical personals involved in such types of analysis.
Preface The analysis of soil, water and plant are the essential tool for the optimization of crops productivity as well as quality of produce. Soil testing for the available nutrient status is prerequisite before the sowing of crops to predict the response of crops to added fertilizer nutrients and to avoid the excess use of nutrients. The soil analysis for the available nutrient reserve of soils alone is not sufficient to guide the nutrient status of plants. So the complementary soil and plant analysis can give almost true picture of soil nutrient status and factors affecting the nutrient availability to plants. At present more than 400 soil testing laboratories are engaged for the analysis of soils all over the country and to advice the farmers to use the fertilizers for optimum crop productivity based on their field’s soil tests. In nature it is difficult to get pure water for agricultural as well as for drinking purposes. The conventional agriculture production system added additional problem to pollute water for safe use. Thus water may be saline, alkaline, acidic, turbid, pesticide residues, etc., so analysis for the both purposes is very much essential for animals including human being health. This book will be of great help to graduate/post graduate students of agriculture, forestry and environmental sciences, subject matter specialists (soil and agronomy) of the Krishi Vigyan Kendras engaged in the transfer of technology to the farmers to optimize the productivity. This book will be of great help to those who are engaged to analyze the soil, water and plant in their laboratories for carrying out routine analysis. Some basic conversion factors have also been given for beginners and further common soil science glossary for ready reference. Authors sincerely hope that the book can play a significant role to popularize the fertilizer use on the basis of soil and plant tests for boosting the food production.
Crop production broadly depends on the fertility of the soil where a crop is raised. There are several factors like the kind and quality of seed, climate, water supply, and plant protection measures etc. that affect the crop production. Among these factors, the fertility status of the soil largely determines the ultimate yield even if all these factors are optimum for crop production. A clear distinction should be made between soil fertility and soil productivity. Soil fertility deals with the inherent capacity of soil to provide nutrients in adequate amounts and in proper balance, for the growth of specified plants when other growth factors such as light, water and temperature, and the physical condition of the soil are favourable. Soil productivity is concerned with the capability of soil to produce a specified plant or plant parts or a sequence of plants under well defined and specified systems of management inputs and environmental conditions, viz. climatic conditions. It does not mean that a fertile soil is always productive. A fertile soil, under a bad management system, may be unproductive for a crop. In this book, plant nutrient elements and their available forms, functions and deficiency symptoms are briefly described for the better understanding of soil testing and fertilizer recommendation.
Soil testing is a useful tool that can help to ensure the efficient use of applied plant nutrients. Soil tests provide a means for assessing the fertility status of a soil, but soil tests do not provide a direct measure of the actual quantity of plant available nutrients in the soil. Instead, soil tests measure the quantity of a nutrient element that is extractable from a soil by a particular chemical extracting solution. The measured quantity of extractable nutrient in a soil is then used to predict the crop yield response to application of the nutrient as fertilizer, manure, or other amendment. As soil test levels increase for a particular nutrient, the expected crop yield response to additions of that nutrient decreases. A soil-testing programme has four phases as follows: 1.Collection of soil samples, 2.Chemical analysis of soil samples, 3.Calibration and interpretation of the results of chemical analysis, and 4.Nutrient/Fertilizer Recommendation.
3.1 Important Soil Physical Properties 3.1.1 Analysis of Soil Texture Soil texture refers to the relative proportions of sand, silt, and clay on weight basis. Soil texture was recognized from very early times by experienced farmers from the feel of moist soil placed between the thumb and forefinger. The size groups arbitrarily classified by the International Society of Soil Science (ISSS) into clay (< 0.002 mm), silt (0.002 0.02 mm), fine sand (0.02-0.2 mm), and coarse sand (0.2 2.0 mm). Each soil textural name specifies the weight percent of each fraction falls within certain defined limits. The determination of the percentage of the soil separate present in a sample is called particle-size analysis. Each type of particle present makes its contribution to the nature of the soil as a whole. Sandy soils are usually quite permeable to air, water, and roots, but they have two important limitations. One is their relatively low water-holding capacity; the second is that they are poor storehouses for plant nutrients. These limitations of sandy soils can, of course, be overcome if both fertilizer and irrigation water are available, but the costs are large. Clay not only have a large surface area per gram, it also has electrically charged particles. These charges give clay the capacity to attract plant nutrient ions to its surface in forms available to plants, but sand lacks this capacity. Clay holds much more water than sands because they have a large surface area to be coated with water. One important problem with clay soils is their stickiness. When wet, they stick to ploughs, boots, or whatever they contact. Loam and silt loam soils are highly desirable for most uses. They have enough clay to store adequate amount of water and plant nutrients for optimum plant growth but not so much clay as to cause poor aeration or to make working with them difficult.
4.1 Sampling and Preparation for Analysis The determination of nutritional need of crops is an important aspect of nutrient management of any plant analysis programme. The need of fruit plants for mineral nutrients differ from those of annual crop species in a number of ways, many of which are related to the perennial nature of tree crops. In perennial tree crops, there is a need to supply nutrients both for ultimate fruit production, the fruits and the vegetative organs, which persist from year to year. The need for leaf analysis in perennial horticultural crops and forest trees has proved its superiority over soil diagnostic methods. This is essentially because of their deeper root system and the fact that nutrients supplied in one year may have its effect on both the nutrition and crop production in following years. However, it is largely being used not as an alternative method to soil testing, but as a supplement to soil testing. Results of foliar analysis are usually interpreted using the critical nutrient level (CNL) approach. Accurate interpretation of foliar analysis using the CNL approach is possible only when sampling is restricted to the same growth stage at which standard reference values have been established (Beaufils, 1971, 1973). The general purposes of plant analyses are:
5.1 Sampling There are different sources of water such as rain, streams, canals, lakes, tanks, ponds, large reservoirs, shallow and deep wells, shallow and deep tube wells, as well as sewage effluents and sea water. The composition of the different sources of water vary with the season, rate of flow, the extent of effluents from the industrial units and sewage effluents from the municipal area during rainy season, the river tank and pond water becomes salty and muddy due to soil erosion. The depth of ground water also varies with the seasons. The sources of water available to the farmer for irrigation of crops are generally few such as canal, shallow and deep wells, pumping sets, tube wells and runoff water collected in excavations along roads, natural drains and adjoining areas under impeded drainage. The composition of water also varies with the season. Whatever may be sources of water, the water sample is taken along with the soil sample to soil testing laboratory for its analysis by way of assessing the suitability of water for irrigation. For drawing maximum benefit the samples taken be representative of the water in bulk and it should be collected in a clean vessel. One to three litres capacity plastic bottles duly washed with a detergent are satisfactory. However, before filling with water samples the bottles must be rinsed with water samples three times. The information such as farmers name, owner of pumping sets, date and month of sampling depth of ground water, crops and soils being irrigated, any specific agricultural or human problems encountered to be briefly recorded along with the name of village, block, tehsil and district. The water sample should be properly labeled and submitted to soil testing laboratory for its analysis.
India is recovering from the euphoria of the Green Revolution and battling the residual effects of the extensively used chemical fertilizers and pesticides in the country’s soils. The decade from 1980 to 1990 alone saw the area under pesticides in India, increased a whopping 20-fold, from six million hectares to 125 million hectares. After a high annual consumption of nearly 75000 MT reached in the early ’90s, interventions in the form of Integrated Pest Management (IPM) practices have only now started to show a declining trend in the use of pesticides in India. Interestingly, India’s consumption of pesticides per hectare is low (0.288 kg/ha) when compared with world averages—0.5 kg/ha against Korea’s 6.60 kg/ha and Japan’s 12.0 kg/ha. According to the pesticides industry statistics, India spends US $3/ha on pesticides compared with US $24/ha spent by Philippines, US $255/ha spent by South Korea and US $633/ha by Japan. Yet, despite a comparatively low use of pesticides in India, the contamination of food products in the country is alarming. About 20 per cent of Indian food products contain pesticide residues above tolerance level compared to only 2 per cent globally. No detectable residues are found in only 49 per cent Indian food products compared to 80 per cent globally. A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides and various other substances used to control pests. Pesticides and their metabolites have received particular attention in the last few years in environmental trace organic analysis because they are regularly detected in food products, surface/ground waters and soil strata throughout the world as consequence of their widespread use for agricultural and nonagricultural purposes. So it is the need of the hour to study the levels of pesticides residues in plants, water and soil and their fate in environment after its degradation. It would be necessary to work out tolerance limits of pesticides residues in/on crops, soil and water and the efforts, therefore, are directed towards various residue analytical methods like TLC, GLC and HPLC etc. which are suitable for the purpose.
Soil testing kit is developed to determine the available nutrient status of soil by rapid test methods. With this system of soil testing, a farmer can test his own soil as often and, in as many places as he feels necessary, and after gauging the need of his soil, he can apply the fertilizers as required. The present mode of soil testing in laboratories usually takes few days and sometime weeks and the farmers may have to travel long distances to submit the soil sample.
To set up a soil-testing laboratory the minimum requirements are as follows: 8.1 Laboratory floor area Minimum four rooms are needed. They are as follows: 1. Office room, floor size: 18’x 12’ This room is used for registration of the soil samples received, recording recommendations along with soil test results in laboratory book and in report sheet, their dispatch, accounts etc.
The analytical work in a soil-testing laboratory mainly involves standard chemical methods, suitably modified to permit handling of a large number of soil samples with the required degree of accuracy and speed. Many of the analytical operations are carried out more conveniently with help of common as well as sophisticated instruments. The various instrumental measurements followed in soil and water-testing work in the laboratory can be broadly divided into two groups: 1) Determination of pH and electrical conductivity 2) Colorimetric, spectrophotometric
Glossary Accelerated erosion: Erosion resulting from human involvement is called accelerated erosion because it is typically many times as fast as geological erosion. Acid: Substance containing active hydrogen, which dissociates on solubilizing in water to produce H+ ions. Lowry-Bronsted defined an acid is a substance that gives up a proton during chemical reaction. According to Lewis, an acid is a substance that can accept an electron pair and the base is a substance that can donate an electron pair. The number of hydrogen ions that can be replaced by a metal determines the basicity of an acid. For example H2SO4 is a dibasic acid, HCl is a monobasic and H3PO4 is a tribasic acid. Acid soil: Soil with a pH value less than 7.0. Acidification: Process whereby soil becomes acid (pH < 7) because acid parent material is present or in regions with high rainfall, where soil leaching occurs. Acidification can be accelerated by human activities (use of fertilizers, deposition of industrial and vehicular pollutants). Adsorbed cation: The cations held by the soil micelles are often called adsorbed cations. They are held in place by the attraction between the positive charge of the cation and the negative charge of the micelle.
