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Article 1- SOIL ANALYSIS & TISSUE TESTING – A USEFUL TOOL FOR MAXIMIZING CROP YIELD

Mr. R.R SHAH

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Planning scientific nutrient management needs estimation of nutrient content in materials that are used for supplying these nutrients. In order to assess the soil fertility condition, an estimation of available nutrients in the soil needs to be carried out first. This is known as soil testing and it is used by farmers around the world to arrive at optimum fertilizer application rates. The need for estimation of "available" nutrients arises because only a small fraction of what the soil contains is in the plant available form and this fraction too is not directly proportionate to the total nutrient content of the soil. Soil tests are calibrated by correlating them with crop response and the results form the basis for working fertilizer recommendations.

Soil Sampling & Soil Preparation

The soil sample should be representative of the area sampled. A field should be treated as a single sampling unit only if it is appreciably uniform in all respects. Variation in slope, texture, colour, crops grown and management practices followed should also be taken into account. Separate sets of composite samples need to be collected from each such area. Recently fertilized plots, bunds, channels, spots, near trees must be avoided during sampling. Also, when crops are planted in rows, samples can be drawn in between the lines. Sampling depth of 15-20 cm is desirable in case of field crops, vegetable crops & floriculture crops. For deep rooted crops like sugarcane and horticulture crops, samples from different depths or layers may be needed.

Under intensive cultivation ,sampling should be done every year for sampling soft and moist soil, the tube auger, spade or khurpi or pointed wooden peg (especially in case of micronutrient estimation) should be used. The collected soil sample should be thoroughly mixed on a polythene sheet and the bulk is then reduced by 'quartering' so that about 500 gm composite samples are retained. Then the sample must be kept in a polythene bag.

The sample brought to the laboratory is then made free from stones, pieces of roots and other undecomposed organic residues. Large lumps of moist soil are broken by hand. The soil should be air dried (shade drying). Sample is then mixed once again and are crushed gently in pestle and mortar. The crushed samples are then passed through 2 mm sieve & material larger than 2 mm is discarded.

The fertilizer recommendations are based on estimation of the following soil testing parameters -

1.	pH
2.	Electrical Conductivity (EC)
3.	Available Nitrogen
4.	Available Phosphorus
5.	Available Potassium
6.	Available Sulphur
7.	Available micronutrients –
	a) Zn b) Fe c) Mn d) Cu
8.	Exchangeable Calcium and Magnesium
9.	Available sodium
10.	Available Boron
11.	Available Molybdenum
12.	Chloride content
13.	% Calcium Carbonate
14.	% Carbonates & % Bicarbonates

Proper estimation of these nutrients and categorizing the soil sample in low, medium or high nutrient status can lead us to formulate proper fertilizer doses considering the growth stage and nutrient requirement of the crop.

TISSUE TESTING

The determination of nutritional need of crops is an important aspect of nutrient management for the farmers. Information and advice on nutrient use must be made available prior to bud differentiation, expression of the potential yield and before the crop load is known. Considerations of economy, energy and pollution hazards make it imperative that manures and fertilizers be used efficiently to ensure high crop yield and to sustain the available nutrient status at the maintenance level or raise it to the sufficiency level for the specific crops. Information required for deciding the quantity and type of manures and fertilizers to be used can best be achieved by having combined data of soil test values as well as analysis of growing plants in fabricating the need based fertilizer schedules.

Sampling & Sample Preparation:

For plant analysis to be meaningful, collection of particular plant part (tissue) at the right stage of growth as per technical specifications is very important. Index tissue sampling procedure given for various crops should be followed for nutrient diagnosis, monitoring and efficient nutrient management for optimum yield and for excellent quality.

Sr. No.	Crop	Index Tissue	Growth Stage	Sampled Size
1.	Cucumber	5th leaf from lip	Flower bud start to small fruit	12
2.	Tomato	Leaves adjacent to inflorescences	Midbloom	15
3.	Carnation	5 & 6 leaf pairs of non flowering shoots.	Initial stage	50
4.	Gerbera	Most recently developed leaf	Initial stage	15
5.	Orchid	Most recently developed leaf	Initial stage	12
6.	Rose	Most recent developed compound 5th leaflet leaf	Flower bud pea size	10

After sample collection, the fresh tissues should be decontaminated from dust and other foreign material.

The fresh tissues should be washed in sequence using detergent solution, dilute HCl and deionized water. Liquid detergent will remove waxy coatings, dilute HCl will remove metallic contaminants and de-ionized water will wash the previous two solutions. After wiping the extra moisture, the sample is kept in paper bags and dried in oven at 70°C. Then grind the dried samples. After grinding, the samples are kept in oven at 70°C for drying. Then the dry powder is weighed on high sensitive electronic weighing scale for further digestion process. The ground dried plant sample is then acid digested and digested extract after sufficient dilution should be used for estimating the concentration of various elements in it.

Critical Level:

The values of nutrient concentrations obtained from the analysis indicate the composition and nutritional level of the plant at the time of sampling. By comparison with pre-established standard norms, these values indicate whether the level of nutrient is in deficiency, sufficiency, optimum, excessive and toxicity stage. As a diagnostic tool, this is of tremendous value as it can form a sound basis for taking corrective measures.

Article-2 EFFECT OF WATER SOLUBLE FERTILIZERS ON IMPROVEMENT OF CALCAREOUS AND ALKALINE SOILS

Mr. R.R SHAH

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About 11 Million Hectares of cultivable soils in India are alkaline or saline (including coastal saline) in nature. The productivity of crops grown in alkaline soils is low, basically because the pH of these soils ranges from 8 to 10. The suitable pH for most crops to yield high produce is between 6.5 to 7.5. Very few crops can grow in Acidic (Coastal Sandy Acidic) or Alkaline soil (pH more than 8.5). While most acidic soils can be improved by the process of liming; improving alkaline or calcareous soils is difficult and long duration process. The nature of the soil vis-a-vis alkalinity or acidity is important because the uptake of nutrients by the plant roots is strongly influenced by soil pH. This is especially true for vital micronutrients. As the pH increases in alkaline soils, the availability of Nitrogen, Phosphates, Iron, Manganese, Copper, Zinc and Boron decreases. Absorption eventually is blocked completely, even when there is generous supply in soil. If the acidity increases beyond pH 5.0, excepting Iron & Manganese very less nutrients can be absorbed by the plant roots. The phenomenon is due to leaching of Nitrates and fixation of nutrient Ions in the soil matrix. All nutrients are taken up by roots and plants in ionic form as water solution in the conventional method of agriculture and fertilization. Plants depend for their nutrition on nutrients present in the soil and applied through fertilizers.

Due to alkaline and saline nature of the soil, many nutrient elements are lost due to leaching and fixation and are not absorbed by the plants. Annexure 1 gives suitable pH for good uptake of nutrients by the plants.

Annexure 1: Suitable pH for plant nutrient uptake

Nutrient	Optimum pH Range
Nitrates	6.0-7.0
Potassium	6.0-7.0
Calcium	7.5-8.0
Phosphates	6.0-7.0
Magnesium	5.5-7.5
Sulphur	5.5-7.5
Iron	4.0-6.5
Manganese	5.0-6.5
Zinc	5.0-6.5
Copper	5.0-6.5
Boron	5.0-7.5
Molybdenum	6.5-9.0

In areas with considerable rains, land under crop production gradually acidifies. In arid areas, regular irrigation combined with improper drainage results in salt accumulation and raises pH. In both cases availability of nutrients to plants decreases.

In alkaline and saline soil, problem of fixation of nutrient ions with the clay particles is common. Application of Phospho Gypsum replaces sodium levels with calcium thus releasing sulphate ion which in contact with moisture generates acid and reduces pH of the soil. However, this may increase salinity of subsoil water due to leaching of sodium salts or may increase EC of soils. The process has long term affectivity. The solution to this problem is drip irrigation, mini sprinkler irrigation and foliar spray of dilute water solution of water soluble acidic fertilizers. In this system of Fertigation (Irrigation + Fertilization), the nature of soil plays a minor role where it acts only as growing base for plants. Complex water soluble fertilizers consist of all required nutrients (except Calcium) and are acidic in nature, yielding acidic water solution (pH 5.5 - 6.5).

Below is an example of NPK Grade 19:19:19 (Water soluble complex fertilizer) whose nutrient contents are as follows:

Nitrogen (N)	19%
Phosphate (P₂O₅)	19%
Potash (K₂O)	19%
Magnesium (MgO)	1%
Sulphur (S)	3%
Iron (EDTA)	0.1%
Manganese (EDTA)	0.05%
Copper (EDTA)	0.01%
Zinc (EDTA)	0.05%
Boron	0.02%
Molybdenum	0.001%

It is acidic due to raw material used in its manufacturing process such as phosphoric acid, nitric acid, sulphuric acid and sulphate of micronutrients. When dissolved in water, nutrients become their Ions like NO3-, K+ and P- etc. and become chemically active. One single fertilizer contains all nutrients (except Calcium) in balanced ratio, thus providing full nourishment for healthy growth and high yield. For using these fertilizers via drip, mini sprinkler or foliar spray system, a dilute water solution is prepared and this solution is applied to root zone and their leaves.

The residual solution in root zone reacts with calcareous or alkaline soil elements and reduces the pH of the soil towards neutrality over a period of time. Thus, using water soluble complex acidic fertilizers through drip, mini sprinkler or foliar spray systems over a long period of cultivation will improve the nature of soil toward suitable pH and improved fertility.