Soil, the sustainer of the whole civilization, is the media of producing food, fiber, and fuel for mankind. Without soil, there is no life on earth. Soil fertility refers to that the portion of plant nutrients in the soil that can be absorbed and assimilated by the plants and such available nutrients constitute only a small fraction of the total nutrients contained in the soil. Evaluation of soil fertility by soil testing and application of plant nutrients (manures and fertilizers) on that basis is a must for proper and sustainable management of soil, maximum production of food, fiber, and fuel for the well-being of the human race without deteriorating soil health.
Developing the concept and formulating the scientific basis for soil testing are the most important contributions of soil scientists towards the production of food and fiber. Over the past two and a half decades due to the tremendous advancement in the field of electronic and computer-based rapid techniques, soil testing has become an easy and powerful tool in the hands of soil scientists for balanced plant nutrients (manures/fertilizers) recommendation for sustainable crop production.
The Soils of Odisha
The State of odisha covering a geographical area of 15.57 million ha lies in the tropical belt in the eastern region of India between 170 47’- 22033’ N latitude and 81031’-870.30’E longitude. The climate is characterized by high temperature and medium rainfall. The average annual rainfall of the state is 1500 mm with mean summer and wintertemperature 30.30 and 21.30 C, respectively.
The physiographic classification of the State is as follows.
1. The Northern Plateau
2. Central table Land
3. Eastern Ghat and
4. Coastal Plain
Integrating the effect of landform, topography, climate, soil and crop adaptabilitythe state has been divided into ten (10) agro climatic zones . The soils of odisha have been divided into 8 broad soil coastal groups such as red, mixed red and yellow, black,laterite, deltaic, alluvial, brown forest soil coastal saline and mixed red and black soils.
Taxonomically these 8 broad groups of soil come under 4 orders as:-
1. Inceptisols (49 %)
2. Alfisols (35 %)
3. Entisols (10 %)
4. Vertisols (6 %)
These four orders are classified into 10 suborders and 18 great groups. Administratively, the state of odisha has been divided into 30 districts and 314 development blocks.
Agro-climatic Zones of Odisha (Click here)
Soil Fertility Status
soil fertility is the ability of a soil to sustain plant growth by providing essential plant nutrients and favorable chemical, physical, and biological characteristics as a habitat for plant growth. Plant nutrients include the macronutrients nitrogen, phosphorus and potassium, sulfur, calcium and magnesium. Micronutrients are essentially boron, chlorine, copper, iron, manganese, molybdenum and zinc. Fertilizers are chemical or natural substance or material that is used to provide nutrients to plants, usually via application to the soil, but also to foliage or through water in rice systems, fertigation or hydroponics or aquaculture operations. Nutrient sources include chemical and mineral fertilizers, organic fertilizers, such as livestock manures and composts, and sources of recycled nutrients.
- As far as soil reaction is concerned on a district wise basis, 69% soil of Odisha are acidic, 6% saline and rest 25%neutral. (Fig. 1,2 & 3).
- 73 % soils are medium and 27% are low in available phosphrous . (Fig. 4,5 & 6).
- With respect to available potassium 7% soils are low, 86% are medium and 7% are high (Fig. 7,8 & 9). It is worth mentioning here that the district of Boudh and Phulbani are high where as the districts of Ganjam and Gajpati are low in available potassium content.
- 60% soils are medium and 40% soils are low in organic carbon (Fig. 10 &11)
Such variations in the major available nutrient status among the different districts have a direct bearing on the fertilizer recommendations for different crops in Orissa.
Fertilizer Consumption (kg/ha)
Management of the fertility of soils of Orissa demands its build up and sustenance at a high level to produce adequate food for the ever increasing population.Therefore, fertilizer assume a great significance and constitute one of the key inputs for achieving high productivity of crops. Balanced application of fertilizer on the basis of soil testing is the key to achieve the above goal. The present per hectare fertilizer application in different districts of the state is given in Table.
id District 2004-05 2005-06 2006-07
1 Angul 22 23 22
2 Balasore 73 80 101
3 Bargarh 93 99 94
4 Bhadrak 87 96 103
5 Bolangir 19 21 32
6 Boudh 33 34 41
7 Cuttack 40 37 51
8 Deogarh 33 29 26
9 Dhenkanal 22 19 25
10 Gajpati 26 31 40
11 Ganjam 58 53 48
12 Jagatsinghpur 32 35 42
13 Jajpur 43 37 54
14 Jharsuguda 80 68 68
15 Kalahandi 38 36 51
16 Kendrapara 25 26 25
17 Keonjhar 24 24 29
18 Khurda 34 31 44
19 Koraput 19 19 30
20 Malkangiri 25 18 25
21 Mayurbhanj 28 28 38
22 Nawapara 18 22 –
23 Nawarangpur 38 46 70
24 Nayagarh 27 28 29
25 Phulbani 2 4 7
26 Puri 39 51 61
27 Rayagada 23 31 33
28 Sambalpur 86 78 83
29 Sonepur 33 33 34
30 Sonepur 18 19 25
31 *Average* 39 39 47
Fertilizer Recommendations For Different Crop
Fertilizer Recommendation
Three types of fertilizer recommendations are in vogue in the state. They are :
1. Blanket recommendation or recommended dose (RD).
The recommended dose of fertilizers for the three major nutrients (N, P and K) for different crops have been arrived at as a result of different field experimentation in different locations of the state in past. As in the ambiance of any soil test report these are the doses recommended to the farmers, therefore, these doses are also called as Blanket recommendations. The recommend doses (RD) of N, P, K for different major crops of Orissa are given in Table.
2. Soil test based fertilizer recommendation
In order to recommend fertilizer does for different crops on the basis of soil test values, a rating of soil test values for three major nutrients is necessary. They are rated as low, medium and high on the basis of their availability in the soil and the response of crop to applied fertilizers. The terms used for rating are,
Very high : Soil test value is much above the critical value. Least probability of response to applied fertilizers. A small maintenance dose may be necessary.
High : Soil test value just above the critical value. Probability of response is low. In addition to the fertility maintenance dose, a small dose may be recommended.
medium : Soil test value is just below the critical value. Moderate response to added fertilizer. Recommended doses suggested by a Breeder may be advocated.
Low : Soil test value is sufficiently below the critical value. Good response to added fertilizer. More than the recommended dose may be advocated.
Very low : Soil test value is much below the critical value. Probability of response is very high. Higher doses are recommended.
The rate limits adopted by the soil fertility laboratories of the state/country at
present are:
3. STCR concept of fertilizer recommendation
READY RECkONER OF FERTILIZER DOSES FOR DIFFERENT CROPS.
The fertilizer requirement of different crops at varying soil test values for specific yield targets are presented in following tables. These equations are applicable for red and laterate soils (Inceptisols and Alfisols) with sandy loam, loam and clay loam texture and accidic soil reaction. These are applicaple in the district of Khurda, Puri, Nayagarh, Cuttack, Angul, Dhenkanal, Sambalpur, Baragarh, Jharsuguda, Sundergarh.
1. Rice (cv. Lalat) 2. Groundnut (cv. Smruti) 3. Sesamum (cv. Nirmala)
4. Pumpkin (cv. Guamal) 5. Lady’s finger (cv. B.O.2) 6. Brinjal (cv. Utkal Anushree)
Soil Testing Methods
Soil pH
The pH is defined as the negative logarithm of hydrogen ion concentration or simply the log or reciprocal of hydrogen ion concentration.
Principle: A glass electrode in contact with H+ ion of the solution acquires an electrode potential which depends on the concentration of H+ ions. This is measured potentiometrically against some reference electrode, which is usually a calomel electrode. The potential difference between glass electrode and calomel electrode is expressed in pH units.
Procedure: 10gm of soil is taken in a 50 ml plastic beaker and 20 ml of distilled water is added and stirred for 30 minutes. Then with help of a pH meter pH reading is taken.
2. Electrical Conductivity (EC):
The electrical conductivity measurement gives the total amount of soluble salts present in the soil and is expressed as dSm-1. As the amount of soluble salts in a solution increases, the electrical conductivity also increases.
Principle: This electrical conductivity is measured in terms of the resistance offered to the flow of current using a conductivity bridge.
Procedure: 10 gms of soil is taken and 20ml distilled water is added to it and stirred well. The solution is kept for 30 minutes and then the electrical conductivity measurement is taken using a conductivity bridge.
3. Organic carbon:
Principle: Organic carbon present in soil is oxidized by chromic acid in the presence of conc. H2SO4. Potassium dichromate on reaction with carbon forms CO2. The H2SO4 enables easy digestion of organic matter by rendering heat of dilution. Only a certain quantity of chromic acid is used for oxidation. The excess chromic acid left unused by the organic matter is determined by back titration with 0.5 N ferrous ammonium sulphate using diphenylamine (or ferroin) indicator.
Procedure: 1 to 2 gm of soil is taken in a 500ml conical flask; 10ml of 1N K2Cr2O7 is added to it and shaken well. Then 20ml of cone. H2SO4 is added and mixed by gentle shaking. Then it is allowed to stand for 30 minutes after which 200ml of distilled water is added to it. Then 10ml of phosphoric acid and 1ml of diphenylamine (or ferroin) indicator is added to it. The solution is titrated against 0.5 N ferrous ammonium sulphate ( to a bright parrot green end point in case of diphenyl amine indicator and wine red in case of ferroin indicator).
Calculation:
% Organic Carbon= 10 (1- S/B) x 0.0039 x 100/w
Where
B= Blank reading
S= Sample Reading
W= Weight of soil sample taken
% Organic matter = % O.C. x 100/58
Available Nitrogen (By Alkaline Permanganate method):
Principle: A known weight of soil is mixed with excess of alkaline KMnO4 (Permanganate) and distilled. Organic matter present in soil is oxidized by the nascent oxygen liberated by KMnO4 in the presence of NaOH and then ammonia is released. This released ammonia is absorbed in boric acid (2%) containing mixed indicator and is converted to ammonium borate. This ammonium borate is titrated against standard H2SO4
Procedure: 20gm of soil is taken in a distillation flask. 30ml of distill water is added just to moist the soil and 1ml of liquid paraffin is added to avoid frothing, a few glass beads are added to avoid bumping. 100ml of freshly prepared 0.32% KMnO4 and 100 ml of 2.5% NaOH are added to the soil in the distillation flask.100ml conical flask containing approximately 20ml of 2% boric acid with mix indicator is kept below the delivery end of the condenser and the distillation is continued until the release is free of ammonia or about 30ml of distillate is collected. (It can be tested bringing red litmus paper near the outlet of condenser which will turn blue as long as ammonia is being evolved.) The ammonia collected in boric acid is titrated with 0.02 N H2SO4.
Calculation:
Available N (kg/ha) = R x 0.02 x 1 x 0.014 x 2.24 x 106= R x 31.36
Where R = Volume of 0.02N H2SO4 required for titration.
Available Phosphorus:
Olsen’s Method: (For Neutral, alkaline and calcareous Soil)
Principle: Phosphorus is extracted from soil with 0.5 M NaHCO3 adjusted to pH8.5 Blue colour in developed by ascorbic acid method. The intensity of blue colour is measured using spectrophotometer.
Procedure: 2gm of soil is taken in a 100ml Conical flask (or polythene shaking bottle). 20ml of 0.5ml M NaHCO3 (pH 8.5) and a pinch of Darco G. 60 (to make the extraction colourless) is added. The content is shaken in a mechanical shaker for 30 minutes. The content is filtered through Whatman filter paper No. 42 to another conical flask. 5ml of the filtrate is pipetted out into a 25 ml volumetric flask and 4ml of ascorbic acid reagent (1.056 gm of ascorbic acid dissolved in 200 ml of ammonium molybdate antimony potassium tartarate reagent) is added to it. The volume is made up to 25ml with distilled water. The content is shaken and allowed for few minutes for colour development. The intensity of blue colour is measured in spectrophotometer at 660nm wavelength. A blank is simultaneously run to calibrate the instrument. Using the standard curve, the concentration of P (ppm) is found out.
II. Bray’s I Method (For Acid Soils):
Principle: The combination of HCL and NH4F extracts acid soluble form of P such as monocalcium phosphate. The fluoride ion has the special property of complexing Al3+ and Fe3+ ions in acid solution with consequent release of P held in the soil by these ions . The ‘P’ so released into the soil solution is estimated calorimetrically as available P.
Procedure: 2 gm of soil is taken in a 100ml conical flask (or polythene shaking bottle.) 20ml of Bray’s No. 1 extractant (0.03M NH4F + 0.02NHCI) is added to it. The content is shaken in a mechanical shaker for five minutes and than filtered through a Whatman No.42 filter paper. A blank is also simultaneously run. Then 5ml of filtrate is pipetted out into a 25ml volumetric flask. 5ml of chlormolybdic acid reagent is added to it and gently swirled for several times, so that all the CO2 escapes out. Distilled water is added to make the volume up to 20ml. Then 1ml of dilute stannous chloride solution (0.5ml of stannous chloride stock solution diluted to 66ml) is added to it and the volume is made upto 25ml mark and the content is mixed. After colour development the intensity of blue colour is measured in spectrophotometer at 660 nm wavelength.
Calculation
Available P (kg ha-1)
= R *
Where R= ppm P in the aliquot (to be seen from the curve)
Available Potassium:
Principle: The K+ ion in the exchange sites of clay in the soil is replaced with NH4+ ions thereby K+ ions are released. The concentration of K+ ion in the solution is then determined using flame photometer.
Procedure: 5gm of soil is taken in a 100 ml conical flask (or polythene shaking bottle) and 25ml of 1N ammonium acetate is added to it and the content is shaked in a mechanical shaker for 5 minutes. The contents is filtered through a Whatman No. 42 filter paper. The filterate is aspirated in a flame photometer and the reading is recorded. The available potassium content is calculated using a standard curve.
Calculation:
Available K (Kgha-1)
Where R= ppm K in the extract (obtained from standard curve)
Data sources:-Dept. of soil & Agricultural science, OUAT