1. SOIL AND WATER QUALITY FOR AGRICULTUREBy
ZEESHAN AKRAM
SOIL CHEMIST
Fatima Sugar Research and Development Center – Fatima Group

2. What is Soil ?
The unconsolidated material or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants.

3. SOIL FERTILITY
The ability of a soil to support satisfactory plant growth
Ensures nutrient and water supplies
Provides pleasent conditions for root growth, development and harvesting of potential yield.

4. Soil Quality
Soil quality is the capacity of soils within landscapes to sustain biological productivity, maintain environmental quality, and promote plant and animal health
Protecting soil quality like protecting air quality and water quality should be fundamental goal of our Nation’s Environmental Policy
Poor Good

5. Soil Analysis
The standard techniques are employed for analysis of soil. These techniques are mainly based on potentiometry, electrical conductance, atomic absorption spectrophotometery, flame photometry.
Results are expressed in units acceptable in national and international literature.

6. Method of Soil Sampling
Divide the field into different blocks on the basis of soil variability.
Samples are collected from each block with soil auger from different depths.
For the field crops samples are collected from the depth of 0–15 & cm
Samples are collected in zigzag pattern across the field.
For the orchards samples are collected up to the depth of 150 cm.
The samples should be taken under the crown of trees.
Put the samples in polythene bags labeled as under:
- Farmer’s name
- Block No.
- Depth

7. Precautions for Soil Sample Collection
Samples should not be taken:
Along the water channel, roadside, pathway and boundaries
Under the tree shade
Close to the heaps (manure)
Areas where the plant population is not uniform
Areas where domestic refuse are thrown
Places in the field where fertilizers are dumped
Sampling in low lying area.

8. Methods of soil Analysis

9. SOIL REACTION (pH): pH (paste) Remarks
Soil pH is the most important parameter which indicates soil reaction and ultimately affects availability of many soil nutrients to plants. In classifying soils for their reaction, they are categorized in three distinct groups; acid, neutral and alkaline. The pH value is determined potentiometrically using combination electrode. The pH value of soil paste can be interpreted as following:
pH (paste) Remarks
Soil contains no alkaline earth carbonates.
Alkaline, some quantity of bicarbonate is present ESP may or may not exceed15.
> Alkali, carbonate is dominant anion and ESP may exceed 15.

10. Soil pH 14
Acidic Zone
Alkaline Zone
pH Range

11. SOIL SODICITY (SAR) EC (dS m-1) SAR Remaks
Sodium adsorption ratio (SAR) of soil extracts and irrigation waters indicates relative activity of sodium ions in exchange reactions with soil.
SAR = Na / (SQR ((Ca + Mg) / 2))
The ionic concentrations are in milliequivalent per liter.
The criteria being used to classify the soils according to salt type and amount is as under:
EC (dS m-1) SAR Remaks
< <13 Non Saline - non Sodic soils
> <13 Saline soils
< >13 Sodic soils
> >13 Saline - Sodic soils

12. SOIL ORGANIC MATTER Organic Matter (%) Remarks
Soil sample is treated with potassium dichromate in presence of sulfuric acid and excess of chromate (not reduced) is determined with standard ferrous sulphate (Walkley and Black method).
Organic Matter (%) Remarks
< Poor
Satisfactory
> Adequate

13. Nitrogen Distillation Unit

14. SOIL PHOSPHORUS
The Olsen method is used which is standard method for soils of arid and semi-arid regions. Phosphorus is extracted with 0.5-M sodium bicarbonate solution buffered at pH 8.5. Phosphorus is extracted with 1:20 ratio (soil: extractant) for thirty minutes and P is estimated spectrometrically at 880 nm after developing a blue colour by ammonium molybdate and ascorbic acid. The soil P indices are as follows:
Phosphorus Rating Remarks
(mg / kg -Soil)
< Very low The yield would be less than 50%,potential without P application.
Low Optimum yields of all crops can not be obtained without P application.
Medium All crops need P application.
Adequate High P requiring crops need P application.
> High P is recommended for soil fertility maintenance or to balance N:P ratio.

16. SOIL POTASSIUM
The method used for the assessment of soil K status is comprised of 1 N ammonium acetate extraction with 1:20 ratio (soil: extractant). The shaking time is thirty minutes and K is estimated on flame photometer. Fertilizer recommendations are made on the basis of soil K indices, which are as follow:
Potassium Rating Remarks
(mg /kg soil)
< Very low The yield would be less than 50% potential without K application.
41 – Low Optimum yields of all crops can not be obtained without K application.
81 – Medium All crops need K application..
181 – Adequate High K requiring crops need K application..
> High No need of K application to all crops but K fertilizer is recommended to balance its mining.

17. Flame photometer Analysis

18. SOIL MICRONUTRIENTS Micronutrient Deficiency limit (mg / kg soil)
Zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) are determined by extracting with diethylene triamine penta acetic acid (DTPA). The extractant is buffered at pH 7.3. The concentrations of Zn, Cu, Fe and Mn are determined on atomic absorption spectrophotometer using air-acetylene flame and appropriate standards for calibration. The critical levels for DTPA extractable micro-nutrients are as follows: -
Micronutrient Deficiency limit
(mg / kg soil)
Zn < 1.0 (1.5 – Rice Only)
Cu < 0.2
Fe < 4.5
Mn < 1.0
B (0.1 Normality HCl, extractant) <0.6

19. Atomic Spectroscopy Analysis

20. Soil Fertility Criteria
OM (%)
Class
Soil-P (ppm)
Soil-K (ppm)
<0.86
Poor
< 7
Low
0-80
0.86 – 1.29
Satisfactory
7-14
Medium
81-180
> 1.29
Adequate
15-21
>180
>21
Contd….

21. THANKS