RANGES OF ELEMENTS PARAMETERS IN SOIL AND IRRIGATION WATER

 

 

QUESTION: Find the range of the following parameters in the soil for plant growth

a)      Boron concentration

b)      Zinc

c)      Calcium

d)     Sodium

e)      Magnesium

f)       Potassium

g)      Phosphorus

h)      Sodium adsorption ratio (SAR)

i)        Electrical conductivity (EC)

 

 

1. BORON CONCENTRATION

Boron (B) is a micronutrient critical to the growth and health of all crops. It is a component of plant cell walls and reproductive structures.

Boron deficiency commonly results in empty pollen grains, poor pollen vitality and a reduced number of flowers per plant. Low B supply can also stunt root growth

Boron is a micronutrient needed in small amounts. Boron toxicity may occur if the concentration in irrigation water or fertigation solution exceeds 0.5 to 1.0 mg/L, particularly with long-term slow-growing crops. High boron levels can be treated using anion exchange or reverse osmosis treatment systems but pH adjustment is sometimes needed to improve treatment efficiency.

2. ZINC

Zn (zinc) must not exceed in the range of 2.0            as may become toxic to many plants at widely varying concentrations; reduced toxicity at pH > 6.0 and in fine textured or organic soils.

The function of zinc is to help the plant produce chlorophyll. Deficient in zinc can cause Stunted Growth, Brown spots on Upper Leaves and Distorted Leaves. Also growth hormone production and internode elongation.

 

C.     CALCIUM

Calcium has the desirable range of 0 to 100 ppm calcium carbonate for irrigation water is Levels between 30 and 60 ppm are considered optimum for most plants. Irrigation water tests should always include both pH, hardness and alkalinity tests, so calcium determination is related to magnesium

 

4. SODIUM

Sodium in the soil does not play any nutrient requirement on the plant but it does play a role in soil health. High levels of sodium indicate salinity problems

Sodium in excess of 50 mg/L may cause toxicity in sensitive plants, particularly in recirculating irrigation systems. Sodium can be further evaluated based on the sodium adsorption ratio (SAR) which is described below.

The majority of sodium sources in soil are from concentrated runoff of pesticides, fertilizers and other soil amendments. Fossil salt runoff is another cause of high salt content in soils. The sodium tolerance of plants is also tested in coastal areas with naturally salty ambient moisture and leaching from shorelines

 

5. MAGNESIUM

Magnesium is the one provide much role to the chlorophyll molecule in plant tissue. Thus, if Mg is deficient, the shortage of chlorophyll results in poor and stunted plant growth. Magnesium also helps to activate specific enzyme systems.

Ideally, for healthy and productive soil the concentration of manganese should be below 2 mg/L.

6. POTASSIUM

It is also very important for the development of plant cell walls so among other things, it helps plants resist frost and cold damage. It also controls a plant's ability to cope with drought and helps plants combat disease and insect damage.

Ideally, for healthy and productive soil you should aim for a potassium concentration of at least 0.5 meq/100g (milliequivalents - this is a special term used to describe the amount of some elements in soil).

 

7. PHOSPHORUS

Phosphorus is a primary macronutrient (it's the P in NPK). It is required for plant respiration and photosynthesis as well as cell division and growth (and thus plant growth). It is also vital for the production of fruit and seeds and is an important part of proteins, enzymes and DNA.

Ideally, for healthy and productive soil you should aim for a phosphorus concentration of 20‑100 mg/kg.

Symptoms of Phosphorus Deficiency can Leaf tips appear burnt, Plants will be stunted and leaves will become spotted with necrotic tissue.

 

8. SODIUM ADSORPTION RATIO (SAR)

The Sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils. It is also a standard diagnostic parameter for the salinity and sodicity hazard of a soil, as determined from analysis of pore water extracted from the soil.

Table showing range of SAR in irrigation water

Tolerance	SAR of irrigation water	Crop
Very sensitive	2-8	Fruits, nuts, citrus.
Sensitive	8-18	Beans
Moderately tolerant	18-46	Clover, oats, rice
Tolerant	46-102	Wheat, barley, tomatoes, beets.

 

9. ELECTRICAL CONDUCTIVITY

The required Optimal EC levels in the soil range from 110-570 MilliSiemens per meter (mS/m). Too low EC levels indicate low available nutrients, and too high EC levels indicate an excess of nutrients.

Soil electrical conductivity (EC) is a measure of the amount of salts in soil (salinity of soil). It is an important indicator of soil health. Soils containing excess salts occur naturally in arid and semiarid climates. Salt levels can increase as a result of cropping, irrigation, and land management.