#47 Plant's mineral requirements and fertilisers

Plants need minerals for healthy growth.

Plant is in need for mineral ions to control chemical activities, grow, and produce materials. The most important minerals are Magnesium ions and Nitrates.

1.Importance of nitrate and magnesium ions

   a. Nitrates

• plants absorb nitrate ions from the soil, through their root hairs
• nitrate ions combine with glucose -----> amino acids
• amino acids bond together -----> protein
• deficiency causes poor growth, especially of leaves. The stem becomes weak, lower leaves become yellow and die, while upper leaves turn pale green

Nitrates deficiency: Growth severely restricted, few stems;
                 yellowing of older foliage.

   b.Magnesium

• plants absorb magnesium ions from the soil solution
• used for the manufacture of chlorophyll
• each chlorophyll contains one magnesium atom
• deficiency makes leaves turn yellow from the bottom of the stem upwards and eventually stops photosynthesis 

Magnesium deficiency in potato plant.

(Growth fairly normal; foliage slightly pale; older leaflets develop central necrosis, turn yellow or brown and wither prematurely). 

Magnesium deficiency: yellowing between the veins of leaves. 

2. Nitrogen fertilisers

Sometimes the soil is lacking of the mineral ions needed, this problem can be solved by adding fertilisers to the soil. Fertilisers are chemical compounds rich in the mineral ions needed by the plants. They help the plants grow faster, increase in size and become greener, they simply make them healthier and increase the crop yield.  

Ammonium Nitrate fertiliser

Intensive farming (repeatedly using the same land fro crops) removes nitrates from the soil. These need to be replaced to prevent a drop in yield. Nitrates can be replaced in 3 ways:

• applying animal manure
• crop rotation – growing leguminous plants such as peas, beans and clover every 2 or 3 years: these plants develop root nodules containing nitrogen-fixing bacteria, and the roots are ploughed into the soil, boosting nitrate levels
• adding artificial fertilisers such as ammonium nitrate

  Danger of overuse

Apply too much nitrogen fertiliser ----> water is drawn out of plant roots (osmosis) ----> plant wilt/die.

Eutrophication:

Nitrates can be leached out of the soil and enter a nearby river polluting it, creating a layer of green algae on the surface of it causing lack of light in the river thus preventing the aqua plants photosynthesising ----> death of algae ----> decomposers (bacteria) multiply and decay, respire using O₂ ----> death of aquatic animals from lack of O₂ = Eutrophication.

Overuse of nitrogen fertiliser can have nasty environmental consequences.

Additional resource: xtremepapers.com