How are nutrients replenished in the soil?
Answers
Plants get their mineral nutrients from the soil. If crops/plants are grown year-after-year, the soil will become poorer in such nutrients. Nitrogen, Phosphorus, Potassium, Magnesium, Calcium are the major nutrients. In addition to these, plants also need Iron, Copper, Maganese, and Zinc etc. in smaller amounts. So, if the soil becomes poorer in these nutrients, it loses its fertility and crop yield falls. Therefore, it is important to replenish (to make up the loss) these nutrients in the soil.
This is done by one or more of the following methods :
• By using manure
• By using fertilizers
• By crop rotation method
Usually plants require a lot of nitrogen to make proteins Nitrogen in the soil can be replenished by using
• Manure or spent slurry from the biogas plant.
• Nitrogenous fertilizers such as Urea, Ammonium nitrate, Ammonium
sulphate etc.
• By crop-rotation method. The practice of sowing a cereal crop alternately to a leguminous crop.
Gram, Peas, Moong, Beans etc., are legumes. The roots of these crops have nodules on them. These nodules have symbiotic bacteria. These bacteria have a property to convert atmospheric nitrogen into nitrates. Nitrates are soluble in water and can provide nitrogen to plants. Thus Rhizobium can convert atmospheric nitrogen into soluble salts of nitrogen.