Fill in the amount of nutrients that is added to the soil so that the sufficient elements can be absorbed
by the plant. Also answer the questions that follow.
Amount of nutrient
Amount of nutrient
Nutrients absorbed (Kg/ha) by
Nutrients absorbed (Kg/ha) by
the plant
the plant
N
Mg
Р
S
K
Fe
Ca
Mn
(a)
How many essential nutrients are required by the plant?
(b)
Name the other essential plant nutrients which are not mentioned in the above table.
Answers
Answer:
Nitrogen, phosphorus and potassium are known as primary plant nutrients; calcium, magnesium and sulphur, as secondary nutrients; iron manganese, copper, zinc, boron, molybdenum and chlorine as trace elements or micro-nutrients. The primary and secondary nutrient elements are known as major elements. This classification is based on their relative abundance, and not on their relative importance. The micronutrients are required in small quantities, but they are important as the major elements in plant nutrition.
Nitrogen
K Importance
Nitrogen, the most important nutrient for rice, is universally limiting the rice productivity.
Nitrogen encourages the vegetative development of plants by imparting a healthy green color to the leaves.
It seems that majority of Indica varieties are adapted to relatively low levels of nitrogen in the region of 25 kg N/ha.
Rice plant depends mainly for its nitrogen upon the decomposition of organic matter under anaerobic conditions and in the early stages of growth takes up nitrogen in the form of ammonia which is the stable form of nitrogen in submerged soils.
There are two stages in the growth of rice crop when nitrogen is most needed; early vegetative and panicle initiation stages.
Fertilizing the crop during early vegetative growth promotes tillering leading to higher yield. Application at panicle initiation or early booting stage will help the plant produce more and heavier grains per panicle.
Phosphorus
Phosphorus is particularly important in early growth stages.
It is mobile within the plant and promotes root development (Particularly the development of fibrous roots),tillering and early flowering.
Addition of mineral P fertilizer is required when the rice plants root system is not yet fully developed and the native soil P supply is inadequate.
Phosphorus is remobilized within the plant during later growth stages if sufficient P has been absorbed during early growth.
It also increases resistance to disease and strengthens the stems of cereal plants, thus reducing their tendency to lodge. It offsets the harmful effects of excess nitrogen in the plant.
Potassium
K Importance
Potassium enhances the ability of the plants to resist diseases, insect attacks, cold and other adverse conditions.
It plays an essential part in the formation of starch and in the production and translocation of sugars, and is thus of special value to carbohydrate-rich crops.
Involves in working of enzymes.
Helps in production and movement of photosynthates to sink.
Helps in proper uptake of other nutrients.
Influences tillering or branching of plant and size and weight of grain.
Over 80 per cent of the absorbed potassium by the plant is found in straw. Need for potassium is most likely to occur on sandy soils.
Calcium
Calcium combines with pectin in the plant to form calcium pectate, which is an essential constituent of the cell-wall.
It also promotes the activity of soil bacteria concerned with the fixation of free nitrogen or the formation of nitrates from organic forms of nitrogen.
Furthermore, it is necessary for the development of a good root system.
Ca Importance
agnesium
Mg Importance
Magnesium is an essential constituent of chlorophyll.
It is usually needed by plant in relatively small quantities. Hence its deficiency in the soil is experienced later than that of potassium.
Answer:
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