24.10 ELEMENTS REQUIRED IN PLANT GROWTH
1. Macronutrients:
♤ Based on the relative abundance in plants, viz., Nitrogen (N); Phosphorous (P), Potassium (K), Sulfur (S), Calcium (Ca) and Magnesium (Mg)
♤ Their concentration is very small. They are also referred to as minor elements.
♤ Iron (Fe); Zinc (Zn); Manganese (Mg),Copper (Cu),Boron (B), Chlorine (Cl) and Molybdenum (Mo) .In some plants, other than the above, Sodium (Na), Cobalt (Co), Vanadium (Va), Nickel (Ni) and Silicon (Si) are considered as essential micronutrients
Nitrogen (N)
a] N is an essential constituent of proteins and is present in many other compounds of great physiological importance in plant metabolism
b] N is an integral part of chlorophyll, which is primary observer of light energy needed for photosynthesis. c] N also imparts vigorous vegetative growth and dark green colour to plants.
♤ Phosphorus (P) is an essential part of the enzymes which help the crop to fix light energy. It forms an integral part of nucleic acids, the carriers of genetic information, and is important in stimulating root growth
♤ Potassium (K) is involved in processes which ensure carbon assimilation and the transportation of photo- synthates throughout the plant for growth and the storage of sugars and proteins. The potassium ion is also important for water regulation and uptake. Furthermore, the presence of potassium in sufficient amounts ensures resistance to frost, drought and certain diseases
♤ Magnesium occurs in chlorophyll and is also an activator of enzymes,
♤ Sulphur forms part of two essential amino acids which are among the many building blocks of protein. It is also found in vitamin B1 and in several important enzymes.
♤ Calcium is required for plant growth, cell division and enlargement. The growth of root and shoot tips and storage organs is also affected by calcium as it is a component of cell membranes. Calcium is also vital for pollen growth and to prevent leaf fall
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♤ Manures are plant and animal wastes that are used as source of plant nutrients They release nutrients after their decomposition .Manures can be grouped into bulky organic manures and concentrated organic manures
Fertilizers
♤ Fertilizers are industrially manufactured chemical containing plant nutrients Nutrient content is higher in fertilizers than organic manures and nutrients are released almost immediately
Role of manures
1. Organic manures bind the sandy soil and improve its water holding capacity.
2. They open the clayey soil and help in aeration better root growth.
3. They add plant nutrients in small percentage and also add micro nutrients which are essential for plant growth the microbial activity is increased which helps in releasing plant nutrients in available for e.g. bulky organic manures- FYM, compost from organic waste, night soil, sludge, sewage, sheep folding, green manures, concentrated organic manures- oilcakes (edible, non-edible), blood meal, fish meal, bone meal.
4. Organic manures should be incorporated before the sowing or planting because of slow release of nutrients
Classification of Organic manures Farm Yard Manure
♤ This is the traditional manure and is mostly readily available to the farmers. Farm yard manure is a decomposed mixture of Cattle dung and urine with straw and litter used as bedding material and residues from the fodder fed to the cattle..
Compost Manure
♤ Compost is well rotted organic manure prepared by decomposition of organic matter. Composting is largely a biological process in which micro-organisms of both types, aerobic (require oxygen for deep development) and anaerobic (functions in absence of air or free oxygen), decompose the organic matter and lower down the C:N ratio of refuse. The final product of composting is well rotted manure known as compost
Sheep and Goat droppings
♤ It is also valuable organic manure. It contains about 0.5 to 0.7 % N, 0.4 to 0.6% P2O5 and 0.3 -1.0%
K2O. It is effective to all types of crops
Concentrated organic manures Oil cakes
♤ There are many varieties of oil cakes which contains not only nitrogen but also some P and K along with large percentage of organic matter. These oil cakes are of two types.
i. Edible oil cakes- suitable for feeding cattle.
ii. Non-edible oil cakes-not suitable for feeding cattle.
♤ Oil cakes are quick acting organic manure. Though they are insoluble in water, their nitrogen became quickly available to plants in about a week or in 10 days after application.
Bone Meal
♤ Bones from slaughter houses, carcasses of all animals and from meat industry constitute bone meal, which is the oldest phosphatic fertilizer used. It also contains some N.
Fish meal
♤ Fish manure or meal is processed by drying non-edible fish, carcasses of fish and wastes from fish industry. It contains 4.0-10.0 % nitrogen, 3.0-9.0 % P and 0.3 to 1.5 % K. Fishmeal is quick acting organic manure and is suitable for application to all crops on all soils.
Green Manuring
♤ It is a practice of ploughing in the green plant grown in the field or adding green plants from outside and incorporating them into the soil for improving the physical structure as well as fertility of the soil. E.g.: Sannhemp, Dhaicha, Pillipesara, Shervi, Urd, Mung, Cowpea, Ber-seem, Senji, etc.
Green leaf Manuring
♤ Green leaf manuring refers to adding the green leaf and green twigs from legume plants or trees to a field and then incorporating them into the soil by ploughing. E.g.: Glyricidia, wild Dhaicha, Karanj (pongamia), leucaena.
Bio-fertilizers
♤ Bio-fertilizers are the preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolyotic micro-organisms used for application to seed or composting areas with the objective of increasing the numbers of such micro-organisms and accelerating those microbial processes which augment the availability of nutrients that can be easily assimilated by plants. Bio- fertilizers harness atmospheric nitrogen with the help of specialized microorganisms which may be free living in soil or symbiotic with plants.
Nitrogen fixers
1. Symbiotic: - Rhizobium, inoculants for legumes.
2. Non-symbiotic: - For cereals, millets and vegetables.
a) Bacteria:-
i) Aerobic:-Azatobacter, Azomonas, Azospirillum.
ii) Anaerobic:- Closteridium, chlorobium
iii) Facultative anaerobes- Bacillus, Eisherichia
b) Blue green algae- Anabaena, Anabaenopsis, Nostoe
A. Phosphate solubilizing micro-organisms.
B. Cellulolytic and lignolytic micro organisms.
C. Sulphur dissolving bacteria.
D. Azolla.