Crop Nutrition
Essential Plant Nutrients
The plant needs 18 essential chemical elements for its growth which are- Carbon (C), hydrogen (H), oxygen (O), nitrogen(N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), Iron(Fe), Boron (B), Magnesium (Mg), Manganese (Mn), Nickel (Ni) Copper (Cu), Chlorine (Cl), Cobalt (Co), Zinc (Zn) and Molybdenum (Mo).
Plant obtain carbon as CO2 and oxygen partially as oxygen gas (O2) from the air. The remaining elements are obtained mainly from the soil. Plants will grow normally until it is restricted by the supply of one of the essential elements and it cannot be corrected by the addition of other crop inputs.
This gives the basis of Liebig’s “Law of minimum”, which states that the level of crop production is limited by the nutrient in the shortest supply.
The availability of these nutrients is influenced either directly or indirectly by the presence of organic matter & pH. The elements which are needed in large amounts are called macronutrients. Example- carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium magnesium, sulfur.
The other essential elements, called micronutrients, needed in small amounts.
Primary Nutrients: Nitrogen (N), Phosphorus (P), &Potassium (K) vary in ratios & are represented by the 3 numbers seen on the fertilizer packaging. NPK is not in excess in certain soil systems therefore tend to be the most frequently applied nutrients. They are normally applied in larger quantities than other crop nutrients.
Nitrogen
Vital for vegetative plant growth &development.
N is a major part of the chlorophyll molecule therefore it is necessary for photosynthesis.
N is biologically combined with C, H, O, and S to produce amino acids, which are the building blocks of proteins.
Essential for plant cell division. Also, Aids in the production and use of carbohydrates.
Phosphorus (P)
Promotes early root formation & growth involved in photosynthesis,cell division, respiration, energy storage & transfer and enlargement
Improves the quality of fruits, grains & vegetables
Vital to flower & seed formation
Helps plants survive severe winter conditions
Increases water-use efficiency
In photosynthesis and respiration, P plays an important role in energy storage and transfer (as ADP & ATP)
P is part of the RNA & DNA structures, which are the important components of genetic information.
Seeds have the highest concentration of P in a mature plant. P is also required in large quantities in young cells, like shoots & root tips, where metabolism is high & cell division is rapid.
P aids in root development, flower initiation, and seed & fruit development.
P has been found to reduce disease incidence in some plants & has been found to improve the quality of certain crops.
Potassium
Improves the quality of seeds and fruit.
Increases disease resistance, Carbohydrate metabolism & the breakdown and translocation of starches Tuber and fruit development.
Essential to carbohydrate and protein synthesis
Increases photosynthesis
Increases water-use efficiency
Important in fruit formation
Activates enzymes and controls their reaction rates
Potassium is an essential plant nutrient & is needed in large amounts for the proper growth and reproduction of plants.
Potassium is considered second only to nitrogen, when it comes to nutrients needed by plants, and is commonly considered as the “quality nutrient.” It affects the plant shape, size, colour, taste and other measurements attributed to healthy produce.
Plants absorb potassium in their ionic form, K+.
In Photosynthesis, potassium regulates the opening & closing of stomata. So, regulates CO2 uptake.
Potassium triggers the activation of enzymes & is essential for the production of Adenosine Triphosphate (ATP).
Micro Nutrients
-Boron, chlorine, copper, iron, manganese, molybdenum, zinc, nickel, cobalt, etc.
Used in very small amounts.
Important to plant development
Work "behind the scene" as activators
Mobile Nutrients
Nutrients that move to areas where they are lacking. Moves from older leaves to younger tissue results in discolouring in older leaves
Eg- Nitrogen, Phosphorus, Potassium, Magnesium Chloride, Molybdenum
Immobile Nutrients
The nutrients which cannot move
Deficiencies will appear in younger leaves
Eg- Boron, Calcium, Copper, Iron, Manganese, Nickel, Sulfur and Zinc
Manures and Fertilizers
There are many ways of classifying fertilizers and manures, the classification is based on one or two properties of the materials.
Natural manures
Artificial manures
Mineral manures
Nutrient content
Single manures
Compound manures
Complete manures
Incomplete manures
Organic manures
Inorganic manures
Indirect manures
General manures
Special manures
Stimulative substances
Soil amendments or soil conditioners
Critical consideration of the above-mentioned classification reveals that none of the classifications is satisfactory. Each of the classifications is based on only one property and may not be suitable to cover a wide range of materials. They are commonly classified into Bulky organic manure & concentrated organic manures
ORGANIC MANURES
The word manure derived from the French "Manoeuvrer', means to manipulate, to work, to produce the crop. In general, manure means the excreta of animals. The term bulky organic manure generally includes those materials of natural origin, organic in a composition having greater volume per unit content of nutrients and being used to increase the nutrient status of the soils as well as organic matter content of soils. They are obtained mainly as natural products. The materials included in this group are farmyard manure, compost, sewage sludge and green manure.
Of this FYM, compost & green manure are the most important and widely used bulky organic manures.
Farm Yard Manure (FYM)
The FYM refers to the refuse from farm animals, mainly sheep, cattle and poultry. This is one of the oldest manure known and is highly valued for its many beneficial properties that are said to be produced when this manure is added to the soil. It not only adds the constituents to the soil but also adds organic matter to the soil.
Composition of farm manure
Several factors influence the composition of farm manure and they are the following
Source of manure
The feed of the animals
Age of the animals
Condition of the animals
Manner of storage and handling
Litter use etc.,
On average, the composition of FYM is usually 0.5 % N, .25 % P2O5 and 0.5 % K2O.
Methods of collection
Many methods of collecting the cattle manure are in vogue and this include,
Use of ordinary cattle shed with Kacha floor
Use of cattle shed with impermeable floor and provision for collecting urine in separate urine pit
Dry earth system
Loose box system
Other special methods
The method of collection and storage is the most important factor which decides the final composition of the manure. The following are recognized methods of storing FYM
The heap method
The pit method
Various losses during collection and storage of FYM can be prevented or at least minimized by adopting the following procedures
Better methods of collection
Better methods of storage
Use of cow dung gas plant
Use of chemical preservatives like gypsum, superphosphate etc
Organic Wastes :
Organic wastes are the wastes of biological / animal / agro-industry origin and can be converted to valuable manure by composting.
Green manures
Growing the plants in situ &incorporation in the field.
Oilcake, Sewage sludge, Biogas plant slurry, Plant & animal refuges
Green leaf manure: Addition of green or plant tissues obtained from elsewhere viz., trees, herbs, shrubs pruning & unwanted weeds.
The benefit of Green manure or Green leaf manures
Addition of organic matter.
Adds Nutrient – Macro, Secondary & micronutrients.
It improves the physical condition of the soil.
Act as a soil amendment to the reclamation of problem soils.
It acts as a cover or catches crop to prevent soil erosion, conserve moisture, prevent nutrient leaching.
Leguminous crops fix the atmospheric – N by the roots and improve N status of the soil.
Characteristics of Green manure
It should have rapid growth and shorter duration so that can be fitted in a crop rotation
It should yield abundant biomass and should be succulent to have rapid decomposition
It should have the ability to grow on poor soils
COMPOSTING OF ORGANIC WASTES
Composting is a process of allowing organic materials to decompose in more or less controlled conditions to produce a stabilized product that can be used as manure or soil amendment. Composting is basically a microbial process, which changes the property of the organic material or mixtures.
Compost is the material resulting from the decomposition of plant residues under the action of bacteria and fungi. Composting is simply an acceleration of natural process or organic matter mineralization. The final product is dark brown in colour and resembles FYM in its properties and appearance.
Essential requirements for composting
A bulky organic manure
A suitable starter
Addition of enough water
Aeration
Main systems of composting
ADCO process (Hutchinson and Richards of England)
Activated compost process (Fowler and Rege)
The Indore process (Howard and Wad)
The Bangalore process (C.N.Acharya)
The Coimbatore method
Benefits of composting:
∗ Enables clean environment
∗ Absorbs odours, degrade toxic substances and heavy metals
∗ Avoids unnecessary dumping of wastes
∗ Supply valuable organic manure
Composting technologies
1. Crop residue composting
Collect the available crop residues and weeds
Shred them to a size of 2 to 2.5 cm in length
Mix these wastes with green residues (freshly collected), if available
Form the compost heap ( 4 feet height)
Add the bio-inoculants (2 kg of bio-mineralizer or 40 kg of cow dung for 1 tonne of waste)
Properly aerate the compost either by providing perforated PVC pipes or by mechanical turning
Maintain the moisture at 60 % by regular watering
The compost will mature in 60 days
2. Vermicomposting
Vermicomposting is a process of degradation of organic wastes by earthworms.
The species like Eisenia foetida and Eudrilus eugeniae are effective in converting agricultural wastes into compost. The various steps involved in making vermicompost are as follows
Methods followed:
Pit method – aboveground and belowground
Belowground method pit size : 10 X 1 X 0.3 m
Each layer: 6-7cm thick
Sprinkle water once in 8-10 days
Release : 2-2.5 kg worms / pit
Steps:
Place it in the pit/container layer by layer
Moist the residues at 60 % moisture
Allow the verms into the feed material/residues @ 1 kg/ tonne of residue
Protect the pit or container from ants and rats (which are the enemies of verms)
The residue will be composted in 30 to 40 days
Remove the composted materials layer by layer at a weekly interval so as to avoid any damage /disturbance to the feeding verms.
Nutritive value of vermicompost
The nutrients content in vermicompost vary depending on the waste materials that is being used for compost preparation. If the waste materials are heterogeneous one, there will be a wide range of nutrients available in the compost. If the waste materials are homogenous one, there will be only certain nutrients are available.
Organic carbon = 9.5 – 17.98%
Nitrogen = 0.5 – 1.50%
Phosphorous = 0.1 – 0.30%
Potassium = 0.15 – 0.56%
Sodium = 0.06 – 0.30%
Calcium and Magnesium = 22.67 to 47.60 meq/100g
Copper = 2 – 9.50 mg kg-1
Iron = 2 – 9.30 mg kg-1
Zinc = 5.70 – 11.50 mg kg-1
Sulphur = 128 – 548 mg kg-
3. Coirpith composting
Coirpith is an agricultural waste produced from the coir industry. Approximately 180 grams of coirpith is obtained from the husk of one coconut. Coirpith contains Carbon: Nitrogen in the ratio of 112:1 and contains 75 per cent lignin which does not permit natural composting as in other agricultural wastes.
Mushroom Pleurotus has the capacity to degrade part of the lignin present in coirpith by production of enzymes like cellulases and lactases. The carbon: nitrogen ratio of coirpith is reduced from 112:1 to 24:1 as a result of composting.
Composting method
Select a shaded place of 5 x 3 m dimension and level it after removing weeds. Spread 100 kg of coirpith uniformly. Spread 100 g of Pleurotus spawn on this and cover with a second layer of 100 kg of coirpith. On the surface of the second layer, spread one kg of urea uniformly.
Repeat this sandwiching of one layer of coirpith with spawn followed by another layer of coirpith with urea up to one-metre height.
Sprinkle water to keep the heap moist. Allow the heap to decompose for one month.
Manure conversion
The coirpith is converted into good manure after 30 to 40 days and the lignin content is reduced from 40 per cent to 30 per cent. The nitrogen content is increased from 0.20 per cent to 1.06 per cent. Coirpith compost contains macronutrients and micronutrients. It can absorb water up to eight times its weight. Coirpith, when added to sandy soil at 2 per cent increases the water holding capacity up to 40 per cent. It can be applied to a wide variety of crops and can be used to prepare the potting mixture and can be applied as organic manure in kitchen gardens.
4. Composting of crop residues and weeds:
Composting is one of the useful ways for utilizing some of the weeds and noncommercial plants like Parthenium, Water hyacinth, ipomoea etc. instead of their eradication.
The plants can be composted using Trichoderma viridi and Pleurotus sajorcaju as a microbial consortium with supplementation of urea. Select an elevated shady area of a thatched shed and mark an area of 5x1.5 meter. Cut the composting materials into 10 – 15 cm size. Spread 100 kg of these materials over the marked area. Sprinkle 1 bottle of microbial consortia over this layer.
Again spread another 100 kg of composting materials over this layer. Spread 1 kg of urea uniformly over this layer. Likewise, repeat these processes of spreading composting materials, then microbial consortia, again composting materials followed by urea application until a minimum of 1-meter height is reached. Sprinkle water to attain a moisture level of 50% to 60%.
The surface of the heap is covered with a thin layer of soil. Water should be sprinkled depending upon the necessity to maintain the moisture around 50%. A turning is given at the end 20 days to give a thorough mixing of outside material with that of the inside ones. The bio-converted compost will be ready in about 40 days time.
5. Method of composting the Municipal Solid Wastes
Biodegradable municipal solid waste should be separated and collected for composting. Five hundred kg of material should be heaped in the compost yard. In that heaped waste, 1 kg of TNAU microbial consortium should be applied in the form of slurry to cover the full waste material. This 1 kg microbial consortium can be mixed with 5 litres of water to make a slurry. This slurry is sufficient to cover 0.5 tonnes of material.
Then, 50 kg of cow dung should be mixed with 30 litre of water to form cow dung slurry. This cow dung slurry should be sprayed over the heap of municipal solid waste Then, 1 kg of urea should is mixed with solid waste. 60% moisture should be maintained throughout the period of composting. Compost should be turned up once in 15 days to create good aeration and for thorough mixing. Because of this practice, a uniform composted material will be obtained. Solid waste can be composted within 90 days by this the method with the indication of the reduction in the volume, appearance of dark-coloured materials and a small of earthy odour.
After the completion of composting, compost should be sieved through normal mesh to separate unwanted and partially composted material
6. Value addition of poultry waste compost
A known quantity of poultry droppings and coir pith @ 4:5 ratio should be mixed well to attain a C/N ratio of 25:1 to 30:1 is considered to be the optimum C/N ratio for compositing. Pleurotus sajor-caju, a lignocellulolytic organism, should be inoculated into the mix in 2 packets per tonne of waste in order to speed up the composting process. The mix should be heaped under the shade. The moisture content of the mix should be maintained within 40 – 50%. Periodical turning should be given on the 21st, 28th and 35th day of composting. Another two packets of
Pleurotus sajor – caju is to be added when turning is given on the 28th day of composting. A good quality compost will be obtained in 45 days, which contains 2.08% N, 1.93 % P and 1.41 % K with C/N ratio of 10-16
7. Enriched Farm Yard Manure (EFYM)/ Reinforced FYM
Phosphorus content in FYM is relatively low and complete utilization of nitrogen and potassium in the manure is seldom realized. Hence, heavy quantities intended to supply the needed quantity of phosphorus will result in the wastage of nitrogen in most soils. To overcome this P insufficiency, addition of superphosphate to the manure is recommended and the process is called reinforcing / enriching and the resultant material is called “enriched farmyard manure”. The Single Super Phosphate (SSP) can be sprinkled either in the cattle shed or on the manure heap. Rock phosphate can also be recommended for this purpose.
Factors affecting the Composting Process:
I. The Type and Composition of the Organic Waste
II. The Availability Of Microorganism
III. Aeration
IV. The C, N and P Ratios
V. Moisture Content
VI. Temperature
VII. pH
VIII. Time
Preparation of Coir Waste Compost Using Yeast Sludge:
Yeast sludge is a waste product by alcohol distilleries @ 2t/day. This waste contains 6% N, 0.3% P and 0.9% K with other micronutrients, vitamins and growth-promoting substances. The coir waste should be sieved so as to remove all the fibrous materials. For one tone of coir waste 200 kg of yeast sludge and 10 kg of rock phosphate should be added and mixed thoroughly. Moisture should be maintained at 60%. After mixing the material should be formed as a heap. Within 4-5 days the temperature of the heap will be raised to 50-60° C. Within 40 to 50 days the coir waste and yeast sludge will become mature compost. The matured compost will turn from brown to black. There will not be any odour. The volume of the compost heap will be reduced to 1/3. The temperature of the heap will be 25-30°c and it should be constant. The compost will be very light and fine-textured. The compost prepared by this means of the above method contains N-1.09%, P- 1.35%, K-1.95% besides copper, manganese, iron and zinc. This compost doesn’t have any phytotoxicity and used for all agricultural crops.
Preparation of sugarcane trash compost using yeast sludge:
Sugarcane trash collected from sugarcane field has to be cut into small bits using chaff cutter or shredder to a size of 1-2cm. for every tone of sugarcane trash 200 kg of yeast sludge and 10kg of rock phosphate are added and mixed thoroughly. Moisture is maintained at 60%. the heap is formed to a height of 1-1½ m. within 45-50 days sugarcane trash compost will be ready for application to crops. The sugarcane trash compost consists of N-1.2%, P-0.7%, K- 1.5% and considerable quantities of micronutrients. This compost can be applied at the rate of 5t/ha.
Japanese method of composting:
Instead of pits in a conventional composting system, vats of 18-30’ in length, 3-4’ in width and 2.5- 3.0’ height are made of bamboo stakes of 2.5-3.0’ width. For growth a non-leaky surface is prepared with broken stone stable or brick and plastered with cement. About 2 feet space is kept free on one side of the vat to facilitate turning the residues regularly. Sliced and broken pieces of coconut, shells, leaves, fibrous materials, tender tree barks or pieces form the bottom 10-15 cm layer. The second layer of dry leaves, grass residues, groundnut haulms are of 10-15 cm height. Cow dung, urine, biogas slurry are sprinkled over and this layer of soil and ash is spread over.
Nitrogen-rich green leaves of Pongamia, albizzia, daincha, sesbania and crop residues form third layer of 10-15 cm. The fourth layer of 10-15cm contains organic wastes rich in phosphorous and potash. Over these 2-3 buckets of cow dung and biogas, slurry are sprinkled. The fifth layer contains paddy or ragi straw that is rich in carbon and provides energy for microorganisms. Sixth layer contains exclusively of dried and powdered cow dung of 20- 30cm. Over these small quantities of old compost, tank silt and ash are sprinkled. For rapid degradation Aspergillus, Penicillium, Trichoderma should be inoculated. Pleurotus and Polyporus should be inoculated for degradation of high lignin contained residues. Azotobacter and Phosphobacteria can be mixed for enriching the composts.
Classification of fertilizers
Commercial N, both organic and inorganic is desired from a wide variety of materials which are found to differ very widely in their sources, properties, method of preparation and their reactions in the soil. Classification based on chemical form seems to be more satisfactory as indicated below.
Nitrogenous Phosphatic Potassic Compound Mixed Fertilizers and manures
1. Bulky organic manures (FYM, compost, Green manure)
2. Concentrated organic manures (Oil cakes)
3. Artificial fertilizers
1. Bulky organic manures (FYM, compost, Green manure)
2. Concentrated organic manures (Oil cakes)
3. Artificial fertilizers
1. Inorganic ammoniates (Ammonical-N Nitrate-N, Ammonical+ Nitrate –N )
2. Organic ammoniates (Amide- N/synthetic Plant origin )
1. Natural (Ground rock phosphate Bone meal)
2. Treated or processed (Superphosphate Bone char)
3. Industrial byproduct (Basic slag)
4. Chemical or synthetic Ammonium phosphate
Potassic
1. Natural (Potash mineral )
2. Processed ( MOP SOP )
3. Synthetic (Pot.nitrate & Pot.phosphate)