In the Indo-Gangetic plains, Islamic rulers of the medieval period (13th to 16th centuries) classified agricultural land based on the inherent level of soil fertility and crop patterns (Abul Fazal, 1595). Arnon and Stout (1939) proposed the following criteria for the essentiality of plant nutrients: (i) the lack of an essential element prevents the plant from completing its life cycle, (ii) the deficiency is specific to a certain essential element, (iii) the essential element is directly involved in the plant's nutrition.
Anion exchange
Root cation exchange capacities
The level of a particular nutrient around the root will fluctuate depending on the balance between the rate at which it reaches that area by mass flow and the rate of uptake by the root. This results in a phenomenon known as "back diffusion". In which there will be a concentration gradient and thus the movement of certain ions away from the surface of the roots back towards the soil solution.
Nitrogen
Rate of nitrogen application
Fertilizer nitrogen efficiency, in most crops, is generally greater at lower fertilizer levels than at higher levels, and decreases significantly when N rates are increased beyond the optimum. 1993) reported that increased fertilizer uptake by maize was greatly reduced beyond 100 kg N/ha.
Methods of application
Time of nitrogen application
Kerala Neem cake mixed urea (1:5 ratio) Top dressing Kerala Soil hardened urea (6:1 ratio) kept for 24-48 hours. Top dressing Karnataka Soil hardened urea (50-100 kg soil) kept for 24 hours Top dressing Karnataka Neem cake mixed urea Basaal Meghalaya Soil hardened urea (5:1) kept for 48-72 hours Top dressing Meghalaya Rock phosphate coated urea Basal. Tamil Nadu Urea mixed with plaster (1:3) Basic Tamil Nadu Neem cake mixed urea (20% cake by weight) Top dressing Tamil Nadu Urea treated with coal tar (100 kg urea, 1 kg coal tar, 1.5 liter kerosene).
Basal Rajasthan Soil-cured urea (5:1), kept for 24 hours. Top dressing Rajasthan Neem cake treated urea (100 kg urea, 0.5 kg coal tar, 1 liter kerosene). Bulky organic fertilizers: Consider FYM, rural compost, urban compost, biogas compost, night soil, sludge, green manures and other bulky sources of organic material. Concentrated organic fertilizers: Consider oil cakes, blood meal, fish manure, meat meal and wool waste.
The humus of organic fertilizers is a colloidal substance with a negative electrical charge and is coagulated with cations.
Phosphorus
Types of clay: Phosphorus is retained to a greater extent by 1:1 clay (kaolinite) than by 2:1 clays, probably due to the higher amounts of hydrated oxides of iron and aluminum
Amount of calcium carbonate: A small fraction of the P sorption capacity of soils originates from CaCO3 and most of the sorption attributed to it, however, may actually be due to hydrous iron oxide impurities. Above pH 8, Ca and Mg ions, as well as the presence of carbonates of these metals in the soil, cause precipitation of added phosphorus and its availability decreases again. The strength of the anion's binding to the adsorption surface determines the competitive ability of that anion.
The influence of organic anions on the reduction of P sorption is related to their molecular structure and the pH of the system. Saturation of the sorption complex: The sorption and desorption of P is strongly influenced by the extent of saturation of the sorption complex. This has been variously described as the result of: (i) formation of phosphohumic complexes, which are more easily assimilated by plants, (ii) anionic exchange of phosphate by humic ions, (iii) coating of sesquioxide particles by humus to form a protective coating and thus reduce the ability to fix P in the ground.
Therefore, the key to effective phosphorus application is deep placement close to growing young crop roots.
Potassium
Potassium fertilizers
Potassium sulfate also contains about 17% S and this is an advantage for sulfur deficient areas.
Choice of K fertilizers
Efficient use of potassium fertilizers
Calcium
The optimal range of Ca saturation of the exchange complex (CEC) varies from 12 to 75%; for temperate regions. The release of Ca from the exchange complex and its availability to agricultural plants depends on the following factors; a number of them are independent. Type of clay mineral present: Soils that have 2:1 layer silicates have higher CEC and thus can hold larger amounts of Ca.
Providing a plant canopy such as grass cover can greatly reduce the leaching of Ca from a soil. Excessive leaching of Ca is a factor responsible for the development of acidity in Oxisols and Ultisols. Since Ca is generally immobile in plants, there is very little translocation of Ca into the phloem.
Ca release from gypsum is affected by particle size, so fine powder material is generally used.
Magnesium
Acute Ca deficiency in maize prevents the formation and opening of young leaves, the tips of which may be covered with a sticky gelatinous substance; the leaves like to stick together and give the appearance of a ladder. The calcium absorbed by the roots is not transferred to the developing pods, which therefore directly absorb the Ca needed for their development during initial fixation and seed development from the soil solution. For this purpose, gypsum is usually applied in a strip or sprayed in the first stage of flowering; the term lime plaster is sometimes used for this practice.
Potassium magnesium sulfate, magnesium sulfate, magnesium oxide and magnesium silicate are used as dry fertilizer formulations for direct application, while magnesium sulfate, magnesium chloride, magnesium nitrate and synthetic and natural magnesium chelates are well suited for foliar sprays.
Sulphur
As long as there is less sulfur in the organic matter than is necessary for microbial proliferation, immobilization will be dominant. The need for mineralization and wheat straw contains only one-third of this minimum required amount, hence the incorporation of wheat straw results in S-immobilization. S S2O3-2 S4O6-2 S3O6-2 SO3 SO4 Sulfide thiosulfate tetrathionate trithionate sulfite sulfate. ferrous oxidans are responsible for sulfur oxidation. Oxidation reactions can be illustrated with hydrogen sulfide and elemental S. Sulfur oxidation in soil is influenced by a number of factors, which are given below: i).
When soil or added sulfur is inoculated with Thiobacillus organisms, sulfur oxidation is greatly increased. ii) Temperature: An increase in temperature up to 40oC increases the rate of oxidation of S in the soil. In fact, the SO42- present in the soil serves as an electron acceptor for sulfate-reducing bacteria. Sulfur has historically been used along with ammonium sulfate, common superphosphate, and potassium sulfate.
Thus, additional S as elemental S, gypsum or pyrite can be used as needed, depending on material availability and crop and soil needs.
Micronutrients
When applied to soil, doses vary from 345 to 350 g ha-1 depending on soil and crop.
Soil Fertility Evaluation and Fertilizer Recommendations
An abnormal appearance of the growing plant can be caused by the lack of one or more nutritional elements. The use of growing plants is understandably very attractive in the study of fertilizer requirements, and much attention has been paid to these methods of measuring soil fertility status. Field Tests: The field chart method is one of the oldest and most popular biological tests.
The soil is mixed with the nutrient solution, a paste is made, spread evenly in the pit of a specially constructed clay dish, grafted onto the surface in the center of the paste and left to incubate for four and a half days. The diameter of the mycelial growth on the tray is used to estimate the amount of phosphorus present. Fertilization recommendations based on soil test data: When interpreting soil tests, an economic evaluation is made of the relationship between the soil test values and the fertilizer response.
The chlorophyll meter can provide a rapid and accurate measurement of leaf N status of rice plants in situ in the field.
Biofertilizers
Azotobacter and Azospirillum : The beneficial effects of Azotobacter on cereals, millets, vegetables, cotton and sugarcane under both irrigated and dryland conditions have
Blue Green Algae: Judicious use of blue green algae could provide the same amount of nitrogen to the entire paddy area of the country as obtained from 15-17 lakh tonnes of urea. Methods for mass production of algae biofertilizers have been developed and this method is becoming popular among the rice growers in many parts of the country (Ventakaraman and Tilak, 1990).
Azolla : Azolla is known as a floating nitrogen factory in low land rice fields and in shallow fresh water bodies. The Azolla anabaena association use the energy from
Associative nitrogen fixation, the ability to produce plant growth promoting antifungal and antibacterial compounds and their effect on root morphology are the main mechanisms responsible for increasing crop yields (Tilak and Annapurna, 1993). These organisms are very useful in the use of low P rock phosphate. They are multiplied in the roots of host plants and the inoculum is prepared using infected roots and soil.
Mycorrhizal fungi help in the uptake of phosphorus and trace metals and have a positive effect on the state of water and nutrients through hormonal influences. The group of rhizospheric bacteria (rhizobacteria) that have a beneficial effect on plant growth is called plant growth-promoting Rhizobacteria or PGPR (Schroth and Hancock, 1981). PGPRs are believed to improve plant growth by colonizing the root system and pre-empting the formation of harmful rhizospheric microorganisms (DRMO) on the root (Schroth and Hancock, 1981).
Production of siderophores is another high-affinity molecular weight Fe+3 chelator that transports iron into bacterial cells and is responsible for increased plant growth by PGPR (Kloepper et al., 1980).
Integrated Nutrient Management (INM)
The humus material that is formed affects the physical, chemical and biological properties of the soil and improves crop growth (Gaur and Sadasivam, 1993). Estimation of the availability of some crop residues in India and their plant nutrition potential. One third of the total NPK potential assuming that two thirds of the total residue is used as animal feed on a national basis.
Fifty percent of the usable NPK, assuming 50% mineralization of NPK per season Source: Bhardwaj (1995). If it is assumed that two thirds of the total residues are used as animal feed, one third of the total NPK potential will be 1.51 MT of N + P2O5 + K2O. The interdependence of ammonia volatilization and denitrification as nitrogen loss processes in flooded rice fields in the Philippines.
Proceedings of the Sulfur Institute – Fertilizer Association of India Symposium, “Sulfur in Indian Agriculture”, held in New Delhi.
