Plants require 17 Essential Elements for growth: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Potassium (K), Sulfur (S), Calcium (Ca), Magnesium (Mg), Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), and Zinc (Zn).
These 17 essential elements, also called nutrients, are often split into three groups. The first group is the three macro-nutrients that plants can obtained from water, air, or both— carbon (C), hydrogen (H) and oxygen (O). The soil does not need to provide these nutrients, so they are not sold as fertilizers.
The other 14 essential elements are split into two groups—soil-derived macro-nutrients and soil derived micro-nutrients. This split is based on the actual amount of nutrient required for adequate plant growth.
The soil derived macro-nutrients:- Nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg).
The soil derived micro-nutrients:- Boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn).
Manures are animal waste including plant’s waste that are used as source of plant nutrients.
On the decomposition, they release nutrients. Manures can be grouped into bulky organic manures and concentrated organic manures.
1. Bulky organic manures – Farm Yard Manure (FYM), compost from organic waste, night soil, sludge, sewage, green manures.
2. Concentrated organic manures – oilcakes (edible, non-edible), blood meal, fishmeal and bone meal.
Fertilizers are artificial chemical plant nutrients manufactured in industries based on laboratory trails. Nutrient content is higher in fertilizers than organic manures and nutrients are released almost immediately. The fertilizers has three groups:-
1. Straight fertilizers – supplies single nutrient
Ex: Urea, Muriate of Potash
2. Complex fertilizers – supplies two or more nutrient
Ex: 17:17:17 NPK complex
3. Mixed fertilizers– supplies two or more nutrient
Ex: Groundnut mixture
About 35–55 percent of the non-living part of organic matter is humus. It is an important buffer, reducing fluctuations in soil acidity and nutrient availability. Compared with simple organic molecules, humic substances are very complex and large, with high molecular weights. The characteristics of the well-decomposed part of the organic matter, the humus, are very different from those of simple organic molecules. While much is known about their general chemical composition, the
relative significance of the various types of humic materials to plant growth is yet to be established.
Humus consists of different humic substances:
- Fulvic acids: the fraction of humus that is soluble in water under all pH conditions. Their colour is commonly light yellow to yellow-brown.
- Humic acids: the fraction of humus that is soluble in water, except for conditions more acid than pH 2. Common colours are dark brown to black.
- Humin: the fraction of humus that is not soluble in water at any pH and that cannot be extracted with a strong base, such as sodium hydroxide (NaOH). Commonly black in colour. The term acid is used to describe humic materials because humus behaves like weak acids.
- Fulvic and humic acids are complex mixtures of large molecules. Humic acids are larger than fulvic acids.
Fulvic acids are produced in the earlier stages of humus formation. The relative amounts of humic and fulvic acids in soils vary with soil type and management practices. The humus of forest soils is characterized by a high content of fulvic acids, while the humus of agricultural and grassland areas contains more humic acids.
List of Fertilizers and Manures as Nutrients
|Carbon||C||Macro-nutrient||Air & Water|
|Hydrogen||H||Macro-nutrient||Air & Water|
|Oxygen||O||Macro-nutrient||Air & Water|
|Magnesium||Mg||Micro-nutrient||Fertilizers and Manures|
|Sulphur||S||Micro-nutrient||Fertilizers and Manures|
|Iron||Fe||Micro-nutrient||Fertilizers and Manures|
|Manganese||Mn||Micro-nutrient||Fertilizers and Manures|
|Boron||B||Micro-nutrient||Fertilizers and Manures|
|Zinc||Zn||Micro-nutrient||Fertilizers and Manures|
|Copper||Cu||Micro-nutrient||Fertilizers and Manures|
|Molybdenum||Mo||Micro-nutrient||Fertilizers and Manures|
|Chlorine||Cl||Micro-nutrient||Fertilizers and Manures|
Role of Manures and Fertilizers in crop production
ROLE OF MANURES
1. Organic manures bind the sandy soil and improve its water holding capacity.
2. Organic manures open the clayey soil and help in aeration for better root growth.
3. Organic manures add plant nutrients in small percentage and also add micronutrients, which are essential for plant growth.
4. Manures increases the microbial activity which helps in releasing plant nutrients to available form.
5. Organic manures should be incorporated before the sowing or planting because of slow release of nutrients.
ROLE OF FERTILIZERS
1. Fertilizers play an important role in crop production as they supply large quantities of essential nutrient to crops
2. Fertilizers are manufactured in forms that are readily utilized by plants directly or after rapid transformation.
3. Fertilizers dose can be adjusted to suit the requirement as determined by soil testing.
4. Balanced application of nutrients based on crop requirement is possible by appropriate mixing of fertilizers.
5. Fertilizers applied as straight fertilizers (providing single nutrient) or complex and mixed fertilizers (supplies two or more nutrients) based on crop requirement.
AGRONOMIC INTERVENTIONS FOR ENHANCING FUE (Fertilizer Use Efficiency)
The following are the agronomic measures to improve the Fertilizer Use Efficiency (FUE).
1. Using best fertilizer source
2. Using adequate rate & diagnostic techniques
3. Usage of balanced fertilization
4. Integrated nutrient management
5. Utilization of residual nutrients
1. Using best fertilizer source:
Identification of best source of fertilizer is pre-requisite for better crop production. Source of fertilizer depends on crop and variety, climatic and soil condition, availability of fertilizer, etc.
• Nitrogen: Ammoniacal or Nitrate
• Phosphorus: Water soluble or Citrate soluble
• Potassium: Muriate of potash
• Sulphur: Sulphate or Elemental S
• Multinutrient fertilizers: MAP, DAP, SSP, Nitrophosphates
• Multi-nutrient mixtures: Several combinations of NPK
• Fortified fertilizers: Neem-coated urea, Zincated urea, Boronated SSP, NPKS mix.
2. Using adequate rate & diagnostic techniques:
The fertilizer recommendation must be in adequate quantity so as to meet the demand of crop at any point of growth. The fertilizer supply is made by diagnosing its requirement by any of the following method.
• State recommended generalized fertilizer dose or blanket recommendation
• Soil-test based fertilizer recommendations
• Soil-test crop response based recommendation
• Plant analysis for diagnosing nutrient deficiencies
• Chlorophyll meter and Leaf colour charts, etc.
3. Balanced fertilization
Balanced fertilization includes adequate supply of all essential nutrients, proper method of application, right time of application and nutrient interrelationships.
- Adequate supply of all essential nutrients: Due to more concentration and application on primary nutrients (NPK), soils developed deficiency symptoms for secondary and micro-nutrients. Hence, ignored elements must be added with the NPK (may be in minor quantity) to get higher yields in crops. Experimental results shown that about 20-25 kg of micro-nutrient application or two foliar sprays increases the yield of crops up to 20%.
- Proper method: N and K can be applied as broadcasting and band placement. Water soluble P fertilizers are preferred to apply as band placement in neutral & alkaline soils. Citrate soluble P fertilizers are applied as broadcast method in acidic soils. Sulphate forms of S fertilizers are applied as broadcasting or band placement, whereas, elemental S and pyrite are applied as broadcasting method. Micronutrients are applied in minor quantity as foliar sprays and water soluble fertilizers are applied in fertigation.
- Right time: (according to physiology of crop)
• Upland crops – 2 splits (seeding, 3-5 weeks after first dose)
• Flooded rice – 3 splits (Transplanting, 3 and 6 weeks after first dose)
- Nutrient interrelationships: Antagonistic nature of fertilizers is to be considered while applying into the soil. Some of the fertilizer application in excess, cause loss of yield and quality of crops. Ex. Application of excessive 120 kg P ha-1 created an imbalance and reduced the seed and oil yields in soybean compared to 80 kg P ha-1.
4. Integrated nutrient management
Organic manures, crop residues, green manures, bio-fertilizers etc. are to be blended in right manner along with inorganic fertilizers to meet the crop demand. All the possible and available organic sources are to be utilized efficiently to reduce the usage of inorganic fertilizers.
5. Utilization of residual nutrients
- Some of the strategies to utilize the crop residues in efficient manner.
- Knowledge on climatic conditions & carry-over effects of residues.
- Blending rightly on cereal-legume rotations
- Mixing shallow-deep rooted crop rotations.