Soil Science

Definition: Manure is an organic material of plant or animal origin added to the soil to improve its fertility, physical properties, and biological activity[span_7](start_span)[span_7](end_span).

Classification of Manures

Manure	Nutrient Content
Farm Yard Manure (FYM) ⭐⭐⭐	Low
Compost	Low
Green Manure ⭐⭐⭐	Medium
Vermicompost ⭐⭐⭐	High
Sewage & Sludge	Variable

Manure	Major Nutrient
Neem Cake	N
Groundnut Cake	N
Castor Cake	N
Bone Meal	P
Fish Meal	N & P
Blood Meal	Nitrogen

Farm Yard Manure (FYM)

Composition: Mixture of Cow dung, Cow urine, Bedding material, and Farm wastes[span_8](start_span)[span_8](end_span).

Nutrient	Percentage
N	0.5%
P₂O₅	0.2%
K₂O	0.5%

Compost

Prepared by decomposition of: Crop residues, Leaves, and Household wastes[span_9](start_span)[span_9](end_span).

Types: Rural Compost, Urban Compost[span_10](start_span)[span_10](end_span).

Green Manuring ⭐⭐⭐

Growing crops and incorporating them into the soil[span_11](start_span)[span_11](end_span).

Crop	Scientific Name
Dhaincha ⭐⭐⭐	Sesbania aculeata
Sunhemp ⭐⭐⭐	Crotalaria juncea
Cowpea	Vigna unguiculata
Green Gram	Vigna radiata

Benefits: Adds Nitrogen, improves soil structure, increases organic matter, and improves microbial activity[span_12](start_span)[span_12](end_span).

Vermicompost ⭐⭐⭐

Organic manure prepared with earthworms[span_13](start_span)[span_13](end_span).

Species	Importance
Eisenia fetida ⭐⭐⭐	Most common
Eudrilus eugeniae	Fast composting
Perionyx excavatus	Indian species

Nutrient	Percentage
N	1–1.5%
P	0.5–1.0%
K	0.8–1.2%

Definition: Fertilizers are chemical substances supplying one or more essential plant nutrients[span_14](start_span)[span_14](end_span).

Classification

Fertilizer	Nutrient %
Urea ⭐⭐⭐	46% N
Ammonium Sulphate	20.6% N
Calcium Ammonium Nitrate (CAN)	26% N
Ammonium Chloride	25% N

Fertilizer	Nutrient %
SSP ⭐⭐⭐	16% P₂O₅
DSP	32% P₂O₅
TSP ⭐⭐⭐	46% P₂O₅
Rock Phosphate	18–20% P₂O₅

Fertilizer	Nutrient %
MOP ⭐⭐⭐	60% K₂O
SOP	50% K₂O

Fertilizer	Grade
DAP ⭐⭐⭐	18:46:0
NPK	15:15:15
NPK	10:26:26
NPK	12:32:16

Straight Fertilizers: Contain only one major nutrient (e.g., Urea, SSP, MOP)[span_15](start_span)[span_15](end_span).

Complex Fertilizers: Contain two or more nutrients chemically combined (e.g., DAP)[span_16](start_span)[span_16](end_span).

Mixed Fertilizers: Prepared by physically mixing fertilizers[span_17](start_span)[span_17](end_span).

Definition: Biofertilizers are living microorganisms which increase nutrient availability[span_18](start_span)[span_18](end_span).

Classification & Organisms

Biofertilizer	Crop
Rhizobium ⭐⭐⭐	Legumes
Azotobacter ⭐⭐⭐	Non-legumes
Azospirillum	Cereals
Blue Green Algae	Rice
Azolla-Anabaena	Rice

Organism / Type	Function
PSB ⭐⭐⭐	Solubilizes phosphorus
VAM ⭐⭐⭐	Increases P uptake

Organism	Nitrogen Fixed
Rhizobium	50–300 kg/ha
Azotobacter	20–40 kg/ha
Azospirillum	20–40 kg/ha
BGA	20–30 kg/ha
Azolla	40–60 kg/ha

Definition: Study of essential mineral elements required by plants[span_19](start_span)[span_19](end_span).

Essential Elements: Total = 17 Essential Nutrients[span_20](start_span)[span_20](end_span).

Non-Mineral Elements: Carbon, Hydrogen, Oxygen[span_21](start_span)[span_21](end_span).

Primary Macronutrients: Nitrogen (N), Phosphorus (P), Potassium (K)[span_22](start_span)[span_22](end_span).

Secondary Nutrients: Calcium, Magnesium, Sulphur[span_23](start_span)[span_23](end_span).

Micronutrients: Iron, Zinc, Manganese, Copper, Boron, Molybdenum, Chlorine, Nickel ⭐⭐⭐[span_24](start_span)[span_24](end_span).

Criteria of Essentiality: Proposed by Arnon and Stout (1939) ⭐⭐⭐[span_25](start_span)[span_25](end_span).

Functions & Deficiency Symptoms of Nutrients

Nutrient	Main Functions	Deficiency Symptoms
Nitrogen (N)	Chlorophyll formation, Vegetative growth, Protein synthesis	Older leaves become yellow ⭐⭐⭐
Phosphorus (P)	Root growth, Energy transfer, Flowering	Purple leaves
Potassium (K)	Water regulation, Disease resistance, Grain filling	Leaf margin scorching
Calcium (Ca)	Cell wall formation, Root growth	Growing tips die
Magnesium (Mg)	Central atom of chlorophyll	Interveinal chlorosis of older leaves
Sulphur (S)	Protein synthesis	Yellowing of young leaves

Micronutrient	Deficiency Symptom / Disease
Zinc (Zn)	Khaira Disease of Rice ⭐⭐⭐
Iron (Fe)	Interveinal chlorosis of young leaves
Boron (B)	Fruit cracking, Poor pollination
Molybdenum (Mo)	Whiptail in Cauliflower ⭐⭐⭐
Copper (Cu)	Dieback in Citrus
Manganese (Mn)	Grey Speck of Oats

Mobility of Nutrients in Plants

Mobile Nutrients: Deficiency first appears on old leaves (N, P, K, Mg)[span_26](start_span)[span_26](end_span).

Immobile Nutrients: Deficiency first appears on young leaves (Ca, B, Fe, Cu)[span_27](start_span)[span_27](end_span).

Important Laws & Stewardship Principles

Law of Minimum: Proposed by Justus von Liebig (1840) ⭐⭐⭐. Plant growth depends on the nutrient available in minimum quantity[span_28](start_span)[span_28](end_span).

Integrated Nutrient Management (INM): Combination of Organic manure, Chemical fertilizers, and Biofertilizers[span_29](start_span)[span_29](end_span).

Fertilizer Use Efficiency (4R Stewardship): Right Source, Right Dose, Right Time, Right Method[span_30](start_span)[span_30](end_span).

Fertilizer	Grade
Urea	46:0:0
DAP	18:46:0
SSP	0:16:0
TSP	0:46:0
MOP	0:0:60
SOP	0:0:50
Ammonium Sulphate	20.6:0:0

Question	Answer
Highest N fertilizer	Urea
DAP grade	18:46:0
MOP contains	60% K₂O
SSP contains	16% P₂O₅
Father of Biofertilizer	Hiltner
Green manure crop	Dhaincha
Earthworm used in vermicompost	Eisenia fetida
Khaira disease	Zinc deficiency
Whiptail	Molybdenum deficiency
Chlorophyll central atom	Magnesium
Law of Minimum	Liebig
Criteria of essentiality	Arnon & Stout

#	Fact / Concept
1	FYM contains about 0.5% N.
2	Dhaincha is the best green manure crop.
3	Sunhemp is a green manure crop.
4	Vermicompost is prepared using earthworms.
5	Eisenia fetida is the most common compost worm.
6	Urea contains 46% nitrogen.
7	DAP grade is 18:46:0.
8	SSP contains 16% P₂O₅.
9	TSP contains 46% P₂O₅.
10	MOP contains 60% K₂O.
11	SOP contains 50% K₂O.
12	Rhizobium is used for legumes.
13	Azotobacter is used for non-legumes.
14	Azospirillum is used for cereals.
15	Blue-green algae are used in rice.
16	Azolla-Anabaena is a biofertilizer for rice.
17	PSB solubilizes phosphorus.
18	VAM improves phosphorus uptake.
19	Arnon and Stout proposed the criteria of essentiality.
20	Liebig proposed the Law of Minimum.
21	Nitrogen deficiency causes yellowing of old leaves.
22	Phosphorus deficiency causes purpling.
23	Potassium deficiency causes leaf scorching.
24	Calcium deficiency affects growing points.
25	Magnesium is the central atom of chlorophyll.
26	Sulphur deficiency appears on young leaves.
27	Zinc deficiency causes Khaira disease.
28	Molybdenum deficiency causes Whiptail.
29	Boron deficiency causes fruit cracking.
30	Copper deficiency causes dieback in citrus.
31	Iron deficiency causes interveinal chlorosis.
32	Mobile nutrients show symptoms on old leaves.
33	Immobile nutrients show symptoms on young leaves.
34	Carbon, hydrogen, and oxygen are non-mineral nutrients.
35	There are 17 essential plant nutrients.
36	N, P, and K are primary nutrients.
37	Ca, Mg, and S are secondary nutrients.
38	Nickel is an essential micronutrient.
39	Straight fertilizers contain one primary nutrient.
40	Complex fertilizers contain two or more chemically combined nutrients.
41	Mixed fertilizers are physical mixtures.
42	Green manuring improves soil organic matter.
43	Vermicompost improves soil microbial activity.
44	INM combines organic, inorganic, and biofertilizers.
45	Fertilizer efficiency follows the 4R principle.
46	FYM improves soil structure.
47	Compost is produced by decomposition of organic wastes.
48	Bone meal is rich in phosphorus.
49	Neem cake is an organic manure rich in nitrogen.
50	Balanced fertilization improves crop yield and soil health.