Tiêu đề ELE-SSAC-364 Model Answer 2021-22.pdf ✅

• Loss of soil biodiversity • They may kill bacteria and other organisms beneficial to the soil • Fumigants have adverse effect on soil fungi and actinomytes, there by slowing down the humas formation in soil. • Decreases the enzymatic action in soil Q.2 a. Define fertilizers. Classify the phosphatic fertilizers with suitable examples. Fertilizers- Any organic or inorganic material of natural or synthetic origin added to a soil to supply certain element essential for plant growth. Classification of phosphatic fertilizers : Phosphatic fertilizers are classified into three groups, depending on the form in which orthophosphoric acid/phosphoric acid is combined with calcium. 1. Water soluble/Monocalcium phosphate: Ca(H2 PO4 )2 i) Single super-phosphate - 16% P2O5 ii) Double super-phosphate - 32 % P2O5 iii) Triple super-phosphate - 48 % P2O5 iv) Ammonium phosphate - 11 % N + 52% P2O5 2. Citric acid soluble/Dicalcium phosphate (CaHPO4) i) Basic slag - 14 to 18 % P2O5 ii) Tricalcium phosphate - 34% to 39 % P2O5 3. Insoluble/Tricalcium phosphate - Ca3(PO4)2 i) Rock-phosphate - 20 to 40 % P2O5 ii) Raw bonemeal - 20 to 25 %10 P2O5 iii) Steamed bonemeal - 22 % P2O5 (1) (3) b. Define complex fertilizers. Write the advantages of complex fertilizer. The commercial fertilizers containing atleast two or more of the primary essential plant nutrients (N, P, K) are called as complex fertilizers. Advantages: 1. Easy for application 2. Balanced crop nutrition 3. High fertilizer efficiency 4. Even distribution of nutrients 5. Saving of labor and time 6. Safe for storage 7. High analysis fertilizers (1) (3) Q.3 a. Explain secondary nutrients and give sources of sulphur fertilizers. Calcium, magnesium and sulphur are the examples of secondary nutrients. They are called “secondary” nutrients because plants require them in smaller quantities than major nutrients (nitrogen, phosphorus, and potassium). Sources of fertilizers for Sulphur : Fertilizers Sulphur (%) Ammonium sulfate 23 Potassium sulfate 18 Single Super phosphate 12 Gypsum 18 Magnesium sulfate 13 (2) (2)

iv. Ammonium sulphate and sodium nitrate : Storage properties good, no difficulties in handling & storage. Phosphatic fertilizers: 1. Single super phosphate: i) It contains small amount of acid which deteriorate gunny bags, hence it should be stored in polythelene lined gunny bags. ii) Cakes formation in moist condition. 2. Dicalcium phosphate - Excellent physical condition. Potassic fertilizers: Potassium sulphate and Potassium chloride: Excellent physical condition for storage and handling. Protect all fertilizer bags from moisture, water and rains. Protect bags against excessive sunshine .and heat by making use to shade of trees structures and covers. Q.5 a. Define biofertilizer. Give the contribution of biofertilizers in agriculture. Biofertilizers: Biofertilizers are defined as the preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilising or cellulolytic microorganisms used for the application to seed, soil or composting areas with an objective of increasing numbers of such micro-organisms and to accelerate certain microbial processes to augment the extent of availability of nutrients in a form which can be easily assimilated by plants. Contribution of Biofertilizer in Agriculture: • They supplement fertilizer supplies for meeting the nutrients needs of crop. • They can add 20 – 200 kg N/ha under optimum conditions and solubilize / mobilize 30 – 50 kg P2O5/ ha. • They liberate growth promoting substances and vitamins and help to maintain soil fertility. • They suppress the incidence of pathogens and control diseases. • They increase crop yield by 10 – 50%. • They are cheaper and pollution free. • They improve soil health in general. (2) (2) b. Write the mode of action of organochlorine and carbamate insecticides. Mode of action of organochlorine insecticides: Chlorinated hydrocarbons are neurotoxicants. Their application causes inhibition or inactivation in the functioning of Na- K ATPase and Ca-ATPase enzymes which are required for proper balance of Na and K in axon. The imbalance of these enzymes results in prevention of normal transmission of nerve impulse in insects and mammals. The imbalance of the enzymes ATPase and Ca- ATPase causing muscles to twist, this may lead to convulsion and death. Mode of action of Carbamate insecticides : Carbamate insecticides affects the enzyme choline esterase, which is responsible for removal of acetyl choline present in synapse (gap between nerve cell). This results in to continuous transmission of nerve impulses and loss of (2) (2)