Title Soil Science Part-9.pdf ✅

www.iaritoppers.in Whatsapp : +91-9694095242 Page | 1 Soil Science 5 th Edition 2024
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 2 Relative and Average Plant Nutrient Concentrations Plant Nutrient Average Concentration H 6.0% O 45.0% C 45.0% N 1.5% K 1.0% Ca 0.5% Mg 0.2% P 0.1% S 0.1% Cl 100 ppm (0.01%) Fe 100 ppm B 20 ppm Mn 50 ppm Zn 20 ppm Cu 6 ppm Mo 0.1 ppm Fertility Index :  It expresses the relative sufficiency as a percentage of soil nutrient amount adequate for optimum yields. The probability of a response to fertilizer application increases with decreasing soil test level.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 3 Soil Test rating Soil Test rating Probability of crop Response (% yield increase) Very low 0-10 95-100 Low 10-25 70-95 Medium 25-50 40-70 High 50-100 10-40 Vary high 100+ 0-10 Hidden Hunger:  Hidden hunger refers to a situation in which a crop needs more of a given nutrient yet has shown no deficiency symptoms.  The nutrient content is above the deficiency symptom zone but still considerably needed for optimum crop production. With most nutrients on most crops, significant responses can be obtained even though no recognizable symptoms have appeared.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 4 Functions of Nutrients and Deficiency Symptoms of Plants:  Carbon, Hydrogen and Oxygen form about 95% of the dry weight of plants and are obtained from CO2 and H2O. These are the major components of carbohydrates, proteins and fats. Nitrogen:  It is absorbed by plants in the ionic form of NO3-, by most of the plants. Some plants require NH4+ form (rice). When applied as foliar nutrition, NH2 (amide from) is also absorbed. Functions of Nitrogen in plants:  Feeds microorganism in the soil. (Asked in AIC 2017)  Important for plant growth.  The Nitrogen is mainly involved in Photosynthesis of plants as it is essential constituent of chlorophyll, a green pigment essential in photosynthesis.  Essential constituent of proteins, nucleotides phosphatides, alkaloids, enzymes, hormones, vitamins etc.,  Imparts green color to plants.  Improves quality and succulence of leafy vegetables and fodder crops.  It stimulates the formation of fruit buds; increases fruit set, and improve quality of fruits.  It governs the better utilization of Potassium, Phosphorus & other elements. Deficiency symptoms of Nitrogen in plants:  Yellowing of lower or older leaves due to inhibition of chloroplasts and chlorophyll synthesis. As the deficiency of Nitrogen becomes severe “Chlorosis” of leaves is observed.  Plants become dwarfed or stunted growth.  Tends to advance the time of flower bud formation and reduce yield.  Fruits become hard, small, low bearing capacity of trees.  Reduces fertilization, premature dropping and fruits may become seed less.  Severe deficiency leads to Necrosis of plant leaves (complete death of leaf) Excess :  Excessive N in plants leads to more vegetative growth.  Delay in maturity and increases succulence.  Leaves become more succulent and more susceptible to pest and disease attack.