Cca International Exam Questions With 100% Correct Answers

Cca International Exam Questions With 100% Correct Answers List the 17 essential nutrients and identify which are micronutrients (8) and which are macronutrients (9) - answerMacro: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur Micro: boron, chlorine, copper, iron, manganese, molybdenum, nickel, zinc Which macronutrients are mobile in plants? Which are not? - answerMobile: nitrogen, phosphorus, potassium, magnesium Not mobile: calcium, sulfur List the chemical uptake forms of each macronutrient: N, P, K, Ca, Mg, S - answerN: Ammonium ion (NH4+) and Nitrate ion (NO3-) P: Phosphate ion (H2PO4- and HPO4 2-) K: Potassium ion (K+) Ca: Calcium ion (Ca 2+) Mg: Magnesium ion (Mg 2+) S: Sulfate ion (SO4 2-) What are the beneficial elements (4) and what do they do? - answerSilicon (Si) - increases cell wall strength, reduces lodging, improves adaptation to stress (ie drought), improves pest resistance, improves plant vigor Sodium (Na) - improves photosynthesis in C4 plants and may be a substitute to K in some degree Cobalt (Co) - essential for N fixation Selenium (Se) - improves plant growth, essential for animals from feed Describe the function of N in plants - answer- Used in the synthesis of amino acids, proteins, enzymes - Found in chlorophyll (photosynthesis), ADP and ATP (energy transfer) Describe the function of P in plants - answer- Important component of energy transfer (ADP, ATP) - Important to photosynthesis and respiration - Part of cell nuclear material important to cell division Describe the function of K in plants - answer- Accelerates growth of meristematic tissue - Regulation of stomatal opening (water loss) - Involved in N and carbohydrate metabolism - Catalyzes some enzymes Describe the function of S in plants - answer- Component of several amino acids (cystine, cysteine, methionine) which are part of many proteins - Involved in protein synthesis and enzyme activation - Forms flavor compounds in mustard, garlic, and onions Define mineralization - answerRelease of a nutrient when an organic material (ie OM, manure, etc.) is decomposed by soil microorganisms. Conversion of a nutrient from the organic to inorganic form. Define immobilization - answerReverse of mineralization. Nutrient is converted from inorganic to organic form. What is uptake antagonism between ions? - answerTwo or more ions may compete for uptake by various mechanisms. One ion is said to be antagonistic with regard to the uptake of another ion. Describe mass flow. What nutrients is this important for? - answerNutrients move to a plant root with the water that is being absorbed by the plant. Important for N, Ca, and Mg. Describe diffusion. What nutrients is this important for? - answerMovement of a nutrient to a plant root due to a concentration gradient between the soil surface and the root surface. Important for P and K. Describe root interception. What nutrients is this important for? - answerOccurs when a root grows next to a clay or OM surface and absorbs the nutrients. Actual uptake of a nutrient at the root surface may be passive or active (by a carrier). This is usually a minor way nutrients are absorbed. Solubility of what nutrients increases in flooded soils? - answerIron and manganese What is ammonification? - answerConversion of organic N to ammonium (NH4+) by microorganisms as they decompose an organic material. N rich materials (C:N ratio <15-20:1) exhibit high levels of ammonification as they are decomposed (ex. manure) What is nitrification? What are the two steps? - answerFirst step: Oxidation of ammonium to nitrite (NO2-) by Nitrosomonas sp. Oxygen is required. Releases H+ decreasing pH. Nitrification inhibitors slow this first step. Second step: Oxidation of nitrite (NO2-) to Nitrate (NO3-) by Nitrobacter sp. This is fairly rapid so nitrite does not commonly accumulate in soils. This step also requires oxygen. What is volatilization? What conditions favor volatilization? - answer- Conversion of ammonium (NH4+) to ammonia gas (NH3) - High temp, high pH, low CEC, moist/wet soils, wind, large amounts of surface residues What is denitrification? - answerWhen soil becomes saturated with water, microorganisms first use oxygen and then, when the oxygen is depleted, they use nitrogen in their metabolism. Products of denitrification are gaseous dinitrogen (N2) and gaseous oxides of nitrogen that move to the atmosphere. What is immobilization? - answerNitrogen poor (C:N >20:1) organic materials (ex. wheat straw) can cause microorganisms to remove large amounts of inorganic N from the soil during decomposition because that N is required to build new microbial cells. Decreases N availability. The immobilized N can be mineralized when the microbial cells decompose. Describe symbiotic N fixation. - answerLegume supplies energy to Rhizobium which uses that energy and the enzyme, nitrogenase, to convert N2 from the atmosphere into ammonium for the plant Describe how phosphorus, sulfur, molybdenum, and cobalt effect symbiotic N fixation. - answerP: needed to provide energy S: important for protein synthesis Mo: part of nitrogenase enzyme Co: cofactor in an enzyme needed for N fixation and nodule growth Describe P fixation in soil - answerP fixation: combination of: - P sorption by soil minerals (ex. iron and aluminum oxides) and kaolinite clay; and - P precipitation as calcium phosphates at high pH or iron and aluminum phosphates at low pH. P fixation reduces soil solution P concentration, plant available P, and P mobility What pH range is P most available? - answer5.5-7 Above or below this increases P fixation When looking at a soil test how do you convert ppm to lb/ac? - answerppm x 2 = lb/ac How is proximal sensing used to assess plant nutrient status? - answerGround based proximal sensors are used to measure specific plant properties. A previously found relationship between nutrient status and plant properties is then used to assess nutrient status spatially or temporally. Describe how chlorophyll meters are used to assess plant nutrient status? - answerMeasures the chlorophyll content of leaves which can be related to N sufficiency in the plant. Describe how remote sensing can be used to assess plant nutrient status? - answerSensors carried by aircraft or satellites are used to measure specific plant spectral properties at a specific location. A previously found relationship between nutrient status and these plant properties is then used to assess nutrient status spatially or temporally. Describe how organic matter serves as a plant nutrient source. - answer- As organic matter decomposes, nutrients (primarily N, P, S) are mineralized. - Soil OM retains cations in available forms. - In some cases (high C:N) they will temporarily immobilize N. - Soluble nutrients can be leached out of plant residues prior to decomposition. What nutrients can be found in irrigation water? - answerCa, Mg, K, S, Cl May contain appreciable levels of metals like iron and manganese. Describe how N losses occur when urea is broadcast. What can you do to minimize it? - answerIf not incorporated, it dissolves and converts to ammonium carbonate by the urease enzyme. Ammonium carbonate increases soil pH, ammonium converts to ammonia and the ammonia is lost via volatilization. Urease inhibitors reduce the rate of the reaction and ammonia losses. What do nitrification inhibitors do? - answerBlock the conversion of NH4 (ammonium) to NO3 (nitrate). Fertilizer remain in NH4 form rather than NO3 which can be leached or denitrified.