sws3022 UF exam 3 Study Guide with Complete Solutions

sws3022 UF exam 3 Study Guide with Complete Solutions Note the various forms of N - Answer️️ -1. Ammonium (NH4+) cation in the soil solution and fixed in secondary clays 2. Nitrate (NO3-) anion in the soil solution 3. Organic N in the soil 4. Ammonia (NH3) gas (released to atmosphere) 5. NO, N2O, N2 gases (released to atmosphere) anion- nitrogen - Answer️️ -it is not held by soil colloids and can be lost from the soil through leaching. However in well aerated soils (plenty of oxygen), most of the NH4+-N (applied for example as fertilizer) changes to the NO3--N form by a process called nitrification cation-nitrogen - Answer️️ -it can be held on the exchange sites of soil colloids which makes it available for plant uptake over a long period of time. Describe one reaction that leads to loss of N from the soil: - Answer️️ -Nitrate leaching into ground water. symbiotic N2 fixation that occurs between legumes and rhizobium ©SOPHIABENNETT EXAM SOLUTIONS_2024/2025 Tuesday, September 3, 2024 10:30 AM Page | 2 species. - Answer️️ -Host plant supplies the N fixing organisms with fixed C (photosynthate which is used for respiration and N2 fixation), and the host plant benefits from the fixed N. N2 fixation is a reduction reaction and happens in the nodule in a completely anaerobic environment inorganic P - Answer️️ -found in insoluble compounds in the soil N is found in two forms: - Answer️️ -1) Ammonium (NH4+) - cation 2) Nitrate (NO3-) - anion NH4 and NO3 in soil solution constitute about 1% of N in the soil. Again most of the N in soils is in organic forms. Due to rapid nitrification in soils, plants absorb predominately NO3. Some plants prefer N in the NH4 form for example rice. Other plans that grow under acidic conditions seem to prefer NH4 too. ATP - Answer️️ -adenosine triphosphate (drives most energy-requiring biochemical processes ex uptake of nutrient) DNA - Answer️️ -DNA - Deoxyribonucleic acid (genetic inheritance) RNA - Answer️️ -RNA - Ribonucleic acid (protein synthesis in plants and animals) ©SOPHIABENNETT EXAM SOLUTIONS_2024/2025 Tuesday, September 3, 2024 10:30 AM Page | 3 Finally P content in plants: - Answer️️ -0.1 - 0.4% in plant tissue depending on plant. Plants' P uptake ranges between 6-26 kg/ha or 5-23 lbs/acre of P. Please note that 1% = 10 000 ppm (mg/ kg) so 0.1% is = 1000 mg P/ kg of plant tissue P deficiency - Answer️️ -1.Stunted growth; thin stemmed dark foliage (bluish green) 2. Purple discoloration on lower leaves (P is mobile in plant therefore deficiency symptoms appear on lower leaves) 3. In severe cases, yellowing and senescence of leaves. • Stunted growth • purple discoloration on lower leaves major components of the P cycle - Answer️️ -a. Plants take up P from soil solution in two forms: H2PO4- and HPO4 2-. These are called orthophosphate ions. b. Inorganic P compounds fall in two major categories: Calcium phosphates (at high pH); Al Phosphates and Fe phosphates (at low pH). c. P gets adsorbed to soil colloids surfaces at all pH ranges of soils. Adsorption is more prominent in low pH soils with Fe and Al oxides and kaolinite as the major colloids. Adsorption of P in such soils is high and reduces the availability