SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment PDF

SWAE4401 Water & Nutrient Cycling in Sultan Qaboos University Soil-Plant Environment SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment: Soil Nitrogen bioavailability to plants Dr. Daniel...

SWAE4401 Water & Nutrient Cycling in Sultan Qaboos University Soil-Plant Environment SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment: Soil Nitrogen bioavailability to plants Dr. Daniel Blackburn Assist. Professor at SWAE - Department of Soils, Water and Agricultural Engineering – CAMS, Sultan Qaboos University, Phone: (+ 968) 2414 3668, Email: [email protected], https://www.researchgate.net/profile/Daniel_Menezes-Blackburn Twitter @danielblac_squ  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen Nitrogen Daniel Rutherford 1772  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Why is Nitrogen important? Nitrogen in plant physiology % 0 20 40 60 oxygen 45% carbon 44% hydrogen 6.3% nitrogen 1.3% silicon 1.2% potassium 0.9% calcium 0.25% phosphorus 0.16% magnesium 0.16% sulfur 0.15% https://quizlet.com/12942759/bio- lecture-17-plant-chemistry-flash-cards/  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Why is Soil N important? Nitrogen in plant physiology – Amino acids and proteins – DNA and RNA http://physicsworld.com/cws/article/news/39512/1/protein http://commons.wikimedia.org/wiki/File:Difference_DNA_RNA-EN.svg  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Why is Soil N important? Fertility – Usually deficient in soils Plant available forms are http://yara.co.uk/images/430- 105702NPK%20image%20600kg%20400x400.jpg easily lost from soils causing environmental problems http://www.appropedia.org/Eutrophication  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Why is Soil N important? Fertility – Usually deficient in soils Plant available forms are http://yara.co.uk/images/430- 105702NPK%20image%20600kg%20400x400.jpg easily lost from soils causing environmental problems http://www.appropedia.org/Eutrophication  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Deficiency, optimum and toxicity  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Deficiency, optimum and toxicity  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Macronutrients N, P, K Deficiencies Leaf Lettuce Control  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Macronutrient Deficiencies Beans  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle http://www.ux1.eiu.edu/~cfruf/bio3002/nitrogen_cycle.htm Fun video: https://www.youtube.com/watch?v=leHy-Y_8nRs  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: atmospheric N Atmospheric N2 : 4 000 000 000 Gt :N N: ::: (78.082% by volume, 75.3% by weight) Nitrous oxide - (0.025%) but with strong greenhouse effect ( 298 x global warming potential of CO2) – Formed by electrical storms after N2 triple bound is broken – Emissions from soils and wastes - denitrification Ammonia NH3 - reacts with sulphuric and nitric acids and contribute to ambient levels of fine particles, and N deposition in ecosystems – Emissions from soils – Urea fertilizer application  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: Atmospheric deposition Amount of wet deposition (NH4 or NOx) is higher than dry deposition.  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: industrial N fixation Birkeland–Eyde process (1903) N2 + O2 → 2 NO 2 NO + O2 → 2 NO2 NO2 + H2O → 2 HNO3 + NO Haber–Bosch process (1910) N2 + 3 H2 → 2 NH3 (ΔH = −92.4 kJ·mol−1) 500°C and 250 atmospheres Ammonium sulfate Fritz Haber, 1918. http://en.wikipedia.org/wiki/Haber_process 2 NH3 + H2SO4 → (NH4)2SO4 Videos: https://www.youtube.com/watch?v=qq5fmhz7N8U Urea https://www.youtube.com/watch?v=tdEE5uvFhOM 2NH3 + CO2 → H2N-COONH4  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: Nitrogen biological fixation Nitrogenase enzyme Rhizobium bacteria are symbiotic / mutualistic with legumes plants http://biology-forums.com/index.php?action=gallery;sa=view;id=1010 (root nodules) Cyanobacteria (photosynthetic) Azotobacter in the rhizosphere of grasslands http://world.edu/wp-content/uploads/2011/12/cyanobacteria1.jpg  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: ammonification Also known as mineralization Decomposition of organic matter by saprotrophic microbes (Chemoorganotrophs) This process liberates a huge amount of energy for the microbes http://www.ginninderralandcare.org.au/sites/default/files/images/ Fungi2.jpg Aminotransferase Amino acids + 11/2O2 CO2 + H2O + NH3 + 736kJ Urease (NH2)2CO + H2O → CO2 + 2NH3  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: Nitrification Discovered by Sergei Wingradsky (1888) Chemoautotrophic (chemolithotrophs) bacteria: Nitrosomas and Nitrobacter Nitrosomas oxidise ammonia into nitrite: http://t3.gstatic.com/images?q=tbn:ANd9GcRDr0PGsrEIHk-4uABjbPB-o- 8eN0iaQng3zONNQLeHs76LUBfxBQ 2 NH4+ + 3 O2 → 2 NO2− + 2 H2O + 4 H+ (+ 276kJ) Nitrobacter oxidise the nitrite to nitrate: 2 NO2− + O2 → 2 NO3− (+ 73 kJ) http://t3.gstatic.com/images?q=tbn:ANd9GcTcXcWYTGFJcsT5vpuDTeve71 wCaAQjHCdEMXNV51knnAGOnXMM http://www.dnr.state.md.us/bay/monitoring/eco/nitrification.gif  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle: Denitrification Heterotrophic anaerobic Bacteria (Pseudomonas facultative aerobes) Nitrates and nitrites are source of oxygen 2NO3- 3O2 + N2 2NO2- 2O2 + N2  Between 20 and 40% of emissions are N2O (greenhouse gas) https://globalmedicaldiscovery.com/wp- content/uploads/2014/10/Pseudomonas-aeruginosa.jpg  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen cycle http://www.ux1.eiu.edu/~cfruf/bio3002/nitrogen_cycle.htm  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility:Pools of N Organic N Inorganic N Atmosphere inputs inputs inputs/outputs Manures, Atm. crop residues, Fertil. deposition Biol. etc. NH 3 - N 2- volatilization fixation Denitrification Mineralization (N 2 , N 2 O) NH 4 + Soil mineral N Nitrification Old soil Plant uptake Labile Microbial organic soil NO 2 - Plant biomass matter organic N assimilation N N NO 3 - N Immobilization N leaching (NO 3 -) Total N is different from available N  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: soil test A soil test is a simple test of readily ‘bioavailable’ nutrients For available N tests a KCl extract for is used for soil nitrate. For total N a Kjeldahl digestion is used. About 98 % N is present in the http://www.ctahr.hawaii.edu/ soil is in organic forms. mauisoil/images/a_profile_clip _image001.jpg  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer sources Urea  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer application efficiency http://www.vabayblues.org/images/Yieldcv.jpg  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer losses Ammonium-based fertilizers = high volatilization Nitrate-based fertilizers = leaching and denitrification. Urea = 1% loss per day Weather : warm soils and windy conditions = high volatilization Soil moisture: dry soil = high volatilization Soil pH: alkaline soils = high volatilization The degree of incorporation: Superficial = high volatilization  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer nitrate losses – Effect of pH  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer nitrate losses – Effect of temp  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer nitrate losses – Effect of moisture  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer recommendation Fixed dose or empirical recommendation tables for the specific crop (eg. 50 kg/ha for wheat) Replenishing crop N offtake (https://plants.usda.gov/npk/main) N dose = (Yield/area)*(kg N/yield unit) / efficiency 1500 kg/ha yield; 14% moisture content; 2% N on the grains; efficiency 70% Urea 46% N; How much Urea should be applied? Dry weight = 1500/1.14 = 1315.79 kg/ha 2% nitrogen = 0.02 kg N / kg grains Kg N=(1500/1.14)*0.02/0.7 = 37.59 kg N /ha Dose = 37.59/0.46 = 81.7 kg Urea/ ha  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Fertilizer application strategy 70-80% of the N required between mid tillering and mid stem elongation and the remaining at flag leaf emergence.  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Green manure and cover crops  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Green manure and cover crops Biomass N tons ha−1 kg ha−1 Sweet clover 4.32 134 Berseem clover 2.71 78 Crimson clover 3.46 112 Hairy vetch 4.32 123  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Organic amendments  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Organic fertilizer recommendation Fixed dose or empirical recommendation tables for the specific crop (eg. 10 T/ha) Replenishing crop P offtake (https://plants.usda.gov/npk/main) N dose = (Yield/area)*(kg N/yield unit) / efficiency 1500 kg/ha yield; 14% moisture content; 2% nitrogen on the grains; efficiency 20% compost 2% N; How much compost should be applied? Dry weight = 1500/1.14 = 1315.79 kg/ha 2% nitrogen = 0.02 kg N / kg grains Kg N=(1500/1.14)*0.02/0.2 = 131.58 kg N /ha Dose = 131.58 /0.02 = 6579 kg Compost / ha  SWAE4401 Water & Nutrient Cycling in Soil-Plant Environment Nitrogen in soil fertility: Rhizobium inoculation of legumes Bacteria: (species specific) R. meliloti - alfalfa R. trifolii - clover R. phaseoli - beans - bacteria require plant to function - inoculation of seed (coat seed with bacteria inoculum)