Plant, Soil, and Nutrients 1
Where do plants get their nutrients? - Atmospheric Deposition (N, S) - Irrigation water - Shallow groundwater 2
What is surface exchange? Soil has an overall charge Overall negative charge Has the ability to hold positive ions (cations) The total number of negative charges determines how many cations can be held Cation Exchange Capacity (CEC) Also determines how tightly cations are held 3
Clays have greater CECs than sand http://www.spectrumanalytic.com/support/library/ff/cec_bph_and_percent_sat.htm 4
How do plants take up mineral nutrients? A. Direct contact with nutrients B. Through ions dissolved in water C. Through soil microbial interactions All are correct, but B is the most frequent 5
Surface Exchange and Transpiration 6
Water movement into plant also pulls in mineral nutrients Helps plants take up nutrients 7
What are the most important mineral nutrients for plants? Macronutrients (high concentrations, 0.1-2%) N P K Ca S Mg Micronutrients (low concentrations, 0.0001-0.01%) Fe Zn Mn Mo B Cu Cl Ni 8
What do plants need nutrients for? Mineral Nutrient Group 1 N S Group 2 P Si B Function Nutrients found in carbon compounds Part of amino acids (make up proteins), DNA, RNA, pigments like chlorophyll Part of some amino acids (needed for proteins), plant defense (breaks down herbicides) Nutrients for energy storage or structural integrity Used for energy (ATP), phosphorylated sugars, part of cell membranes (phospholipids), DNA and RNA backbones Helps cell walls remain strong, fights off pathogen attacks Needed for cell wall strength (binds to parts of the cell wall), needed for cell expansion. Adapted from Taiz et al. (2015), Plant Physiology and Development. 6 th ed, page 121. 9
What do plants need nutrients for? Mineral Nutrient Group 3 K Ca Mg Cl Zn Na Function Nutrients that remain in ionic form Help plants maintain turgor, water regulation, needed for enzymes to work (cofactor) Stomatal opening and closing, needed for cell wall strength, helps enzymes work, plant signaling Helps enzymes turn on/off, center ion of chlorophyll Helps generate oxygen during photosynthesis, balances charges in cells Component of enzymes that break down toxins Needed in C4 plants (like corn) to get the molecules needed for photosynthesis, can act in place of K sometimes Adapted from Taiz et al. (2015), Plant Physiology and Development. 6 th ed, page 121. 10
What do plants need nutrients for? Mineral Nutrient Group 4 Fe Mn Cu Ni Mo Function Nutrients involved in electron movement (redox reactions) Needed for photosynthesis, respiration, involved in detoxification Needed for some detoxifying enzymes, needed for biological N fixation in legume nodules Involved with electron movement during photosynthesis, needed for some enzymes to work Helps legumes fix nitrogen in the nodules, needed for N mobilization A main part of enzymes for N metabolism, needed in nodules Adapted from Taiz et al. (2015), Plant Physiology and Development. 6 th ed, page 11 12
Why do we need fertilizer? Soil supplies nutrients to plants Crop need to produce its optimum yield usually exceeds what the soil can provide Fertilizer is applied Major nutrients needed are: Nitrogen Phosphorus Potassium Soil ph (concentration of hydrogen ions) Can influence nutrient availability if too far from neutral We will hear more about technology use and fertilization throughout the session 12
Nitrogen Cycle 13
Nitrogen is needed for organism growth, maintenance and repair. Examples: Nitrogen building amino acids for proteins (enzymes, muscles) DNA Structure (nitrogen bases) Chlorophyll and pigments 14
Fixing Nitrogen Atmosphere: 78% Nitrogen (N 2 ) This form of nitrogen not usable form for plants Getting nitrogen into the usable form: Lightning, Fires, Bacteria Fertilizers 15
N Symbols and Terms N 2 : Atmospheric Nitrogen NH 3 : Ammonia NH 4+ : Ammonium NO 2- : Nitrite NO 3- : Nitrate 16
Nitrogen Cycle Conversions of Gases Nitrogen Fixation: Atmospheric nitrogen (N 2 ) converted into ammonium (NH 4 + ) by nitrogen-fixing bacteria Denitrification: Return of nitrogen back to the atmosphere by converting nitrogen compounds to atmospheric nitrogen (N 2 ) by denitrifying bacteria 17
Nitrogen Cycle Conversions of Gases Volatilization: Return of ammonia gas to atmosphere Dependent on soil ph (above 7.5), temperature (increases as temp increases), moisture (evaporation promotes it) Type of fertilizer and method of placement 18
Nitrogen Cycle Organic Material Ammonification/ mineralization: Organic compounds from crop residue, wastes or dead organisms converted into ammonium (NH 4 + ) by decomposing bacteria Immobilization: Conversion of mineral nitrogen forms (NH 4 + and NO 3 - ) into organic material and biomass like plants and microbes 19
Nitrogen Cycle Ammonium to Nitrate Nitrification: Two step reactionconverting ammonium (NH 4+ ) to nitrite (NO 2- ) to nitrate (NO 3- ) by nitrifying bacteria 20
Nitrogen Cycle Which process takes the longest? What happens to excess N? 21
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N Deficiency in Corn 23
N Deficiency in Soybeans and Alfalfa Pale green plants Pale yellow leading to brown older leaves Veins not prominent Can cause stunting and reduced branching Occurs when nodulation is limiting (usually early in the season) or low N soils 24
P Deficiency in Corn Purpling of leaf margins Older leaves Emerging leaves look normal Reduced growth rate Can have poor root development or injury 25
P Deficiency in Soybean Stunted growth Dark green color Necrotic spots on the leaves Purpling of the older leaves 26
K Deficiency in Corn Yellowing of leaf margins Older leaves Emerging leaves look normal Reduced growth rate 27
K Deficiency in Soybean Older leaves Bright yellow leaf margins Interveinal chlorosis Stunting 28
Which nutrients are of most concern for environmental protection? 29
Water Quality Concerns Eutrophication: Excess nutrients in a waterbody Stimulates algal growth, can lead to hypoxia P is major driver in freshwater N also contributes Alters light availability for plant growth Bacteria decomposing algae dissolved reduce O 2 Hypoxia: Condition of a waterbody that is deficient in oxygen (low oxygen conditions) Less than 2-3 ppm O 2 Nitrogen is a major driver in saltwater P also contributes Caused by decomposition of algal blooms by bacteria 30
Fertilization practices to reduce the environmental impact: 4 Rs Right Place Right Rate Right Form/Source Right Time How do you know what the right practices are? 31
Nitrogen Management Recommendations Maximum Return to Nitrogen tool Takes price received into account Price of N input Determines a range of N to provide most profit Data for Ohio and Indiana http://cnrc.agron.iastate.e du/ 32
Soil Testing for other properties Soil Samples Bulk Samples Grid Test for major nutrients P K Texture Organic Matter 33
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Using the Results Calculate predicted crop removal Predicted yield % nutrient in the yield Use current levels to make decisions 1. Buildup Soils lower than critical level Add more than is expected for removal 2. Maintenance Soils in the maintenance range Only replace removal 3. Drawdown Soils higher than maintenance range Apply less than removal rates 35
Make a Map Variable Rate Tech Soil test data Soil topography and type Allows for variable fertilizer application practices https://websoilsurvey.sc.egov.usda.gov/a pp/homepage.htm 36
Monday Activity 1: Using Lamotte Soil Test Kits 1. Work in groups of two or three Choose a soil property to test: N, P, K or ph 2. Use the soil corer to collect a soil sample 3. Follow the instructions for each soil test Use collected soil provided for the test 4. Set samples aside until tomorrow for interpretation 37
Light Filter Activity 38
Different pigments in plants have differential light absorption 39
Light as a particle Photosystem II and I Reaction Centers Each electron that is excited is caused by a single photon, regardless of the wavelength 40
Light as an individual packet of energy Light can act as a particle or wave Smaller wavelength, greater energy Some of the plant response is determined outside of the visible spectrum, but most plant response is within the photosynthetically active radiation (PAR), ranging from 400-700 nm 41
What is NDVI? Normalized Difference Vegetation Index Provides a measure of how green the canopy is FR = Far-red reflection R = Red reflection FR R NDVI = FR + R Why do we only focus on red and far-red light? Why mostly for N? 42
What can cause NDVI values to be low? Stress Color change Nutrient deficiency Water stress Insect or disease Development Smaller plants have more background present Older plants have more brown tissue Nitrogen uptake and partitioning curve in corn yielding 230 bu/ac (Bender et al., 2013) 43
Experiments using Technology What nutrients are currently in our soil? (Activity 1) Can we use NDVI or a similar absorbance ratio to make management comparisons, like N application rate and planting date? (Activity 2 and 3) How does NDVI compare to other methods? UAV imagery Canopeo App 44
Monday Activity 2: Using NDVI to predict N response 1. Work in groups of two or three 2. Get a Greenseeker unit and review the instructions 3. Use the map provided to collect NDVI values in each plot Use chart to complete data table 4. Hold onto your results and compare to the UAV image 45