What is an essential nutrient? Please Do Not Feed the Trees: 1. Nutrient element directly involved in Proper Tree and Shrub Nutrition in the metabolic processes Urban Landscape 2. Cannot be replaced by another element Dr. Laura G. Jull 3. Plant cannot complete it’s life cycle Dept. of Horticulture without the element UW-Madison 17 Essential Elements Where Do Essential Nutrients Come From? 94% of dry weight is C, H, O from air and water P Mn ♦ Atmospheric Sources: N2 deposition, acid rain (S) ♦ Mineral Sources: parent material, fertilizers K Zn 80% 20% ♦ Organic Sources: biological breakdown of organic N S Cu matter and biological components of the soil that of the essential mineral elements Ca B aid in P uptake or N fixation taken up by plants on an annual basis Mg Mo ♦ Plants do not distinguish between ions from inorganic and organic sources Elements Derived Cl From Soil: parent Fe ♦ All organic forms must be converted to inorganic material and organic ions to be absorbed by plants Ni* matter Organic Sources of Not all OM is the Same Essential Elements Source C:N Ratio Wood 100-500 Sawdust 200-700 The process is driven by soil Fallen Leaves 30-80 inhabiting organisms The type, abundance, and activity of micro- Fresh Leaves 20-30 organisms are influenced by soil and environmental conditions and substrate Grass Clippings 15-25 they feed upon Inside Cell Cell Membrane Outside Cell Soil pH Affects + K Passive Diffusion Solubility Uptake and Most essential Assimilation of elements sufficiently Essential soluble around pH 7 Elements Often K+ Requires Energy Cl- Co-Transport Ions can form complexes with other ATP minerals that make the ionic forms insoluble H+ K+ Energy Requiring and unavailable for plant uptake ADP http://ohioline.osu.edu/anr-fact/0005.html Limiting or Deficient? Essential Elements Acquired through the Roots are in Soil Solution ♦ Limiting condition does not mean tree death ♦ Perennial plants regulate growth in response to availability ♦Conditions that Negatively Influence Uptake: ♦ With the exception of N, the abundance of essential elements in most soils is sufficient Solubility: pH, element becomes for tree growth insoluble or soluble as pH changes ♦ Deficiency: low concentrations of an essential element that reduces plant growth and prevents completion of Soil Structure: compaction, poor the normal plant life cycle drainage ♦ Limiting: low concentrations of an essential element that reduces plant growth but still is able to complete its Soil Characteristics: texture, CEC normal plant life cycle Is Fertilization of Trees Always Is Fertilization of Trees Always Beneficial? Beneficial? If nutrient not needed or applied incorrectly, ♦ Trees growing satisfactorily with no visual can lead to: ♦ signs of deficiency may not need fertilizer Lost by leaching, volatilization (gaseous loss), surface and groundwater pollution (runoff) ♦ Older trees may not need additional fertilizer Accelerate decline if tree is stressed ♦ Trees growing in heavily fertilized lawns may Uptake of nutrients into roots and conversion to not need additional fertilizer available forms is largely an energy requiring process (ATP from respiration) ♦ So….. Why fertilize trees? Nutrient toxicities Growth increases: vegetative, flowers, fruit, ♦ May increase pest susceptibility wood production Spider mites, aphids, adelgids, psyllids, scale, whiteflies, lacebug, some caterpillars Maintenance: increase vitality Fireblight, pine pitch canker Correct deficiencies Herbicide injury becomes more pronounced Nutrient Management Why Fertilize Trees and Shrubs with N? ♦ Trees are long-lived plants ♦ N is constituent of proteins, chlorophyll ♦ Critical to photosynthesis and metabolism ♦ Diversity of landscape situations ♦ Under natural ecosystems (forests, prairies), N ♦ Large selection of landscape plants comes from soil organic matter ♦ Soil organisms decompose organic matter, ♦ Soil disturbance releasing NO3- and NH4+ ions ♦ Management objectives: growth vs. ♦ NH4+ ion adsorbed to negatively charged clay maintenance particles (higher CEC), but not in sandy soils (Low CEC) ♦ Urban Stresses: compaction, pollution, poor drainage and aeration, high pH ♦ NO3- ion are not adsorbed by clay particles Can leach into groundwater or away from roots Can be absorbed by plant roots Nitrogen Loss Nitrogen Deficiency ♦ Slow growth, small leaves, ♦ Much of N in soil lost due to leaching or reduced growth from year volatilization (returned to atmosphere in to year gaseous form) ♦ Symptoms: yellowing of ♦ Removal of leaf litter and organic matter leaves, especially older disrupts N cycle in soil leaves due to mobility of N in xylem ♦ Annual raking and removal of leaves can take 1-3 lbs. N out of ecosystem! ♦ Whole plant looks stunted and off color ♦ Suggest mulching leaf litter with mower over lawn to return N, P and organic matter to soil, ♦ Difficult to measure in soil, many forms available not into your gutter ♦ Foliar analysis and visual assessments are better Tree Factors that Influence N Uptake & Influence of Growth Phase: Juvenile or Assimilation Mature Trees (Annual Demand) ♦Trees get taller, larger with age Species ♦Growth rate slows down Growth Phase: Mature or Juvenile ♦Photosynthetic rate slows down Growth Form: Indeterminate or Determinant ♦Demand for resources associated with photosynthesis slows down Evergreen or Deciduous ♦Utilization of internal stores of previously Successional Stage assimilated mobile nutrients increases Influence of Leaf Habit: Evergreen Influence of Growth Form: Indeterminate or Deciduous vs. Determinate ♦Trees with long-lived leaves (needle- ♦Trees with a single growth period leaved evergreens) require fewer (determinant) require fewer nutrients nutrients and water ♦Trees with multiple flushes of growth Trees with short-lived leaves (indeterminate) require more nutrients ♦ (deciduous) require more resources on annual basis (nutrients, water) ♦Resources primarily associated with the Nutrient Use Efficiency (NUE) is high process of photosynthesis ♦ for trees with long-lived leaves Influence of Successional Stage: Highest Relative Nutrient Demand: Early or Late Young, early successional stage, deciduous tree with an indeterminant growth form growing in soils with a high capacity to retain nutrients ♦Early successional stage trees (pioneer (high CEC) species) require more nutrients per unit of biomass produced (low NUE) ♦Early successional stage trees behave more like annual plants Lowest Relative Nutrient Demand: ♦Late successional stage trees (climax Old, late successional stage, coniferous tree with forest) require less nutrients per unit of a determinant growth form growing on soils with biomass produced (high NUE) a low capacity to retain nutrients (low CEC) Growth phase N research: Werner and Jull, 2008 Fertilization significantly enhanced total N in juvenile trees Trees remove, store, and re-use mobile ♦No differences among the N treatments in N essential elements mature trees before shedding tissues ♦Fruit represented an additional N sink in mature trees (required more N) ♦Nutrient management regimes extrapolated N from recommendations developed for juvenile Assimilation, removal, Removed trees may not be appropriate for mature trees storage, and re-use Growth phase N research: Werner and Growth phase N research: Werner Jull, 2008 and Jull, 2008 Fertilizer recovery rates of only 15-25% ♦Mature trees had more N than juvenile trees, in mature and juvenile trees but the N in tree was NOT from fertilizer Greater than 61% of fertilizer applied Mature trees are larger which translates into a not recovered in soil, gravitational water, greater capacity to store previous N from foliage or turfgrass prior to leaf abscission Where did it go? Tree growth slows with age/size, hence, annual demand for N slows with age/size 36-46% either in tree roots, below sampling depth, or volatilization Annual demand in mature trees remobilizes the stored N to a greater extent to support development We Have to Do Something! of new leaves rather than rely on external sources of N (fertilizer) Fertilization Objectives ♦Overcome a visible nutrient deficiency Tree Fertilization: ♦Eliminate a deficiency that is not obvious, but was detected through soil Selection, Timing, Rates, or foliar analysis, and pH tests to and Methods determine acidity or alkalinity of soil ♦Increase vegetative growth, flowering, or fruiting ♦Increase vitality of the plant (overall appearance) When Not to Fertilize Fertilizer Selection ♦ Inorganic fertilizers ♦ Tree has sufficient levels of all essential Release elements quickly when dissolved in water, nutrients except for super and triple super phosphate ♦ Growth rate, condition, and health are Inorganic ions absorbed by opposite charged sites on acceptable root membrane Some are prone to fertilizer burn, high salt index ♦ During drought or when ground is frozen Salt index > 50 is considered high ♦ Potential for certain pest problems ♦ Acidic fertilizer: NH4NO3, (NH4)2SO4, Spider mites, aphids, adelgids, psyllids, scale, NH4H2PO4, (NH4)2HPO4, KH2PO4, use in lacebugs, whiteflies, some caterpillars, pine alkaline soils pitch canker, and fireblight are attracted and have increased injury with fertilization (Dan ♦ Neutral fertilizer: super phosphate, triple Herms, OSU) super phosphate, KCl, K2SO4 ♦ Herbicide injury with residual activity in ♦ Alkaline fertilizer: KNO3, Ca(NO3)2, use in the plant: N would make it worse acidic soils Fertilizer Selection Fertilizer Selection ♦ Organic fertilizers ♦ Conifers and Ericaceous