Soil Nutrients

Olga S. WalshAssistant Professor

Soil Nutrient ManagementMontana State University

Western Triangle Agricultural Research Center

Nutrients and plant growth

o Plant’s sufficiency range = range of nutrient necessary to meet plant’s nutritional needs and maximize growth

o Nutrient levels outside of a plant’s sufficiency range cause crop growth and health to decline due to either a deficiency or toxicity

Mc Cauley et al., 2009

Mobile and Immobile Nutrients

BLA BLA

BLA BLA

Roger Bray, “A Nutrient Mobility Concept or Soil-Plant Relationships. 1954. Soil Science.

MT soils:Common deficiencies /toxicities

• Most common: N and P• Sometimes – K, S

• Micronutrient deficiencies are fairly uncommon with deficiencies of B, Cl, Fe, and Zn occurring most often

• Toxicities – uncommon, result of over-fertilization

Essential plant nutrientsTotal of 16 essential nutrients

3 Macronutrients from air and water: Carbon, Hydrogen, Oxygen (C, H, O)

13 MACROnutrients from soil:3 Primary nutrients - Nitrogen, Phosphorus and Potassium

(N, P, K)3 Secondary nutrients - Calcium, Magnesium and Sulfur

(Ca, Mg, S)7 MICROnutrients - Iron, Manganese, Zinc, Copper, Boron, Molybdenum, and Chlorine (Fe, Mn, Zn, Cu, B, Mo, Cl)

Essential plant nutrients

Deficiency disrupts plant’s growth and reproduction

Deficiency can be prevented or corrected only by supplying the element

Nutrient is directly involved in the nutrition of the plant

Macronutrients

Nutrients from air and waterCarbon, Hydrogen, Oxygen

Base of all organic molecules, building blocks for growth Absorbed as CO2

Combined with H and OTransformed into carbohydrates in leaves in the process of photosynthesis

Essential Macronutrients

N, P, K

Needed in greater amounts for growth

Lacking from soil firstGreater response

N deficiency Light green upper (young) leavesYellow lower (older) leaves

Essential Macro nutrients: P Catalyses biochemical reactions

Component of DNA (genetic memory)

Component of energy molecules Key element in photosynthesis

P deficiency Dark purple discoloration on the leaf tips, advancing down the leafStunted plants with fewer shoots

Essential Macro nutrients: K Photosynthesis and movement of nutrients

Protein synthesis

Activation of plant enzymes

Regulation water use

K deficiency Marginal chlorosis and necrosis on older leavesShorter internodes, stunting

Essential Secondary nutrients Ca, Mg, S

Needed in moderate amounts

Essential Secondary nutrients: Ca Cell structure, membranes

Nutrient uptake

Reaction to negative environmental factors

Defense against disease

Ca deficiency Poor root growth, stunted dark rotting rootsSymptoms – in new growth (necrotic spots in young leaves), leaves collapse before unrolling

Essential Secondary nutrients: Mg

Chlorophyll formation

Light-absorbing pigments

Amino acids and proteins

Resistance to drought and disease

Mg deficiencyPale green, chlorotic young leavesFolded or twisted leavesSymptoms similar to drought

Essential Secondary nutrients: S

Component of amino acids and proteins

Component of enzymes and vitamins

Formation of Chlorophyll

S deficiencySeedlings: pale yellow chlorosis on young leaves

S deficient leaf (left) normal (right)

Micronutrients

Micronutrients

Fe, Mn, Zn, Cu, B, Mo, Cl

Needed in very small amounts

Involved in metabolic reactions as part of enzymes (reused, not consumed) Can be corrected with a fraction of pound per acre rate

Iron (Fe)

RespirationPhotosynthesisEnzymatic ActivatorChlorophyll Synthesis

Fe deficiencyFailure to produce sufficient chlorophyllInterveinal chlorosis, green/yellow stripesNew leaves turn white

Manganese (Mn)

Component of various enzyme systems for:• energy production• protein synthesis, and• growth regulation

Mn deficiencyInterveinal chlorosis Brown necrotic spots on leavesWhite/gray spots on leaves Premature leaf drop and delayed maturity

Zinc (Zn)

RespirationPhotosynthesisEnzymatic ActivatorChlorophyll Synthesis

Zn deficiencyFirst appear on middle-aged and old leavesMuddy gray-green leaf colorLeaves appear drought stressed, with necrotic spots

Copper (Cu)Catalyst in photosynthesis and respirationConstituent of enzymes Involved in building and converting amino acids to

proteins Carbohydrate and protein metabolism Plant cell wall constituent

Cu deficiency Leaf tip die-back followed by a twisting or wrapping of the leaves Delayed maturity Stunted, misshapen heads

Boron (B)

Cell wall strength and developmentCell divisionFruit and seed developmentSugar transport

B deficiency Saw tooth effect on younger leavesPale, “water-soaked” new shootsHead sterility

Molybdenum (Mo)

Conversion of nitrates (NO3 ) into amino acids in the plant

Conversion of inorganic P into organic forms in the plant

Protein synthesisSulfur metabolism

Mo deficiency Stunted plantsFlowering/Seed formation affectedHollow stemsBrittle, discolored leaves

Chloride (Cl)Photosynthesis

Stomata regulation

Gas and water balance in cells

Nutrient transport (K, Ca, Mg)

Disease resistance

Cl deficiencyPhysiological Leaf Spot SyndromeWhite to brown spots on leavesStarts in lower leaves at tilleringSimilar to tan spot, smaller spots, no “halo”

Micronutrient deficiencyHigh soil pH (uptake decreases as pH increases) – all but MoMT typical pH = 7-8, varies from 4.5 to 8.5

Low organic matter MT typical OM = 1-4%

Cool, wet weather

Micronutrient products

Citri-Che Crop Mix 1 (N, S, Cu, Mn, Zn)Gainer High Phos (N Nitrogen, Phosphate, Potash, Sulfur, Boron, Copper, Iron, Manganese, Molybdenum and Zinc

Acknowledgements

• Information is based on Montana State University’s Extension Module 9 by McCauley et al, 2009: http://landresources.montana.edu/NM/Modules/Module9.pdf