Potassium and Phosphorus as Plant Nutrients Secondary Nutrients and Micronutrients Potassium is required in large amounts by many crops Yield K 2 O taken up Crop level/ac in total crop, lb Alfalfa 8 tons 480 Lettuce 830 boxes 207 Oranges 540 cwt 330 Almonds 3,000 lbs 270 Corn 160 bu 213 Tomato 35 tons 200 Wheat 60bu 122 Cotton (lint) 1,000 lb 85 1
Potassium in Soils Soils may contain as much as 20,000 lb/a total K, or more. Most of this K is held in undissolved minerals (1 o ) Only a small amount of K is plant available during the growing season. Potassium Cycle Singer and Munns, Soils: An Introduction. 2002, page 229 2
K deficiency in almond K deficiency in cotton 3
K deficiency in pears Roots contact only a small percentage of available nutrients 4
Fate of Fertilizer K in the Soil Held in exchangeable form Remains in soil solution Move to roots largely by diffusion. Taken up by growing crop Leached in sandy or organic soils Fixed (unavailable or slowly available) by clays or silts of certain mineralogy. Factors Reducing Rate of Diffusion and Root Growth Impact K Uptake Soil aeration K fixation Cation Exchange Capacity (CEC) Compaction Soil test K Soil temperature Soil moisture 5
Method of fertilizer application depends on crop, soil and other management practices Row application of K 6
Broadcast application of K Banding Potassium sulfate in Almonds 7
Fertigation Certain Soil Stresses Warrant Placement of K in Root Zone to improve plant K availability Cold soils Compacted soils Dry soils High CEC soils Weathered igneous parent material 8
Phosphorus Phosphorus Cycle Singer and Munns, Soils: An Introduction. 2002, page 229 9
Phosphorus Is Taken Up by Plants as: primary orthophosphate ion: H 2 PO 4- (ph < 7.0) secondary orthophosphate ion: HPO 4 = (ph > 7.0) Solution P The form most common is a function of soil ph both equally present at neutral Seeds Contain More Phosphorus than Other Plant Parts Plant Yield P content, P removal, Crop part level % lb/a Corn Grain 150 bu 0.22 18 Stover 7,500 lb 0.17 13 Cotton Seed 2,000 lb 0.66 13 Stalks 2,500 lb 0.24 6 Soybeans Grain 50 bu 0.42 13 Straw 7,000 lb 0.18 13 Wheat Grain 60 bu 0.42 15 Straw 5,400 lb 0.12 6 10
Some Roles Phosphorus Plays in Plant Growth Photosynthesis and respiration Energy storage and transfer Cell division and enlargement Early root formation and growth Improves quality Vital to seed formation Transfer of hereditary traits Relative Movement of N, P, K in the Soil 11
Factors Influencing Amount of P Recovered During First Year After Fertilization Amount of clay Type of clay Time of application Temperature Soil ph Crop grown Aeration Moisture Compaction Other nutrients Soil P status Several Factors Influence Phosphorus Placement Soil fertility levels Olsen test (bicarbonate extraction) alkaline soils Bray-1 test (mild acid extraction) (acid soils) Crop(s) to be grown Tillage methods, equipment and timing P fixing capacity of the soil 12
N Improves P Uptake When applied with N, P is more available to plants Ammonium (NH 4+ ) N has significant effects on P availability and absorption. In high concentrations, NH 4+ - N slows P fixation reactions Ammonium absorption helps maintain an acidic condition at the root surface, improving P absorption Detroit Western Lake Erie, summer, 2011 Toledo Cleveland 13
http://nutrients.utah.gov/ Micronutrients 14
Element Essential elements for plant growth and development. Symbol Typical leaf concentration (dry weight basis) Form(s) taken up from soil Nitrogen N 2-5% NO 3-, NH 4 + Phosphorus P 0.2-0.6% HPO 4 2-, H 2 PO 4 - Potassium K 2-5% K + Calcium Ca 0.5-4.0% Ca 2+ Magnesium Mg 0.4-1.0% Mg 2+ Sulfur S 0.25-1.0% SO 4 2- Chlorine Cl 0.3-1.5% Cl - Iron Fe 50-250 PPM Fe 2+, Fe 3+ Manganese Mn 30-250 PPM Mn 2+ Boron B 20-80 PPM H 3 BO 0 3 Zinc Zn 20-70 PPM Zn 2+ Copper Co 5-20 PPM Cu 2+ Molybdenum Mo < 1 PPM MoO 2-4 Cobalt Co < 1 PPM Co 2+ Nickel Ni < 5 PPM Ni 2+ The Nine Micronutrients Boron (B) Chloride (Cl) Copper (Cu) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Nickel (Ni) Zinc (Zn) Cobalt (Co)* *Needed in legumes, only, for microorganisms fixing N 2 15
Use Diagnostic Tools to Determine Need for Micronutrient Fertilization Soil testing Plant analysis Field demonstrations Field observations Micronutrient Contents in Soils and Crop Removal Est. crop removal, oz/a Range in soils, Corn Cotton Nutrient total, lb/a 150 bu 1,000 lb lint Boron 20-200 1 0.8 Copper 2-400 0.8 0.5 Iron 10,000-1.6 1.1 200,000 Manganese 100-10,000 1.3 4.8 Molybdenum 1-7 0.5 0.3 Zinc 20-600 2.4 1.0 16
Soil ph affects availability of certain nutrients. Liming Influences the Availability of Micronutrients in Different Ways Reduces toxicity of Mn Increases availability of Mo Has no affect on Cl 17
Boron deficiencies are widespread in many parts of the world Some Roles of Boron in Plants - Essential: In germination of pollen grains For growth of pollen tubes For seed and cell wall formation For protein formation For sugar translocation 18
Boron Deficiency Symptoms on Crops Celery Crooked stem Peanuts Hollow heart Apples Corky core Alfalfa Rosetting, yellow top, death of terminal bud Beets Black heart Cotton Ruptured squares, dieback of terminal bud, rosetting Responsiveness of Crops to Boron Most response Medium response Least response Alfalfa Cauliflower Celery Sugarbeets Table beets Turnips Peanuts Cotton Apples Clover Broccoli Cabbage Carrots Lettuce Spinach Sweet corn Tomatoes Asparagus Canola Radish Beans Blueberries Cucumbers Corn Onions Potatoes Small grains Sorghum Sudan grass Soybeans 19
Factors Affecting Boron Availability Organic matter B Weather conditions Soil ph Soil texture Leaching Boron deficiency symptoms 20
Excess Boron Symptoms Copper Deficiency Symptoms 21
Organic soils are most likely to be Cu deficient Iron (Fe) deficiency in prune 22
Functions of Manganese in the Plant Part of the plant enzyme system Activates several metabolic reactions Aids in chlorophyll synthesis Accelerates germination and crop maturity Increases plant availability of P and Ca High soil ph Some Causes of Manganese Deficiency Imbalance with other nutrients such as Ca, Mg and Fe Soil moisture High organic matter soils during cool spring when soils are waterlogged 23
Manganese (Mn) deficiency Zinc (Zn) Deficiency 24
Some Plant Functions of Zinc Aids in the synthesis of enzyme systems Promotes certain metabolic functions Necessary for the production of chlorophyll and carbohydrates Key for growing points Factors and Conditions Affecting Zinc Availability Soil texture and ph Soil phosphate levels Soil organic matter Leveling for irrigation Leaching Cold, wet soils Soil biological activity Zn 25
Some Functions of Chloride in Plants Involved in energy reactions, including the chemical breakdown of water Activates several enzyme systems Involved in the transport of cations Regulates stomatal guard cells, thus controlling water loss and maintaining turgor 26