Substrate Management Practices for Better Plant Growth Andrew G. Ristvey Extension Specialist Commercial Horticulture University of Maryland Extension Wye Research and Education Center College of Agriculture and Natural Resources University of Maryland The University of Maryland is an Equal Opportunity Employer and Equal Access Programs La Universidad de Maryland es una institución con Igualdad de Oportunidades de Empleo y con Igualdad de Acceso a Programas
Smarter Substrate Management There are three lines of defense against nusery plant diseases Prevent pathogens from entering the production systems Create cultural conditions that work for good plant growth and against disease development Correct and timely treatment of disease problems that do arise But first Prevention! is crucial successful plant health management
Smarter Substrate Management Why substrate management is important in pathogen risk management? Important understand the root environment Substrate supports root environment Substrate components create various mixes Substrate physical and chemical characteristics determine: Irrigation Management - availability of water Nutrient Management - availability of nutrients A substrate s characteristics will change in time Appropriate substrate Best Management Practices will create a healthy root environment and a healthy plant
Smarter Substrate Management Objectives for this pic include: Relating substrate physical property facrs air and water availability and effects on management Relate substrate chemical properties facrs healthy plants Review soilless substrate handling from delivery potting Soilless Substrate Evaluation and Moniring methods
Pore Space When we buy substrate we are buying pores! What can affect substrate Air-Filled Porosity and Water Holding Capacity? Component structure (shape and size) Handling Irrigation Container geometry Age
Variability of Components Highly Variable Physical properties Very porous Leach very easily Various combinations Irrigation management depends on knowledge of these characteristics Plant Available Water the % volume of water that plants can retrieve Peat Moss Pine bark Perlite Coir Rice Hulls Peanut Hulls Sand Gravel Vermiculite
Plant Available Water Soils and substrates have the ability hold and release water Some water is available for the plants Some water is not available for the plants even though the substrate or soil may seem moist Why?
Plant Available Water Plant Available Water is the water held by the soil or substrate that is divided in: Easily Available Water Water Buffer Capacity Unavailable Water the portion that is progressively unavailable the plant
Plant Available Water Electron micrograph of Sphagnum Peat
Water Availability - (5cm desorption columns) % of Total Water 100% Perlite 80 Pine Bark : 20 Peat 100% Coir 100% Pine Bark 80 Peat: 20 Perlite Pressure (kpa) Distribution of Water (%) EAW (1 5) 36.0 40.0 32.6 34.6 43.7 WBC (5 10) 1.2 7.0 2.1 2.2 13.1 PUW ( >10 ) 62.8 53.0 65.3 63.2 34.1* Total volume of the 5-cm column = 722 ml. Note that CC = TP - AS. Use CC values interconvert data. * An additional 9.1 % water was expressed from this substrate between 10 and 60 kpa ( tal 100%) Easily Available Water = EAW Water Buffer Capacity = WBC Arguedas, 2008 Progressively Unavailable Water = PUW
Soilless Substrates: Chemical Properties Potting substrates, largely organic have little anion exchange capacity Depending upon aging, they do have some cation exchange capacity For the most part, soilless substrates are acidic and maintained as such The most optimal ph for nutrient availability is between 5.5 and 6.2 in soilless substrates. This is lower than suggested soil ph. Why?
Soilless Substrates: Chemical Properties Moniring ph is vital so that micronutrients maintain optimal availability Moniring Electrical Conductivity helps ascertain the salt load on the roots Moniring should start at the time of receiving the substrates Then as often as possible throughout the nursery as a proactive moniring program
Smarter Substrate Management Objectives for this pic include: Initial quality Srage of substrates Handling of substrates Moniring procedures
Initial Quality What do you first look at when your substrate is delivered? 1. Physical Consistency 1. Components what s are they made of? 2. Particle Size and shape
Initial Quality
Initial Quality Bark chips Cambium Wood (cellulose)
Production and Aging Pine bark substrate production component particles Cellulose and Lignin Why some substrates degrade faster than others 1. Cellulose is a sugar 2. Lignin is a more complicated molecule and more difficult degrade Cellulose Lignin
Initial Quality What do you first look at when your substrate is delivered? 1. Physical Consistency 1. Components what s are they made of? 2. Particle Size and shape 3. Physical Properties Test AFP and WHC
Initial Quality 25% AFP 35% AFP
AFP and WHC based on Container Size 100 90 80 70 60 50 40 30 20 10 0 6 inch 4 inch 48 cell 512 cell % Water % Solid % Air Adapted from A Grower s Guide Water, Media, & Nutrition for Greenhouse Crops, Ed. David Wm. Reed, 1996.
Initial Quality What do you first look at when your substrate is delivered? 1. Physical Consistency 1. Physical Properties Test AFP and WHC 2. Chemical property test 1. Pour-Though 2. Saturated Media Extract ph and Electrical Conductivity
Initial Quality - Composting and Aging When it goes wrong 1. Compounds like alcohols acetic acid and methane are developed in anaerobic composting 2. An indication of anaerobic aging may be a very low initial ph ~ 3.2 or less. 3. If so substrate needs be and thoroughly leached and turned (aerated).
Srage of Substrates
Srage of Substrates Srage high and dry!
Srage of Substrates
Substrate Handling
Substrate Re-use
Substrate Age 1. Naturally, a substrate will age 2. How long break down? 3. What are the components? 4. Within a year? 5. Pore space changes 6. AFP decrease and WHC increases 7. This has consequences of irrigation management 8. See the plants up-grade container size with new substrate
Substrate Moniring Procedures 1. Field determination of AFP and WHC 2. ph and EC Testing - Pour-Through and Saturated Media Extract
Materials Field Test for AFP 1. Scale in metric (can be ounces but must convert) 2. Bucket or large container (21 gallon srage bins) 3. Containers of known volume (can be measured) 4. Substrate Measurements (1 g H 2 0 = 1 ml = 1 cc) W1 = Saturated container media W2 = Drained container (at least 1 hour later) W3 = Volume of Substrate W4 = Weight of Container W5 = Weight of Dry Media
Field Test for AFP W1 = Saturated container media W2 = Drained container (at least 1/2 hour later) W3 = Volume of Substrate W4 = Weight of Container W5 = Weight of Dry Media % AFP = W1 W2 X 100 W3 W4 WHC = % W2 (W5 + W4) W3 Saturation AFP X 100 Total Volume
Substrate Moniring 1. A Saturated Media Extract Saturate substrate in a container glistening Let sit for at least 15 minutes more is better 2. A Pour-Through Irrigate your crop container capacity Allow the container sit for 1 hour Add 150 ml of water for 1 gal container. Avoid channeling down the container side. Collect leachate from the drain holes Can also tip the container
Electrical Conductivity Deciphering EC units ohm mmhos/cm mho ds/m ms/cm
Growing Media - Moniring Electrical Conductivity: EC is a measure of tal available salts in the soil / substrate solution Most of the nutrients are available as salts Salts - ionic compounds (electrolytes) Na+ Cl- Careful! EC does not tell you which nutrients are available Measure Pour thru extract or SME
0 1:5 1:1.5 SME PourThru Indication 0.11 0.11 0.35 0.35 0.65 0.65 1.1 Low nutrient levels may not be sufficient for some plants. High-end of range suitable for seedlings and salt sensitive plants. Normal Standard root range for most established plants. Lower-end of range typical for normal fertility. High suitable for salt lerant plants but mid high end of this range may damage roots. Very High May result in salt injury, reduced growth and root death. Dilution or Leaching by irrigation necessary. > 1.1 Extreme Immediate leaching is required. 1 Adapted from: On-site testing of growing media and irrigation water. 1996. British Columbia Ministry of Agriculture. 2 Due the variability of the PourThru technique results, growers should always compare their results the SME method establish acceptable ranges.
1:5 1:1.5 SME PourThru Indication 0 0.35 0.35 1.25 1.25 2.5 2.5 3.5 Low nutrient levels may not be sufficient for some plants. High-end of range suitable for seedlings and salt sensitive plants. Normal Standard root range for most established plants. Lower-end of range typical for normal fertility. High suitable for salt lerant plants but mid high end of this range may damage roots. Very High May result in salt injury, reduced growth and root death. Dilution or Leaching by irrigation necessary. > 3.5 Extreme Immediate leaching is required. 1 Adapted from: On-site testing of growing media and irrigation water. 1996. British Columbia Ministry of Agriculture. 2 Due the variability of the PourThru technique results, growers should always compare their results the SME method establish acceptable ranges.
1:5 1:1.5 SME PourThru Indication 0 0.50 0.50 2.0 2.0 3.5 3.5 4.5 Low nutrient levels may not be sufficient for some plants. High-end of range suitable for seedlings and salt sensitive plants. Normal Standard root range for most established plants. Lower-end of range typical for normal fertility. High suitable for salt lerant plants but mid high end of this range may damage roots. Very High May result in salt injury, reduced growth and root death. Dilution or Leaching by irrigation necessary. > 4.5 Extreme Immediate leaching is required. 1 Adapted from: On-site testing of growing media and irrigation water. 1996. British Columbia Ministry of Agriculture. 2 Due the variability of the PourThru technique results, growers should always compare their results the SME method establish acceptable ranges.
1:5 1:1.5 SME PourThru Indication 0 0.50 0. 50 2.0 2.0 4.6 4.6 6.5 Low nutrient levels may not be sufficient for some plants. High-end of range suitable for seedlings and salt sensitive plants. Normal Standard root range for most established plants. Lower-end of range typical for normal fertility. High suitable for salt lerant plants but mid high end of this range may damage roots. Very High May result in salt injury, reduced growth and root death. Dilution or Leaching by irrigation necessary. > 6.5 Extreme Immediate leaching is required. 1 Adapted from: On-site testing of growing media and irrigation water. 1996. British Columbia Ministry of Agriculture. 2 Due the variability of the PourThru technique results, growers should always compare their results the SME method establish acceptable ranges.
0 1:5 1:1.5 SME PourThru Indication 0.11 0.11 0.35 0.35 0.65 0.65 1.1 0 0.35 0.35 1.25 1.25 2.5 2.5 3.50 0 0.50 0.50 2.0 2.0 3.5 3.5 4.5 0 0.50 0. 50 2.0 2.0 4.6 4.6 6.5 Low nutrient levels may not be sufficient for some plants. High-end of range suitable for seedlings and salt sensitive plants. Normal Standard root range for most established plants. Lower-end of range typical for normal fertility. High suitable for salt lerant plants but mid high end of this range may damage roots. Very High May result in salt injury, reduced growth and root death. Dilution or Leaching by irrigation necessary. > 1.1 > 3.5 > 4.5 > 6.6 Extreme Immediate leaching is required. 1 Adapted from: On-site testing of growing media and irrigation water. 1996. British Columbia Ministry of Agriculture. 2 Due the variability of the PourThru technique results, growers should always compare their results the SME method establish acceptable ranges.
Smarter Substrate Management Salient points for day 1. Components vary and gether will have different physical and chemical properties manage 2. Irrigation management decisions are, in large part, based on these characteristics 3. Moniring must begin upon arrival and continue through the cycle of the plants 4. Good substrate management is good pathogen management
Suggested Websites North Carolina State Floriculture Deficiency Series www.ces.ncsu.edu/depts/hort/floriculture/def/ North Carolina State Floriculture Fact Sheet # http://www.ces.ncsu.edu/depts/hort/hil/hil-558.html University of Florida: Nutrient Deficiencies in Production of Annual Floral Crops http://edis.ifas.ufl.edu/ep325
For more information about Substrate Management http://waternut.org/knowledgecenter.html
Questions?
Soilless Substrates Physical Properties Three Phases of Growing Media by volume Solid (matrix) 33% 50% Liquid (water) 15% 65% Gas (air) 10% 50% Water % + Air % = Total Pore Space Matrix Component Porosity: determines the ratio between Water % Air % Total Pore Space 33% 50% Solid (matrix) 10% - 50% Air 15% - 65% Water
Plant Available Water (Handreck & Black, 1994)
Volume % (20 cm high pot) 100 Unavailable Total Pore Water Easily Space (progressively) Available Air Readily available water Air Air Filled Porosity (at container capacity) Solids Water Buffer capacity 0 (Handreck & Black, 1994) 0-1 set points -5-10 Suction applied (kpa) 7 kpa = 1 PSI
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On a humus molecule OH COOH COOH
On a humus molecule - OH - COOH - COOH
On a humus molecule O Fe COO Mn COO Cu
On a humus molecule O - Fe COO H - Mn H H COO - Cu H H H