Chapter 18 Unit 17 Greenhouse Soils Soilless

Chapter 18 Unit 17: Greenhouse Soils & Soilless Culture

Objectives Challenges & rewards of greenhouse plants Materials used for rooting media Formulating & pasteurizing rooting media Timing & methods of watering Fertilizers & amendments common in greenhouse cultures

Introduction Horticulture vastly growing industry Great reliance on container-growth plants Ability to start/grow plants in favorable conditions Match plant preferences to potting media Greater ability to manipulate climate, fertility, water etc.

Root Media Soilless culture can yield much higher per acre than soil culture –not realistic Expensive Difficult to manage More consistent aeration, water retention Important Properties of Root Media Stable organic matter or low C: N Water retention w/ adequate aeration Moderate/high CEC Suitable p. H

Root Media Stable organic matter Moderately decomposed – don’t want it to shrink too much decreasing aeration Greenhouse media tends has little natural fertility, needs ability to retain nutrients Components of Root Media Mixes Peat moss ▪ Decompose slowly ▪ High water-holding capacity ▪ Can be acidic

Root Media Bark ▪ Can replace peat moss ▪ Less expensive ▪ Should be composted Sawdust, straw, manures ▪ Sawdust & straw should be composted 1 -2 mos. ▪ Manures ▪ Used little due to ammonium toxicity ▪ Can be good in certain situations

Root Media ▪ Vermiculite ▪ ▪ Silicate material High water holding capacity Great aeration High CEC, w/ some K, Ca, Mg ▪ Sand ▪ Best drainage & aeration ▪ No CEC or nutrient availability ▪ May work for starting plants ▪ Perlite ▪ Heated volcanic rock ▪ Sterile & inert ▪ Good substitute for sand

Root Media Mixes Soil-Based Root Media 1/3 sand, 1/3 peat moss, 1/3 soil Keep clay content low Can make at home/lab w/ ability to sterilize soil Soilless Root Media Materials to use ▪ Vermiculite, organic matter, sand, perlite, sphagnum peat moss ▪ Can mix yourself, or buy premixed Pay close attention to fertility management

Pasteurization of Media Pasteurization controls Weed seeds, pathogens, insects, nematodes Steam pasteurization Most used Pump steam through soil mixture to kill most pathogens Chemical pasteurization Cheaper Must allow to aerate after treatment Chemicals are nasty to handle

Pasteurization of Media Methyl bromide ▪ Severely injurious to humans ▪ Can be damaging to some plants Chloropicrin (tear gas) ▪ Can’t use where plants are growing

Watering Incorrect watering most frequent cause of reduced crop quality or failure Watering Guides Use well drained rooting medium Wet entire root media w/ each watering (till it drips) ▪ Leaching can then remove excess soluble salts ▪ All root area is wet Wet before dry stress occurs

Watering Systems Hand ▪ Frequency often questionable ▪ Quantity inconsistent ▪ Plant damage Automated ▪ Sprinklers, drip, microirrigation, water tables & capillary action ▪ More consistent timing, and amount ▪ Must have good equipment, proper air flow, humidity control

Fertilizing Plant Nutrients Vary w/ rooting media & crop May need to pay close attention to micronutrients ▪ May are available as mixtures or can be incorporated into irrigation Slow-Release Fertilizers Release over first 3 -4 mos ▪ Some may be 6 -15 mos

Soil & Tissue Testing Many greenhouse production problems related to soil fertility Can sample root media (every 3 mos) Tissue sampling can be done to troubleshoot a problem May be critical in large greenhouse production operations w/ high value crops

Hydroponics: Solution Culture All nutrients must be supplied in solution Can control fertility very specifically Takes specific equipment for metering Plant support Fixed above, or floating Keep aeration in water, or w/ wool, perlite, sand ▪ Used commonly in research on roots to keep soil out of way

Hydroponics: Solution Culture Root Aeration & Darkness Bubble air Baffles in water flow Keep root system in dark ▪ Inhibits algae growth

Assignment