Greenhouse Plant Management Plant Nutrition and Fertilization Megan Burgess

Overview  Essential Plant Nutrients  Fertilizer Reaction on Media Ph  Total Soluble Salt Concentrations –Causes of High Total Soluble Salts –Reduction of Soluble Salts –Symptoms of Salt Injury  Fertilizing Methods  Fertilizer Rates

Essential Plant Nutrients  17 required to support growth  Ph of media and solution changes –Iron availability changes  Raising ph to alkaline levels causes calcium and magnesium to become extremely available  Soilless media ph should be between 5.5 and 6.2

Fertilizer Reaction on Media ph  Fertilizers change media ph –Commonly lowers ph, so incorporate lime to cancel expected decrease  Test media ph frequently  Take quick action with visual plant problems –Use hydrated lime at a rate of 1.5 lbs/100 square feet or 1 lb/5 gallons of water

Total Soluble Salt Concentrations  All fertilizers are salts  TSSC is a measure of all ions in the medium solution –Sodium –Calcium –Magnesium –Potassium –Nitrates and sulfates

Chart of TSSC Mineral Peat-lite Soil Mix

Causes of High Total Soluble Salts  Excessive rates of fertilizer  Not enough water  Subirrigation watering method  Poor drainage  Water with high levels of salts

Reduce Soluble Salts by:  Leaching with plain water  Applying moderate fertilizers at frequent intervals  Applying water to allow a small amount of solution to drip

Symptoms of Salt Injury  Wilting  Chlorosis and leaf drop  Burning of leaf margins  Browning and dying of roots

Fertilizing Methods  Slow release fertilizers –Incorporated into growing medium –Applied as a topdressing to container –No specific equipment needed –Doesn’t waste fertilizer

Fertilizing Methods  Liquid fertility programs –Weekly liquid fertility program  High rate of nutrients one day a week  Clear water the rest the week  Starves plants then over fertilizes –Constant liquid feed program  Supplies moderate levels of nutrients all the time  Requires more equipment and maintenence

Fertilizer Rates  Depends on crop being grown –Light feeders ppm N –Heavy feeders 300 ppm N  Equal amounts of nitrogen and potassium – peat-lite are very popular  Recommendations given in ppm (parts per million) or ounces/100 gallons –Typical rate is 200 ppm N and K 2 O

Crop Nutrient Requirements Violets, bedding plants, mums, gloxinias, roses Ferns, geraniums, foliage pot plants Blubs

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