Nutrition in Container Crops Dr. James Altland
The Nutrition Triangle Fertilizer Substrate Irrigation
Substrate ph Douglas fir bark has an abundance of available nutrients. Nutrient availability in the bark is dependent largely on substrate ph. Nutrient availability changes widely over the range of ph values.
Effect of ph on nutrient availability
Lime affects ph of bark 11 10 9 Substrate ph 8 7 6 Calcitic lime Dolomitic lime Quick lime Fresh Aged 5 CCE = 97 CCE = 106 CCE = 126 4 0 10 20 40 10 20 40 10 20 40 Lime rate (lb/yd 3 )
Substrate ph affects P availability 16 14 12 10 8 6 4 2 0 4 5 6 7 8 9 Substrate ph
P availability with lime rate 12 10 Available P (ppm) 8 6 4 2 0 0 1 2.5 5 7.5 10 15 20 7.5 10 15 20 30 40 ---Calcium carbonate (lb/yd 3 )--- --Calcium hydroxide (lb/yd 3 ) --
Lime affects on available P As ph increases, P availability decreases True for soils and bark Ca ions bond with phosphates Calcium phosphate is largely insoluble Calcium phosphate is either unavailable, or leaches in mass flow of water
Phosphorus We know high levels are available initially. This should make you reconsider your premix fertilizer amendments. Wait until we know more before you change your CRF or liquid feed program.
Phosphorus OR nurseries contain their runoff water during the growing season. What about P leaching during the winter months?
Substrate ph affects Fe availability 45 40 35 30 25 20 15 10 5 0 R 2 = 0.88 4 5 6 7 8 9
Substrate ph affects Mn availability 0.7 0.6 0.5 0.4 R 2 = 0.5345 0.3 0.2 0.1 0 4 5 6 7 8 9
Substrate ph affects B availability 0.3 Levels 0.7 to 2.5 are recommended. 0.25 0.2 0.15 R 2 = 0.8119 0.1 0.05 0 4 5 6 7 8 9
Results first trial (6 WAP) No differences in growth or color Despite deficient substrate B, plants had sufficient foliar B.
Summary of bark Nutrient availability very ph dependent ph is very easy to change with lime products At typical ph (>6), P and some micronutrients are not sufficiently high in bark Maintain lower ph, reduce applied fertilizers?
Nitrogen Virtually no N in irrigation water. Even from recycle ponds, anticipate very low levels. Very low N levels in bark N immobilization.
Geranium growth 12 10 Shoot dry weight (g) 8 6 4 2 Aged Fresh 0 200 300 400 Fertilizer N rate (ppm)
Nitrate availability in substrate 3.5 3 2.5 Foliar N (%) 2 1.5 1 0.5 Aged Fresh 0 200 300 400 Fertilizer N rate (ppm)
Nitrate availability in substrate 160 Nitrate availability (ppm) 140 120 100 80 60 40 20 Aged Fresh 0 200 300 400 Fertilizer N rate (ppm)
NDI for fresh and aged bark 1 0.8 0.6 0.4 0.2 0 Aged 1 Fresh 1 Aged 2 Fresh 2
Summary of Nitrogen Nitrogen is not available from bark Nitrogen will be immobilized by bark Immobilization is not biological Fresh bark will immobilize more N than aged bark Nursery fertilizer rates offer excessive N Compensates for differences in immobilization
The Nutrition Triangle Fertilizer Substrate Irrigation
Water quality over time in OR ph 10 8 6 4 2 Irrigation ph over time Alkalinity 250 200 150 100 50 Alkalinity over time 0 2 4 6 0 2 4 6 Na (ppm) 60 50 40 30 20 10 0 Sodium levels over time 2 4 6 HCO3- (ppm) 300 250 200 150 100 50 0 Bicarbonates over time 2 4 6
Hardness Hardness refers to the concentration of Ca and Mg in water. This term is closely related to alkalinity, but they refer to two different chemical properties.
Water quality in Oregon 120 100 Calcium (ppm) 80 60 40 20 0 R 2 = 0.9347 0 50 100 150 200 250 300 350 Hardness
Alkalinity The measure of a water s ability to neutralize acids. Alkalinity is the concentration of Carbonates and bicarbonates CO 3 2- + HCO 3 - Depending on lab, the sum of carbonates, bicarbonates, and/or hydroxides.
Water quality in Oregon 120 Calcium (ppm) 100 80 60 40 20 0 R 2 = 0.2616 0 50 100 150 200 250 Alkalinity (ppm)
Alkalinity affects P availability Carbonates raise substrate ph P becomes less available Ca reacts with phosphates to form: Calcium phosphate Precipitates from solution, not readily available for plant uptake.
Water quality in Oregon 250 Alkalinity (ppm) 200 150 100 50 R 2 = 0.249 0 5 6 7 8 9 ph
Summary Alkalinity affects substrate ph Irrigation water ph has little/no affect on container ph Alkalinity and hardness (Ca levels) affect P availability. Low irrigation alkalinity is ideal, irrigation ph is irrelevant.
The pour-through method Consistency is problematic Use the same person Use the same equipment Use the same protocol
Water placement affects results 12 10 a a Extract ph 8 6 4 b b b b 2 0 center middle edge center middle edge -----------Fine bark------------ ---------Medium bark--------
Substrate type, water volume and water application method 14 12 10 a a Extract ph 8 6 4 bc bc bc b c bc 2 0 Fine - 100 Fine - 200 Medium - 100 Medium - 200 Drip Pour
Pour-through procedure Slow application of water produces more consistent results. Apply the water along the entire substrate surface. Time consuming BAMB 2005 WB
BAMB Model 2010 Automated, multi-container pour-through system Pressure compensating Uniform placement of water, slow application Consistent results!
Summary OSU is beginning to document nutrient availability in bark. Also documenting factors that affect nutrient availability. This will allow nursery growers to make better fertility decisions.
Website http://oregonstate.edu/dept/nursery-weeds/