[Note: brackets indicate holes in the notes that I will fill for permanent copies, wanted to get this done today, so you know I haven’t disappeared.]
Soil, Nutrition, Fertilizers, and Amendments
Lorraine Brooks, Cornell University Cooperative Extension 11/5/09
Soil – should:
– preserve plant growth
– reserve and purify water
– function as Nature’s recycling system
– provide habitat for a variety of living organisms
Tilth – the workable quality of soil
Soil Texture – description of how fine or coarse
The particles in soil are: sand, silt, and clay.
With ideal pore space, soil is: 45% mineral, 25% air, 25% water, 5% organic matter.
Sand has the largest particles, measuring 2.0 – 0.05 mm, and provides macropores.
Silt is next, 0.05 – 0.002mm
Clay is the smallest, aggregate > structure
Spaces between aggregates are macropores, which improve permeability and drainage. Most pores are micropores.
– Structure may be destroyed by compaction or excessive
tillage.
– Tillage of wet soils can damage structure.
– Loss of organic matter (no worms, no aeration; no
bacterial breakdown of leavesand insects, no
refinement of gross materials)
– Compaction squeezes aggregates into horizontal
strata.
Permeability – the rate at which water flows through the soil
Soil Pores
– micropores responsible for soil’s waterholding capacity
– with macropores – faster water flow
– with micropores – takes longer to dry out
Factors Affecting Soil Porosity
– texture
– structure
– compaction
– organic matter
Permeability – of sand, rapid; of clay, the opposite
Soil Organisms
– a 1/4 tsp. has 1 billion microorganisms
– located closest to roots
– main functionis to breakdown plant debris, etc.
– releases energy, nutrients, carbon dioxide
– creates soil’s organic matter
– most active at 70- 100 degrees F.
Ecohabitat of Soil
organic matter – plants – fungi ( mycorrhizal and
saprophytic) – nematodes (root feeders, and fungal and bacterial feeders) – arthropods –
– roots need oxygen for growth, and produce CO2 that
needs to leave the soil
Earthworms
– earthworms increase porosity by making permanent
burrows
– consume two tons of dry matter per acre per year
– partly digest organic matter, and mix it with the soil
There is an invasive problem with worms in the NE U.S. increasing the rate of breakdown of matter, so that it doesn’t coordinate with other species’ use of nuntrients/materials.
Plant Nutrition
– commercial fertilizer is synthetic; has fast release; can leach nitrogen into groundwater, if excessive for amount needed.
– organic preferred
– there are 17 nutrients plants need
carbon, hydrogen, oxygen, nitrogen, phosporus, potassium,
iron, zinc, molybdenum, manganese, boron, copper, salt, [______________]
– roots take up nutrients primarily as ions dissolved n the soil’s water
– an ion is an electrically charged atom/grop of atoms; positively charged are cations, negatively are anions
– fertilizer only increasesplant growth if the plant is deficient in the nutrient applied.
Nitrogen – Phosphorus – Potassium
– N – nitrogen is for rapid growth, dark leaves
– P – phosphorus: cell division
– K – potassium: thickening of cell walls
– sulfur: nodulation of legumes, seed production of all plants, [________]
Ca – calcium: [___________]
[ ] – chlorophyll
Zn – zinc – growth hormones, starch, seed development
Fe – iron – chlorophyll formation
Deficiencies of Nutrients – most common are of the primary nutrients
– phosphorus and potassium are usuallly p lentiful in natural soil for landscape plants; might be needed for vegetables
– nitrogen is very mobile, goes to young growth first — lack: stunting, small leaves, slow to fruit — in excess: dark leaves, heavy
growth, [________]
Fertilizers
Previously, 5-10-5 proportion of the primary nutrients was usual; now some organics have the same, some not.
[Ex.: Home Depot 10-6-4, check online for affordable 50 lb. bags]
Ph is the one soil test done, if any — low number=acid, high=alkaline
– 6.2 – 6.8 is the desirable range
– Cornell has test kit to order
– if ph is low, apply lime – prevents butterfly moth egg deposits
– in North, soil tends to be alkaline
– if 5.0 – 6.2 [ ]
– if 7.8, apply granular sulfur (not available here, mail order cheap from Peaceful Valley Supply at groworganic.com) –
– rhododendrons and azaleas like acid soil
– Spring – green aphids, Fall – grey ones — with good soil, plants have more resistance to pests
– compost spikes high ph when new, and goes down later, which is why it’s good for it to be aged more than a couple of years
– concrete in city environment contributes to “sweetening” the soil — Bx. gardens are where brick buildings with cement have been
knocked down, soil is 8.0ph
For soil testing, call Donna the soil tester at the [GreenThumb/Cornell Extension] office.
Cornell Univ, Cooperative Extension, Urban Environment, 40 E. 34th St. – Suite 606, New York NY 10016-4402
t. 212.340.2997, f. 212.340.2908 llb84@cornell.edu http://nyc.cce.cornell.edu
NYC Grows 