Making Your Garden Green and Healthy

The Perfect Soil It doesn’t exist, but you can come close Components of the perfect soil Good texture Good structure Good water content Good oxygen content Good nutrient content Good pH Good management can improve most of these.

Soil Texture The percentage of sand, silt, clay in soil Mineral fraction Sand Silt Clay Organic fraction Living Dead

Texture, Water and Nutrients Water Holding capacity CEC Clay content Sand content Clay content Sand content Infiltration capacity Clay content Sand content

Texture, Water and Nutrients Soil colloids: a portion of the mineral and organic fractions Clay Humus K+ Fe2+ Zn2+ H2O H2PO4- H2O Cu2+

Texture and Water capacity As discussed, clay and organic matter increase water holding But why is clay bad and OM good?

Texture and Water Capacity Understanding soil-water dynamics Three important water contents Saturation Field capacity Wilting point Plant available water is the difference between field capacity and wilting point

Texture and Water Capacity sands loams clays Soil Texture Plant available water Field capacity Wilting point Water Volume in Soil Effect of OM Field capacity with OM additions Plant available water w/ OM Field capacity Wilting point with OM additions Water Volume in Soil Plant available water Wilting point sands loams clays Soil Texture

Managing Texture What is the best texture? Loam: maximize the benefits of sand and clay, minimize the negatives How do you minimize the effects of bad texture? Add organic matter: the benefits of clay without the negatives Wouldn’t recommend adding sand. Sand adds no fertility to soil, plus very, very heavy.

Soil Structure How soil solids are arranged together Soil solids clump together into little aggregates called “peds” Macropores between peds, micropores within peds Sand does little to create structure, but the pores between sand grains are often macropores already

The importance of soil structure Soil’s composition: 50% solid material 25% water 25% gas Gas Water Solids

Good structure Strong peds with lots of macropores in between Peds are granular or blocky The 50% solid, 25% gas, 25% water ratio is maintained most of the time

Good structure How do you get it? How do you maintain it? Good texture Can’t be managed Good OM content Can be managed How do you maintain it? Talk about how OM attracts biology that can help to create structure

Good Structure Maintaining structure Manage tillage carefully Keep soil covered Cover crops? Avoid compaction Incorporate OM

Good nutrient content Greatly dependent on management Fertilizers Concentrated nutrient source Conditioners Organic matter Management can result in direct changes. In most other management, you are conditioning the soil to be better at its functions in the future. Here, you can directly add nutrients and see quick results

Fertilizers All fertilizers provide one or more plant essential nutrients Macronutrients: Nitrogen (N), Phosphorous (P), Potassium (K), Sulfur (S), Calcium (Ca), Magnesium (Mg) Micronutrients: Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo), Nickel (Ni), Cobalt (Co), Chlorine (Cl)

Fertilizers N-P-K: what do they do General rule N is for growth, especially leaves and shoots P is for root and shoot production K is for hardiness and durability A lot more roles tham this. N is part of most plant proteins and chlorophyl. Phosphorous is part of ATP enzyme which creates energy, as well as DNA and RNA. K ascts as activator for many enzymes and as salt solution to increase osmotic pressure in roots

Soil Conditioners Many types, but have some general characteristics OM rich Lower nutrient concentration than fertilizer So, why use them? Well conditioned soil needs less fertilizer Conditioning improves structure, water holding capacity, CEC Feeds the soil food web Compost can come from a compost pile, composted leaf litter from a municipality, composted manure or sewage sludge. Can make your own or can buy it commercially

Soil Conditioners Soil food web 1 to 4 billion bacteria per teaspoon 40 yards to 40miles of fungi roots per teaspoon

Soil Conditioners Soil food web Soil biology releases nutrients from OM, from each other, and from the mineral material of soil. There are more than enough nutrients in soil to feed all your plants without any fertilizer additions …….it just has to be made available.

Good pH What is the ideal pH? How does it affect plant growth Depends on the plant How does it affect plant growth It affects nutrient availability

Soil pH and Nutrients

Keys to Healthy Soil Do: Add organic matter! This will…. Feed soil biology Power the soil food web Increase water and nutrient holding capacity Increase structural formation and infiltration

Keys to Healthy Soil Don’t Compact the soil Leave the soil bare Overtill

The End! Dan Schwartz Soil Scientist 703-324-1422 Dan.Schwartz@ Fairfaxcounty.gov