Soils Eat, Drink and Breathe the Good Life Dr. Alan Stevens Kansas State University
“Grow the roots and the top will take care of itself” . . . . Old Willy
How toenable your plant roots to eat, drink and breathe the good life
What does soil provide? • –Anchorage . . . hold on • –Nutrients . . . . . Eat • –Water . . . . . . . Drink–Oxygen . . . . . breathe
Mineral Composition• Particle • Relative Diameter • • Clay • 1 x • • Silt • 100 x • • Coarse Sand • 10,000 x
Soil Texture • The relative proportion of clay, • silt, and sand particles present • in the soil.
Soil Textural Triangle illustrates 12 textural classes
Soil Structure•Clay, silt and sand particles are organized (glued together) into aggregates or soil structural units. • How they are organized within aggregates and the aggregates organized within the soil influences water movement and retention, aeration, nutrients, and root growth.
Soil Structure• Think of a sugar cube. • Hundreds of individual grains of sugar glued together to form an aggregate in the form of a cube.
Soil Structure•What happens if I step on the sugar cube ? •Can I put the sugar cube back together ? •What would be needed ? • Glue !
Specific Surface Areaa given volume of soil has differing specific • surface areas depending on the proportion of clay, silt and sand in the soil. • • Particle • Specific Surface Area • • Clay • 100,000 x • • Silt • 100 x • • Coarse Sand • 1 x
Specific Surface Area •A thimble full of clay particles has 100,000 times the surface area of the same thimble filled with sand particles.
Specific Surface Area • Water holding capacity • Internal drainage • Runoff potential • Nutrient retention • Herbicide application
Porosity• The size of pore spaces between soil particles determine the air and water characteristics of the soil. • Aggregated soils have excellent porosity. • Soils with excellent porosity have excellent permeability for air exchange, water movement, and root growth.
Aeration & Drainage •Not because A comes before D
Photosynthesis & Respiration • • Photosynthesis • Makes the food for the plant and stores it in plant tissues. Requires water from the soil. • • Respiration Breaks the food down into the basic building blocks for plant health and growth. Requires • oxygen from the soil and gives off carbon dioxide into the soil.
Soil Aeration • Soils must contain sufficient large pore space to allow oxygen to penetrate to the deepest of roots and carbon dioxide to exit from the soil.
Soil Aeration• Respiration – Oxygen limited roots are only 25% efficient •Nutrient Uptake – Decreased levels of oxygen in the root zone decrease the uptake of N, P, K, Zn, Cu, and B •Microbial Activity – Oxygen deficient soils have decreased numbers of beneficial organisms and increased numbers of pathogenic organisms •Root Growth – Oxygen deficiency or carbon dioxide toxicity kills root cells •Seed Germination – Germination is reduced when oxygen levels are reduced
Aeration Management• Promote soil particle aggregation • Maintain large, open pore spaces • Avoid destructive practices • Don’t smash the sugar cubes ! •If you must, then supply some glue to reform them.
Aeration Management • Maintain high organic matter in the soil
Manage the soil to provide a healthy environment for growth
Why do we : • • Use an aerator ?• Verti–cut or dethatch ? • Topdress a lawn ?
What is the effect of a layer of mulch in a shrub bed ? • • Can too much be a bad thing ?
Amendments to Garden Soils • • Organic materials –Compost –Manure –Peat moss • • Sand• Gypsum • • Other • – Snake oils
“Grow the roots and the top • will take care of itself”
Fertility & Fertilizers • • Nitrogen • – Highly soluble • • Leaches down out of root zone • – Volatilizes • • Exits soil as a gas into atmosphere • – One of three main fertilizer elements • – Vegetative growth • • The addition of nitrogen stimulates plant growth in ever increasing amounts
Phosphorus • Relatively insoluble • Attaches strongly to soil particles • Used by the plant • One of three main fertilizer elements • Primary function is energy transfer within plant process • Is not responsible for stimulating flowering
Phosphorus• Applying fertilizers containing high percentages of phosphorus does not increase flowering of plants in the landscape! • • High % P fertilizers only serve to cause extraordinary high levels of P to build up in the landscape over time. • • High % P fertilizers increase the pollution potential of our landscapes.
Nitrogen/Phosphorus Ratio• Is Nonsense! • • Phosphorus has nothing to do with flowering! • • It is the level of nitrogen that controls vegetative growth vs. flowering • • The presence or absence of excess nitrogen influences flowering!
Phosphorus • • A plant only needs sufficient phosphorus to meet its needs. • • More than enough is a waste and goes unused by the plant. • • The unused phosphorus carries over in the soil. If more is added next year, the buildup only continues.
Fertilizer • • Apply only what the plant will use • • Fertilize to maintain plant health and controlled vigor • • Fertilize with knowledge of what you are doing and the effect on plant growth and pollution potential.