6/23/14 Factoids on SC soils Over 100 different soil types Soils Soil type covering largest areas 7.0% Ben Lomond Complex 50-70% slope 5.6% Lompoc – Felton Complex 50-75% slope Managing Soils 5.8% Lompoc – Felton Complex 30-50% slope 5.7% Nicene – Aptos 50 - 70% slope Must be hilly around here 2.8% Watsonville Loam What is Soil? Variability of soils in your yard • Unconsolidated • Horizons – Layers • Thin layer on the surface of rock • Master horizons • Variable layer of – O, A, E, B,C and R mineral and OM • Usually biologically active • Three dimensional (really 4) Soil Tilth Soil Components • Physical condition of soil • Minerals (solids) – in relation to its suitability for planting or growing a – Rocks originally, breaking down to minerals crop. and secondary minerals • Factors influencing tilth include • Organic material (solids) – formation and stability of aggregated soil particles – moisture content – Mostly humus – degree of aeration • Pores – rate of water infiltration – drainage – Air and water • The tilth of a soil can change rapidly 1
6/23/14 What are these made up Soil Texture from? • Sand • Sand - Granite, few minerals – SiO 2 • Silt • Silt - Feldspar and Granites – K, Na, Ca • Clay • Clay – minerals. K, Al, Mg, Fe, Ca • Soil Texture is the proportions of these • So, this is were the plant nutrients come sizes from, aside from C, H, O and N – Sandy soil, clay soils Parent Material USDA Soil Texture Triangle • Since we know that rocks are the origin of soils, and rocks are made up of minerals and minerals are made up of ions … – Different soils coming from different PM will have different amounts of various ions. – Serpentine soils? Different amount of the bits Impact of soil particle sizes make up the soil texture • Look at the spaces • Think balls in a bucket 2
6/23/14 What can texture tell you? What can texture tell you? • Water? • Water? – Holding capacity • Nutrition? – Infiltration rate • Nutrition? – Sandy soils are typically low in nutrients • Soils with as little as 20% Clay act like clay – high whc and high fertility Texture Quiz • What texture do you think the soils are in Ben Lomond? • What texture do you think you find in the strawberry fields? • What texture do you think you will find on Beach Rd? Structure Particle Size Arrangement • Remember that soil tilth is influenced by • Aggregates influence physical the soils ability to form aggregation. characteristics of the soil • Structure is the particle arrangement – Increases pore space into aggregates (clay and humus being – Reduces soil density the “ glue ” ) – Water movement in large pores and held in small pores • Don ’ t plow that field if its too wet.. – Less erosion due to wind or water • Why? 3
6/23/14 Particle Size Arrangement Soil Pores • These aggregates are where all the • Soil is a 3 phase action is system, – Mineral uptake, water uptake, microbial communities, • Solids, liquid and – Aggregates will contain spaces between gas the different aggregates and inside aggregates, • Pores are of – Some large, some small, what we call different sizes pores Aeration Opps, no soil at all • Roots need air • Spaces or pores provide the space for air to move to the root zone • You do not overwater your plants, you under oxygenate them – How many of you have germinated an Avocado in a glass of water? Pores Lots of pores is good right? Water Holding Capacity • Water is held in the pores of soils • A soil with 50% porosity is great right? • Small pores hold water, larger pores – What if those pores are mostly small? hold air – What if those pores are mostly large? • The amount of water a soil can hold – Pore size distribution is key … . Not just the after saturation and draining away the total of pores but the percent that will hold excess is called the whc. water or air 4
6/23/14 Generalities on Soils Managing Sandy Soils • Lower total pores space but most pores • Sandy soils are large so they have great infiltration – Lower total pores space but most pores are rates but hold on to very little. large – Watering = more frequently – Water holding capacity is low (all big pores) • Nutrient holding capacity is low (no clay – Nutrient holding capacity is low (no clay and little OM) and little OM) – Fertilizing = more frequently but be careful not to leach lots Generalities on Soils Managing Clay Soils • Clay soils • Higher total pores space but most pores are small thus less aeration and WHC is – Higher total pores space but most pores high (all small pores) are small thus less aeration – Water holding capacity is high (all small – Slow infiltration rates, water slowly but pores) infrequently – Nutrient holding capacity is high • Nutrient holding capacity is high – Little fertilizer is needed Managing both Soils Organic Matter • Add a high quality OM • Organic Matter – Mostly dead – Not the same as mulch – Large and small – Fork it in – Plants, fungi, bacteria, algae, protozoa, worms, insects, mammals 5
6/23/14 Soil Food Web Living OM • Each micro organism has a very specific ecological niche in the soil • They occupy different spaces and different time • Each utilizes a particular source of material for energy • They prefer moist soils with lots of aeration Mineralization Mineralization • The soil organic matter is subject to • What are the microbes getting out of mineralization this? – Conversion of OM to inorganic nutrients – Microbe “eats” something, grows and makes more microbes – Nitrogen is not found in rocks, only OM – They gain energy by breaking down carbon bonds and use N for growth. – A bacteria has a C:N ratio of about 8:1 Natural System Natural System • What happens when man in not • What happens when man is involved? involved? – Plants grow – parts harvested – crop removed - microbes lack OM – nutrients – Plants grow – parts die – microbes (OM or fertilizers) must be added – plants mineralize – nutrients become available – grow plants grow – Where does that OM come from? 6
6/23/14 Inoculation Compost Tea • Adding microbes to soils • What is this stuff? – Why? – Unless the soil is subsoil, killed by toxic • Its not minerals you are brewing its chemicals, or flooded for years it will have microbes microbial activity • Put in compost – add sugar – pull out • Its just slow – so feed the microbes OM compost - – Planting legumes for the first time – inoculate with Rhizobium Nutrients Adding Nutrients • Plant need the nutrients in the soil - 16 - • Do you or don ’ t you? 18 depending on your resources • Tough question – Most soil borne nutrients have one or more – Why are you adding something? sources in the soil • Do you know what ’ s missing? – C, H and O are provided by the air and the • Can you guess from the soil type? water. • What if you add too much? – N comes from the air or from a bag … .. • Prescription without diagnosis is Malpractice Adding Nutrients Fertility of Soils • Adding too much fertilizers • Cation exchange capacity – Inorganic fertilizers are quickly taken up by – The soils ability to hold on to necessary microbes and plants plant nutrients • but the nutrients are also subject to leaching • Where? On the surface of clay and OM which is water running through the soil particles – Organic fertilizers are slowly broken down – Depends on what the soil was made from – What happens when you add more than • Granite vs basalt needed? • Mineralization – free ions – irrigation – leaching 7
6/23/14 Soil pH Soil pH • Soil pH can range from 1-14 • Major factors influencing soil pH • 7 is neutral, lower numbers are more – Parent material acid, higher are more basic • Lots of our soils are from rock made from calcium carbonate – Rain fall • No real generalizations apply here, • Rain with CO 2 makes carbonic acid some plants like an acid soils, some like – Majority of our soils are slightly acidic a more basic soil, generally has to do – Most subsurface water has high alkalinity with where the plant is native to Soil pH Soil pH • The key behind the importance of soil • For crops like Blueberries you need pH is that nutrients are not all soluble at acidic soils all pH ranges. – Do so before planting – Sulfur – finely ground – Some nutrients are “ tied up ” under low pH or high or both. – Add lots of Peat moss to containers – Our water is alkaline so you will need to continue to add acid • Its really hard to change • Use pine needles as much (not much help) – Especially with lots of OM and clay in the • Use Vinegar soil. What is my soil like? Artificial Soils • SC county has 100 different soil types • Wide variation of what is in the bag – Does it really matter exactly which one you – Potting mixes have? • Bark, coco fiber, peat moss, perlite, vermiculite – Not really, but it sure helps to know the texture. – Veggie mixes • http://websoilsurvey.nrcs.usda.gov/app/ • Maybe 1/3 soil, 1/3 bark and 1/3 compost HomePage.htm 8
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