LESSON FIVE: SOIL MANAGEMENT AND FERTILITY High Tunnel Fruit and Vegetable Production

Objectives Recall soil’s physical and chemical properties and how they affect nutrient management. Calculate the fertilizer needs in a high tunnel based on soil test recommendations. Identify characteristics of compost and what affects the decomposition rate. Recognize salinity issues associated with high tunnel production.

Soil Management Considerations Site location is key to high tunnel production  Sunlight  Drainage  Wind protection Soil type is of less importance  Can grow in modified raised beds and soilless media In this lesson, assuming that structure is moveable and soil management is key consideration

Importance of Soil Anchor plant in place Provide water and some needed nutrients Oxygen for root growth Major Components of Soil  Physical Properties  Chemical Properties  Air  Water

Physical Properties Sand, Silt and Clay Characteristics of A High Clay Content Soil:  High water-holding ability  High cation exchange capacity  Low infiltration rate  Warms up slowly in the Spring  Resists change to pH Soil Particle Sizes Sand = 2 mm to 0.05 mm Silt = 0.05 to mm Clay = less than mm

Physical Properties Characteristics of a High Sand Content Soil:  Low water-holding capacity  Some nutrients are prone to leaching  Warms up quickly in the Spring  Shows a rapid change in pH Good location for high tunnel (soil standpoint)  Well-drained loam soil with high organic matter  Less than 28% clay ideal  pH of 6.5 on upper part of landscape  Northwest windbreak

Chemical Properties 17 elements are needed by plants  Three are never limiting  14 may or may not be in adequate amounts  Depend upon soil type and pH Ideal pH for most vegetables: 6.2 to 6.8 Soil tests and plant analyses can determine if essential nutrient levels are adequate

pH and Liming Recommendations Adequate pH is single most important soil amendment factor Low pH can be improved through amendments Liming Sources  Ground Limestone  Calcite (CaCO 3 )  Dolomitic [CaMg(CO 3 ) 2 ]  Calcium Oxide (CaO)  Calcium hydroxide (Ca(OH) 2 )

pH and Liming Recommendations Use agricultural limestone  Requires certification Be careful, do not over apply:  Change in pH, detrimental to plant growth  Decrease in availability of P  Deficiencies in Fe, Mn, Zn and sometimes Cu  Reduced root uptake of B

pH and Liming Recommendations In most soil tests, N is not reported  May request report of N content for high tunnels Be careful not to purchase more than needed  Calculate fertilizer needs

Calculating Application Rates Always determine need based on soil test recommendations Most recommendations give in lbs/acre  43, 560 square feet in an acre If applying compost  1 cubic yard = 182 gallons  1 inch of surface compost over 1,000 ft 2 = 3.1 yd 3  Must have an analysis of compost done Must know dimensions of high tunnel

Calculating Application Rates Practice Problem 1 Recommendation from soil test: 1 lb. N/1000 ft 2 Utilizing pre-mix fertilizer High tunnel dimensions: 24x48 1) Divide amount recommended by percentage in mix - 1 lb/1,000 ft 2 /.24 = 4.16 lb/1000 ft 2 2) Determine square feet of high tunnel - 24 x 48 = 1,152 ft 2 / 1000 = ) Multiply recommended application by adjusted size of high tunnel lbs x = 4.79 lbs of mix

Calculating Application Rates Practice Problem 2 Recommendation from soil test: 1.5 lbs K/1000 ft 2 Utilizing premix fertilizer High Tunnel dimensions: 20 x 36 1) Divide amount recommended by percentage in mix lbs K/1000 ft 2 /.60 = 2.5 lbs/1000 ft 2 2) Determine square feet of high tunnel - 20 x 36 = 720 ft2 720/1000 =.72 3) Multiply recommended application by adjusted size of high tunnel lbs/.72 = 1.8 lbs of mix

Calculating Application Rates Problem 3 – Utilizing Compost Manure Compost Application Problem Handout Given:  Nitrogen recommendation is 60 lbs per acre  High tunnel dimensions are 21 ft x 96 ft  1 cubic yard = 182 gallons  1 inch of surface compost over 1,000 ft 2 = 3.1 yd 3  Compost analysis

Organic Matter Soil organic matter is derived from: Decomposition of organic residues + excretions from microorganisms and microbial cells End product called humus

Organic Matter Decomposition Rate Depends On:  Environmental conditions  Particle size of organic material  Cultivation frequency  Depth of tillage  Irrigation  Type of organic matter  Crop rotation

Organic Matter Benefits of Adding Organic Matter to Soil:  Provides a nutrient reservoir of N, P, and S  Retains nutrients in an available form  Increases aggregate formation  Increases soil porosity

Organic Matter Considerations when adding organic amendments to the soil  They are highly variable in composition & quality  No standards for labeling exist  Make sure you analyze each load or shipment  They are more expensive to transport, store, purchase and apply  Some may contain sewage sludge

Compost Chemical Analysis pH – 6.0 to 7.5 Ec (electric conductivity or salinity) – 5.0 or less C:N Ratio – recommend an initial of 30:1 Bulk Density – Soilds/moisture content  Expressed as lbs/yd 3  Useful in determining rate of application Heavy Metals – Zn, Cd, Ni, Pb, Hg, Mo, As, Cr, Co Overall Nutrient Profile – essential plant nutrients

Salinity Salt buildup in high tunnel soils is prevalent issue  Particularly when cover is left on year round Leave sides rolled up in winter  Snows and late winter rains leach salt from root zone Symptoms of High Soil Salinity  Root dieback, root tips burn off  Plant stunting  Leaf burn  Wilting

Salinity High Salinity in Root Zone May Result From:  Poor placement of fertilizer  Fertilizer salts mainly due to K and nitrate  Evapotranspiration greater than irrigation  Too much fertilizer applied  High water table

Salinity To Reduce High Salt Levels:  Monitor salt levels with the Ec test  Place tunnel on well-drained site, add tile line  Be careful with nutrient applications,  Do not over fertilize  Limit use of organic sources containing manures  Keep sides rolled up in winter  Leach salt downward in soil profile via irrigation  Constant watering with trickle irrigation techniques

Soil Management & Fertility: In Review Why is soil management and fertility important to growing produce in a high tunnel? What are the physical properties of soils? From the standpoint of soil physical properties, what is ideal for the placement of a high tunnel? How do soil chemical properties influence nutrient management? Why is soil pH important to plant health? What is the ideal soil pH for most vegetables? How can soil pH or nutrient value be altered?

Soil Management and Fertility: In Review Why is it important to calculate fertilizer applications? What are some characteristics of compost? What influences the decomposition rate of compost? What are benefits of adding organic matter to soil? What should be considered before applying compost? Why is salinity an issue for high tunnel production? What happens when soil salinity gets too high? What can be done to reduce salt levels in soils?