High Tunnel Fruit and Vegetable Production

1. High TunnelFruit and Vegetable Production Lesson Five: Soil Management and Fertility

2. 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.

3. 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

4. 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

5. 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 0.002 mm Clay = less than 0.002 mm

6. 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

7. 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

8. 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 (CaCO3) • Dolomitic [CaMg(CO3)2] • Calcium Oxide (CaO) • Calcium hydroxide (Ca(OH)2)

9. 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

10. 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

11. 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 ft2 = 3.1 yd3 • Must have an analysis of compost done • Must know dimensions of high tunnel

12. Calculating Application Rates Practice Problem 1 • Recommendation from soil test: 1 lb. N/1000 ft2 • Utilizing 24-4-12 pre-mix fertilizer • High tunnel dimensions: 24x48 • Divide amount recommended by percentage in mix • 1 lb/1,000 ft2 / .24 = 4.16 lb/1000 ft2 • Determine square feet of high tunnel • 24 x 48 = 1,152 ft2 / 1000 = 1.152 • Multiply recommended application by adjusted size of high tunnel • 4.16 lbs x 1.152 = 4.79 lbs of 24-4-12 mix

13. Calculating Application Rates Practice Problem 2 • Recommendation from soil test: 1.5 lbs K/1000 ft2 • Utilizing 0-0-60 premix fertilizer • High Tunnel dimensions: 20 x 36 • Divide amount recommended by percentage in mix • 1.5 lbs K/1000 ft2 /.60 = 2.5 lbs/1000 ft2 • Determine square feet of high tunnel • 20 x 36 = 720 ft2 720/1000 = .72 • Multiply recommended application by adjusted size of high tunnel • 2.5 lbs/.72 = 1.8 lbs of 0-0-60 mix

14. 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 ft2 = 3.1 yd3 • Compost analysis

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

16. 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

17. 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

18. 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

19. 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/yd3 • Useful in determining rate of application • Heavy Metals – Zn, Cd, Ni, Pb, Hg, Mo, As, Cr, Co • Overall Nutrient Profile – essential plant nutrients

20. 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

21. 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

22. 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

23. 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?

24. 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?