Correction of Soil Problems
Topic #4: Correction of Soil Problems – [Nov. 18, 2011] Dr. Eric Hansen, Dept. of Horticulture, Michigan State University; Eric grew up in Connecticut and earned degrees at Nasson College (BS), the University of Maine studying lowbush blueberries (MS), and Oregon State University working in orchard nutrition (PhD). He is now a Professor and Extension specialist in Horticulture at Michigan State University. His primary responsibility is to provide production information to berry crop producers. He also researches a variety of production topics, including fertilization, weed management, high tunnel berry production, growth regulator use, and organic production challenges for blueberries and raspberries. Teaching includes classes on Plant Mineral Nutrition and Berry Crop Production.
This was part of a 12-part “Soil and Nutrient Management for Berry Crops” webinar series, a project that was funded by NE SARE (Northeast Sustainable Research and Education Program), and which was organized by Marvin Pritts (Professor of Horticulture at Cornell Univ.) and Cathy Heidenreich (Extension Berry Specialist at Cornell Univ.).
Key Points and/or Points of Interest for Maine Cranberry Growers:
- Eric’s opinion is that it’s best to work with just one lab for having your analyses done, since the methods for nutrient extraction and analysis from different labs are, likewise, different.
pH and Sulfur:
- Optimum pH range is key! Use lime if it’s too low, and elemental sulfur (the preferred material) if it’s too high – comes as prills, chips, and powder, containing 90-95% sulfur. Some other acidifying agents: Iron sulfate reacts quickly in soils, but is more expensive than S because six times as much is required for the same pH reduction. It also may result in salt stress. Aluminum sulfate also reacts quickly, but requires high rates and may result in aluminum toxicity. Acidifying N fertilizers (e.g. ammonium sulfate) help maintain soil pH, but result in excessive N if used to adjust pH – 500 lb of S is equivalent to 1,400 lb (NH4)2SO4 (ammonium sulfate) or 294 lb N!
- In moist, warm, aerated soils, bacteria oxidize S to sulfuric acid; reaction of S may require a year; apply a year before planting and incorporate it for quickest reaction.
- If more than 500 lb is needed, split the application (over two seasons ideally); S can produce hydrogen sulfide in poorly drained soils, which is toxic to roots.
- Rock phosphate, in a low pH environment, can be a nice material for providing a slow release of a small amount of phosphorus over time. It is not very soluble in a high pH environment.
- Pre-plant Potassium – incorporate prior to planting at rates based on soil test results (choose materials based on: cost per unit of K2O, the need for other nutrients, and the potential hazard from chlorine). Sul-Po-Mag (Potassium-magnesium sulfate) is a good choice if you also need magnesium; otherwise, potassium sulfate, or potassium chloride (usually cheaper, but chance of chlorine toxicity; less risk if low amounts used and if used in the Fall).
- Pre-plant Magnesium and Calcium – incorporate prior to planting based on soil test results (choose materials based on: cost per unit of nutrient, need for pH adjustment, and need for other nutrients). If you need magnesium, but don’t want to raise your pH, then magnesium sulfate is a good choice. Likewise, if you need calcium, but don’t want to raise your pH, then calcium sulfate is a good choice.
- Ca, Mg, and K ratios are important, and here are the desired ranges for relative percentages: K (10-20%), Ca (60-70%) and Mg (20-30%) – in terms of the cation exchange sites.
Summary – Pre-plant Considerations
- Understand how soil texture, pH, nutrient content, and drainage vary across a site.
- Understand the properties of amendments and fertilizers before applications.
- Adjust pH well before planting.
- Build soil P, K, Ca, and Mg based on recommendations from soil tests.