1/30/2016. Soil management. Essential Plant Nutrients. Regular soil sampling Nutrient management Soil ph and EC Soil organic matter

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1 Potassium management for Vegetable Production Dr. Ajay Nair Department of Horticulture Iowa State University Essential Plant Nutrients Carbon, Hydrogen, Oxygen Macronutrients Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur Micronutrients Manganese Zinc Boron Copper Iron Molybdenum Sodium, Chloride, Nickel, Cobalt, Silica Soil management Regular soil sampling Nutrient management Soil ph and EC Soil organic matter When to Take Soil Samples? For fall planting, sample should be taken in the spring. For spring planting, sample should be taken in the fall. Spring Fall What does a soil test indicate? ph and lime recommendations Organic matter Cation Exchange Capacity Phosphorus and Potassium Nutrient recommendations based on crop Mg and Ca Micro nutrients upon request Nitrogen Recommendation, but not generally based on tests Where to send samples? Iowa State University Soil Testing Laboratory G501 Agronomy Hall, Iowa State University, Ames, Iowa A&L Heartland Laboratories, Inc. 111 Linn Street, PO Box 455 Atlantic, IA

2 High tunnel challenge: nutrient supply o Crops under high tunnels often outperform field grown plants o Nutrient management is critical o Nutrient imbalance can cause deficiency or toxicity Importance of potassium o Potassium is used in carbohydrate metabolism and increases water-use efficiency o It promotes flower and fruit production and is vital for maintaining growth and helping plants resist diseases o Regulates transpiration by stomata and transport of assimilates o Increases leaf area and chlorophyll content o Delays leaf senescence and thus contributes to greater canopy photosynthesis and crop growth o Chemical fertilizers Sources of potassium o Potassium chloride (Muriate of potash) (50% K) o o Potassium nitrate (37% K, 13% N ) o Potassium sulfate (40 43% K, 18% S) Commercial Forms of potassium Apply 1/2-1/3 of the total potassium before planting o Potassium chloride (0-0-60) o Potassium sulfate (0-0-50) Potassium Sources OMRI approved o Potassium Sulfate (0-0-50, 18S) o K-Mag (0-0-22, 22S, 11Mg) o Langbeinite o Muriate of potash (0-0-60) KCl, only if mined, chloride buildup o Kelp (0-0-2) 2

3 Compost Compost nutrient levels o Excellent organic amendment o Incorporate 4-6 inches o Be careful about the quality o Key issues Needed in large quantity high salt content herbicide residue Manure type Nitrogen P K % dry weight basis Dairy manure Feedlot manure Poultry manure Crop residue Calculation of N credit from compost Say you apply 10 t/a 50% is moisture so technically you applied 5 t/a (10,000 lbs) N present = 1.5% of 10,000 = 150lbs Only 20% is available in the first growing season Crop availability = 30lbs Tomato crop requires around lbs/a nitrogen Calculation of K credit from compost Compost applied 5t/A (dry weight basis) 1.5% P = 150 lbs/a P 2 O 5 equivalent 1.5% K = 150 lbs/a K 2 O equivalent Compost application can result in excessive P and K P rapidly accumulates Material Organic form % P content in Inorganic form Dairy manure Poultry manure Composted manure Swine manure 9 91 Earlier example of P 75% available = 112 lbs Optimum nutrient management o Preplant o Phosphorus is usually completely applied preplant o Fertigation: Mostly used to apply nitrogen and potassium 3

4 SOIL ORGANIC MATTER Soil organic matter Ranges Low Medium High Less than 3% More than 10.1 Relative soil test levels for Phosphorus and Potassium (ppm) Low Medium Med.-High High V. High P K Potassium management for tomato production Potassium from soil test (ppm) Apply (lb/a) Fertigation schedule At pre-plant apply 50 and 100 lb/a of N and K 2 O respectively Days after planting Weekly N lb/a Weekly K 2 0 lb/a Pre-plant - - Up to 3 weeks weeks weeks weeks weeks Availability of soil nutrients depends upon soil ph ph is a measure of the soil s level of acidity and is the single most important factor to know about your soil! ph Tolerance of vegetables to ph If ph >7, less available Phosphorus Boron Copper Iron Manganese Zinc Asparagus Beets Cabbage Muskmelon Peas Spinach Celery Chives Lettuce Onion Radishes Cauliflower Sweet corn Pumpkins Tomatoes Most sensitive Snap beans Carrots ph <5.5, less available Calcium Magnesium Molybdenum Best range for most veggies on mineral soils Cucumbers Parsnips Peppers Hubbard squash Eggplant Watermelon Potatoes Source: Swiader and Ware 4

5 Check your soil EC Based on saturated paste extract method < 2 mmhos/cm = optimum 3-4 = plants show initial symptoms 5-7 = growth affected > 8 = detrimental; plant death Deficiency Symptoms of Potassium in Tomato o Woody stems and slow growth. Stems become weak and fall down o Leaves may also have a bronzed appearance and yellow and orange patches may develop on some of the leaflets o Older leaves may look scorched around the edges and/or wilted. Symptoms first appear on older leaves Deficiency symptoms of K in leaves Source: 5

6 Tomato water needs Cover crop for high tunnels o An excellent opportunity to build organic matter o Improve soil physical, chemical, and biological properties o Nutrient management o Crop rotation Lewis Jett, WVU Yellow mustard 6

7 Many Thanks Brandon Carpenter Dana Jokela Jennifer Tillman Ray Kruse Kyle Tester Bernie Havlovic Nick Howell Vince Lawson Blossom end rot in pepper Contact Dr. Ajay Nair Phone: Its gonna come! iowavegetables.blogspot.com extension.iastate.edu/vegetablelab 7