Soil Fertility and Forage Availability. Travis Harper Agronomy Specialist University of Missouri Extension

Transcription

1 Soil Fertility and Forage Availability Travis Harper Agronomy Specialist University of Missouri Extension

2 Outline Introduction Soil Testing Fertilizer Application Saving Money on Fertilizer

3 Introduction Forage management begins and ends with soil Soil provides: Support for the plant Aeration Water Nutrients

4 Plant Nutrient Requirements Macronutrients Nitrogen Phosphorus Potassium Sulfur Calcium Magnesium Micronutrients Iron Zinc Manganese Copper Boron Chloride Molybdenum Cobalt Selenium Sodium Silicon Nickel Vanadium

5 Nitrogen Primary component of a plant s growth processes In other words, it s what makes plants grow Almost always the most limiting nutrient in forage production

6 Phosphorus Extremely important nutrient Root growth and development Seed production Fruit production

7 Potassium The most important function of potassium is the osmotic pull that draws water into a plant s roots

8 Calcium Cell structure Uptake of nitrate Cell growth Soils are rarely deficient if limed

9 Magnesium Constituent of chlorophyll Chlorosis is a common deficiency symptom Grass tetany Magnesium sulfate Dolomitic limestone

10 Boron Nodule formation in legumes Soybean Alfalfa

11 Soil ph and Liming Extreme ph affects nutrient availability ph less than 5.0 causes aluminum toxicity ph less than 4.5 causes hydrogen toxicity ph for grasses needs to be at least 5.0 For many legumes, the minimum is 5.5 or higher Liming is the most important thing you can do for your soil

12 ph and Nutrient Availability

13 Outline Introduction Soil Testing Fertilizer Application Saving Money on Fertilizer

14 How do we know? Natural indicators Only way to know for sure is to test your soil

15 Proper Soil Testing 20 acres or less In MIG, each paddock separately Avoid trees, water and feeding areas Stay away from roads

16 Proper Soil Testing Take samples in a random pattern Sampling depth is 6 inches Best to use a soil probe or auger Discard organic material from top of sample Mix samples in a PLASTIC bucket Remove 1 pint to send to the lab Improper soil sampling is a waste of time and money!

17 Soil test data from one core is highly variable Soil test P (Bray-I, lbs./acre) Mean: 44 STD: Core number

18 Accuracy can be increased by dividing fields based on known variability Soil test P (Bray-I, lbs./acre) Overall Mean: 44, STD: 48 Old manure piles Pasture Pasture mean: 20, STD: 17 Feeding area mean: 114, STD: 52 Core number Feeding areas

19 Outline Introduction Soil Testing Fertilizer Application Saving Money on Fertilizer

20 Nitrogen Forms Plants uptake nitrogen in the form of either nitrate (NO 3 ) or ammonium (NH 4 ) Urea is converted to ammonium and carbonate ions Carbonate ions cause an increase in ph At high ph, ammonium is converted to ammonia (as much as 30% lost in 3 days) Agrotain delays this reaction from happening for up to 2 weeks

21 Nitrogen Sources Fertilizer Source Yield (tons per acre) Ammonium Nitrate 4.5 Urea 4.6 Ammonium Sulfate 5.3 Urea treated with Agrotain 4.8 Kallenbach, 2005

22 Nitrogen Application In grazing systems you may not need nitrogen fertilizer! Nitrogen also comes from organic matter, legumes, atmosphere If these sources provide adequate forage growth/distribution, additional nitrogen input may be unnecessary

23 Forage Availability Why do you raise cattle? How do you make more money? What is your biggest cost in raising cattle? What is the cheapest way to feed cattle? What forage provides the most grazing?

24 Nitrogen for Tall Fescue Unfertilized Forage Yield Herd feed requirement April June August October

25 Nitrogen for Tall Fescue Hay Traditional spring fertilization for Hay: - apply nitrogen in mid March - maximizes natural growth curve Forage Yield Herd feed requirement April June August October

26 Nitrogen for Tall Fescue Pasture Spring fertilization for Pasture: - apply nitrogen in early May - extends spring forage into July - less response, higher potential value Forage Yield Herd feed requirement April June August October

27 Nitrogen for Tall Fescue Pasture Forage Yield Herd forage demand Fall fertilization for Pasture: - apply nitrogen in mid August - increases and extends fall forage - less response, higher potential value April June August October

28 Outline Introduction Soil Testing Fertilizer Application Saving Money on Fertilizer

29 Soil Fertility Poor soil fertility is often the cause of poor yields, thin stands, legume failure, and plays a major role in weed pressure Applying needed lime, phosphorus, and potassium is critical You should follow recommendations on soil test

30 Fertilizer is Just Too Expensive New Seeding: Lime Phosphorus Potassium Nitrogen Established Seeding: Lime Nitrogen Potassium Phosphorus Better to use the Bucket principle

31 Bucket Principle

32 Alternative Fertilizer Sources Poultry Litter Ton of litter contains 63 lbs N, 55 lbs P 2 0 5, and 47 lbs K dollars worth of fertilizer Nitrogen is 10% inorganic, 90% organic Organic portion becomes available over time Distributes nitrogen more evenly over growing season

33 Poultry Litter Inorganic portion can be lost to volatilization, same as urea A portion of the rest can be lost to leaching Only about 50% of nitrogen is ever plantavailable Typical application rate is 2 tons/a Excessive phosphorus is an issue

34 Your Own Cattle 1400 lb cow 0.63 lbs of nitrogen per day 126 lbs per year lbs of phosphate per day 60 lbs per year lbs of potash per day 97 lbs per year Based on 200 grazing days per year

35 Your Own Cattle

36 N 2 Fixation in Mixed Stands Species N 2 Fixed (lb./a) Ndff Year 1 Older (%) Alfalfa Birdsfoot trefoil Red clover White clover (Ledgard and Steele, 1992; West and Mallarino, 1996)

37 Nitrogen or Legumes?

38 Legumes Stands with greater than 30% legumes need no nitrogen fertilizer Legumes must be inoculated prior to first seeding Legumes require higher soil fertility than grasses Legumes work very well in MIG systems 99% of pasture herbicides kill legumes

39 Questions? Test Your Soil!