Chapter 15 Organic Amendments

Objectives After completing this chapter, you should be able to: Explain the benefits of organic amendments Describe how to use animal manure Describe how to use biosolids Explain composting List environmental side effects of fertilizers and amendment

Organic Amendments Benefits Raise soil nutrient levels Contain a mixture of nutrients and secondary and trace elements Act as soil storehouse for nutrients Contain much organic matter that improves soil physical condition Support growth of beneficial organisms Can produce higher yields than complete fertilizers Good use of waste products

Animal Manure Benefits Good amounts of nitrogen and potash Adds organic matter to the soil Longer-lasting effects than chemical fertilizers

Animal Manure (cont’d.) Problems Excessive application of phosphorus Excessive application of manure Nitrates leaching under animal confinement areas Organic runoff to lakes and streams Transporting human pathogens Gaseous air pollutants Human health considerations

Animal Manure (cont’d.) Content Primarily animal urine and feces Liquid Solid Nutrient content factors Type of animal Amount of animal bedding Age and health of animals

Animal Manure (cont’d.) Nutrient losses from manure composed of urine Contains about 50% of the nutrients A great deal of it drains away through barn floors, feedlots, and manure heaps

Animal Manure (cont’d.) Handling manure Solid Best spread immediately on unfrozen ground and quickly plowed into soil If cannot be mixed into the soil immediately, it should be stored properly and then applied when it can be plowed Liquid Best for saving nutrients Can be spread through irrigation Best injected into soil

Animal Manure (cont’d.) Best management practices Test manure and soil for nutrients Base application rates on phosphorus needs Spread evenly with calibrated equipment Incorporate or inject into soil as soon as possible Increase time animals spend on pasture rather than on a feeding operation Design the animal feeding program to reduce phosphorus content of manure

Animal Manure (cont’d.) Sensitive areas Environmental concerns Nearby waters Soil or terrain that promotes runoff or leaching

Animal Manure (cont’d.) Regulations for CAFOs Require a nutrient management plan if large animal numbers (1000 cattle or 2500 swine) are present Minimize nutrient excretions Store manure properly Land application at agronomic rates for N and P Setbacks and buffers Periodic soil testing

Biosolids Sewage sludge Benefits Problems Disposes of human waste Provides plant nutrients Problems Pollutants: heavy metals and pesticides Human pathogens: diseases and parasites Pest vectors: insects and rodents Soluble salts Odor

Biosolids (cont’d.) Application guidelines Federal rules set standards application Apply to common sites of land application, such as agricultural land, nurseries, or reclamation sites EPA classifies biosolids that can be spread on land as Exceptional Quality (EQ) or High Quality (HQ)

Compost Benefits Reduces carbon to nitrogen ratio Reduces weight and volume of organic wastes Mineralizes slowly; better enhances soil Heat in piles may kill weed seeds Can encourage organisms that suppress root pathogens

Compost (cont’d.) Three stages of composting Mesophilic: decay begins and temperature rises Thermophilic: temperature rises to around 150°F Curing: stabilization occurs

Fertilizers and the Environment Concerns Animal and human health Nitrates Eutrophication Overgrowth of algae Hypoxia Low oxygen conditions in water Phosphorus discharge

Fertilizers and the Environment (cont’d.) Energy costs High energy costs Increased farming costs Human changes to the global nitrogen cycle Humans now create as much biologically active nitrogen (e.g., nitrates, ammonia) as all the natural processes combined by fertilizing and cultivating legumes

Fertilizers and the Environment (cont’d.) Best management practices Conservation tillage and efficient irrigation Proper handling of manure Efficient delivery times and application methods Precise application and careful use of fertilizers Use of slow-release fertilizers and controlled drainage Vegetative buffers and cover cropping Budgeting nutrient inputs Organic and sustainable agriculture practices

Summary This chapter reviewed several topics Manure, biosolids, and composting provide benefits by adding nutrients and organic matter to the soil It is better to use these wastes rather than just dispose of them They do present some environmental concerns Managed properly, these organic amendments are a safe and an important resource