Understanding Manure, Slurry and Digestate: A Guide to Natural Fertilizers
The scent of manure often signals the arrival of spring in rural areas, but many are unaware of the distinctions between manure, slurry, and digestate – all valuable organic fertilizers that enrich the soil. Recent discussions have highlighted confusion surrounding these terms, underscoring the need for clear definitions.
Subtle Differences in Composition
Maren Ziegler, managing director of the Main Agricultural Association for East Frisia, defines manure as a mixture of feces and urine with bedding material like straw or litter. Slurry is primarily liquid urine, while manure is a solid combination of feces and urine with added straw or litter.1 All three serve as valuable fertilizers, returning essential nutrients to the soil to support plant growth.
Regulations and Timing for Application
Applying manure, slurry, and digestate isn’t a free-for-all. Regulations dictate the timing and quantity of application to minimize nutrient loss and prevent contamination of surface and groundwater.1 Agricultural operations are required to have sufficient storage capacity, with a minimum of two months’ worth of manure storage mandated.
Fertilizing Based on Plant Needs
While storage requirements exist, there are no rigid rules governing when to fertilize. Application should coincide with plant nutrient demands, varying based on crop type, weather conditions, and season.1 For example, grassland on dairy farms is typically fertilized in February or March, and then after each cut, which occurs every four to eight weeks.1 Essentially, each time forage is removed, nutrients are depleted from the soil, and manure or slurry replenishes them for continued growth.
Storage Requirements and Roofing
Storage facilities must be designed to prevent uncontrolled release of rainwater or seepage into the ground or water sources, often requiring features like sealed manure plates with collection systems. Though, installing a roof over storage areas is “not a mandatory legal requirement.”1
Recent concerns about a requirement to roof all manure heaps sparked debate, particularly among horse owners. Ziegler clarifies that all agricultural operations, regardless of size, are subject to the same legal standards regarding fertilizer, water, and environmental protection.1 Larger operations often have more advanced technology and verified storage capacities, but this doesn’t equate to environmental negligence.
The Necessity of Fertilization
Fertilization is crucial for maintaining nutritious food production. Plants require nutrients for growth and yield, and completely eliminating fertilization is impractical.1 Increasingly stringent fertilizer regulations can impact product quality, potentially affecting the suitability of grains for baking purposes.
1 Ziegler, Maren. (Main Agricultural Association for East Frisia – East Frisian Rural People, Norden-Emden district association). Personal communication.