Recycling nutrients from horse manure: effects of bedding type and its compostability

Abstract

Manure constitutes a nutrient resource that should be efficiently recycled in agriculture. We assessed the nutrient cycling properties of three bedding materials (peat, wood shavings and pelleted straw) in horse manure by comparing their compostability, ability to retain nitrogen (N) and phosphorus (P) under rainfall and capacity to release N when mixed with soil. Manure with pelleted straw bedding had superior composting characteristics as it lost half of its dry mass, reached temperatures >60 °C and ended up having a carbon (C) to N (C:N) ratio of <15. In percolated water, 4-11% of total manure N and 5-23% of total manure P was leached during a 2 h 15 min event of artificial rainfall. Peat manure was most susceptible to P loss. In all fresh manures, C:N ratio exceeded 30, which led to net N immobilization in soil. Composting decreased the C:N leading to a slight positive or an insignificant fertilizer effect.

Trace Mineral Leaching from Equine Compost

“…The DM disappearance averaged 50% across all treatments (p > 0.10; Table 2). A comparable 50% DM loss has also been reported in other studies composting equine manure and pelleted straw [3,6].…”

“…Briefly, feces from horses supplemented with trace minerals (ING and ORG) had significantly greater concentrations of Cu and Zn, and tended to have greater concentrations of Co compared to CON [18]. Other studies have also reported an increase in mineral concentration after composting [6]. Despite greater concentrations of minerals in compost, these minerals have been shown to be more stable and less water soluble [6].…”

“…Over the course of the entire composting process involving multiple rain events, approximately 69% of initial P had disappeared from the compost pile [2]. In another experiment using equine straw-based compost, 7% of the initial P and 6% of the initial N leached during one simulated rainfall event [6].…”

The Effect of Diet Composition on the Digestibility and Fecal Excretion of Phosphorus in Horses: A Potential Risk of P Leaching?

“…Total P was analyzed spectrometrically (ICP-OES, Thermo Jarrel Ash Iris advantage, Franklin, MA, USA). The proportion of soluble P (phospahte-P, PO 4 -P) was analyzed from 1:60 water extracts using a continuous photometric flow analyzer (Aquakem 250, Thermo Fisher Scientific Inc., Vantaa, Finland) as described by Keskinen et al [31]. Because only a very low proportion (about 1%) of the phosphorus is excreted in the urine [8,10,12], urine was not collected in this experiment.…”

“…There may also be economic motives to catch the P in feces and absorb it in bedding materials, because the use of horse manure may reduce fertilizing costs. When horse manure is composted, its nutrients can be recycled and utilized [31], which reduces the use of inorganic fertilizers.…”