Large dairies often use liquid manure handling systems because of their ease of mechanization and low labor requirements. Some of Idaho Magic Valley dairies use flushing systems that result in large amounts of liquid dairy manure that are applied via irrigation systems to adjacent cropland during the growing season. Solids and nutrients found in liquid dairy manure pose challenges to manure handling processes and cause environmental concerns. Separating solids and nutrients from liquid dairy manure is a critical step to improve nutrient use efficiency, reduce the negative environment impacts, and reduce manure handling costs. To better address solids/nutrients separation issue, a critical question needs to be answered: what are liquid dairy manure solid particle and nutrient distributions? Experiments were conducted to study the particle density, particle size, and nutrient (total nitrogen and total phosphorus) distributions of flushed dairy manure. Flushed liquid dairy manure samples were collected from three commercial dairies in the Magic Valley region of Southern Idaho. The particle densities of manure solids were determined by the pycnometer method using a methanol medium. Solid particle distribution was determined using a set of 6 sieves (4, 2, 0.5, 0.25, 0.125m and 0.063 mm) combined with the hydrometer method ASTM D7928-17 for particle sizes less than 0.063mm. Total nitrogen (TN) and total phosphorus (TP) was analyzed using a Hach spectrophotometer (DR 5000) based on Hach methods. The Pipette Methods ASTM D6913/D6913M-17 was used in conjunction with ASTM D7928-17 to exact liquid manure samples. The test results showed that particle densities of flushing dairy manure ranged from 1.32 g/cm3 to 2.20 g/cm3, which are smaller than the density of soil particles (2.65 g/cm3), solids of particles larger than 0.5mm were less than 50% of total solids (dry mass basis) for all three dairies, and liquid dairy manure phosphorus was mainly attached to particles with sizes smaller than 0.5mm.
