Inexpensive In-Field Manure Solids Tester

Manure losses from crop fields via surface and subsurface pathways following land application can lead to eutrophication and habitat destruction in surface waters. High solids manure has less susceptibility to runoff and leaching, which is particularly important in high risk fields with increased loss potential. Unfortunately, the determination of manure solids content is typically conducted by laboratory analysis where results are provided after field application has occurred. An inexpensive solids tester (less than $40 to construct) was developed out of readily available materials for manure applicators to determine the solids content of liquid dairy manure in-field and in real time prior to application. As manure samples are passed through the screen, solids are captured on the screen while more dilute manure passes through. In order to evaluate the solids tester, 33 manure samples were collected from 6 separate dairies with a variety of bedding types (3 farms used sand and 3 farms used recycled digested solids for bedding) and manure handling and processing systems. Results indicated that the manure volume that is retained on the screen can be related to the solids content of dairy manure from 3% to 9%. An equation was produced to relate manure solids to the volume retained on the screen, TS=1.7953e(0.0046Vr), with an r-squared value of 0.82. Manure samples with less than 3% solids were shown to pass through the screen completely, therefore results were inaccurate for low TS content. The results did not vary significantly for dairies which used sand bedding and those that used recycled manure solids. This quick in-field measurement of total solids content allows for application to appropriate fields, thus reducing the risk of manure losses to nearby waterways.