Abstract The use of anaerobic digesters is increasing to produce energy, and digested manure is used as a soil amendment. These studies continued experiments that evaluated the effects of replacing translocated topsoil (soil–landscape rehabilitation). Crop response and soil properties were evaluated in highly eroded land with (a) no amendment; (b) 15–20 cm of soil added once in Fall 2005; (c) 40 Mg ha −1 of manure solids added once in Fall 2011; and (d) both soil (2005) and manure solids (2011) added. Crop and soil parameters were monitored for 5 years, during which weather conditions were near normal. Corn ( Zea mays L.) yields increased an average of 14%–15% by adding soil and/or manure, and by 23% in the combined treatment. Soybean ( Glycine max L.) yields increased an average of 18%, 22%, and 28% in the soil, manure, and combined treatments, respectively. Manure solids had no impact on soil C concentrations, whereas soil addition increased surface soil organic C concentrations by 2× and decreased inorganic C by about 45%. Soil nutrients in the combined treatment were approximately the sum of the increases due to the individual treatments. Changes in P were mostly due to manure solids, and changes in N and K were due to soil addition. There were strong relationships between soil properties and crop responses. These results showed that soil amendment with digested dairy manure solids has the potential to improve crop yields, producing under favorable growing conditions a yield response similar to that achieved by replacing topsoil 6 years earlier.
Schneider et al. (Sun,) studied this question.