ABSTRACT.
The effects of mulches of dairy manure solids (DMS) and composted dairy manure solids (CDMS) on soil N and P dynamics, nematode community structure, and root growth were studied over three years in a new field of raspberry planted in northwestern Washington. Five fertilizer/mulch treatments were applied to 16-m-long row plots: (1) 34 kg N ha−1 applied as granular fertilizer in April; (2) 34 kg N ha−1 applied in May; (3) split application of 34 kg N ha−1 April + 34 kg N ha−1 May; (4) 34 kg N ha−1 fertilizer + DMS; and (5) 34 kg N ha−1 fertilizer + CDMS. Cumulative applications of DMS and CDMS were 28 and 49 Mg dry material ha−1 concentrated on the raspberry row, respectively. Adsorption of NO3-N and P onto anion-exchange resins, and October soil NO3-N concentrations, were lower in mulched soil than in non-mulched soil, but leaf N concentrations were greater in mulch treatments. Fine root biomass and the abundances of bacterivorous, fungivorous, and omnivorous-predacious nematodes, and the nematode Structure Index were greater in mulched soil than in non-mulched soil. Mulches had no effect on root-lesion nematodes (Pratylenchus penetrans) infecting roots. Our results suggest that mulches of composted or non-composted DMS can enhance root growth, overall soil biological activity, and nutrient acquisition while also reducing soil mineral N pools and the risk of nitrate leaching. There were no substantial differences between composted and non-composted DMS.
ACKNOWLEDGMENT
The authors thank Mike Particka, Washington State University, for field technical assistance.