Dairy Manure Compost Effects On Soilless Substrate EC and Plant Nutrient Uptake

The effects of mature dairy manure compost (DMC; EC=5.0 mS∙cm^-1; pH=7.7) on EC, pH and nutrient contribution in a peat moss-perlite substrate were evaluated. In six substrates, peat moss plus DMC (DMC at 5 to 30% as partial peat substitute) was held constant at 75% volume and perlite at 25% without limestone addition. Two additional control treatments of 75% sphagnum peat moss and 25% perlite were formulated with and without agricultural dolomitic limestone. Five rooted cuttings of pot chrysanthemum ‘Kory’ (Dendranthema x grandiflora (Ramat.) Kitam) were transplanted into each 16.5 cm diameter (1.4 L) plastic pot. Just after watering the newly transplanted plants with deionized water, substrate EC and pH, measured in pour-through extracts, were higher with each incremental increase of 0 to 30% DMC without limestone. EC and pH values ranged from 0.16 to 1.43 mS∙cm^-1 and 3.7 to 6.2, respectively. With the exception of the transplanting day, plants were fertilized at each irrigation with 17N-2.2P-14.1K neutral fertilizer at 250 mg∙L^-1 N for 12 weeks. On each of seven dates over 77 days of production, the EC levels of the unaltered substrate solution obtained by Rhizon samplers increased with increasing DMC rate. These EC levels of all substrates remained below the maximum general crop recommendation of 4.6 mS∙cm^-1 for unaltered substrate solution except in the 25 and 30% DMC substrates at days 56 and 77. Analysis of recently matured leaves at days 35 and 84 indicated that additions of DMC, compared to the control with limestone, resulted in higher concentrations of K, S, Fe, Mn, Zn, and Cu, but lower concentrations of N, P, B, Mo, and Na. When compared to the unlimed control, uptake was moderately higher for Ca at 35 and 84 days in the 10 to 20% DMC treatments and for Mg at 84 days in the 10% DMC treatment. At higher DMC levels, Ca and Mg declined to levels below the control. When compared to the control with limestone at day 84, Ca and Mg were lower in the DMC substrates, most likely due to the residual supply of these nutrients in the limestone. Maximum growth occurred in the 10% DMC substrate and declined at higher rates of DMC to the level in the control with limestone. Plant shoot dry weight in the 15 to 30% DMC substrates did not differ from the control with limestone.