ARS | Publication request: Impact of Composted Dairy Manure on pH Management and Physical Properties of Soilless Substrate

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2010
Publication Date: May 19, 2011
Repository URL: http://hdl.handle.net/10113/50056
Citation: Jeong, K., Nelson, P., Frantz, J. 2011. Impact of composted dairy manure on pH management and physical properties of soilless substrate. Acta Horticulturae. 891:173-180.

Interpretive Summary: Composted dairy cow manure was evaluated as a growth substrate substitute for commonly used components peat moss and limestone in two experiments. The three objectives were to quantify the impact of the compost on substrate pH throughout crop time, to see how compost influenced the physical properties of the growth substrate, and to evaluate compost's contribution to the plant's nutrition. Peat moss was mixed with 5, 10, 15, 20, 25, and 30% by volume of compost without limestone. The control treatments of 75% peat moss and 25% perlite were formulated with and without limestone. Pot chrysanthemum was used as the test species. They were transplanted into pots and fertilized at each irrigation with a complete fertilizer mix that did not contribute to root zone acidity in two different growing seasons. Additions of 5 to 30% compost raised initial substrate pH levels from 4.7 to 7.3. Although pH declined during plant production, the decline was similar in the typical, control treatments as in the compost treatments. Thus, pH buffering capacity of compost was similar to the limestone. The difference in shrinkage (compaction of substrate within the pot) of substrate throughout plant growth insignificant. Substrate density increased from 0.1 to 0.23 g•cm-3 as compost increased to 30%. Porosity decreased with increased compost while airspace was unaffected. The amount of water substrate mixes could hold was lower in the compost-containing substrate but did not vary with different amounts of compost. Plants grown with compost had higher leaf concentrations of K, S, Cu, Fe, and Mn and lower, but sufficient, Ca and Mg concentrations. The largest plants were grown in substrates containing 10 to 15% compost; all limestone and a portion of peat moss were effectively replaced with compost. In some situations, well characterized dairy compost can successfully be used as a locally-available, renewable substrate.

Technical Abstract: Dairy cow manure compost (DMC) was evaluated as a soilless substrate substitute for peat moss and dolomitic limestone in two experiments. The objectives were 1) to quantify the impact of DMC on substrate pH establishment and stabilization throughout crop time, 2) to test the effect of DMC on physical properties of substrate, and 3) to evaluate DMC as a nutritional source for plant growth. Peat moss plus DMC (at 5, 10, 15, 20, 25, and 30% by volume) was held constant at 75% volume and perlite at 25% without limestone. The control treatments of 75% peat moss and 25% perlite were formulated with and without dolomitic limestone (6g•L-1). Pot chrysanthemum ‘Kory’ (Dendranthema x grandiflora (Ramat.) Kitam.) plants were transplanted into 16.5 cm azalea pots and fertilized at each irrigation with 17N-2.2P-14.1K neutral fertilizer solution for 12 weeks in two different seasons. Additions of 5 to 30% DMC resulted in initial substrate pH levels of 4.7 to 7.3. Although pH declined during plant production, the decline was similar in the agricultural limestone and the DMC treatments. Thus, pH buffering capacity of DMC was similar to the limestone. The difference in shrinkage of substrate from initial irrigation to end of crop across the treatments was 2.9mm in Expt. 1 and 1.8 mm in Expt. 2. Shrinkage did not relate to addition of DMC and was of little commercial significance. Initial substrate measurements included dry bulk density (Db), total porosity (TP), container capacity (CC), air space at CC (AS), and available water between CC and 1.5 MPa (AW). Substrate Db increased from 0.1 to 0.23 g•cm-3 with DMC increases from 0 to 30%. TP decreased with increased DMC while AS was unaffected. CC and AW was lower in the DMC substrate but did not significantly differ across the DMC addition rates. DMC resulted in higher leaf concentrations of K, S, Cu, Fe, and Mn and lower, but adequate, Ca and Mg concentrations. Maximum plant growth (dry weight) occurred with 10 to 15% DMC. All limestone and a portion of peat moss were effectively replaced with DMC.