| heal.abstract |
A field study evaluated composted olive mill waste (OMC) as a soil amendmentin Cynodon dactylon (bermudagrass; C4) turf establishment and maintenance. The study comprised two substudies, each of which had discrete goals: 1) an evaluation of OMCeffects on overall bermudagrass growth over the course of 2.5 years when established byseed and subsequently from sprouting of existing rhizomes (2002 to 2004); and 2) a reevaluationof OMC effects on bermudagrass establishment by seed (2003). Twenty-fourplots (1.44 × 1.44 m) were filled with sandy-loam soil and supplemented with one of threeOMC proportions (low= 12.5%, medium = 25%, and high = 50% by volume, indicatedas substrates S:OMCL, S:OMCM, and S:OMCH, respectively), and non-amended soilserved as a control (S). The study evaluated: 1) the substrate's chemical and physicalcharacteristics, including bulk density, water retention curves, pH, and electricalconductivity (EC) measurements; 2) the establishment rate of C. dactylon, either byseed or by sprouting of existing rhizomes after dormancy as determined by measurementsthat included vertical detachment force (VDF), root growth, and substratemoisture; and 3) the growth rate of C. dactylon as determined through measurementsof visual quality, clipping dry weight, root growth, and VDF. The results show that OMCdecreased substrate pH in proportion to the OMC supplementation rate and increasedEC only at the end of the study and only in the plots with the highest supplementation rate(S:OMCH). Water retention was improved byOMCincorporation except from S:OMCL,which increased water retention only at low tensions. Compared with soil alone, bulkdensity decreased by 13.5%, 19.7%, and 32.8% as the OMC rate increased, respectively,from 12.5% to 50%. The OMC rate of 50% v/v resulted in a minor reduction in plantvisual quality during the cold periods but in a slight improvement during the warmperiods. The clipping dry weights were increased by OMC amendments in 2003, whichwas considered a disadvantage because of the insignificant visual quality differencesbetween substrates during the 2 study years. In 2004, the clipping yields were unaffectedby OMC rate. Root dry weight response to OMC varied. For the highest OMC rate, rootdry weight was lower during the cold and wet periods, greater during the first stages ofbermudagrass establishment by seed, and similar compared with soil without OMCduring turf establishment from the sprouting of existing rhizomes after dormancy. ThehighestOMCrate reduced resistance to vertical detachment force at four sampling dates(of six) during the 2002-2003 study, because the reduced root dry weight and/or increasedmoisture of the substrate facilitated bermudagrass detachment. In contrast, OMCsupplementedsubstrates resulted in increased VDF at the first sampling date ofestablishment both by seed (2003) and by rhizome sprouting after dormancy (2004). Itwas concluded that, when speedy establishment is imperative (such as in sod farms) orwhen irrigation is limited, an OMC rate of 50% by volume should be selected. Incontrast, for sustainable bermudagrass growth, a rate of 12.5% by volume is preferred,because it increases the visual quality of the grass and root growth. |
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