PHYSICAL CHARACTERISATION OF THREE COMPOSTS MIXED WITH ONION WASTES

The compost produced from organic waste is increasingly used in horticultural production, as an organic amendment or substrate for seedlings. The aim of this study was to determine the physical quality of three compost obtained from the waste mixture onion, alfalfa and cattle manure; OMA onion-manure-alfalfa, OM onion-manure and OA onion-alfalfa, obtained after six months of composting. Sampling three replicates were performed for each mixture, reaching a volume of 10 L for natural compost determinations. The particle distribution more uniform showed EC 41% of particles located in the middle fraction, whereas OMA (28%) and OA (57%) did not show good particle distribution. Thickness showed the highest index aeration capacity and water retention in the OM (50%) and OA (49%) compost, while with 80% OMA, represent a lower drainage and excess water retention. The total pore space (EFA) with values ​​ranging between 70 and 80% in the three studied compost would be favorable for the circulation of air and water, allowing proper root growth. Substrate density (Ds) in the three compost were in the range of 500 to 700 kg m-3, whereas the true density or particles (Dp) values ​​of 2.360, 2.312 and 2.291 kg m-3 to OMA , OM and OA, respectively, coincided with those suggested by the authors for use as growth substrate. The aeration capacity 30% for OMA, 24% versus 26% for OA showed values ​​within acceptable ranges. The values ​​of water retention capacity (WRC) were: 40% (OMA), 46% (OM) and 47% (OA), less than those recommended for substrates. The results indicate that the OM onions and composted cow manure would be most appropriate for use in horticultural production as a component of substrate for seedlings and /or compost.