Yard trimming-biosolids compost: Possible alternative to sphagnum peat moss in tomato transplant production

Large volumes of yard trimmings (YT) and biosolids (BS) co-compost have rec ently become available to the Florida vegetable industry. Compost used as v egetable transplant medium may be less expensive than traditional Sphagnum peat moss, since it can be locally produced. 'Agriset 761' tomato (Lycopers icon esculentum Mill.) seed were sown in five combinations of compost, peat , and vermiculite amended media: 0:70:30 (control), 18:52:30, 35:35:30, 52: 18:30, and 70:0:30 % by weight, respectively. The experiment was repeated 3 times over a one-year period to accommodate the Florida transplant product ion season. YT-BS compost were sieved to a particle size less than 2.4 mm ( 33% by weight) to be utilized as a transplant media. The YT-BS compost had a high initial EC that restricted plant growth in one of the three batches used. By mixing YT-BS compost with peat and vermiculi te the EC was reduced to an optimal 0 to 2 dS.m(-1) in the Fall 1997 and Sp ring 1998a experiments, but not for Spring 1998b. Transplant media with YT-BS compost increased tomato seedling leaf area and shoot dry weight 21, 28, and 35 DAS (days after seeding) compared with the control. Additionally, YT-BS compost increased root dry weight 28 DAS and final stem diameter 35 DAS compared to the untreated control. Leaf area and shoot dry weight 21 DAS and shoot and root dry weight 28 DAS decreased lin early as compost rate increased. Although root dry weight differences among YT-BS compost rates 21 and 28 DAS were evident, these differences disappea red 35 DAS indicating no effect of compost rate on transplant characteristi cs. Number of leaves 21, 28 and 35 DAS were similar among all treatments. U tilization of YT-BS compost in the Spring 1998a experiment at any rate prov ided a slow-release source of nutrients that produced a tomato transplant w ith higher quality characteristics compared with the traditional peat:vermi culite medium and mineral fertilizer application Once transplanted to the f ield, the differences that existed in the transplants grown in compost amen ded soilless medium disappeared. Fruit yields and size (i.e., large, extra- large, average fruit weight) between the control and compost treatments or among the compost rates were similar, except for the third harvest where th e control had more tomato size medium than YT-BS compost treatments. The results suggest that YT-BS compost can be used as an alternative to pea t media for tomato transplant production, and that the percentage of substi tution for peat is not critical. However, a lack of product physical and ch emical consistency would compromise vegetable transplant and bedding plant production. Our results indicate more quality control is required with this YT-BS compost before it can be used wholesale in these markets.