402 Compost and Solarization Affect Broccoli Head Weight, but Not Yield

Some possible alternatives to soil fumigation with methyl bromide include soil solarization and the use of composts to modify soil microorganism populations. We tested combinations of solarization and compost on a broccoli ( Brassica oleracea var. botrytis L.) crop on an organic farm. Treatments were: solarization with compost (SC); solarization without compost (SW); compost only (NC); and an untreated control (NW). Dairy manure compost was applied manually to compost plots at 22 Mg/ha, raised beds were constructed, and solarization plots were covered with clear polyethylene from 13 July to 26 Aug. Black polyethylene mulch was applied to all plots, covering the clear polyethylene. Broccoli, cv. Packman, transplants were planted into the beds and fertilized with fish emulsion fertilizer three times for a total of ≈22 kg/ha N. Broccoli heads were harvested on 1, 5, and 9 Dec., trimmed to 15 cm, weighed and counted. Marketable yields were 8704, 7117, 8169, and 8374 (kg/ha) and mean head weights were 353, 228, 286, 313 (g) for SC, SW, NC, and NW, respectively. Under these conditions, head weights were highest with compost and solarization, and marketable yields were similar.