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Matthew D. Taylor, Rachel Kreis and Lidia Rejtö

The pH of peatmoss generally ranges from 3.0 to 4.0 and limestone is typically added to raise pH to a suitable range. Compost is also used as a substrate component and typically has a high pH of 6.0 to 8.0. When using compost, lime rates must be reduced or eliminated. The two objectives of this study were to determine the resulting pH of substrates created with varying amounts of limestone and compost and assess the impact of the various amounts of limestone and compost on pH buffering capacity. Compost was created from a 1:1:1 weight ratio of a mixture of green plant material and restaurant food waste:horse manure:wood chips. The first experiment was a factorial design with five compost rates (0%, 10%, 20%, 30%, and 40% by volume), four limestone rates (0, 1.2, 2.4, and 3.6 g·L−1 substrate) with five replications. The experiment was conducted three times, each with a different batch of compost. With 0 lime, initial substrate pH increased from 4.5 to 6.7 as compost rate increased. This trend occurred at all other lime rates, which had pH ranges of 5.2–6.9, 5.6–7.0, and 6.1–7.1 for rates of 1.2, 2.4, and 3.6 g·L−1 substrate, respectively. Substrate pH increased significantly as either compost or lime rates increased. The second experiment was a factorial design with four compost rates by volume (0%, 10%, 20%, and 30%), the same four limestone rates as Expt. 1, and five replications. Each substrate treatment was titrated through incubations with six sulfuric acid rates (0, 0.1, 0.2, 0.4, or 0.7 mol of H+ per gram of dry substrate). Substrates with a similar initial pH had very similar buffering capacities regardless of the compost or limestone rate. These results indicate compost can be used to establish growing substrate pH similar to limestone, and this change will have little to no effect on pH buffering capacity.

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Rachel A. Kreis, Holly W. Lange, Stephen Reiners and Christine D. Smart

Twelve commercial cauliflower (Brassica oleracea var. botrytis) varieties were evaluated for horticultural traits and susceptibility to alternaria leaf spot (Alternaria brassicicola) at the New York State Agricultural Experiment Station in Geneva, NY, in 2014 and 2015. Data including total yield, curd weight, curd width, plant height, days to maturity, and length of harvest were collected for each variety. A duplicate trial was planted in each year and inoculated with A. brassicicola, the causal agent of alternaria leaf spot, and the percentage of disease was assessed for each commercial cauliflower variety. Most of the commercial varieties were similar in susceptibility to disease and yield. ‘Artica’ and ‘Apex’ were ranked among the highest yielding varieties each year of the trial. The varieties ‘Graffiti’ and ‘Violet Queen’, both of which produce purple curds, had significantly less alternaria leaf spot compared with other varieties. Differences were seen between the 2 years of the trial in performance of individual varieties as influenced by temperatures during the growing season. This study demonstrates that some cauliflower varieties perform better than others under New York State growing conditions.