Increasing Plant Density in Eastern United States Broccoli Production Systems to Maximize Marketable Head Yields

Abstract

<jats:p>Increased demand for fresh market crown-cut broccoli (<jats:italic>Brassica oleracea</jats:italic> var. <jats:italic>italica</jats:italic>) has led to increased production along the eastern seaboard of the United States. Maximizing broccoli yields is a primary concern for quickly expanding eastern markets. Thus, a plant density study was carried out in Fall 2012 and 2013 using the hybrid cultivar Emerald Crown on a commercial farm in Summerton, SC, and in Fall 2013 using ‘Emerald Crown’ and another hybrid, ‘Durapak 19’, on a research farm in Charleston, SC. The objective was to determine the effect of variable within-row spacings of 4, 6, and 8 inches (using a system with double rows spaced 12-inches apart) on marketable yields and quality in the three environments. Our results indicated that increasing plant density by reducing within-row spacing to 4 inches significantly increased overall yield per hectare over the 6- and 8-inch spacing treatments at two of three environments. Stem diameter and average head weight were unaffected by plant density; however, heads harvested from plots with the highest plant densities had significantly (<jats:italic>P</jats:italic> &lt; 0.01) lower bead uniformity in the Summerton 2012 trial, and significantly (<jats:italic>P</jats:italic> &lt; 0.05) larger bead size in the two trials conducted in 2013. In general, the highest total marketable yields were from the 4-inch within-row spacing, but increased competition at the highest density may increase the risk of plants producing heads with lower quality characteristics. With the increased risk of producing lower quality marketable heads along with the increased production costs associated with the 4-inch spacing, yield and head quality attributes may be optimized at the 6-inch within-row spacing.</jats:p>

Performance of Broccoli Cultivars in Spring and Fall Evaluations in Pennsylvania

“…Higher plant populations can result in higher total yield (Ward et al, 2015). However, head and/or stem diameter was negatively correlated to plant population (Sterrett et al, 1991) or not dependent on plant population (Ward et al, 2015) likely due to cultivar and plant population used. A higher plant population than used in this study could be used in the mid-Atlantic region for markets where smaller heads are preferred.…”

“…When using bare ground or plasticulture systems with drip irrigation as used in this study, following pest management recommendations, and harvesting as heads reach maturity, growers can expect most cultivars to have similar head weights, regardless of production system and spring or fall growing season. 'Gypsy' and 'Emerald Crown' were common cultivars in two studies involving fall broccoli conducted in South Carolina (Farnham and Bj€ orkman, 2011b;Ward et al, 2015). 'Gypsy' was grown in a bare ground system with raised beds spaced 102 cm apart with a single row of plants spaced 15 cm apart for a population of about 25,000 plants/acre (Farnham and Bj€ orkman, 2011b).…”

“…In our fall study, mean head weight was 1.07 and 1.28 lb in the southwestern site and 0.58 and 0.56 in the southeastern site, both using plant populations between 6,800 and 17,000 per acre and cutting stems to 5 inches long. 'Emerald Crown' was part of a study evaluating plant density (Ward et al, 2015) and was planted in a plasticulture system using white 1-mm polyethylene mulch with populations of 43,724, 29,149, or 21,862 plants/acre. Mean individual head weight for the 29,149 population, which optimized head quality, was 0.48 to 0.63 lb.…”

“…Research has recently been conducted on breeding and evaluating broccoli adapted to high temperatures for summer production Bj€ orkman, 2011a, 2011b). Currently, in the mid-Atlantic, recommendations for plant populations can reach 32,000 plants/acre (S anchez et al, 2015) compared with California where plant populations reach 69,636 plants/acre (Ward et al, 2015). Recent research determined that head quality for crown-cut broccoli grown in South Carolina was optimized at a plant population of 72,000 plants/acre (Ward et al, 2015).…”

“…Currently, in the mid-Atlantic, recommendations for plant populations can reach 32,000 plants/acre (S anchez et al, 2015) compared with California where plant populations reach 69,636 plants/acre (Ward et al, 2015). Recent research determined that head quality for crown-cut broccoli grown in South Carolina was optimized at a plant population of 72,000 plants/acre (Ward et al, 2015). Determining the best yielding commercially available cultivars is another factor in commercial broccoli production.…”