HORTSCIENCE 48(12):1496–1501. 2013. (Francescangeli et al., 2006). In artichoke, Miguel et al. (2004) evaluated early- and late- maturing cultivars at 0.6 · 1.67 m and 1.2 · Planting Configuration 1.67 m (in-row · between-row). Increas- ing planting density increased early but not and Plasticulture Effects on total yield for early cultivars, whereas it did not affect either early or total yield for late Growth, Physiology, and Yield cultivars. Santoiemma et al. (2004) reported that yield of artichoke was unaffected by within- of Globe Artichoke row plant spacing of 0.5 to 1.4 m, although Daniel I. Leskovar1,2, Chenping Xu, and Shinsuke Agehara the total number of heads per unit area in- Texas A&M AgriLife Research, Department of Horticultural Sciences, Texas creased with closer spacing. Also Mauro et al. (2011) found that total head number based on A&M University System, 1619 Garner Field Road, Uvalde, TX 78801 area planted increased and early harvest yield Additional index words. Cynara cardunculus, earliness, ‘Green Globe Improved’, ‘Imperial decreased with increasing plant density over 2 Star’, photosynthesis a range of 1.0 to 1.8 plant/m . In terms of planting configuration, Sayre (1959) found Abstract. Globe artichoke is typically grown in Mediterranean and coastal areas. Because that tomato (Lycopersicon esculentum Mill.) of the high profitability as a specialty crop, demand to develop production systems plants in twin rows produced a high-quality optimized for other semiarid and water-limited regions is rising. Field experiments were crop with few fruit defects as compared with conducted over three seasons (2008–09, 2010–11, and 2011–12) in southwest Texas to standard single rows. In bell pepper, Kahn investigate plant growth, physiology, and yield of artichoke grown as an annual system. and Leskovar (2006) reported that a fixed Three strategies were evaluated: planting configuration (single and double lines per bed), plant population in a single-row arrangement plasticulture (bare soil and black plastic mulch), and cultivars differing in maturity resulted in an increase of full-season pro- (‘Imperial Star’, early; ‘Green Globe Improved’, late). Each fall, transplants were duction as compared with double-row arrange- established in the field at 2.03 m between rows and 0.90 m between plants (single line) or ment. In artichoke, planting configuration has 4.06 m between rows and 0.90 m between plants (double line). In both cultivars, black received very little attention, except for a plastic mulch enhanced plant growth (leaf number, plant height and width) and increased study in Italy where a single-row arrange- early yield; however, its effect on total yield and yield components was not consistent. ment increased artichoke earliness and total Single line per bed significantly increased head number of jumbo and large size per plant as head number per unit area as compared with a compared with double line in the 2009 season. Chlorophyll index was unaffected by either double-row arrangement (Mauro et al., 2011). planting configuration or plastic mulch. Comparing cultivars, ‘Green Globe Improved’ Plastic mulches are attractive in the cul- had lower marketable yield but bigger head size than ‘Imperial Star’ in one and two tivation of numerous horticultural crops. The seasons, respectively. Our results indicate that single line with black plastic mulch can be benefits of using plastic mulch include im- recommended to improve earliness and water savings as compared with the bare soil proved weed control, reduced evaporation system for annual artichoke production. and fertilizer leaching, savings in irrigation water, and prevention of diseases and insect vectors. These combined benefits result Commercial production of globe artichoke Valley regions of Texas and Yuma county in in enhanced plant growth, cleaner fruits, [Cynara cardunculus L. var. scolymus (L.) Arizona. and earlier and higher yields (Dı´az-Pe´rez and Fiori] in the United States is almost exclu- In semiarid regions, artichoke is typically Batal, 2002; Ham et al., 1993; Kasirajan and sively in California with major areas located grown as annuals (seed propagation trans- Ngouajio, 2012; Lament, 1993). Other stud- along the central and south coast, the Coach- plants) for 6 to 7 months. Transplants are set ies (Dı´az-Pe´rez and Batal, 2002; Hatt et al., ella Valley in the southern inland desert, and in the field in single lines on raised beds 1995; Lament, 1993) also reported that black the central valley. The total cultivated area at 0.45 to 0.75 m in-row and 1.6 to 2.0 m mulch greatly enhanced root-zone temper- has shown a decline in the last 2 years, from between-row spacing (Schrader et al., 1992; ature during spring, which might be benefi- 3480 ha in 2009 to 2990 ha in 2011 (U.S. Schrader and Mayberry, 1992; Socrat and cial to globe artichoke, because it is typically Department of Agriculture, 2012). How- Jani, 2000). Artichoke plants develop a dense grown during the winter/spring season of the ever, the average yield has increased to and large foliage biomass with a canopy reach- year (Basnizky, 1985; Shinohara et al., 2011). 14,570 kg·ha–1 with a total crop value of ing up to 2 m wide and 1 m high at maturity Research on the combined effects of black $48.5 million in 2011. A small number of for the early cultivar Imperial Star or even plastic mulch and planting configuration on hectares is also grown in the semiarid areas higher for new hybrid cultivars (Ryder et al., globe artichoke in southern regions of the of the Wintergarden and Lower Rio Grande 1983). Optimizing plant density and planting United States has not been reported. The aim configuration (arrangement between and within of this 3-year study was to determine plant rows) are important cultural practices of vege- growth, physiology, head yield, and yield table production because of their effects on components in response to planting configu- Received for publication 18 July 2013. Accepted for publication 9 Oct. 2013. plant growth, yield, and quality (Caliskan et al., ration and plasticulture of two artichoke This material is based on work partially supported 2009; Jett et al., 1995; Leskovar et al., 2012; cultivars differing in maturity. by the National Institute of Food and Agriculture, Nerson, 2002). Low plant stands can signif- U.S. Department of Agriculture under Agreement icantly reduce yield and economic returns as Materials and Methods No. 2008-34402-19195, ‘‘Designing Foods for a result of inefficient use of resources, whereas Health,’’ and Agreement No. 2008-34461-19061, high density may lead to plant competition Cultural practices. Experiments were car- ‘‘Rio Grande Basin Initiative,’’ and Texas Depart- for growth resources (Schotzko et al., 1984). ried out in three seasons, 2008–09, 2010–11, ment of Agriculture, Specialty Crop Grant Agree- Studies have been published on plant den- and 2011–12 (herein 2009, 2011, and 2012 ment 2011-SCFB-1112-020. sity for several vegetable crops including seasons, respectively) at the Texas A&M We thank Juan Esquivel, Manuel Pagan, and Ezequiel bell pepper (Capsicum annuum L.) (Cavero AgriLife Research Center, Uvalde, TX (lat. Cardona for their assistance in the field and Condor # # Seeds for providing seed materials. et al., 2001; Locasio and Stall, 1994), onion 29°1 N, long. 99°5 W, elevation 283 m). The 1Professor. (Allium cepa L.) (Leskovar et al., 2012; Russo, soil was a silty clay (fine-silty, mixed, hyper- 2To whom reprint requests should be addressed; 2008), muskmelon (Cucumis melo L.) (Nerson, thermic Aridic Calciustolls) with an available e-mail [email protected]. 2002), and broccoli (Brassica oleracea L.) soil moisture holding capacity of 17%. The 1496 HORTSCIENCE VOL. 48(12) DECEMBER 2013 main climatic difference among the three described by Shinohara et al. (2011). Total plasticulture treatments were the main plots, seasons was the average minimum temper- water inputs (rainfall and irrigation) for planting configuration treatment were the sub- ature in February, which was 8.9, 5.9, and each season are described in Table 1. Total plots, and cultivars were the sub-subplots. 8.7 °C for 2009, 2011, and 2012 seasons, fertilization applied as fertigation was 97N– Each replication consisted of 10 individual and rainfall received, which was 97, 146, and 25P–31K kg·ha–1 in the 2009 season, 120N– plants. All data analyses were run in SAS 243 mm for 2009, 2011, and 2012, respec- 33P–23K kg·ha–1 in the 2011 season, and (SAS Institute, 1993). Unless otherwise noted, tively (Table 1). In addition, the 2011 season 135N–43P–50 K kg·ha–1 in the 2012 season. P values # 0.05 were considered statistically had 9 d in February with minimum temper- Weeds, pests, and diseases were controlled significant. Main and interaction effects were ature below 0 °C, whereas only 3 and 5 d in as previously described (Shinohara et al., 2011). tested by analysis of variance. Multiple com- 2009 and 2012 seasons, respectively. Plant growth and leaf gas exchange parisons of least squares means were per- Three strategies were evaluated: planting measurements. Four plants per plot were formed by the Tukey’s Studentized range configuration (single and double line per bed randomly selected before the first measure- test. When there was no significant interac- with the same plant density of 5378 plants per ment. The following growth variables were tion, multiple comparisons were performed hectare), plasticulture (bare soil and black repeatedly measured on the selected plants within each main effect. plastic mulch), and cultivars differing in throughout development at various days after maturity (‘Imperial Star’, early; ‘Green Globe planting (DAP): leaf number per plant (only Results Improved’, late; herein IS and GGI, respec- green, not dry or senesced leaves), plant height tively).