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Hot pepper (Capsicum annuum cv. Battle) was grown in a 1:1 v/v sand-to-cotton stalk compost and subjected to four irrigation treatments: 100% of water-holding capacity (control) and 85%, 70%, and 55% of water-holding capacity, which were considered deficit irrigation treatments. All treatments were given to the plants at the first day of transplanting and continued during the whole growing season. Our results demonstrated that deficit irrigation had a negative effect on plant growth and yield. Increasing irrigation deficiency exhibited a reduction in vegetative growth, fruit parameters, and yield and a nonsignificant increase in irrigation water use efficiency and a corresponding reduction in the amount of irrigation water. Vitamin C content in fruit was significantly decreased by deficit irrigation treatments at various ripening stages. Water-holding capacity of 100% and 85%, respectively, resulted in the highest content of vitamin C obtained at the ripening stage. We concluded that ‘Battle’ hot pepper is sensitive to deficit irrigation. Supplying this cultivar with water at 85% of water-holding capacity could be a practical irrigation technique for high value of vitamin C production as well as saving a large amount of water, which outweighs the decrease in total fresh yield of fruit, especially in areas suffering from water shortage. Available water for agriculture is becoming limited all over the world, and there is an urgent necessity to adopt effective strategies of irrigation management. Deficit irrigation is a strategy that allows a crop to tolerate some degree of water deficit to reduce costs and potentially increase income. It can lead to increased net income where water costs are high or where water supplies are limited (English and Raja, 1996). Hot pepper (Capsicum annuum) is a crop of major economic importance and is commercially cultivated in China, Korea, East Indies, the United States, and many other countries. Its cultivation is confined to warm and semiarid countries where water is often a limiting factor for production, which makes the optimization of water management necessary. Pepper is among the most sensitive horticultural plants to deficit irrigation because of the wide range of transpiring leaf surface, high stomatal conductance (Alvino et al., 1994), and its shallow root system (Dimitrov and Ovtcharrova, 1995). Pepper fruits are a rich source of antioxidant compounds (Howard et al., 2000; Marı́n et al., 2004; Palevitch and Craker, 1995). Dietary antioxidants are beneficial because of their protective roles against multiple diseases such as cancer, anemia, diabetes, and cardiovascular diseases, and it is becoming increasingly important for growers who want to satisfy the demand of consumers for products with a high content of healthpromoting constituents. Vitamin C is an important antioxidant compound of pepper fruits, chelating heavy metal ions (Namiki, 1990), reducing the risk of arteriosclerosis, cardiovascular diseases, and some forms of cancer (Harris, 1996). The effect of deficit irrigation on hot pepper growth and yield is controversial. Although negative effects of deficit irrigation on pepper fruit yield have been reported by several investigators such as Abayomi et al. (2012), Dagdelen et al. (2004), Dorji et al. (2005), Ferrara et al. (2011), Gencoglan et al. (2006), Ismail (2010), Kirda et al. (2007), and Kulkarni and Phalke (2009), others found that fruit dry mass was increased (Chartzoulakis and Drosos, 1997) or unaffected by water stress (Ruiz-Lau et al., 2011). This was accompanied by a decrease in plant height, root dry weight, and root/ shoot relation compared with those plants irrigated daily. Although increasing water use efficiency by decreasing water application was proposed unattainable by Abebe (2009) because yield reduction is remarkably higher as a result of decreased water supply, Ismail (2010) found that giving 85% and 70% of the field capacity saved 41% and 85%, respectively, of the irrigation water. Several investigators have reported a negative effect of water stress on fruit content of vitamin C such as Mahendran and Bandara (2000) on chili cultivar Arunalu and Vijitha and Mahendran (2010) on tomato. On the contrary, vitamin C content showed a 23% increase when peppers were less watered compared with high-irrigated fruit (Marı́n et al., 2009). An increase in vitamin C content with moderate water deficits was demonstrated by Toivonen et al. (1994) on broccoli and the same results observed in leeks grown under low irrigation frequency (Sorensen et al., 1995). Maturity stage also affects vitamin C content. Marı́n et al. (2009) found that green peppers grown under low irrigation frequency had similar content of vitamin C to red fruits and only the highly irrigated green fruits showed lower content of vitamin C with respect to red fruits. Navarro et al. (2006) found that red peppers had more vitamin C content than green ones. Other authors have found that vitamin C increased or remained constant as pepper fruits matured (Howard et al., 1994, 2000; Osuna-Garcia et al., 1998) and declined with further ripening (Gnayfeed et al., 2001). Thus, because of varied effects of deficit irrigation on fruit, yield, and vitamin C content in hot pepper, this study was conducted to evaluate the effects of deficit irrigation on morphological and fruit parameters, growth, and yield of ‘Battle’ hot pepper as well as vitamin C content at different ripening stages. We aimed also at determining the critical deficit irrigation level for good growth, fruit yield, and high vitamin C content of this cultivar to save a high amount of water irrigation. Materials and Methods A greenhouse experiment was conducted at the Soilless Culture Department, Vegetables and Flowers Institute, Chinese Academy of Agricultural Sciences, Beijing, China from May to Aug. 2012. During the growing season, the average temperature and relative humidity were 26.3 C and 67.8%, respectively. Growth medium and plant materials A sand-to-cotton stalk compost (1:1 v/v) was used as a growth medium; 7 L were used per pot. The physical and chemical properties of the growth medium used in this study are presented in Table 1. The seedlings of hot pepper (Capsicum annuum cv. Battle) were transplanted at the eight-leaf stage, one plant per pot. Fertilization A mixture of organic and inorganic fertilizers, containing nitrogen, phosphorus, and Received for publication 3 Mar. 2014. Accepted for publication 31 Mar. 2014. This work was supported by the earmarked fund for the China Agricultural Research System (CARS-25-C-09), the Science-Tech of Agri-industry Project (201203095, 201203001) of the Ministry of Agriculture, P.R. China. and the national key project (2011BAD12B01) of the Ministry of Sciences and Technology, P.R. China. These authors contributed equally to this work. To whom reprint requests should be addressed; e-mail jiangweijie@caas.cn. 722 HORTSCIENCE VOL. 49(6) JUNE 2014 potassium 25% or greater, organic 25% or greater, water 20% or greater, and the effective number of living bacteria 0.2 hundred million per gram or greater was used. Before transplanting, the fertilizer was mixed with the growth medium at 10 kg·m. After transplanting, a dosage of 10 g fertilizer per pot was added three times at 20, 40, and 60 d after transplanting. Irrigation treatments and experimental design The maximum amount of water can held by soil or medium is known as water-holding capacity (WHC). Water-holding capacity of medium was calculated from the following equation: water-holding capacity (%) = [total porosity (%) – air space (%)]. Four irrigation treatments, 100%, 85%, 70%, and 55%, of WHC were used during the whole growing season, which will be referred to in the text as T1, T2, T3, and T4, respectively. A full irrigation treatment (T1) was considered as a control. The second, third, and the fourth treatments (T2, T3, and T4) were considered as deficit irrigation treatments. All water treatments were given to the plants on the same day of transplanting. The desired moisture contents of pots were daily monitored by HH2 moisture meter Version 4.0 (Delta-T Devices Ltd., U.K.) and maintained through water application, if required. The experiment was organized in a completely randomized design with three replications per treatment; each replication had seven plants (21 plants per treatment). Measurements Morphological characteristics. At the end of the experiment, three plants were randomly selected from each treatment replication to measure some morphological parameters per plant as follows: Plant height (cm) was measured by a ruler from the soil surface of the pot to the top of the plant. The number of branches was counted by the naked eye. Stem diameter (cm) was measured by calipers (soil surface). Leaf area (cm) was measured by an Area meter (AM 300 Bio Scientific Ltd., U.K.). Fresh weight of shoots (g) was weighted with digital balance. Dry weight of shoots (g) samples were dried at 60 C until a constant weight and then weighted by the same balance. Days to flower set were calculated as the number of days from transplanting to flower set. Days to first harvest were calculated as the number of days from transplanting to first fruit maturity. The root system was carefully removed from the pot to obtain the complete root. After several washes in water, root length (cm), fresh weight of roots (g)/plant, dry weight of roots (g)/plant, and root-to-shoot ratio were determined. Dry weight of roots (g)/plant was obtained after the samples were dried at 60 C until they had a constant weight. Root-to-shoot ratio was calculated by dividing fresh weight of roots by the fresh weight of shoots. Harvesting Fruits were harvested at three periods during the season. The early period of harvesting started 48 d after transplanting (which is 30 d after flowering). The middle and late periods of harvesting started after 11 and 30 d of the first harvest

Deficit Irrigation Affects Growth, Yield, Vitamin C Content, and Irrigation Water Use Efficiency of Hot Pepper Grown in Soilless Culture