Growth, yield and water use efficiency response of greenhouse-grown hot pepper under Time-Space deficit irrigation
Research highlights
▶ Time-Space deficit irrigation (TSDI) with varying degree and irrigation strategies at different growth stages reduced the fruit growth rate of hot pepper, but the re-watering had over compensatory effect to reduce the negative influence on fruit growth. Water deficit treatment at seeding stage obviously suppressed the vegetative growth of hot pepper and was advantageous to transfer more stored photosynthesis product and nutrition substances to the reproductive organ after the flowering stage. ▶ With regard to irrigation water use efficiency in the production of fresh fruit weight, a certain amount of deficit succeeds in improving it, the greatest efficiency is achieved by the treatment of DFDP. As a rule, the treatments with deficit at several stages prove to be more efficient, except for FDDD and PPDF. ▶ Further orthogonal analysis showed that appropriate degree of deficit irrigation at the first growth period, irrigation renewal in time at the second and third growth period, partial rootzone drying at the fourth growing period could result in high yield, total biomass and better yield components in hot pepper in a greenhouse environment. ▶ The optimum soil water deficit levels with highest yield, total biomass, water use efficiency, were proved to be 50%–60%, 80%–90%, 60%–70%, and 50%–60% of field capacity at the four growth stages above mentioned, with the corresponding optimum total irrigation water of 176 mm which was distributed as following: 30 mm during the seeding stage, 70 mm during the bloom and fruit setting stage, 53 mm during the vigorous fruit-bearing stage, and 23 mm during the later fruit-bearing stage. ▶ The results of this study suggest that the difficulty to generally apply TSDI for increasing shoot biomass production but the DFDP practices can be viable and advantageous option next to FFFF to prevent crop yield reduction when and if there is water shortage or to improve crop quality. The ultimate profitability of a given watering regime for plant growth in the greenhouse requires fine-tuning of the pattern and level of water supply to the responses of the plant during different stages.
Introduction
The greenhouse industry has expanded in many parts of the world and particularly throughout mild winter areas in the south of China. Hot pepper (Capsicum annuum L.) is one of the vegetable crops commonly grown in greenhouse and consumed in a variety of ways in China, Korea, East Indies, USA, and many other countries, not only because of its economic importance, but also for the nutritional value of its fruits, which is an excellent source of natural colors and antioxidant compounds, like vitamin C and carotenoids (Howard et al., 2000, Russo and Howard, 2002, Navarro et al., 2006). In the greenhouse, irrigation is necessary to ensure stable yield of high quality, because it is considered one of the most susceptible crops to water stress in horticulture. However, inappropriate irrigation method may result in waste of water resources and poor fruit quality.
The world's apparent warming climate has caused fresh water reserves to fall across the globe consequently waking people up to the importance of water saving. The decline in water availability for irrigation and the positive results obtained in some fruit tree crops have renewed the interest in developing information on deficit irrigation for a variety of crops (FAO Report, 2002, Dorji et al., 2005, Fereres and Soriano, 2007, Wakrim et al., 2005, Paul and Goodwin, 2003, Zegbe-Dominguez et al., 2003). Deficit irrigation should be applied at those phonological stages that are least sensitive to water deficits, in the case of vegetable crops such as pepper, water stress should be avoided during flowering and fruit set, a difficult task given the long duration of these processes in most pepper cultivars. Regulated deficit irrigation (RDI) is one way of maximizing water use efficiency (WUE) for higher yields per unit of irrigation water applied. In this method, the crop is exposed to a certain level of water stress either during a particular period or throughout the whole growing season (English and Raja, 1996). RDI scheduling is applied by reducing irrigation rates only in those periods when fruit growth is less sensitive to water and irrigation reductions are often defined as a percentage of an optimal irrigation rate (Chalmers et al., 1981, Girona et al., 1993, Marsal and Girona, 1997). Over the past 20 years, evidence has accumulated to suggest that the leaf growth response to soil drying cannot always be explained by the plant's water relations alone (Bacon et al., 1998, Davies and Zhang, 1991). Under water-deficit conditions, partial stomatal closure occurs (Croker et al., 1998, Sauter et al., 2001), signaled by ABA produced by temporarily dried roots together with an increase in xylem pH (Davies et al., 2000, Sobeih et al., 2004). The results of such plant response have led to the development of a new irrigation technique called partial rootzone drying where two halves of plant-rooting zones are exposed alternately to dry and wet cycles (Kang et al., 1997). Irrigation water use efficiency of plants in the greenhouse has been shown to benefit from this type of irrigation and thereby reduction in irrigation water supply. For example, Grimes et al. (1968) and Shao et al. (2008) used partial rootzone drying method. They concluded that the use of partial rootzone drying method allows for a reduction in volume of irrigation water and completion of irrigation in shorter time, thus reducing labor use when compared to conventional furrow (every furrow) irrigation method. The partial rootzone drying method (PRD) provides the means to control plant–water stress to slow down vegetative growth and promote a favorable balance in crop production (Grimes et al., 1968). Yield response of tomato to partial rootzone drying method, however, remained contentious. Recent PRD studies conducted on pot-grown pepper (Kang et al., 2001) and pear orchard (Kang et al., 2002) also showed that PRD can increase IWUE with no significant reduction in crop yield.
Regulated deficit irrigation and partial rootzone drying were proposed long ago as a technique to reduce irrigation water use while maintaining farmers’ net profits, and they are common practices worldwide. However, for many crop systems the best deficit irrigation strategy for improving water productivity has not yet been established (Fereres and Soriano, 2007). RDI applied at those phonological phases less sensitive to water stress (Chalmers et al., 1981, Mitchell et al., 1984) has been successfully studied for fruit trees and vines (Fereres and Soriano, 2007), but less attention has been paid for other crop systems, especially greenhouse crops (Katerji et al., 1993), for which water and nutrients are usually applied at non-limiting rates. The initial goal of RDI was to improve yield and increase irrigation water use efficiency in arid and semi-arid zones, the focus is primarily related to the efficient management of limited water resources at both sides of root system during the growth stages of the crops, otherwise, the irrigation method ignores the response of plant growth under partial rootzone drying. On the other hand, PRD focus on the effect of partial rootzone drying on plant growth without thinking about the sensitivity to irrigation water of plant growth at different growth stage. Based on PRD and RDI, Time-Space deficit irrigation (TSDI) was put forth with full coverage with optimal distribution of irrigation water and the influence of partial rootzone drying on plant growth. In current, the research on the effects of Time-Space deficit irrigation on hot pepper growth in the greenhouse is scanty.
The main aim of this work was to assess the effects of Time-Space deficit irrigation on yield, WUE and growth of greenhouse-grown hot pepper. The experiment was carried out in a glasshouse to avoid interference by rain and to minimize the adverse effects that frequently changing weather might have on plant response.
Section snippets
Experimental conditions and plant material
The experiment was conducted during warm-wet season, May 2006 through October 2006 in the glass greenhouse of Key Laboratory of Efficient Irrigation-Drainage and Agricultural Soil-Water Environment in Southern China, Ministry of Education (latitude 31°57′N, longitude 118°50′E 144 m above sea level). Greenhouse air temperature and relative humidity at 1.5 m above the soil were measured daily. Mean daily temperature during the experiment ranged from 21 to 38 °C (Fig. 1). The soil type was clay loam
Crop water requirements
Table 2 shows the volume of water consumption for each treatment at four stages. The total amount of water consumption ranged from 157.84 mm in FPPP to 288.65 mm in FFFF. The average water use was 1.65, 2.66, 5.77, 3.42 mm per day for FFFF at four stages, the fact would be found that the least volume of water consume emerged in the stage of seedling, and the largest one in the stage of vigorous fruit-bearing, as the evapotranspiration increased with air temperature rising and the plant growing.
Effects of Time-Space deficit irrigation on water consumption
All the Time-Space water-deficit treatments resulted in a mild stress during four particular periods. Although the TSDI plants received the same water supplied, such as DFDP and PFPD, DPFD and PDFP, the drought level was not severe enough to decrease plant growth and yield to the same degree (Table 3, Table 4, Table 5, Fig. 2), the reason may be attributed to the difference of transpiration for root development and evaporation for partial rootzone drying. An advantage for the smaller surface
Acknowledgements
This work was funded by key program granted by the National Nature & Science Foundation of China (no. 50839002) and supported by the fundamental research funds for the central universities (no. 2009B09014). We extend our gratitude to editor and the anonymous reviewers for substantial comments on earlier versions of this article and to Tarawawalie Ismail Foday, Xing wen gang and Zhang juan for considerable language improvements and technical assistance and support provided.
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