Evapotranspiration, Crop Coefficient and Growth of Two Young Pomegranate (Punica Granatum L.) Varieties Under Salt Stress
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Agricultural Water Management 97 (2010) 715–722 Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat Evapotranspiration, crop coefficient and growth of two young pomegranate (Punica granatum L.) varieties under salt stress Parashuram Bhantana, Naftali Lazarovitch * The Wyler Department of Dryland Agriculture, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel ARTICLE INFO ABSTRACT Article history: Pomegranate (Punica granatum L.) is a drought-hardy crop, suited to arid and semi-arid regions, where Received 14 June 2009 the use of marginal water for agriculture is on the rise. The use of saline water in irrigation affects various Accepted 21 December 2009 biochemical processes. For a number of crops, yields have been shown to decrease linearly with evapotranspiration (ET) when grown in salt-stressed environments. In the case of pomegranate, little Keywords: research has been conducted regarding the effect of salt stress. Our study focused on the responses of ET, Pomegranate crop coefficient (Kc) and growth in pomegranate irrigated with saline water. Experiments were Salt stress conducted using lysimeters with two varieties of pomegranate, P. granatum L. vars. Wonderful and SP-2. Evapotranspiration The plants were grown with irrigation water having an electrical conductivity (EC ) of 0.8, 1.4, 3.3, 4.8 Lysimeter iw À1 Irrigation scheduling and 8 dS m . Plants were irrigated with 120% of average lysimeter-measured ET. Seasonal variation in Crop coefficient ET, crop coefficient (Kc) and growth were recorded. Variation in daily ET was observed 1 month after initiation of the treatments. While significant seasonal ET variation was observed for the EC-0.8 treatment, it remained more stable for the EC-8 treatment. Salinity treatment had a significant effect on both daily ET (F = 131, p < 0.01) and total ET (F = 112.68, p = 0.001). Furthermore, the electrical conductivity of the drainage water (ECdw) in the EC-8 treatment was five times higher than that of the EC-0.8 treatment in the peak season. Fitting the relative ET (ETr) to the Maas and Hoffman salinity yield response function showed a 10% decrease in ET per unit increase in electrical conductivity of the À1 saturated paste extract (ECe) with a threshold of 1 dS m . If these parameters hold true in the case of mature pomegranate trees, the pomegranate should be listed as a moderately sensitive crop rather than a moderately tolerant one. Fitting 30-day interval ETr data to the Maas and Hoffman salinity yield response function showed a reduction in the slope as the season progressed. Thus using a constant slope in various models is questionable when studying crop–salinity interactions. In addition, both of the varieties showed similar responses under salt stress. Moreover, the calculated value of Kc is applicable for irrigation scheduling in young pomegranate orchards using irrigation water with various salinities. ß 2010 Elsevier B.V. All rights reserved. 1. Introduction As the amount of water used by plants for metabolic processes is insignificant (less than 1%), the term ET is synonymous with Plant water demand is described in terms of evapotranspiration consumptive use (Cu)(Michael, 2006). Seasonal Cu values are (ET), which combines two important phenomena occurring useful in scheduling irrigation, and are obtained by summing the simultaneously in the cropped field: evaporation and transpira- daily ET values in a cropped field throughout an entire season. Peak tion. The ET measured with lysimeter and the potential evapora- period Cu is particularly useful for irrigation system design, as ET, tive demand (Eo) measured with class ‘A’ pan evaporation are Kc and Cu are also affected by crop type, plant growth stage and useful for estimating the crop coefficient (Kc) and scheduling weather conditions (Michael, 2006). Peak period Cu is obtained irrigation. Generally, Kc is estimated as the ratio of ET to Eo, but from the average of daily water use during the days of highest Cu. several other approaches have also been used. ET and Kc are With the same crop type and weather conditions, the major factor affected by climate, crop type and crop physiological stage (Allen affecting Cu is crop growth and development. et al., 1998). In the case of deciduous crops such as grapevine, the days after bud burst (DAB) play a major role in seasonal changes in ET (Shani and Ben-Gal, 2005). Towards winter, deciduous plants shed leaves * Corresponding author at: POB 101, Midreshet Ben-Gurion, 84990, Israel. and transpiration decreases to zero. However there is still some E-mail address: [email protected] (N. Lazarovitch). evaporation from the soil surface. This is why immediately after 0378-3774/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2009.12.016 716 P. Bhantana, N. Lazarovitch / Agricultural Water Management 97 (2010) 715–722 bud burst, less water is used as transpiration but in the peak gradient, should not be affected under salt stress, although this season, more water is used. Netzer et al. (2009) showed a 1.46- and conclusion remains ambiguous. Favorable root-zone salinity can 3.82-fold increase in evaporation and ET, respectively, in a be maintained by using a suitable leaching fraction (LF) under vineyard in the peak season relative to immediately after bud varying ECiw levels (Dudley et al., 2008a). The LF adjusts the burst. ET is highly correlated to leaf area expansion (Graham et al., balance between soil solution salinity and ECiw by changing the 2009), with leaf area increasing asymptotically with DAB. A typical amount of water percolating down from the root zone under a hemispherical curve of leaf area index (LAI) versus DAB for apple given ECiw (Beltran, 1999). Since drainage water is not only a trees shows a LAI of 0.1, 3.2 and 0.1 m2 mÀ2 after bud burst, in the waste product but also a potentially valuable resource, its late summer and at the leaf-fall stage, respectively (Gong et al., successful handling in irrigation can be achieved by low-flow 2007). Similarly, a rapid increase in LAI from 0.54 to 4.8 m2 mÀ2 is with high-frequency irrigation along with LF adjustments (Dudley evident in the vineyard from bud burst to peak season (Netzer et al., 2008b). et al., 2009). In the case of date palm, the relative ET and relative Pomegranate (Punica granatum L.) is one of the oldest known plant vegetative cover are significantly correlated (Tripler et al., edible fruits, among the seven kinds of fruit mentioned in the Bible 2007). At some point during the peak season, ET begins to decline. (Blumenfeld et al., 2000). It is native to Iran and grown extensively This occurs when the plant reaches its highest Cu and switches in arid and semi-arid regions worldwide (Sarkhosh et al., 2006). from vegetative to reproductive growth. Regarding the floral biology of pomegranate, Holland et al. (2009) Incorporation of saline water in irrigation causes a reduction in reviewed three types of flowers: male (bell-shaped), bisexual transpiration (Dudley et al., 2008a), which subsequently results in (vase-shaped), and an intermediate type that has a short style and reduced ET. Linear reductions in ET have been shown for several developed ovary which is sometimes fertile. Flowering in crops with varying irrigation-water electrical conductivities pomegranate occurs in three waves, and lasts for 1 month. The (ECiw), including corn (Zea mays L.), alfalfa (Medicago sativa L.), ratio of vase- to bell-shaped flowers determines the fruit’s yield melon (Cucumis melo L.) (Shani and Dudley, 2001; Skaggs et al., potential, and a possible reduction in this ratio is expected with 2006), tomato (Lycopersicon esculentum Mill.) (Ben-Gal et al., increasing ECiw. Pomegranate is also important in human 2003; Shani et al., 2007), grapevine (Vitis vinifera L.) (Shani and medicine, and its components have a wide range of clinical Ben-Gal, 2005; Shani et al., 2007), tall wheat grass [Agropyron applications (Lansky and Newman, 2007). The anthocyanins from elongatum (Host) P. Beauv.] (Skaggs et al., 2006), date palm pomegranate fruit have been shown to have higher antioxidant (Phoenix dactylifera L.) (Tripler et al., 2007), onion (Allium cepa L.), activity than vitamin E (a-tocopherol), vitamin C (ascorbic acid) or bell pepper (Capsicum annum L.) and sunflower (Helianthus annus b-carotene (Shukla et al., 2008). Moreover, commercial pome- L.) (Shani et al., 2007; Ben-Gal et al., 2008). A good correlation granate juice has been shown to have three times the antioxidant between relative yield and relative ET was observed with the activity of green tea and red wine (Gil et al., 2000). Nevertheless, aforementioned crops under varying levels of ECiw.Inthecaseof few studies have been conducted on the ET, Kc and growth of cucumber, a 4.6% reduction in ET per unit increase of ECiw was pomegranate in response to varying ECiw. Pomegranate is observed by Blanco and Folegatti (2003). Assouline et al. (2006) considered to be moderately tolerant to salinity (Maas, 1993; observed a reduction in leaf area at a electrical conductivity of Allen et al., 1998): cuttings from pomegranate var. Malas Shirin 4.2 dS mÀ1 versus 1.8 dS mÀ1 in bell pepper, and an approximate showed tolerance to up to 40 mM NaCl in potted cultures of 1:1 60% reduction in leaf area was observed upon irrigation with sand–perlite medium irrigated with complete Hoagland’s solution. 171 mM NaCl versus non-salinized treatment in tomato (Maggio However, the performance of other pomegranate varieties, such as et al., 2004). Likewise, an approximate 86% reduction in leaf area Alak Torsh and Malas Torsh, in the presence of salinity showed a was recorded in both Serena and Seredo varieties of sorghum at decline from 0 mM NaCl, as indicated by number of internodes, 250 mM versus 0 mM NaCl (Netondo et al., 2004).