Partial Rootzone Drying (PRD) is a New ... - Acta Horticulturae

Partial Rootzone Drying (PRD) is a New Technique for Soilless Grown Vegetables H.Y. Dasgan Cukurova University Agricultural Faculty Department of Horticulture 01330 Adana Turkey

C. Kirda Cukurova University Agricultural Faculty Depart. of Agric. Struct. and Irrigation 01330 Adana Turkey

Keywords: PRD, split root, eggplant, Solanum melongena L., fruit, plant gowth Abstract A short term (66 days) greenhouse experiment was conducted to investigate Partial Rootzone Drying (PRD) technique for soilless grown eggplant. PRD is a newly developing irrigation-fertigation technique to save water, nutrients and care environment. The PRD practice simply requires wetting of one half of the rooting zone and leaving the other half dry, thereby utilizing reduced amount of irrigation water and nutrients. The wetted and dry sides are interchanged in the subsequent irrigations. Two treatments were tested during a 66-day-of-growing period in perlite open system; (1) FULL, control treatment where the full amount of nutrient solution, which was measured using drainage data, was applied to the roots on all sides of the plant; (2) PRD, 30% deficit nutrient solution application with PRD in which wetted and dry sides of the root zones were interchanged with every irrigation. PRD treatment had 25% and 17% decreases in shoot fresh weight and leaf area of plant, respectively, however, had 39% increase in fruit production in comparison to the full amount of nutrient solution apply. Plant analysis for N, P, K, Ca, Mg, Fe, Mn, Zn and Cu showed that macro and micro nutrients were higher from 8% to 42% and 10% to 85%, respectively in PRD plants. The PRD plants were adequately fed for all nutrients however FULL treated plants had less N and K concentrations in their tissues according to the reference values. INTRODUCTION In recent years, partial root drying (PRD) has been proposed as a new deficit irrigation technique to improve water use efficiency and standardize crop yield and quality. The water use efficiency of crop is important phenomena especially for waterscarce regions of the world. In PRD, half the roots are watered whilst leaving the other half to dry out which use about 50% less water than in full-watered plants (Dry et al., 1996; Düring et al., 1997; Loveys et al., 2000). The aim of this technique is to control excessive vegetative vigour and save irrigation water without influencing fruit yield and quality (Cifre et al., 2005). This technique induces ABA synthesis (the chemical signals) in the dried part of the root. The increased concentration of abscisic acid (ABA) in the xylem flow from root to leaves leads to partial stomatal closure without reducing leaf water status (Davies and Zhang, 1991; Davies et al., 1994, 2002; Dry and Loveys, 1999; Dry et al., 2000). Other mechanisms controlling stomatal aperture include hydraulic signals (Auge and Moore, 2002) and pH changes of xylem sap (Wilkinson and Davies, 1997; Davies et al., 2002). The proportions of the roots that are irrigated adjust saving large amount of water with only small reduction of photosynthesis (Stoll et al., 2000). The PRD has been used in commercial vineyards in Australia and has shown a significant reduction in vegetative growth while maintaining fruit yield, quality and saving in irrigation (Dry et al., 2001; de Sauza et al., 2005). Crop physiological responses to PRD and their incidence on yield and fruit quality have been recently documented in grapevines (Stoll et al., 2000; de Sauza et al., 2003; dos Santos et al., 2003), processing tomato in open field (Zegbe et al., 2004), table tomato in greenhouse (Kirda et al., 2004), Proc. VIIIth IS on Protected Cultivation in Mild Winter Climates Eds.: A. Hanafi and W.H. Schnitzler Acta Hort. 747, ISHS 2007

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hot pepper (Dorji et al., 2005), common bean (Wakrim et al., 2005) and maize (Kirda et al., 2005) in open field showed that PRD system appeared to be an effective and water saving method. However, to our knowledge, none of the earlier work assessed how the evolving irrigation/fertigation practice would affect plant growth, nutrient uptake and fruit production in hydroponically grown plants in soilless greenhouses with PRD’s claimed benefits of water saving. The objective of this work to assess PRD treatment in soilless grown eggplant for saving of nutrient solution, water and nutrients, also environmental pollution in short term experiment in Mediterranean type climate under the greenhouse. MATERIAL AND METHODS Experimental Conditions The short term greenhouse experiment was conducted during 66 days of a period in Research Greenhouse of Cukurova University, Faculty of Agriculture (36o59’N, 35o18’E, 20 m above sea level), Adana, Turkey, in the summer planted eggplant (Solanum melongena L. cv. ‘F1 Faselis’) cultivar in the year 2004. A randomized complete block experimental design with 6 replicates, and 6 plants in each replicate, consisting of two irrigation treatments was used. Seedlings were transplanted to perlite on 12 July and the experiment was ended on 16 September 2004. Mean temperature from July to October was about 28oC. The relative humidity was changed within the range from 40–80% during the period. The plastic house oriented in north-south direction, were 12 m x 30 m in size and the cover material was UV+ IR+ antifog added polyethylene. Ventilation openings of the greenhouse were open in day and night during the experiment to cool down temperature inside the greenhouse in summer. Seedlings were planted in density of 2.16 plants m-2 in perlite filled container which made of black PVC. Each container had 6 plants and ten litres of perlite was used for each plant. Nutrient solution was applied according to open system. The amount of nutrient solution applied was determineted according to amount of drainage. It was changed from 15% to 40% during the experimental period. Irrigation/Fertigation Treatments Two irrigation treatments used; (1) FULL irrigation/fertigation with all root wetted in every irrigation, it was control treatment and applied as conventional way by one line drip irrigation. (2) PRD, compared to FULL irrigation 30% less nutrient solution (it means water and nutrients together) was applied; irrigated sides of the root zone were interchanged with every irrigation. In PRD treatment the roots system of the plants was divided two parts by polyethylene sheet and leaching of the nutrient solution was not allowed from one half to the other. Two drip irrigation lines were used; each line operated to one side of the root system. During the experiment the plants were supplied with following nutrient solution (Savvas and Lenz, 1999) containing 15.5 mmol L-1 NO3-N, 0.75 mmol L-1 NH4-N, 1.50 mmol L-1 P, 7.75 mmol L-1 K, 3.75 mmol L-1 Ca, 2 mmol L-1 Mg, 15 µmol L-1 Fe, 10 µmol L-1 Mn, 5 µmol L-1 Zn, 0.75 µmol L-1 Cu, 25 µmol L-1 B, and 0.5 µmol L-1 Mo. Plant Measurements FULL and PRD treated plants were compared for shoot fresh weight including stem and leaves, leaf area, dry matter production in shoot. The water use efficiency was calculated for total fresh biomass and also for fruit productions. Plant analysis for N, P, K, Ca, Mg, Fe, Mn, Zn and Cu was conducted in leaves and stems separately in order to compare nutritional status of the FULL and PRD treated eggplants. The amount of fruit produced and number of fruit were also compared in two treatments. Data Analysis Treatment effects in the experiment were analyzed using analysis of variance (ANOVA) procedure. Treatments means were compared using a TUKEY procedure. 434

RESULTS The amount of nutrient solution used in PRD and FULL treated plants were 41.2 L and 58.8 L per plant, respectively during 66 days of short term experimental period in the greenhouse (Fig. 1). The shoot fresh weight (leaves + stem) and the leaf area per plant were higher, although not statistically significant, under FULL irrigation treatment relative to PRD practice, 25% and 17% respectively (Table 1). Decreased vegetative growth observed under PRD practice (Table 1) was consistent with commonly known adverse effects of water stress on plant development. The dry matter production in shoot was similar in both PRD and FULL irrigated plants at the end of 66 days (Table 1). The lower nutrient solution use efficiency was recorded under FULL irrigation treatment for total fresh mass of plant (TFMP) including leaves + stem + fruit (Fig. 2). The higher fruit yield was obtained under the PRD irrigation treatment. As shown in Table 2, fruit production increased under PRD treatment where the wetted half of the root was changed every other irrigation time (at maximum of 2 hours intervals) was 39% higher and significantly different (P≤0.05) than FULL irrigation. PRD treatment had higher yield benefits compared with conventional FULL practice. As regards to fruit number, PRD treatment had statistically significant (P≤0.01) effect and had 62% higher amount of fruit, compared to FULL irrigation treatment. However, mean fruit weight was 16% lower in PRD treated plants than FULL treated ones. Therefore PRD treated plants produced higher number of fruit but with less amount of weight (Table 2). The nutrient solution efficiency that calculated only for the fruit production was remarkably lower under FULL-irrigation treatment, compared to PRD practice (Fig. 3). Plant analysis for N, P, K, Ca, Mg, Fe, Mn, Zn and Cu showed that macro and micro nutrients were higher from 8% to 42% and 10% to 85%, respectively in PRD plants (Tables 3, 4 and 5). The PRD plants were adequately fed for all nutrients however FULL treated plants had less N and K concentrations in their tissues according to the reference values. DISCUSSION Results of this short term greenhouse study showed that PRD practice in soilless grown of eggplant can save up to 30% of irrigation water and the same time nutrients with the increase in fruit production The reduced vegetative growth and leaf area observed in PRD treated plants suggest that photosynthetic assimilates were predominantly partitioned to fruit growth so that significant fruit production increase was performed under PRD treatment (Tables 1 and 2) (Gautier et al., 2001; Stoll and et al., 2002; Kirda et al., 2004). Although we did not measured ABA content in plant, which is expected consistently the higher under PRD practice in compare to FULL treatment. According to earlier reports (Davies and Zhang, 1991; Davies et al., 1994, 2002; Dry and Loveys, 1999; Dry et al., 2000; Kirda et al., 2004) the higher ABA content in PRD plants may indeed be an important mean of chemical signaling, regulating stomatal control. Increased concentration of ABA in the xylem flow to plant shoot triggers closure of stomata (Zhang and Davies, 1990; Gollan et al., 1991; Kirda et al., 2004), and thereby enables the plant to use sparingly supplied water efficiently through partially wetted roots. While partial closure of stomata reduces transpiration, leaf turgidity is maintained and photosynthesis is affected the least (Jones, 1992; Kirda et al., 2004). Plants under PRD practice can use water the most sparing way, without wilting of leaves (Jones, 1980; Cowan, 1982) having hormonal stomata control mechanism, may protect leaf turgidity, which no adversely affects photosynthesis between the irrigations. In the soilless grown eggplants it was found that PRD treated plants had no yield reduction, and there is significant increase in fruit production, therefore the water and nutrients use efficiency will have been increased (Fig. 3, Tables 3 and 4) (Stoll et al., 2002). Since part of the root system well watered, there should be some defense against water stress and adequate supply of water to the fruits is maintained. The fruits in PRD 435

plants as stronger sink for photoassimilates could compete with other plant parts. The vegetative growth was lower in PRD plants than FULL irrigated plants, which shows higher sink strength of fruit than the rest of plant organs (Zegbe et al., 2004). It is also speculated that xylem derived signals may only reach the fruit earlier however at later stage of fruit development the fruit may rely more on a phloem derived transport (Davies et al., 2000; Stoll et al., 2002). According to the competition of photosynthetic assimilates the number of fruit and fruit size is inversely related to each others. The PRD treated plant had higher number of fruit than FULL treated ones, therefore fruit size is reduced. CONCLUSION The results of this work showed that PRD treated plants with saving of water and nutrients had lower vegetative growth with increased fruit yield. This suggests that the PRD practice in soilless cultivation of greenhouse crops can be viable and advantageous option when water and nutrients savings are important, but also should be valued for its environmental friendly attributes. Future studies must conduct to investigate long term soilless experiments including whole production period in the greenhouse. ACKNOWLEDGEMENTS The authors thank to Bulut Ekici for his assistance during the experiment set up in the greenhouse. Literature Cited Cifre, J., Bota, J., Escalona, J.M., Medrano, H. and Flexas, J. 2005. Physiological tolls for irrigation scheduling in grapevine (Vitis vinifera L.) an open gate to improve wateruse efficiency? Agricul. Ecosystems & Environment 106:159–170. Cowan, I.R., 1982. Regulation of water use in relation to carbon gain on higher plants. pp.589–614. In: O.L. Lange et al. (eds.), Physiological Plant Ecology, vol. 2. Springer, Berlin. Davies, J.W., Tardeu, F. and Trejo, C.L. 1994. How do chemical signals work in palnt that grow in drying soil? Plant Physiol. 104:30–314. Davies, W.J., Bacon, M.A., Thompson, D.S., Sobeih, W. and Rodriguez, L.G. 2000. Regulation of leaf fruit growth in plants in drying soil: exploitation of the plants’ chemical signaling system and hydraulic architecture to increase the efficiency of water use in agriculture. J. of Exp. Bot. 51 (350):1617–1626. Davies, W.J., Wilkinson, S. and Loveys, B. 2002. Stomatal control bu chemical signaling and the exploitation of this mechanism to increase water use efficiency in agriculture. New Phytologist 153:449–460. Davies, W.J., Zhang, J. 1991. Root signal and the regulation of growth and development of plants in drying soil. Ann. Rev. Plant Physiol. Plant Mol. Biol. 42:55–76. de Souza, C.R., Maraco, J.P., dos Santos, T.P., Rodriques, M.L., Lopes, C., Pereira, J.S. and Manuella Chaves, M. 2005. Control of stomatal aperture and carbon uptake by deficit irrigation in two grapevine cultivars. Agric. Ecosystem & Environment 106:261–274. de Souza, C.R., Maroco, J.P., dos Santos, J.P., Rodrigues, T.P., Lopes, M.L., Pereira, J.S. and Chaves, M.M. 2003. Partial rootzone drying: regulation of stomatal aperture and carbon assimilation in field-grown grapevines (Vitis vinifera cv. ‘Moscate’). Funct. Plant Bil. 30:653–662. Dorji, K., Behboudian, M.H. and Zegbe-Dominguez, J.A. 2005. Water relations, growth, yield, and fruit quality of hot pepper under deficit irrigation and partial rootzone drying. Scientia Horticulturae 104:137–149. dos Santos, T.P., Lopes, C.M., Rodrigues, M.L., de Souza, C.R., Maroco, J.P., Pereira, J.S., Silva, J.R. and Chaves, M.M. 2003. Partial rootzone drying: effect on growth and fruit quality of field-grown grapevines (Vitis vinifera). Funct. Plant Biol. 30:663–671. Dry, P.R. and Loveys, B.R. 1999. Grapevine shoot growth and stomatal conductance are 436

reduced when part of the root system is dried. Vitis 38:151–156. Dry, P.R., Loveys, B.R., Botting, D. and Düring, H. 1996. Effect of partial roor-zone drying on grapevine vigour, yield, composition of fruit and use of water. In: C. Stockley, A. Sas, R. John-stone and T. Lee (eds.), Proceedings of the ninth Australian wine industry technical conference, Adelaide, pp.128–131. Dry, P.R., Loveys, B.R. and Düring, H. 2000. Partial drying of the rootzone of grape. I. Transient changes in shoot growth and gas exchange. Vitis 39:3–7. Düring, H., Loveys, B.R. and Dry, P.R. 1997. Root signals affect water use efficiency and shoot growth. Acta Hort. 427:1–14. Gautier, H., Guichard, S. and Tchamitchian, M. 2001. Modulation of competition between fruits and leaves by flower pruning and water fogging, and consequences on tomato leaf and fruit growth. Ann. Bot. 88:645–652. Gollan, T., Passioura, J.B. and Munns, R. 1992. Soil-water status affect the stomatal conductance of fully turgid wheat and sunflower leaves. Aust. J. Plant Physiol. 13:459–464. Hochmuth, G., Maynard, D., Vavrina, C., Hanlon, E. and Simonne, E. 2006. Plant Tissue analysis and interpretation for vegetable crops in Florida. University of Florida. IFAS extension. Jones, H.G. 1980. Interaction and integration of adaptive responses to water stress: the implications of an unpredictable environment. pp.353–365. In: N.C. Turner and P.J. Kramer (eds.), Adaptation of Plants to Water and High Temperature Stress. Wiley, New York, . Jones, H.G. 1992. Plants and Microclimates: A Quantitative Approach to Environmental Plant Physiology, second ed. Cambridge University Press, Cambridge. Kirda, C., Cetin, M., Dasgan, Y., Topcu, S., Kaman, H., Ekici, B., Derici, M.R. and Ozguven, A.I. 2004. Yield response of greenhouse grown tomato to partial root drying and conventional deficit irrigation. Agric. Water Management 69:191–201. Kirda, C., Topcu, S., Kaman, H., Ulger, A.C., Yazici, A., Cetin, M. and Derici, M. 2005. Grain yield response and N-ferliser recovery of maize under deficit irrigation. Field Crop Research 93:132–141. Loveys, B.R., Dry, P.R., Stoll, M. and McCarthy, M.G. 2000. Using plant physiology to improve the water efficiency of horticultural crops. Acta Hort. 537:187–197. Savvas, D. and Lenz, F. 2000. Effects of NaCI or nutrient-induced salinity on growth, yield and composition of eggplants grown in rockwool. Scientia Hortic. 84:37–47. Stoll, M., Jones, H.G. and Infante, J.M. 2002. Leaf gas exchange and growth in red raspberries is reduced when part of the root system in dried. Acta Hort. 585:671–676. Stoll, M., Loveys, B.R. and Dry, P.R. 2000. Hormonal changes induced by partial rootzone drying of irrigated grapevine. J. Exp. Bot. 51:1627–1634. Stoll, M., Loveys, B. and Dry, P.R. 2000. Hormonal changes induced by partial rootzone drying of irrigated grapevine. J. Exp. Bot. 51:1627–1634. Wakrim, R., Wahbi, H., Tahi, H., Aganchich, B. and Serraj, R. 2005. Comparative effects of partial root drying (PRD) and regulated deficit irrigation (RDI) on water relations and water use efficiency in common bean (Phaseolus vulgaris L.). Agric. Ecosystem & Environment 106:275–287. Wilkinson, S. and Dawies, W.J. 1997. Xylem sap pH increase: a drought signal received at the apoplastic phase of the guard cell that involves the suppression of saturable abscisic acid uptake by the epidermal symplast. Plant Physiol. 113:559–573. Zegbe, J.A., Behboudian, M.H. and Clothier, B.E. 2004. Partial rootzone drying is a feasible option for irrigating processing tomatoes. Agric. Water Management 68:195– 206. Zhang, J. and Davies, W.J. 1990. Canges in the concentration of ABA in xylem sap as function of changing soil water status will account for changes in leaf conductance. Plant Cell Environ. 13:277–285.

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Tables Table 1. Plant growth parameters of eggplant plants grown with PRD and conventional FULL irrigation/fertigation 66 days after transplanting.

PRD FULL Tukey’s D % Difference PRD vs. FULL

Shoot (leaves+stem) Fresh Weight (g plant-1) 971 1295 ns - 25

Leaf Area (cm-2 plant-1) 13204 15907 ns - 17

Dry matter production in shoot (%) 16.88 16.66 ns 1.3

Table 2. Fruit production of eggplant plants grown with PRD and FULL irrigation/fertigation 66 days after transplanting.

PRD FULL Tukey’s D %Difference PRD vs. FULL

Fruit Production (g plant-1) 563.17 a 406.50 b 114.12* 39

Fruit Number (fruit plant-1) 4.72 a 2.92 b 0.60** 62

Fruit Weight (g fruit-1) 120.18 b 139.86 a 18.41* -14

*: P≤0.05 **: P≤0.01

Table 3. Leaf nutrient concentrations of eggplant plants grown with PRD and conventional FULL irrigation/fertigation 66 days after transplanting. Fertilizers PRD FULL Tukey’s D % Difference *: P≤0.05

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N (%) 4.24 3.92 ns 8

P (%) 0.25 b 0.41 a 0.14 - 39

K (%) 3.46 a 2.44 b 0.63* 42

Ca (%) 1.30 1.09 ns 19

Mg (%) 0.81 0.72 ns 13

Fe (ppm) 127.0 113.8 ns 16

Mn (ppm) 74.8 a 40.5 b 23.7* 85

Zn (ppm) 34.0 30.8 ns 10

Cu (ppm) 32.0 26.3 ns 22

Table 4. Adequate ranges for macro and micro nutrients for eggplant (matured whole leaf plus petiole during early fruit), (Hochmuth et al., 2006). Nutrients Ranges

N P (%) (%) 4.2–5.0 0.3–0.6

K (%) 3.5–5.0

Ca (%) 0.8–1.5

Mg (%) 0.3–0.6

Fe (ppm) 50–100

Mn (ppm) 50–100

Zn (ppm) 20–40

Cu (ppm) 5–10

Table 5. Stem nutrient concentrations of eggplant plants grown with PRD and conventional FULL irrigation/fertigation 66 days after transplanting. Fertilizers PRD FULL Tukey’s D % Difference

N (%) 1.81 1.61 ns 12

P (%) 0.08 b 0.13 a 0.031 - 38

K (%) 1.85 1.50 ns 23

Ca (%) 0.50 0.54 ns 7

Mg (%) 0.67 0.67 ns 0

Fe (ppm) 36.3 31.0 ns 17

Mn (ppm) 31.0 a 17.8 b 12.3 74

Zn (ppm) 35.8 22.3 ns 61

Cu (ppm) 22.5 15.5 ns 45

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Figures

Fig. 1. The amount of nutrient solution (L) used in PRD and FULL treated eggplant plants during 66 days experimental period.

Fig. 2. Nutrient solution use efficiency (g L-1) of PRD and NS treatments for total fresh mass of plant including leaves+stem+fruits.

Fig. 3. Nutrient solution use efficiency (g L-1) of PRD and NS treatments for fruit production. 440