raspberry plants to partial rootzone drying (PRD)

Vegetative and fruiting response of ‘Polka’ raspberry plants to partial rootzone drying (PRD), mulching, and their combinations K. Lepaja1, E. Kullaj1, L. Lepaja1 and V. Avdiu2 1Department

of Horticulture and Landscape Architecture, Agriculture University of Tirana, Kodë r – Kamë z, Tirana, Albania; 2Horticultural Department, Agriculture University of Prishtina, Prishtinë , Kosovo.

Abstract This field experiment was designed to assess the vegetative and fruiting response of ‘Polka’ raspberry plants to partial rootzone drying (PRD), mulching and their combinations. The experiment was conducted in Kosovo (Prishtina region) during 2014 in a raspberry orchard of 1 ha on first year planting. Four levels of budget irritation were studied: 100% ET (control) lateral, two laterals (TL), side lateral (SL), and without irrigation (WI). Each treatment contained 10 plants, of which five plants per treatment were mulched to a 10-cm layer of wood chips (size 1-2 cm). Using a nested experimental design, data were analysed with ANOVA two-way with post hoc testing. Irrigation had significant changes on shoot length, number of leaves, leaf surface and area, LAI, number of fruit, fruit diameter, fruit length, fruit weight and total yield. It should also be stressed that mulching had significant changes in leaf surface and area, LAI, number of fruit and total yield. PRD and mulching had a combined effect on leaf surface, fruit length and fruit weight. Two laterals treatment gave higher values of these vegetative parameters compared to control and consequently to all other treatments while, the highest values of productive parameters were found in two laterals treatment, followed by normal irrigation (control), side lateral and lastly without irrigation. Keywords: water stress, Rubus idaeus, evapotranspiration, drip irrigation, wood chips INTRODUCTION Regulated deficit irrigation (RDI) and partial root drying (PRD) are two irrigation methods that attempt to decrease the agricultural demand for water. PRD is an irrigation technique based on alternately wetting and drying opposite parts of the surface soil under which the plant root system is thought to be located (Posadas et al., 2008; Tatullo et al., 2007). PRD improves irrigation water productivity (IWP, yield per unit applied irrigation water) with respect to controls receiving substantially more water, but similar gains are often achieved with conventional deficit irrigation (Sadras, 2009). PRD is a new irrigation and plant growing technique which improves water use efficiency without significant yield reduction (Stikic et al., 2003). PRD is commonly applied as part of a deficit irrigation program because it does not require the application of more than 50-70% of the water used in a fully irrigated program (Marsal et al., 2008). Production of raspberry (Rubus idaeus) is considered of particular importance for the economy of Kosovo. Until now about 500 ha are planted with raspberry. Water shortages in the territory of Kosovo, especially during the growing season, necessiate intervention with supplemental irrigation, but the application of PRD can start from the beginning or middle of June due to the fact that Kosovo has sufficient rainfall during May. The quantity of water in raspberry production is important throughout the life of the planting. Too much water over a long period of time on poorly drained soil will cause plant root disease and plant loss (Funt and Ross, 2013). Climatic conditions determine water needs. When calculating the amount of water needed for rasperries using drip irrigation, only the root zone area needs to be irrigated. Drip irrigation applies water to a part of the root zone and does not broadcast the water as an overhead or flood method does, so it

Acta Hortic. 1133. ISHS 2016. DOI 10.17660/ActaHortic.2016.1133.35 Proc. XI Int. Rubus and Ribes Symp. Eds.: G.E. Fernandez and K.E. Hummer

227

allows more efficient application of water to the desired crop (Funt and Ross, 2013). PRD is a variant of defict irrigation (DI), a technique with plenty of advantages, ranging from water saving, reduction of costs, minimization of nutrient and pesticide leaching to ground water (Pulupol et al., 1996), reduction of excess vegetative growth (Marsal et al., 2002) and quality improvements. DI is a system for the management of soil water to impose periods of water deficit to the plant in such a way as to be economically advantageous. It involves the use of a smaller amount than the calculated need for water (Kullaj, 2007). In other words, DI aims at stabilizing yields and at obtaining maximum crop water productivity rather than maximum yields (Zhang and Oweis, 1999). There was some evidence that the PRD treatment even enhanced yield while it simultaneously reduced vegetative growth (Stoll et al., 2002; Dry et al., 1996, 2000; Spreer et al., 2007). Pot experiments with split-root plants and two years of field experiments with manipulation of soil water content have shown that PRD does not affect yield in raspberries, ‘Glen Ample’ and ‘Glen Prosen’. In some cases PRD can reduce stomatal conductance, thus reducing water loss (Grant et al., 2004). According to Downer (2009) there are several reasons to apply mulch. Mulches prevent weeds from germinating, reduce evaporative loss from soil surfaces, add organic matter to soils thereby increasing their mineral content, increase soil-borne disease suppression, and finally as shown in some studies, increase the growth of trees (Downer, 2009; Greenly and Rakow, 1995). The objective of this study was to determine the impact of PRD in combination with mulching on the vegetative and productive parameters where water resources are limited. MATERIALS AND METHODS This field experiment was designed to assess the vegetative and productive response of ‘Polka’ raspberry plants after the application of PRD combined with mulching, used in a commercial raspberry orchard. The experimental set up was a nested design, whereby the categories of nested factor within each level of the main factor are different, i.e., different plants of ‘Polka’ raspberry give rise to the leaf/fruit samples within each of the main irrigation treatment. Four levels of irrigation were applied: 100% of evapotranspiration (ET) as control standard lateral (one lateral-normal irrigation), with two laterals, side lateral and without irrigation (Figure 1). The orchard was planted in April 2014. Drip distance in the lateral pipe (euro drip irrigation) was 0.20 m while drip irrigation delivers 1.6 L of water h-1 emitter-1. A total of 20 irrigation sets (an irrigation equalled 1 h 30 min) were applied. PRD was applied from July until end of September. Each treatment (each level of irrigation) was in a row. For each treatment we used 10 plants, 5 of which were mulched with 10 cm thick layer of wood chips (1 to 2 cm, Holzdekor), totalling 40 plants for the entire experiment. Mulching material was placed in a row at a width of 0.80 m on July 20, 2014. Planting distances were 3 m between the rows and 0.40 m in the row. To evaluate the effects of partial rootzone drying and its combination with mulching, we compared both vegetative and fruiting parameters. Shoot length was measured (in cm) on all plants on September 28. Numbering of leaves for all plants was carried out on October 1. Leaf surface cm2 of 10 leaves per plants was conducted on September 21. Leaf area and LAI measurement (m2) was conducted on October 1. All fruits in all plants were counted. Their size (diameter and length of fruits) was measured (mm) at the equator with a calliper (electronic digital calliper) using all fruits per plant, all the time during every harvest (first measurement on August 17 and last measurement on November 2). Average fruit weight was measured (g) using an analytical balance for all fruits, each harvest. Yield (in g plant-1) was calculated in the whole period of the harvest time measuring the total weight of all fruits per plant. Our state has a moderate continental climate with a coastal impact which penetrates through the valley of the Drini i bardhë moderating markedly continental climate elements (Lepaja et al., 2014, 2015b). In Kosovo average temperature (1951-1980) is 10.3°C, that of vegetation 16.5°C, the coldest month is January (-0.9°C) while the hottest month is July with 228

20.1°C. The annual rainfall is 744.8 mm, and during vegetation it is 346.7 mm which shows the need to intervene with supplementary irrigation (Zajmi, 1996). Water shortages in the territory of Kosovo, especially during the growing period, need supplemental irrigation.

Figure 1. Schematic of the irrigation: a). normal irrigation, b). two laterals, c). side lateralPRD, and d). without irrigation. The amount of rainfall for Prishtina region for a 30-year period is 608 and 325.9 mm during the growing season. Rainfalls during the period of the study were much lower compared to the average 30-year period with a total of 892.7 and 624.4 mm during the growing period. The first irrigation was applied at the end of May when temperatures started to rise and there were no rainfalls. The temperature during the growing season was 17.01°C. The average temperature and the temperature during the growing period was 1°C higher compared to the 30-year average. Data from the measurements were analysed using ANOVA two-way with post hoc testing with StatPlus 2010 from AnalystSoft Inc., USA. RESULTS AND DISCUSSION Tables 1 and 2 summarize the results after application of PRD and mulching on the vegetative and fruiting parameters of ‘Polka’ raspberries, and differences between treatments. We found significant changes in a series of vegetative and fruiting parameters which confirms the results of other authors (Davies et al., 2000). All values of productive parameters were higher in two laterals treatment. Using ANOVA two-way with post hoc testing we found that treatments without irrigation and side lateral had a reduced vegetative growth, with significantly lower values of shoot length, number of leaves, leaf surface, leaf area and LAI. However, two laterals treatment gave higher values of these vegetative parameters compared to control and consequently to all other treatments. It should also be stressed that mulching had significant changes in leaf surface, leaf area and LAI. PRD and mulching had a combined effect on leaf surface. With mulch the highest values of vegetative parameters were found in two laterals treatment, followed by normal irrigation (control), side lateral and lastly without irrigation. As it can be seen from the results of vegetative parameters (Table 1), in all parameters (number of leaves, leaf surface cm2, leaf area m2, LAI m2 and shoot length cm) we observed a reduction in vegetative growth without being influenced in the productive parameters (Stoll et al., 2002; Dry et al., 1996, 2000; Spreer et al., 2007; Grant et al., 2004). 229

Table 1. Average data for vegetation parameters with differences between treatment according LSD testing Parameters Without irrigation Two laterals Side laterals Normal irrigation

Mulch + Mulch Mulch + Mulch Mulch + Mulch Mulch + Mulch -

Number of leaves a 131.20 136.20 a b 182.00 183.60 b a 124.20 135.80 a b 170.60 162.80 b

Leaf surface (cm2) a 41.73 50.16 a b 50.54 60.22 b b 48.48 45.00 c b 50.87 52.11 a

Leaf area (m2) a 5.470 6.830 a b 9.231 11.011 b a 6.026 6.104 a b 8.659 8.470 c

LAI (m2) a 4.38 5.46 a b 7.38 8.81 b a 4.82 4.88 a b 6.93 6.78 c

Shoot length (cm) a 116.00 104.40 a a 118.00 112.00 a b 84.60 98.20 a a 111.00 106.60 a

In the fruiting measurements, the treatment without irrigation showed a reduced generative growth compared to control, with significant changes in the number of fruits, fruit diameter, fruit length, fruit weight and total yield. The side lateral treatment gave a lower number of fruits and total yield (g plant-1) but other parameters were not different from the control. The highest values of productive parameters were found in two laterals treatment, followed by normal irrigation (control), side lateral and lastly without irrigation. Mulching had significant changes in the number of fruit and total yield while PRD and mulching had a combined effect on fruit length and fruit weight. In mulch the highest values of productive parameters were found in two laterals treatment, followed by normal irrigation (control), side lateral and lastly without irrigation. Concerning some parameters (fruit weight and total yield) researched by the authors (Stoll et al., 2002) our results are consistent with the authors concerned. As shown in Table 2, the number of fruits influences other fruiting parameters, especially in their average weight than in diameter and length of fruit and total yield. Table 2. Average data for reproductive parameters with differences between treatment according LSD testing Parameters Without irrigation Two laterals Side laterals Normal irrigation

Mulch + Mulch Mulch + Mulch Mulch + Mulch Mulch + Mulch -

No of fruits a 151.40 147.00 a b 200.20 175.60 b a 152.80 152.20 a b 209.00 180.40 b

Diameter of fruit (mm) a 19.16 18.99 a b 21.06 20.88 b b 20.71 20.29 b b 20.68 20.93 b

Length of fruit (mm) a 23.12 22.37 a b 25.12 24.55 b b 24.37 24.09 b a 23.71 24.46 b

Fruit weight (g) a 3.39 3.12 a b 4.50 4.39 c b 4.20 4.00 b a 3.66 4.24 c

Total yield (g plant-1) a 513.49 458.57 a b 900.30 769.71 b c 651.16 609.53 c c 764.22 765.90 c

CONCLUSIONS Based on our investigations on the partial rootzone drying under the agroecological conditions of Kosovo, and Podujeva in particular under an intensive raspberry growing technology, several conclusions can be drawn. It should also be underlined that, to our knowledge, this is the first investigation on the combined effects of PRD and mulching. At the end of the treatment period (normal irrigation, two laterals, side laterals, without irrigation), of PRD application combination with mulch, we found changes in a series of vegetative and fruiting measurements. We found that withholding irrigation and irrigation of side lateral had significantly reduced both vegetative and generative growth of ‘Polka’ raspberries in terms of shoot length, number of leaves, leaf surface and area, LAI, number of fruit, fruit diameter, fruit length, fruit weight and total yield. Two laterals 230

treatment gave the highest values of vegetative and fruiting parameters. It should also be stressed that mulching had significant changes in leaf surface and area, LAI, number of fruit and total yield. PRD and mulching had a combined effect on leaf surface, fruit length and fruit weight. In mulch the highest values of vegetative and fruit measurements were found in two laterals treatment, followed by normal irrigation (control), side lateral and lastly without irrigation. At the first year of experiment the use of mulch at 10 cm thick layer influenced most of the productive parameters and some vegetative parameters increasing their values as well as suppressing weeds. All values of productive parameters were higher in two laterals treatment. These results can be obtained primarily as a result of weather conditions: temperature and rainfall during the time the experiment, furthermore long-term effects of deficit irrigation, together with climatic conditions, crop techniques variations, type of soil, age of plants, etc. must be considered, because the long-term plant responses to PRD or RDI are more accurate than short-term responses (Lepaja et al., 2015a). As the experiment is continuing, in the next years we expect an attenuation of the PRD effects in combination with mulching. Literature cited Davies, W.J., Bacon, M.A., Thompson, D.S., Sobeih, W., and Gonzá lez Rodrı́guez, L. (2000). Regulation of leaf and fruit growth in plants growing in drying soil: exploitation of the plants’ chemical signalling system and hydraulic architecture to increase the efficiency of water use in agriculture. J. Exp. Bot. 51 (350), 1617–1626 http://dx.doi.org/10.1093/jexbot/51.350.1617. PubMed Downer, J. (2009). Mulch effects on trees. In Western Arborist, pp.30. http://www.santa-clarita.com/ modules/showdocument.aspx?documentid=9410 Dry, P.R., Loveys, B.R., Botting, D., and During, H. (1996). Effects of partial root-zone drying on grapevine vigour, yield, composition of fruit and use of water. Paper presented at: 9th Australian Wine Industry Technical Conference (Adelaide, Australia). Dry, P.R., Loveys, B.R., Stoll, M., Steward, D., and McCarthy, M.G. (2000). Partial rootzone drying - an update. Australian Grapegrower and Winemaker 438a, 35–39. Funt, R.C., and Ross, D.S. (2013). Soil and water management. In Raspberries, Crop Production Science in Horticulture, R.C. Funt, and H.K. Hall, eds, Cabi, series. 23 (Boston,USA: Cabi), p.103–119. Grant, O.M., Stoll, M., and Jones, H.G. (2004). Partial rootzone drying does not affect fruit yield of raspberries. J. Hortic. Sci. Biotechnol. 79 (1), 125–130 https://www.researchgate.net/publication/240612652_Partial_ rootzone_drying_does_not_affect_fruit_yield_of_raspberry. Greenly, K., and Rakow, D. (1995). The effect of wood mulch type and depth on weed and tree growth and certain soil parameters. J. Arboriculture. 21, 225 https://www.researchgate.net/publication/242632561_THE_EFFECT _OF_WOOD_MULCH_TYPE_AND_DEPTH_ON_WEED_AND_TREE_GROWTH_AND_CERTAIN_SOIL_PARAMETERS. Kullaj, E. (2007). Advanced Biology of Fruit Crops (Tirana, Albania: FBM. UBT.), pp.313 (in Albanian). Lepaja, L., Kullaj, E., Lepaja, K., Shehaj, M., and Zajmi, A. (2014). Fruit quality parameters of five pear cultivars in western Kosovo. Journal of International Scientific Publications: Agriculture and Food 2, 245–250 https://www.researchgate.net/publication/262838250_Fruit_quality_parameters_of_five_pear_cultivars_in_West ern_Kosovo. Lepaja, L., Kullaj, E., Lepaja, K., and Zajmi, A. (2015). Effect of regulated deficit irrigation, mulching and their combination on fruit diameter growth of young ‘William’ pears. Paper presented at: 50th Croatian and 10th International Symposium on Agriculture (Opatija, Croatia). https://www.researchgate.net/publication/ 272744249_Effects_of_regulated_deficit_irrigation_mulching_and_their_combination_on_fruit_diameter_growth_o f_young_'William'_pears Lepaja, K., Lepaja, L., Kullaj, E., Krasniqi, N., and Shehaj, M. (2015). Effect of partial rootzone drying (PRD) on fruit quality and nutrient contents of ‘Albion’ strawberry. Paper presented at: 50th Croatian and 10th International Symposium on Agriculture (Opatija, Croatia). http://sa.agr.hr/pdf/2015/sa2015_p0910.pdf. Marsal, J., Mata, M., Arboné s, A., Rufat, J., and Girona, J. (2002). Regulated deficit irrigation and rectification of irrigation scheduling in young pear trees: an evaluation based on vegetative and productive response. Eur. J. Agron. 17 (2), 111–122 http://dx.doi.org/10.1016/S1161-0301(02)00002-3. Marsal, J., Mata, M., del Campo, J., Arbones, A., Vallverdú , X., Girona, J., and Olivo, N. (2008). Evaluation of partial

231

root-zone drying for potential field use as a deficit irrigation technique in commercial vineyards according to two different pipeline layouts. Irrig. Sci. 26 (4), 347–356 http://dx.doi.org/10.1007/s00271-007-0098-4. Posadas, A., Rojas, G., Malaga, M., Mares, V., and Quiroz, R. (2008). Partial Root-Zone Drying: an Alternative Irrigation Management to Improve the Water Use Efficiency of Potato Crop (International Potato Center), p.1–14. Pulupol, L., Behboudian, H., and Fisher, K. (1996). Growth, yield, and postharvest attributes of glasshouse tomatoes produced under deficit irrigation. Hortic. Sci. 3, 926–929 https://www.researchgate.net/publication/ 268429372_Growth_Yield_and_Postharvest_Attributes_of_Glasshouse_Tomatoes_Produced_under_Deficit_Irrigati on. Sadras, V.O. (2009). Does partial root-zone drying improve irrigation water productivity in the field? A metaanalysis. Irrig. Sci. 27 (3), 183–190 http://dx.doi.org/10.1007/s00271-008-0141-0. Spreer, W., Nagle, M., Neidhart, S., Carle, R., Ongprasert, S., and Muller, J. (2007). Effect of regulated deficit irrigation and partial rootzone drying on the quality of mango fruits (Mangifera indica L., cv. ‘Chok Anan’). Agric. Water Manage. 88 (1-3), 173–180 http://dx.doi.org/10.1016/j.agwat.2006.10.012. Stikic, R., Popovic, S., Srdic, M., Savic, D., Jovanovic, Z., Prokic, Lj., and Zdravkovic, J. (2003). Partial root drying (PRD): a new technique for growing plants that saves water and improves the quality of fruit. Bulg. J. Plant Physiol. (Special Issue), 164–171. https://www.researchgate.net/publication/228995752_Partial_root_ drying_%28PRD%29._A_new_technique_for_growing_plants_that_saves_water_and_improves_the_quality_of_fruit Stoll, M., Jones, H.G., and Infante, J.M. (2002). Leaf gas exchange and growth in red rasspberries is reduced when part of the root system is dried. Acta Hortic. 585, 671–676 http://dx.doi.org/10.17660/ActaHortic.2002.585.111. Tatullo, G., Farina, V., and Bianco, R. (2007). Growth, fruit yield and quality of ‘Golden Delicious’ apple trees under fixed partial rootzone drying. Journal of Applied Horticulture. 9 (1), 50–55 https://www.researchgate.net/ publication/257217167_Growth_fruit_yield_and_quality_of_Golden_Delicious_apple_trees_under_fixed_partial_ro otzone_drying. Zajmi, A. (1996). The opportunities of utilizing the natural and biological potentials, in the agriculture productivity in Kosovo. Paper presented at: A Scientific Conference: A Multidisiplinary Aproach of Developing Possibilities of Kosova. ASHAK (Prishtinë , Albania). (in Albanian). Zhang, H., and Oweis, Th. (1999). Water-yield relations and optimal irrigation scheduling of wheat in the Mediterranean region. Agric. Water Manage. 38 (3), 195–211 http://dx.doi.org/10.1016/S0378-3774(98)000699.

232