Hmeljarski bilten / Hop Bulletin 26(2019) ______________ 61 FERTIGATION EXPERIMENT ON SAAZ HOPS IN 2017-2019 Pavel DONNER 1 and Josef JEŽEK 2 Professional article / strokovni članek Arrived / prejeto: 25. 10. 2019 Accepted / sprejeto: 10. 12. 2019 Abstract The three year (2017–2019) fertigation experiment with fine aroma hop variety Saaz was established in the Czech Republic in Saaz hop growing region. The control treatment included the contemporary growing technology without fertigation, just soil and foliar fertilization with 300 kg/ha of ammonium sulphate, 300 kg/ha of ammonium phosphate and 300 kg/ha of potassium chloride in the early spring, followed by 250 kg/ha of ammonium nitrate with limestone in May. Foliar fertilization mainly consisted of N, P, K, Zn and Mg application. The treatment with fertigation got basic dose of fertilizers (640 kg/ha of fertilizer containing NPK 20-7-10 + 4 % S, 2 % MgO) during sprouting, followed by fertigation 5-times (42,5 kg/ha of fertilizer containing NPK 12-12-36 + micro) and foliar application during vegetation period (various fertilizers containing mainly N, P, K, Zn, Mg, B, S). The amount of applied nitrogen, phosphorus and potassium was lower at the treatment with fertigation by 8,3 % N, 53,6 % P and 22,5 % K. The experiment proved the significant increase of yield by 27 %, 33 % and 16 % in 2017, 2018 and 2019 respectively at treatment with fertigation compared to control treatment and also the alpha-bitter acids content in hop cones was significantly higher in 2018 (by 14 %) at treatment with fertigation compared to control tretament. Nevertheless, in the years 2017 and 2019 there was no significant difference in alpha-bitter acids content between treatments. The results suggest that fertigation can intensify hop cultivation. Key words: hop, irrigation, fertigation, water-soluble fertilizers POSKUS FERIGACIJE HMELJA NA SORTI SAAZ V LETIH 2017 DO 2019 Izvleček Triletni poskus (2017–2019) na področju fertigacije hmelja je bil postavljen v hmeljarski regiji Saaz na Češkem. Preučevana sorta je bila fina aromatična sorta hmelja Saaz. Kontrolno obravnavanje je vključevalo klasično pridelavo hmelja 1 PhD student, Hop Research Institute Co., Ltd., Kadaňská 2525, 438 01 Žatec, Czech Republic, e-mail: donner@chizatec.cz 2 PhD, Hop Research Institute Co., Ltd., Kadaňská 2525, 438 01 Žatec, Czech Republic, e- mail: jezek@chizatec.cz 62 Hmeljarski bilten / Hop Bulletin 26(2019) ______________ brez fertigacije, samo gnojenje preko tal in foliarno gnojenje: 300 kg/ha amonsulfata, 300 kg/ha amonfosfata in 300 kg/ha kalijevega klorida zgodaj spomladi ter 250 kg/ha amonnitrata v maju. Foliarno gnojenje je vključevalo v glavnem hranila N, P, K, Zn in Mg. Obravnavanje s fertigacijo je vključevalo osnovni odmerek 640 kg/ha NPK 20-7-10 + 4 % S, 2 % MgO med vznikom, sledila je fertigacija 5-krat v sezoni (42,5 kg/ha NPK 12-12-36 + mikrohranila) in foliarno gnojenje z različnimi gnojili, ki so vsebovala v glavnem N, P, K, Zn, Mg, B in S. Količina apliciranih N, P in K je bila pri obravnavanju s fertigacijo manjša za 8,3 % N, 53,6 % P in 22,5 % K. Obravnavnje s fertigacijo je doseglo v letih 2017, 2018 in 2019 za 27 %, 33 % oziroma 16 % večji pridelek kot kontrolno obravnavanje. Vsebnost alfa-kislin v storžkih je bila pri obravnavanju s fertigacijo v letu 2018 značilno večja (za 14 %) kot pri kontrolnem obravnavanju, v letih 2017 in 2019 pa med obravnavanjema ni bilo značilne razlike v vsebnost alfa-kislin. Rezultati nakazujejo, da s fertigacijo lahko intenziviramo pridelavo hmelja. Ključne besede: hmelj, namakanje, fertigacija, vodotopna gnojila 1 INTRODUCTION Hop growing success depends, among other factors, on natural precipitation. The need of hops for additional water is crucial especially during hot and dry years. When using drip irrigation with drippers above the hop rows, the water is distributed directly to the hop roots. Under rainfed conditions, the soil directly below plants is usually not wet after light rain, because hop’s biomass shades the row from the rain and most of the water stays on the leaves or flows down the leaves and lands around the plant, not directly under it. With drip irrigation the area below the hop plant, with a width of ca 1-1.2 m and with uneven rainwater distribution at ground level, becomes irrigated. Since hop is grown in different soils types, it is hard to state universal pattern of irrigation water distribution in the soil. The experiment was held on loamy fluvisol, where the irrigation water moving in the soil – both vertically and horizontally – forms an onion shape of damp soil around the plant root system. The sandier the soil is, the narrower (and more “carrot” shaped) the damp soil pattern is (Hillel, 1997; Goldy, 2015). The usual way of mineral nutrition of Czech hops consists of application of industrial mineral fertilizers in autumn or early spring around the time of pruning. It is followed by application of nitrate in form of nitrogen-based mineral fertilizers right before first hill-building ploughing. There is optional third fertilization (usually nitrate nitrogen only) before second hilling, but it is based on leaf analysis and is not practiced every year. Foliar application of micronutrients (also based on leaf analysis) together with plant protection products also occurs during vegetation. This way of fertilization is used on farms without drip irrigation. Hmeljarski bilten / Hop Bulletin 26(2019) ______________ 63 The aim of the experiment was to test the effect of water-soluble fertilizers on hop yield and alpha-bitter acids contents compared to control treatment practiced by hop growers without irrigation system. 2 MATERIAL AND METHODS Experimental area was located in a hop garden of Hop Research Institute‘s Farm in Stekník (Saaz hop growing region) which is 8 km from the town Žatec (Saaz). Hop variety Saaz was used for this experiment. The hop rhizomes were planted in 2004. Distance between rows and plants was 3 m x 1 m, the hop bines were trained in V- shape. Theoretical number of plants reached 3333 plants per hectare. Soil type at the experimental hop garden was fluvisol on alluvial sediments located close to river Ohře (Eger), where average annual precipitation doesn’t exceed 500 mm and average annual temperature ranges between 8–9°C. Experiment was set up in a hop garden called „Zastávka V“ (0.52 ha). One treatment covered area of 0.11 ha – seven 55 m long rows. A unified cultivation technology, including plant protection, was held on the whole experiment the same. The whole experiment was irrigated (as required) by a drip irrigation placed on the wiring of hop garden (above the hop plants). Irrigation system consists of one dripline above a row with emitters 1m away from each other, each emitter discharges 2 l/h. Irrigation terms and dosages are shown in Table 1, weather conditions during vegetation periods are shown in Table 2. The hop gardens were irrigated as required, based on the decision of a skilled hop grower. The fertigation took 2 hours and was done at the end of (usually) 24 h long irrigation cycle (2 l/hour = 48 l/cycle). There were two treatments: Control and Fertigation. The used fertilizers with regard to the treatment and contents of nutrients in fertilizers are summarized in Tables 3, 4 and 5. The control treatment, which is currently managed by a skilled hop grower, is presented in Table 3, the Fertigation treatment with water-soluble fertilizers is shown in Table 4. The sum of net content of selected macronutrients and zinc added in fertilizers are calculated in Table 5. Doses and terms of fertigation correspond with the demand on nutrients of hop plants concerning nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and microelements such as zinc and boron. The basic dose of fertilizers was applied during sprouting, followed by fertigation 5-times and foliar application during vegetation period. 64 Hmeljarski bilten / Hop Bulletin 26(2019) ______________ Table 1: Irrigation terms and dosages in 2017–2019 2017 1. 6. 2017 22 l/plant (= 11 h x 2 l/h) 5. 6. 2017 48 l/plant (= 24 h x 2 l/h) 9. 6. 2017 28 l/plant (= 14 h x 2 l/h) 13. 6. 2017 86 l/plant (= 43 h x 2 l/h) 21. 6. 2017 48 l/plant (= 24 h x 2 l/h) 27. 6. 2017 48 l/plant (= 24 h x 2 l/h) 4. 7. 2017 48 l/plant (= 24 h x 2 l/h) 9. 7. 2017 48 l/plant (= 24 h x 2 l/h) total 2017 376 l/plant 2018 8. 6. 2018 48 l/plant (= 24 h x 2 l/h) 16. 6. 2018 48 l/plant (= 24 h x 2 l/h) 21. 6. 2018 48 l/plant (= 24 h x 2 l/h) 29. 6. 2018 48 l/plant (= 24 h x 2 l/h) 6. 7. 2018 48 l/plant (= 24 h x 2 l/h) 9. 7. 2018 48 l/plant (= 24 h x 2 l/h) 18. 7. 2018 48 l/plant (= 24 h x 2 l/h) 21. 7. 2018 48 l/plant (= 24 h x 2 l/h) 27. 7.2018 48 l/plant (= 24 h x 2 l/h) 12. 8. 2018 48 l/plant (= 24 h x 2 l/h) total 2018 480 l/plant 2019 08. 06. 2019 88 l/plant (44 h x 2 l/h 19. 06. 2019 36 l/plant (18 h x 2 l/h) 20. 06. 2019 40 l/plant (20 h x 2 l/h) 28. 06. 2019 48 l/plant (24 h x 2 l/h) 30. 06. 2019 40 l/plant (20 h x 2 l/h) 06. 07. 2019 48 l/plant (24 h x 2 l/h) 07. 07. 2019 40 l/plant (20 h x 2 l/h) 15. 07. 2019 40 l/plant (20 h x 2 l/h) 22. 07. 2019 40 l/plant (20 h x 2 l/h) 05. 08. 2019 40 l/plant (20 h x 2 l/h) total 2019 460 l/plant Hmeljarski bilten / Hop Bulletin 26(2019) ______________ 65 Table 2: Weather conditions during 2017–2019 vegetation period Temperatures (month avg.) [°C] Precipitation (month sums) [mm] 2017 2018 2019 2017 2018 2019 April 8.9 13.7 10.6 April 47.2 15.6 28.4 May 15.6 17.7 12.4 May 21.4 41.8 60.4 June 19.8 19.3 22.8 June 48.6 48.2 19.8 July 20.4 22.1 20.9 July 67.2 17.0 31.0 August 20.1 22.4 20.4 August 65.8 10.2 47.2 Average 17.0 19.0 17.4 Sum 250.2 132.8 186.8 Table 3: Control (hop growing in 2017–2019) BBCH Month Fertilizer Dose Application 01 March ammonium sulphate (21% N; 13% S) 300 kg/ha mounted spreader (m.s.) ammonium phosphate (12% N; 52% P 2 O 5 ) 300 kg/ha potassium chloride (60% K 2 O) 300 kg/ha 31-35 May ammonium nitrate with limestone (27% N) 250 kg/ha m. s. 34 May zinc (700 g/l) 0.5 l/ha spraying machine (sp.m.) magnesium sulphate (15% MgO) 5 kg/ha sp. m. 36-38 June zinc (700 g/l) 0.5 l/ha sp. m. magnesium sulphate (15% MgO) 5.0 kg/ha sp. m. leaf fertilizer 'A' (6% N; 5,7% P 2 O 5 ; 6% K 2 O) 10.0 l/ha sp. m. 51& 55 July leaf fertilizer 'A' 10.0 l/ha sp. m. 63-67 July leaf fertilizer 'A' 10.0 l/ha sp. m. In the middle of each August, we selected 32 random plants from both experimental and control plots. Those plants were selected only from inner rows. Number of bines on each wire was counted. All plants were harvested in the period of technological maturity. Hops harvested from each plant was weighed and recalculated on weight from one bine and weight of dry hops from 1 ha. The conversion ratio was set on the value of 4.1 (raw > dry hops). A sample of hops was taken from each harvested plant and analysed for alpha-acids content (ČSN 46 2520-15, Determination of alpha bitter acid by the conductometric method). The data were compared statistically using 'Microsoft Excel' software (Estimation and Testing > Two Sample Analysis). 66 Hmeljarski bilten / Hop Bulletin 26(2019) ______________ Table 4: Fertigation (hop growing in 2017–2019) BBCH Month Fertilizer (f.) Dose Application 09 & 11 April 'A' f. (20% N; 7% P 2 O 5 ; 10% K 2 O; 4% S; 2% MgO) 640 kg/ha row spreading 35 June 'B' f. (12% N; 12% P 2 O 5 , 36% K 2 O; + micro) 42.5 kg/ha fertigation I (fert.) 35 June 'C' leaf f. (29,5% P 2 O 5 ; 5% K 2 O; 4,5% MgO; 3,1% Zn) 3.0 l/ha spraying machine 'D' leaf f. Boron (10,95% B; 150 g/l) 1.0 l/ha sp. m. 36 June 'B' f. 42.5 kg/ha fert. II 37 June 'E' leaf f. Zinc (40% Zn; 700 g/l) 0.5 l/ha sp. m. 39 June 'C' leaf f. 3.0 l/ha sp. m. 'D' leaf f. 1.0 l/ha sp. m. 39 June 'B' f. 42.5 kg/ha fert. III 51 & 55 June 'B' f. 42.5 kg/ha fert. IV 63 July 'B' f. 42.5 kg/ha fert. V 65-69 & 71 July 'F' leaf f. (15,2% N; 22,8% S; 300 g S/l) 5.0 l/ha sp. m. Table 5: Sum of net amount of selected macronutrients and zinc added in fertilizers [kg/ha] N P K Mg S Zn Control 168 69 151 1.5 39 0.7 Fertigation 154 32 117 7.9 26 0.5 3 RESULTS AND DISCUSSION The yields (averages of all 32 harvested plants) are shown in Table 6. The results of alpha-acid content (averages of 32 samples) are presented in Table 7. The significance difference between the treatments is shown in Tables 6 and 7. The experiment with fertigation proved the increase of yield by 27 %, 33 % and 16 % in years 2017, 2018 and 2019 (Table 6). The aimed application of fertilizers (with mounted spreader and spraying machine) in connection with water-soluble fertilizers can assure an effective use of the nutrients. These results are closely related with the experiment in the USA (Delahunty and Johnston, 2015), where the increase of yield by fertigation, although it was done only in organic hop growing, was also confirmed. Hop growers in Hallertau (Germany) started to use fertigation in lower extent only few years ago after EU support on irrigation systems. The first results from Germany are summed up in master’s thesis of Stampfl (2016), who published one-year results of experiment with fertigation from cultivars Perle and Herkules, stating, that statistical analysis didn’t show expected results because of Hmeljarski bilten / Hop Bulletin 26(2019) ______________ 67 weather conditions in 2016, when the effect of fertigation was limited due to sufficient amount of precipitation water and should be investigated more in the future. Table 6: Average yield of hop cultivar Saaz (dry hops after conversion; 32 plants evaluated) Year Control Experiment Index Statistics [t/ha] [t/ha] [%] [significance] 2017 1.44 1.83 +27 Yes 2018 1.04 1.39 +33 Yes 2019 1.82 2.11 +16 Yes Treatment did not have influence on alpha-acids content in hop cones in 2017 and 2019. The exception was the year 2018, when the significant increase of 14 %, compared to the Control, was recorded in Fertigation treatment. It seems to be caused by the unpredictable weather circumstances, where the negative effect on alpha-acids content is caused by high air temperatures (tropical days with over 30 °C) during second half of July and August (Türkott, 2005; Pokorný, 2011; Srečec et al., 2013). June, July and August in 2018 in the Czech Republic experienced several very hot periods. The fertigated plants seem to thrive better under hot weather conditions. The influence on alpha-acids’ synthetic process is still hardly identifiable. Table 7: Average content of alpha acids in hop cones of cultivar Saaz (Determination of alpha bitter acid by the conductometric method, according to the Czech norm ČSN 46 2520-15) Year Control Experiment Index Statistics [% C-value] [% C-value] [%] [significance] 2017 3.31 3.22 –3 No 2018 3.51 4.01 +14 Yes 2019 4.60 4.63 +1 No 4 CONCLUSIONS Hop irrigation is an important stabilizing factor of profitable hop growing and enables the supply of nutrients in connection with water soluble (mineral) fertilizers (fertigation). In our experiment fertigation (5-times in the season) in combination of foliar fertilization (6-times in a season) significantly increased the hop yield in years 2017–2019 compared to the control treatment with no fertigation, just soil fertilization and foliar fertilization The amount of applied nitrogen, phosphorus and potassium was lower at the fertigation treatment by 8,3% 68 Hmeljarski bilten / Hop Bulletin 26(2019) ______________ N, 53,6% P and 22,5% K compared to control treatment. The year 2018 proved the significant impact on the alpha-acids content in hop cones at the Fertigation treatment by 14% compared to control treatment, however, in 2017 and 2019 alpha-acids content remained unaffected by the treatment. Acknowledgement. The work was supported by Czech Ministry of Agriculture within the Research Project No. MZE-RO1319. 5 REFERENCES ČSN 46 2520-15 Determination of alpha bitter acid by the conductometric method. Czech Standardization Agency. Valid norm into force in December 1997 Delahunty, K., Johnston, J. Investigating best practices for timing and amount of organic soluble nitrate fertigation of hops in the Northeast. USDA Northeast SARE Final Report: FNE 14–796, 2015. Retreived from https://projects.sare.org/project- reports/fne14-796/ [cited 2019-10-23] Goldy, R. Hop fertigation and nutrient management . MSUE Southwest Michigan Research and Extension Center, 2015. Available at https://www.canr.msu.edu/uploads/236/71505/Hop_fertigation.pdf Hillel, D. Small-scale irrigation for arid zones – principles and options. Food and agriculture organization of the United Nations, Rome, 1997, p. 21. ISSN 1020-0819 Meier, U. Growth stages of mono- and dicotyledonous plants: BBCH Monograph. Julius- Kühn Institut, Quedlinburg, 2018, 97-101, 184-185. DOI: 10.5073/20180906-074619 Pokorný, J. Influence of locality and year on hop production and quality. [in Czech] Ph.D. Thesis, 2011, Prague, Czech University of Life Sciences Stampfl, J. Auswirkungen von Fertigation und Tropfschlauchpositionierung auf den Ertrag und die Inhaltsstoffe von Hopfen (Humulus lupulus) – Masterarbeit. Technische Unversität München, 2016. Available at https://www.lfl.bayern.de/mam/cms07/ipz/dateien/masterarbeitstampfl_feb2017.pdf Srečec, S., Čeh, B., Savić Ciler, T., Ferlež Rus, A. Empiric mathematical model for predicting the content of alpha-acids in hop (Humulus lupulus L.) cv. Aurora. SpringerPlus, ISSN 2193-1801, 2013, vol. 2, 59, p. 1-5, DOI: 10.1186/2193-1801-2-59 Türkott, L. Vliv povětrnostních podmínek na růst a vývoj ozdravených a neozdravených klonů chmele [in Czech]. Bioklimatologie současnosti a budoucnosti, Křtiny 12. – 14.9.2005, ISBN 80-86 690–31-08