ࡱ> LNKq`0EbjbjqPqP4J:: !FFFFFFFZB B B B 4v Z'%$  *$,$,$,$,$,$,$$K&h(.P$FP$FF $!!!6F F *$!*$!!FF! .^B $ N!#$<'%!(r!^(!!(F!!t]P$P$! '%ZZZ> ZZZ> ZZZFFFFFF Effect of foliar fertilizers on yield and yield structure of potato tuber grown under water stress conditions Tea Horvat, Milan Poljak, Boris Lazarevi, Tomislav Kara~ija, Zlatko Sve njak Sveu iliate u Zagrebu Agronomski fakultet, Svetoaimunska cesta 25, 10000 Zagreb ( HYPERLINK "mailto:thorvat@agr.hr" thorvat@agr.hr) Abstract The aim of this study was to determine the effect of three foliar fertilizers (Epso Salt, Megagreen and Drin) and control treatment (with no foliar fertilizer) on tuber size and yield of potato crop grown under water stress conditions. The study was conducted in the greenhouse using variety 'Courage' during three growing seasons (2005, 2006 and 2007). The experiment was arranged in a split-plot design with three replications. Foliar fertilization was carried out five times during vegetation at intervals of ten days in the period from the start of tuber formation to the stage of full tuberization. Water stress was induced at the full tuberization growth stage by interruption of irrigation. The results showed that under water stress conditions a significantly higher number of 0-25 mm size tubers, but lower number of 50-75 mm size tubers was achieved. Tuber yield was significantly reduced by an average of 15 % under water stress conditions. Megagreen, Drin and control treatment achieved significantly higher tuber yield under optimum water supply when compared to water stress conditions. In contrast, foliar application of Epso Salt brought about similar tuber yields under conditions of water stress and optimum water supply. Key words: potato, foliar fertilizers, water stress, tuber yield Introduction The potato (Solanum tuberosum L.) is well known as one of the most sensitive crops to water stress. Water stress causes inhibition of growth which is reflected in a restriction of photosynthesis, dry matter formation and yield (Poljak et al., 2005; Hnili ka et al., 2007). During mid and late bulking periods water stress reduces yield while increases the percentage of undersized tubers and causes tubers brown spots (Horvat et al., 2008). In water stress conditions transport of certain nutrients (Ca, Mg, B, Mn) that are transported through the plant by xylem is limited and soil fertilization is not always sufficient to meet the needs of crops. The alternative approach is the application of these nutrients to plant leaves and stems through foliar fertilization (Horvat et al., 2006). Nutrient supply through leaf fertilization acts rapidly as through the leaf surface the ions can join metabolism directly (Takacs-Hajos et al., 2007). Foliar fertilization is not a new practise. However, there is limited research information and use of foliar nutrients on potatoes. Objective The objective of this study was to evaluate the effects of foliar fertilizers on tuber size and yield of potato crop grown under water stress conditions. Materials and methods During three growing seasons (2005, 2006 and 2007) the experiment was conducted in the conservatory of the Faculty of Agriculture, University of Zagreb, in partly controlled conditions. Sprouted tubers cv. Courage (28-35 mm) were planted in pots (25 L) filled with a mixture of soil and perlite at a ratio of 3:1. The basic fertilization, calculated by pot, was carried out with 750 kg ha-1 NPK 7:20:30 and 250 kg ha-1 KAN before planting. The experiment consisted of three foliar fertilizers (Epso Salt (Mg-sulfate, B, Mn),Drin (alpha amino acid), Megagreen (Ca and Mg)) and control treatment (with no foliar ferilizer) and was arranged in a randomized split-plot design with three replications. Foliar fertilization was carried out 50, 60, 70, 80 and 90 days after planting as instructed by manufacturers (Epso Salt at a dose of 25 kg ha-1, Drin 0,5 l ha-1 and Megagreen at a dose of 2 kg ha-1) with the water consumption of 300 l ha-1 calculated per pot. Drip irrigation was used. Water deficit stress was induced by interrupting irrigation 90 days after planting at the stage of full tuberization. Measures were taken during vegetation to protect the plants from weed, insects and diseases. After 20-day exposure of the plants to water stress, fresh tuber yield and the number of tubers by size were calculated. Data were subjected to the analysis of variance. For comparing average values, LSD test was used when F test was significant at the level of P d" 0.05. Results and discussion The potato tuber yield and number of 0-25 mm and 50-75 mm size tubers were significantly influenced by water stress (Table 1). Potato tuber yield was significantly reduced in water stress conditions by an average of 15 % and amounted 370,0 g per plant compared with 433,5 g per plant under optimum water supply conditions. Pereira and Shock (2006) reported also the reduction in yield and specific gravity in potato tuber due to water stress. A significantly higher number of 0-25 mm size tubers, but lower number of 50-75 mm size tubers was determined in water stress conditions. The likely reason is that in water deficit conditions the stoma closure decreased the intensity of photosynthesis, prevented the translocation of assimilates into the tuber and further thickening. Similar results were reported by Walworth and Carling (2002). The potato tuber yield was significantly influenced by foliar treatments under water stress and optimum water supply conditions (Table 1). Plants subjected to control, Megagreen and Drin had a significantly higher tuber yield under optimum water supply when compared to water stress conditions. In contrast, foliar application of Epso Salt brought about similar tuber yields under conditions of water stress and optimum water supply (Figure 1). The positive impact of foliar fertilization by Epso on soya yield was accomplished by Vratari et al. (2006). The smallest yield in stress conditions was obtained under the influence of Drin treatment. In water stress conditions Megagreen treatment achieved a higher yield (418,3 g per plant). The absence of interaction between treatments and stress indicate that treatments responded similarly in the number of tubers by size in water stress and optimum water supply conditions (Table 1). Conclusions Potato tuber yield was significantly reduced in water stress conditions by an average of 15 %. In addition, water stress resulted in a significantly higher number of 0-25 mm size tubers, but lower number of 50-75 mm size tubers. Our findings have shown a positive impact of foliar fertilizer Epso Salt on potato tuber yield in water stress conditions. Ttreatments responded similarly in the number of tubers by size in water stress and optimum water supply conditions. References Hnili ka, F.  Hnili kov, H.  Martinkov, J.  Blha, L.: 2007. The influence of drought and the application of 24  epibrassinolide on the formation of dry matter and yield in wheat. Cereal Research Communications, 35: 2. 457-460. Horvat, T.  Poljak, M. 4 V Z x |   3 4 B C D E F N O * E u } ظzmeZRZRZFhh6mH sH hmH sH hhmH sH h (mH sH hDJ5CJaJmH sH h5CJaJmH sH #hsh (0J5CJaJmH sH "jh (5CJUaJmH sH h (5CJaJmH sH huhu5CJaJmH sH hF#mH sH hc"ImH sH humH sH hc"Ihc"I5\mH sH "h~h5CJ\aJmH sH z | E F O )jkxQRh& $`a$gdv $`a$gdFt$a$gd$a$gdWU$a$gd5 $`a$gdtX$a$gdx~gd ($a$gdv$a$gdc"IgdE} @ Y  @ )34ijkxZt12ǻ~s~s~s~s~s~hhmH sH hmH sH h~h~6mH sH h~h~mH sH h~h~\mH sH h~\mH sH h (\mH sH h5h5\mH sH hhhhmH sH h (mH sH hh5mH sH h5mH sH hmH sH hhmH sH '?Qho"  Vt%步杕~r~r~r~r~h"Ph"PH*mH sH h"Ph"PmH sH hWUhWUH*mH sH hvmH sH h"PmH sH hWUmH sH hhWUmH sH h~\mH sH hWU\mH sH hWUhWU>*mH sH hWUmH sH hwmH sH hWUhWUmH sH hWUhWUCJaJmH sH ,%tFHvz`eF h !!!!!j"~"""""^#b# $ $i$ƾƾƾ~~~~sh"Gh"GmH sH h"GhtXmH sH htXhtXmH sH htXhtXmH sH hE$dhE$dmH sH h"GhE$dmH sH hE$dmH sH hE$dh"G h"Gh"Gh"GmH sH hWUmH sH hFtmH sH h"PmH sH hyhmH sH hWUhWUmH sH -&HJx j$/%0%<%''');}}$@& ^`a$gdw$a$gdI$Eƀa$gdFt$a$gd"G$a$gdWU $`a$gdFti$j$/%0%;%<%%%&&''''())))*:::::h=n===>>2A4AĹ׹}trdd}T}thwhw5CJaJmHsHhwhw5CJH*aJUhw5CJaJhwhwCJaJhwhw5CJaJhWU\mH sH hw\mH sH h"GhFtmH sH hFtmH sH hFthFtmH sH hFt h"GhFthWUmH sH hFtmH sH h"GhyhmH sH h"Gh"GmH sH h"GhE$dmH sH   Maji, A.  Gunja a, J.:2006. Response of potato to foliar fertilization. Proceedings of the 41st Croatian & 1st International Symposium on Agriculture. Faculty of Agriculture, University of J. J. Strossmayer, Osijek, 385-386. Horvat, T.  Poljak, M.  Maji, A.  Sve njak, Z.  Jurki, V.: 2008. Effects of foliar fertilization and water stress on yield and physiological characteristics of potato. Cereal Research Communications, 36: 3. 1659-1662. Pereira, A.B.  Shock, C. C.: 2006. Development of irrigation best management practices for potato from a research perspective in the United States. Sakia.org e-publish, 1: 1. 1-20. Poljak, M.  osi, T.  Herak-usti, M.  Horvat, T.  Buturac, I.: 2005. Potato nitrogen fertilization efficiency. Proceedings of the XL Croatian Symposium on Agriculture with International Participation. Faculty of Agriculture, University of J. J. Strossmayer, Osijek, 369-370. Takacs-Hajos, M.  Szabo, L.  Racz, I.  Mathe, A.  SzQke, E.: 2007. The effect of Mg-leaf fertilization on quality parameters of some horticultural species. Cereal Research Communications, 35: 2. 1181-1184. Vrataric, M.  Sudaric, A.  Kovacevic, V.  Duvnjak, T.  Krizmanic, M.  Mijic, A.: 2006. Response of soybean to foliar fertilization with magnesium sulfate (Epsom Salt). Cereal Research Communications, 34: 1. 709-712. Walworth, J.L.  Carling, D.E.: 2002. Tuber initiation and development in irrigated and non-irrigated potatoes. 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