To investigate the effect of K fertilizer on yield and yield components of three watermelon cultivars, a two-year study (2007-2008) was conducted in Ardestan Agricultural Research Center (Isfahan province) by using of split plot randomized based on complete block design in three replications. Three watermelon cultivars (‘Sugar baby’, ‘Charleston Grey’ and ‘Mahbubi’), were assigned as main plots and four K fertilizer levels (zero, 50, 100, and 150 kg K.ha-1) were assigned as subplots. Two and three times higher than consumption of K fertilizer (100 and 150 kg K.ha-1) in compared to normal conditions (without salinity), led to a 24.8 and 18.5 percent increase in yield of ‘Charlston Gray’ and ‘Sugar Baby’, respectively. The highest fruit yield (39112 kg.ha-1), was obtained using 150 kg K.ha-1 in ‘Charleston Gray’ cultivar. Potassium applications at all levels, increased fruit number in ‘Sugar Baby’ and fruit weight in ‘Charleston Gray’, were considered as the main reason for increasing yield. By increasing of K application, the ratio of Na/K in the leaves from 0.61 to 0.33 and in the stems from 0.81 to 0.4 was decreased. The results indicated that in saline conditions, higher levels of K fertilizers can reduce the deleterious effects of salinity and thus may improve watermelon yield.


1 . آمارنامه کشاورزی (1388) جلد اول: محصولات زراعی. معاونت برنامه­ریزی و اقتصادی، دفتر آمار و فناوری اطلاعات وزارت جهاد کشاورزی. 136 ص.
2 . میرزاپور م. ه.، خوش­گفتار منش ا. ح.، میرنیا خ.، بهرامی ح. و نایینی م. ر (1382) اثرهای متقابل منیزیم و پتاسیم بر رشد و عملکرد آفتابگردان در یک خاک شور. علوم خاک و آب. 17(2): 12-1.
3 . Bhandal IS and Malik CP (1988) Potassium estimation, uptake, and its role in the physiology and metabolism of flowering plants. International Review of Cytology. 110: 205-254.
4 . Cakmak I (2005) The role of potassium in alleviating detrimental effects of abiotic stresses in plants. Plant Nutrition and Soil Science. 168: 521-530.
5 . Colla G, Rouphael Y, Cardarelli M and Rea E (2006) Effect of salinity on yield, fruit quality, leaf gas exchange, and mineral composition of grafted watermelon plants. HortScience. 41: 622-627.
6 . Cuin TA, Miller AJ, Laurie SA and Leigh RA (2003) Potassium activities in cell compartments of
salt-grown barley leaves. Experimental Botany. 54: 657- 661. 
7 . FAO (2000) Global network on integrated soil management for sustainable use of salt affected soils. Country species salinity issues, Iran. FAO, Rome, Available on http://www.fao,org/ag/agl/agll/spush/ degrad.asp?
8 . FAO (2006) Water use, by sector and by source. AQUASTAT information system on water in agriculture available on: dbase/index.stm.
9 . Grattan SR and Grieve CM (1999) Salinity-mineral nutrient relations in horticultural crops. Scientia Horticulturae. 78: 127-157.
10 . Grimes DW, Yamada H and Hughes SW (1987) Climate-normalized cotton leaf water potentials for irrigation scheduling. Agricultural Water Management. 12: 293-304.
11 . Gusmini G and Wehner TC (2005) Foundations of yield improvement in watermelon. Crop Science.
45: 141-146.
12 . Gusmini G, Shultheis JR and Wehner TC (2004) Rind thickness watermelon cultivars for use in pickle production. HortTechnology. 14: 540-545.
13 . Hernandez J, Jimenez A, Mullineaux AE and Sevilla E (2000) Tolerance of pea to long-term salt stress is associated with induction of antioxidant. Plant Cell and Environment. 23: 853-862.
14 . Kanai S, Ohkura k, Adu-Gyamfi JJ, Mohapatra PK, Nguyen NT, Saneoka H and Fujita K (2007) Depression of sink activity precedes the inhibition of biomass production in tomato plants subjected to potassium deficiency stress. Experimental Botany. 58: 2917-2928.
15 . Lester GE (2006) Environmental regulation of human health nutrients (ascorbic acid, beta-carotene, and folic acid) in fruits and vegetables. HortScience. 41: 59-64.
16 . Lester GE, Jifon LJ and Donald JM (2010) Impact of potassium nutrition on postharvest fruit quality: Melon (Cucumis melo L.) case study.Plant Soil. 335: 117-131.
17 . Maathuis FJM and Amtmann A (1999) K+ nutrition and Na+ toxicity: the basis of cellular K+/Na+ ratios. Annals of Botany. 84: 123-133.
18 . Okur B and Yagmur B (2004) Effects on enhanced potassium doses on yield, quality and nutrient uptake of watermelon. IPI regional workshop on potassium and fertigation development in West Asia and North Africa; Rabat, Morocco, 24-28 Nov.
19 . Qadir M, Qureshi AS and Cheraghi SAM (2008) Extent and characterization of salt-affected soils in Iran and strategies for their amelioration and management. Land Degradation and Development.19: 214-228.
20 . Raman SN, Desai D, Solanaki JB and Bhatt SM (1986) The Na/K ratio as index of salt stress in rice culture. International Rice Research. Newsletter. 11: 1- 30.
21 . Ramani S and Apte SK (1997) Transient expression of multiple genes in salinity-stressed young seedlings of rice (Oryza sativa L.). Biochemical and Biophysical Research Communications. 233: 663-667.
22 . Rengel Z, Damon PM and Cakmak I (2008) Crops and genotypes differ in efficiency of potassium uptake and use. Physiologia Plantarum. 133: 624-636.
23 . SAS Institute (2007) SAS Onlinedoc 9.1.3 SAS.
Inst., Cary, NC. Available at http://support. JPS (verified 19 June 2007).
 24 . Shani U and Dudley LM (2001) Field studies of crop response to water and salt stress. American Journal of Soil Science Society. 65: 1522-1528.
25 . Shannon MC and Francois LE (1978) Salt tolerance of three muskmelon cultivars. American Society for Horticultural Science (ASHS). 103: 127-130.
26 . Shen W, Nada K and Tachibana S (2000) Involvement of polyamines in the chilling tolerance of cucumber cultivars. Plant Physiology. 124: 431-439.
27 . Spahn C, Blaha G, Stelzel U, Agrawal RK, Frank J and Nierhause KH (2000) Preparation of functional ribosomal complexes and effect of buffer conditions on tRNA positions observed by cry electron microscopy. Methods Enzymology. 317: 292-309.
28 . Storey R and Wyn Jones RG (1978) Salt stress and comparative physiology in the Gramineae. 1. Ion relations of two salt- and water-stressed barley cultivars, California Mariout and Arimar. Australian Journal of Plant Physiology. 5: 801-816. 
 29 . Sudhaker C, Lakshmi A and Grindarakumar S (2001) Changes in the antioxidant enzyme efficacy in two high yielding genotypes of mulberry ender NaCl salinity. Plant Science. 161: 613-619.
30 . Varlagas H, Savvas D, Mouzakis G, Liotsos C, Karapanos I and Sigrimis N  (2010) Modeling uptake of Na+ and Cl by tomato in closed-cycle cultivation systems as influenced by irrigation water salinity. Agricultural and Water Management. 97: 1242-1250.
31 . Weimberg R, Lerner HR and Poljakoff-Mayber A (1982) A relationship between potassium and proline accumulation in salt-stressed Sorghum bicolor. Physiologia Plantarum. 55: 5-10.
32 . Yetisir H and Uygur V (2010) Responses of grafted water melon on to different gourd species to salinity stress. Plant Nutrition. 33: 315-327.
33 . Zhu JK (2003) Regulation of ion homeostasis under salt stress. Current Opinion in Plant Biology. 6: 441-445.