engleski

Influence of foliar fertilization with Epsom salt (MgSO4.7H2O) on sugar beet quality.

Low sucrose contents (average of 14.03% in the period of 1991-1995) and satisfied root yields (37.5 t ha -1 respectively) characterize sugar beet growing in Croatia. We studied about the possibility to improve sugar beet quality, especially sucrose contents, by Epsom salt foliar fertilization. Survey of 3-year experiences was shown in this study. Recognized (the trial A) and experimental (the trial B) sugar beet genotypes were grown on three localities situated on a large farms for two growing seasons (1995 and 1996) in four replications (size of plot 10 m2). Two replications were fertilized with Epsom salt (ESF treatment), 5% (w/v) MgSO4 . 7H2O solution at rate of 400 L ha-1 twice at 10-day interval in June, while the other were used as a control. Results were shown as an averages of three localities in level of fertilization treatment and any result is average of total individual data as follows (for A and B, respectively): 78 and 140 (1995), 102 and 90 (1996). Total 19 sugar beet hybrids were grown in three localities and eight replications (four ESF and four controls) for the 1997 season (the trial A). In addition, sugar beet crops of small farmers (three localities and ten replications) were included for 1997 season (the trial B). The results for the 1997 season are averages of 228 (A) and 15 (B) individual data. Sucrose contents were determined polarometrically, root K and Na plammenphotometrically and root amino-nitrogen (a-N) colorimetrically. Average of tested properties ranged, depended on the growing season, from 12.14 to 15.92% (sucrose), from 38.1 to 58.0 t ha-1 (root yield), from 4.03 to 4.10 mmol K 100 g -1 (root K), from 1.00 to 2.43 mmol Na 100 g -1 (root Na) and from 1.72 to 2.37 mmol a-N 100 g -1 (root amino-N). Drought and heat stresses characterized the growing season from June 30 to August 9 in 1995: 26 mm of rainfall and average 21.2 oC of air-temperature (Osijek Weather Bureau). In 1996 and 1997 growing seasons, weather conditions were normal. Degree of individual growing season favorability for sugar beet growing is possible to estimate based on rainfall and air-temperatures in July: 2 mm and 23.6 oC (1995), 96 mm and 19.6 oC (1996), 98 mm and 20.7 oC (1997). In general, sucrose contents increased, although low but very significantly, by the ESF as follows (for the 1995, 1996 and 1997, respectively): for 0.25%, 0.18% and 0.26% (A), for 0.20%, 0.16% and 0.65% (B), respectively. Accumulation of amino-N in sugar beet root is harmful because of disturbance of sucrose crystallization. Significant influences of ESF on a-N decreasing were found in the 1996 growing season for both trials, as well in the 1997 for the trial B only. However, K and Na status in sugar beet root were less depended on ESF. In general, weather conditions, soil properties and genotypes influenced yield and sugar quality more than ESF. We would recommend ESF as a practice of crop management for sugar beet, especially under conditions with moderate Mg and/or S supply.

Sugar beet; magnessium; fertilization

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