The effect of selenium application to the soil on the sulphur and phosphorus content in potatoes

ZEMKOVÁ, Ľ. , HLUŠEK, J., LOŠÁK, T. , JŮZL, M. , ELZNER, P.: The eff ect of selenium application to the soil on the sulphur and phosphorus content in potatoes. Acta univ. agric. et silvic. Mendel. Brun. , 2008, LVI, No. 5, pp. 243–250 In a small-plot trial with potatoes were applied increasing doses of selenium to the soil (0, 12, 24, 48 and 72 kg Se . ha−1) and a er harvest were explored the content of selenium, phosphorus and sulphur in raw tubers and in the tops. The trials were conducted in two localities – Žabčice and Valečov using the semi-early variety Ditta. Selenium was applied to the soil in the form of sodium selenite before planting the potatoes. Chemical analyses discovered that with the applied dose the level of se lenium increased in both tubers and tops and that the correlation between the applied selenium dose and its content in tubers and tops was signifi cant (α < 0.05) and positive (r = 0.885 and r = 0.908, respectively). With an increasing dose of selenium the reduction in the level of sulphur in the tops (r = −0.872, α < 0.05) was statistically signifi cant. In both localities the range of the sulphur levels in tubers was very narrow, i.e. 0.16–0.18%, and the eff ect of the selenium dose was not signifi cant. The phosphorus content in tubers and tops did not change signifi cantly a er application of a dose of up to 48 kg Se . ha−1. With the highest dose of selenium the content of phosphorus in both tops and tubers decreased signifi cantly. selenium, doses, potatoes, phosphorus, sulphur, interaction Selenium is an essential element for humans and animals. Many studies have shown that the worldwide consumption of selenium is insuffi cient. Lyons et al. (2005a) proved that many South Australians consume inadequate amounts of Se to maximise selenoenzyme expression and cancer protection. Deprivation of Se is associated with impaired antioxidant protection (Combs, 2001). Clark et al. (1996) detected that patients treated with Se had signifi cant reductions in total cancer incidence and in total cancer mortality. Most papers published in China focused on the relationship between environmental Se defi ciency and Keshan Disease and reported that the incidence of Keshan Disease is closely associated with very low dietary intake of Se (Fang et al., 2002; Tan et al., 2002; Ge and Yang, 1993). Reilly (1998) mentioned other diseases related with Se defi ciency and remarked that dietary intake of Se in the UK is reduced. Lintschinger et al. (2000) mentioned that Se supply in Austria and Germany is below the recom men ded daily intake as well. Data determined by Kvíčala et al. (1995) showed that the Czech Republic belongs among the countries with low Se intake. Agronomic fortifi cation off ers an eff ective strategy to increase the Se content in plant production. Applying Se-enriched fertilizers to crops is an eff ective preventive technique against the Keshan Disease in children in China (Fang et al., 2002). Broadley et al. (2006) mentioned that Se intake in the UK population can be increased in the short term through agronomic biofortifi cation. In Finland all agricultural multinutrient fertilisers have been supplemented with Se since 1984 in order to increase the Se content in domestic foods and to raise the dietary Se intake of consumers (Eurola et al., 1991). Many studies showed that Se application enhanced the Se content in plants. For their trials Liu et al. (2004) used rice, El Ghanam (2004) soybean plants, Vinay-Singh and Malik (1990) berseem, Lyons et al. (2005b) and Ducsay and Ložek (2006) wheat, Kopsell and Randle 244 Ľ. Zemková, J. Hlušek, T. Lošák, M. Jůzl, P. Elzner (1997) and Barak and Goldman (1997) onion, Toler et al. (2007) Brassica oleracea, Munshi and Mondy (1992) and Poggi et al. (2000) potatoes. Lintschinger et al. (2000) showed that a signifi cant accumulation of Se was possible in wheat, alfalfa and sunfl ower seeds during sprouting in a solution containing Se and that these sprouts might provide the starting material for fortifi ed cereal-based diets. An interaction between selenium and some of the elements is expected. The chemical and physical properties of selenium are very similar to those of sulphur (Barker and Pilbeam, 2007; Kabata-Pendias and Pendias, 2000; Reilly, 1998). Increasing levels of selenium in plants may suppress the tissue concentrations of nitrogen, phosphorus and sulphur. It can also inhibit the absorption of heavy metals (KabataPendias and Pendias, 2000). Vinay-Singh and Malik (1990) detected that applied Se decreased P and S uptake. Furthermore, absorption and utilisation of Se decreased in the presence of S and P. Kopsell et al. (2000) proved that Se enrichment decreased the P content in leaf tissue, but the S content increased with increasing Se treatment. In another study, a low concentration of Se enhanced S uptake and accumulation as well (Kopsell and Randle, 1997). Li and Zhu (2007) found that the S content in shoots was not infl uenced by added Se concentration, but that the Se content in shoots considerably decreased by in creasing the S supply. In another study (Barak and Goldman, 1997) discovered that an addition of Se to the solution culture reduced S uptake by the plant, and Se uptake was suppressed by increasing the S concentration in solution culture. That indicated a competitive relationship between these two elements. On the contrary, a synergistic interaction between Se and S was reported by Rani et al. (2005), Mikkelsen (1988), Mikkelsen and Wan (1990), White et al. (2004), Toler et al. (2007), Charron et al. (2001). Lyons et al. (2005b) confi rmed these results but remarked that a high concentration of Se in the soil may inhibit S transport. A few authors investigated the relationship between selenium and phosphorus. Although mutual interaction is not expected, interesting results were achieved. The interaction between selenium and phosphorus was evident (Liu et al., 2004). He et al. (1994) found out that applied P decreased selenite sorption by ryegrass and that P sorption decreased with an increasing concentration of Se in the initial solution. El Ghanam (2004) found that P uptake by soybeans was signifi cantly but negatively aff ected by increasing levels of applied Se. Li et al. (2008) stu died the eff ect of P starvation on Se uptake in a hydroponics experiment. They found that P starvation increased Se uptake and suggested that P competitively inhibited Se absorption by the wheat root. Rani et al. (2005) found that the application of Se had no signifi cant eff ect on the P content of diff erent crops – maize, wheat and rice, except the raya crop. In the present study we applied diff erent doses of selenium into the soil and compared the selenium content in tubers and tops. The next objective was to explore the possible eff ect of supplied selenium on the content of sulphur and phosphorus in potato tops and tubers. In our experiment we used potatoes because they are an important component of the human diet in the Czech Republic. MATERIAL AND METHODS The fi eld experiments were conducted in two localities in the Czech Republic – Valečov (460 meters above sea level) and Žabčice (184 meters above sea level) in 2006. The important agrochemical charac te ris tics of soils are shown in Tab. I. Soil samples were analysed according to Mehlich III (CH3COOH, NH4NO3, NH4F, HNO3 and EDTA). The content of phosphorus was determined by UV-vis spectrophotometry, potassium by atomic emission spectrometry, magnesium and calcium by atomic absorption spectrometry. The content of selenium was determined by atomic absorption spectrometry in an extract of 2M HNO3. I: Agrochemical characteristics of the soil (mg.kg−1) in two localities