Luděk Hřivna, Rostislav Richter*, Jitka Rašková
Mendel University of Agriculture and Forestry in Brno, Department of Food Technology * Department of Agrochemistry and Plant Nutrition
The correction of sulphur nutrition of winter rape
(Brassica napus L.)
*Skorygowanie odżywienia siarką rzepaku ozimego (Brassica napus L.)
Key words: winter rape, sulphur, nitrogen, correction nutrition
In small-plot field trials conducted in 2000–2003 we studied the effect of sulphur applied in the form of liquid SAM 240 with two levels of nitrogen fertilization on seed yields, oil content and concentration of the major nutrients during vegetation. The effect of additional sulphur fertilization on the S concentration in plants in the DC 50 stage was positive. The sulphur concentration increased within the range of ca 0.015–0.085%, which constituted relative increase of 3–18.6%. Correcting the sulphur level in plants under optimal concentrations of the other nutrients increased seed yields statistically significantly and stabilised the oil content. Despite the very high variability of yields in the respective years, sulphur fertilization had a positive effect in all the years. Sulphur application increased seed yields, on average, by 5.94%.
Słowa kluczowe: rzepak ozimy, siarka, azot, skorygowanie odżywienia
W małopoletkowych doświadczeniach polowych prowadzonych w latach 2000–2003, badano wpływ nawożenia siarką w formie nawozu płynnego SAM 240 oraz dwóch poziomów nawożenia azotowego na plon nasion, zawartości tłuszczu i najważniejszych składników pokarmowych w okre-sie wegetacji. Wpływ dodatkowego nawożenia siarką na zawartość S w roślinach w stadium DC 50 był pozytywny. Koncentracja siarki wzrastała w granicach 0,015–0,085%, co stanowiło relatywny wzrost o 3–18%. Poprawa poziomu zaopatrzenia roślin w siarkę, przy optymalnej koncentracji innych składników, statystycznie istotnie zwiększała plon nasion i stabilizowała zawartość tłuszczu. Pomimo bardzo dużego zróżnicowania w poszczególnych latach, nawożenie siarką miało pozytywny wpływ na plon nasion we wszystkich latach badań. Stosowanie siarki zwiększyło plon nasion przeciętnie o 5,94%.
Introduction
The problem of sulphur and its deficiency in agricultural crops is becoming a serious issue in European agriculture. While the consumption of N-fertilizers is markedly increasing, applications of sulphur-containing fertilizers is stagnating or even decreasing (Cecotti, Messick 1994).
Acute sulphur deficiency has been observed in Europe since the 1980s, but in the Czech Republic (CR) it was not evident until 1990. Reducing sulphur emissions and restricting the application of sulphur-containing fertilizers have considerably decreased the content of sulphur available for plants resulting in a sensitive reaction of crops demanding higher levels of sulphur. Plants also draw
sulphur from the atmosphere in the form of SO2, but the most important resources
of sulphur are sulphates taken up by roots (Marschner 1995). The reduction of sulphates is more intensive in leaves where light stimulates their transformation (Fankhauser, Brunold 1978). Permanent primary products containing sulphur in reduced but organically bound form are cysteine, methionine and proteins. Specifically the two amino acids are precursors of other sulphur-containing compounds. Sulphur-containing substances are important in the defence systems of plants against biotic and abiotic effects (Marschner 1995).
The considerable reduction of sulphur emissions in the CR and limited applications of sulphur-containing fertilizers reduces the content of available (water-soluble) sulphur for the plants, the result being a strong reaction of crops requiring high levels of sulphur. The total content of S in the majority of agricultural
soil ranges between 56 and 618 mg kg-1 of soil and according to Matula (1999) on
a number of localities it ranges between 85 and 250 mg kg-1 of soil. A major part of
total sulphur is bound to the organic soil matter and in this respect its transformation in the soil corresponds with the transformations of nitrogen; there is a very close bond between these two nutrients.
So is the part of sulphur in plants considerably bound with nitrogen metabolism and that is why its critical content for a number of plants is expressed in the dry matter or in the form of unbound sulphate (Schnug 1998, Matula 1999, Dijkshoorn and Van Wijk 1967, Hřivna et al. 2001, Richter, Hřivna et al. 1999).
Oil plants, in particular, have very high demands for sulphur, and among them especially winter rape. As a response to the deficiency of biogenic elements the yields of winter rape are lower as is the oil content of the seeds. From the economic and environmental point of view it is necessary to provide an optimal level of water-soluble sulphur in the soil and in this way to contribute to an efficient exploitation of nutrients to ensure high yields (Schnug 1993, Schnug, Haneklaus et al. 1994).
Material and Methods
In small-plot field trials conducted in 2000–2003 in 3 localities of different agrochemical soil properties we studied the effect of nitrogen and sulphur fertilization on the chemical composition of plants and on rapeseed yields (Tab. 1). The experiment was not established in 2002. Table 2 presents the basic data on cultural practice.
Table 1 Agrochemical characteristics of the experimental localities
Charakterystyka chemiczna gleb pól doświadczalnych
mg kg-1 of soil — mg kg-1 gleby Year Rok Locality Miejscowość pH/KCl P K Ca Mg watersoluble 2000 Bystrovany 6.7 164 219 2580 98.2 26.3 2001 Bystrovany 6.8 118 198 2495 122 15.0 2003 Hustopeče 7.4 161 252 5490 314 9.17 Table 2 Cultural practice of the trial — Warunki doświadczenia
Year
Rok Date of sowing Data siewu Preceding crop Przedplon Odmiana Variety
Application of P and K fertilizers Zastosowany nawóz P i K prior to sowing — przed siewem 2000 25.8.1999 wheat — pszenica Bristol 120 kg K2O 50 kg P2O5
2001 24.8.2000 wheat — pszenica Pronto 120 kg K2O 75 kg P2O5
2003 28.8.2002 wheat — pszenica Zorro 100 kg K2O 50 kg P2O5
During vegetation the plants underwent standard treatment against diseases and pests; nitrogen fertilizers were applied 3 times. In the Ia and Ib regeneration fertilization nitrogen was applied in the form of ammonium nitrate (34% N), in production fertilization sulphur was applied to correct the nutritional status of the plants, parallel to nitrogen fertilization. Liquid fertilizers were applied, i.e. DAM 390 (30% N), in the variants without sulphur and DAM 390 in a mixture with SAM (19% N, 5% S) in the sulphur variants. Tab. 3 presents the timing of the applications, including the doses of the individual nutrients. After the correction with sulphur, plants were sampled at growth stage DC 50 to assess the nutritional status. Nitrogen was assessed by wet mineralisation according to the method of Kjeldahl (Zbíral 1994). Sulphur was assessed after burning the plant material
in HNO3 and H2O2 benchmarking to AES – ICP.
Table 3 Splitting the N dose during vegetation — Podział dawki azotu w okresie wegetacji
Regeneration N dose Regeneracyjna dawka azotu
[kg ha-1] Production dose Dawka produkcyjna [kg ha-1] Variant Wariant Pattern of fertilization Symbol nawożenia Ia Ib N S 1 N1 48 48 60 0 2 N1S1 48 68 70 6 3 N2 48 48 60 0 4 N2S1 48 68 70 6
Each variant had 4 replications. The size of the plot was 21.6 m2. The plants were harvested with a small-plot harvester at the stage of full maturity. The yield results were interpreted by means of uni-factorial analysis of variance and establishing the minimal significance of difference 95 and 99%.
Results and Discussion
Winter rape is numbered among crops with high demands for all nutrients (Fábry et al. 1992) and is very sensitive to nitrogen fertilization. However, if the level of nitrogen fertilization is satisfactory, the yield differences are not so marked and it is the potential deficiency of the other nutrients that appears. One of these nutrients could be sulphur.
Schnug (1993) reported hidden deficiency if the content of water-soluble sulphur in the soil was low; in the period of intensive growth distinct symptoms frequently appear on the youngest leaves of winter rape, gradually affecting the flowers and inhibiting the growth of branches with a negative effect on seed yields. Higher intensity of nitrogen fertilization in 2000 had virtually no effect on seed yields (Tab. 1). The yield increment was only 74 kg, i.e. 2.24% in relative comparison. If sulphur was applied together with a higher dose of N-fertilizers (var. 4), seed yields increased significantly (by 9.24%), confirming the conclusions of Schnug, Haneklaus (1994) who put the yields into connection with the nutrient concentration in the upper third of the plant. They considered 0.6% S in the dry matter of leaves as the optimal amount and the 0.564% concentration of S in variant 4 approached this value. Production fertilization with S and a higher level of N-fertilizers increased the S concentration and in both variants with sulphur contributed to a better use of nitrogen by the plants (Tab. 2). Sulphur fertilization boosted up the uptake of the other nutrients, i.e. phosphorus, calcium and magnesium.
In 2001 the application of sulphur was reflected again in the chemical composition of the plants. When we take the average increment of the content of sulphur of both variants and compare it with variants without sulphur, the relative comparison is ca 15.9%. If the level of N-fertilizer was low, sulphur advanced its utilization (var. 2) resulting in its increased concentration in the plants (Tab. 3). Under a lower intensity of nitrogen and sulphur fertilization the concentrations of all the other nutrients increased; higher doses of N (var. 4) suppressed the effect of sulphur on increasing concentrations of the other nutrients. Only the concentrations of calcium and magnesium increased after sulphur fertilization. The yield
increment ranged between 214 and 444 kg ha-1, i.e. in relative comparison 6.69–
8.12%. In the year in question the effect of sulphur fertilization was very positive and contributed to a significant and/or highly significant yield increment (Tab. 3). Schnug, Haneklaus (1994), Hřivna et al. (2001), among others, reported similar yield increments after the application of sulphur-containing fertilizers. On the
contrary a higher intensity of nitrogen fertilization had virtually no effect at all and the nitrogen concentration in variant N2 markedly exceeded the optimal value of 4.2% reported by Vašák et al. (1997), which probably had a negative impact on the yields of this variant.
The smallest differences in yields expressed in absolute values were reported in 2003. This was due to the unfavourable weather conditions in the winter, when the stand was partly damaged, and the following heavy deficit of precipitation during vegetation. Nevertheless, even under such conditions we can see a positive effect of sulphur applications on the chemical composition of the plant biomass during growth stage DC 50 (Tab. 4). In relative comparison the yields increased after sulphur application by ca 9.89% under a lower intensity of fertilization (var. 2) and 2.79% under more intensive nitrogen fertilization (var. 4). In 2003 the impact of sulphur application on the chemical composition of the plants was the strongest. The sulphur content in the dry matter of the plants increased on average in both variants, in relative comparison by ca 18.6%. Sulphur application also had a positive effect on calcium and magnesium concentrations in the plants. In both sulphur variants the seed yields increased significantly (Tab. 1).
Table 4 Rape seed yields — Plon nasion rzepaku (2000–2003)
2000 2001 2003 Variant
Wariant [t ha-1] rel. % [t ha-1] rel. % [t ha-1] rel. %
1 3.311 100 3.351 100 1.628 100 2 3.244 97.98 3.565 106.39 1.789 109.89 3 3.385 102.23 3.179 94.87 1.647 101.20 4 3.617 109.24 3.623 108.12 1.693 103.99 DT0,05 0.217 0.175 0.071 DT0,01 0.300 0.242 0.099
We can sum up our 3-year investigations by saying that applied sulphur increased the content of nitrogen in variant 2 compared to variant 1 by 10 % and in variant 4 compared to variant 3 by only 1.2%. Compared to all the variants without sulphur, the sulphur content in plants increased on average by 8.6% in variant 2 compared to variant 1, and by 16.3% in variant 4 compared to variant 3. In accordance with the results of Schnug et al. (1988, 1989) and Hřivna et al. (2001, 2002) it was confirmed that also the application of sulphur-containing liquid fertilizers could improve the nutritional sulphur status of the plants and create more optimal conditions for higher yields.
On the basis of the results it is evident that the application of sulphur in combination with nitrogen nutrition has a favourable effect on the nutritional status of plants during vegetation and supports the production of higher and more stable yields of rapeseeds.
Table 5 Chemical composition of plants in dry matter of rape (DC 50) in 2000–2003
Skład chemiczny suchej masy roślin rzepaku (DC 50) w latach 2000–2003
Variant Wariant %N %P %K %Ca %Mg %S 2000 1 3.08 0.644 3.21 1.72 0.152 0.491 2 3.40 0.662 3.19 1.78 0.158 0.465 3 3.22 0.669 3.23 1.82 0.168 0.507 4 3.64 0.677 3.23 1.85 0.170 0.564 2001 1 3.87 0.57 3.24 1.45 0.15 0.391 2 4.47 0.67 3.30 1.67 0.17 0.434 3 4.77 0.67 3.39 1.62 0.16 0.376 4 4.48 0.63 3.15 1.60 0.17 0.455 2003 1 3.04 0.45 3.07 1.64 0.26 0.439 2 3.17 0.40 2.92 1.89 0.28 0.528 3 3.13 0.43 2.99 1.70 0.23 0.476 4 3.03 0.39 2.84 1.88 0.26 0.556
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