Fertilizing action [K1]of sulphur from different sources on the yield and content of this component at plants
Jolanta Kozłowska-Strawska1, Aleksandra Badora1, Jolanta Domańska1, Stanisław Chwil2, Renata Matraszek3
1Department of Agricultural and Environmental Chemistry
2Department of Chemistry
3Department of Plant Physiology
University of Life Sciences in Lublin, Poland
Abstract
The study was performed based on a strict three-year pot experiment conducted on the soil material taken from the topsoil of the lessive soil with a particle size of silt loam, which was characterized by a slight acidity and low levels of available phosphorus, potassium, magnesium, and sulfate sulfur. Variable element consisted of sulfur that was used in eight different forms. Sulfur fertilization was applied annually in accordance with the scheme: 1) S0 – without sulfur fertilization; 2)RSMS – sulfate-urea solution with addition of Na2S2O3 5H2O; 3)(NH4)2SO4; 4)K2SO4; 5)Na2SO4; 6)elemental S; 7) CaSO42H2O; 8) H2SO4. In the first year of study, the test plants were wheat and white mustard. In the second year, spring rape and spring barley were grown. And in the third year, the test plants were barley and orchard grass. After harvesting, contents of sulfate sulfur was determined by means of nephelometry and total sulfur by Butters-Chenery method. [K2]The experimental studies support the conclusion [K3]that applied forms of sulfur fertilization had a significant impact on the volume of harvested crop yield. The most yield-producing form of this component was the use of sulfur in the following forms: (NH4)2SO4, RSMS, K2SO4, and Na2SO4. Fertilization applying analyzed forms of sulfur also affected the degree of plant supply in sulfur, which resulted in measurable changes in the contents of total sulfur and S-SO4 in dry matter of crops. The largest increase in the S total per DM of test plants was observed after application of sulfur in the forms of RSMS, K2SO4, H2SO4, and CaSO4 2H2O. Among used forms of sulfur nutrition, the largest impact on S-SO4content was exerted by this component application as RSMS, K2SO4, andelemental S.
Key words: sulfur fertilization, sulfur forms, crop yield, content of S-SO4, content of total sulfur
INTRODUCTION
Besides nitrogen, potassium and phosphorus, sulfur belongs to the group of necessary elements that perform a number of important physiological functions in plant’s metabolism. Its deficiency leads from one side to lower yields of plants, and on the other hand, to a deterioration of their quality parameters(Bednarek et al.2008,Podleśna 2009).[K4]
Despite its importance, until the early 80s of previous century, the importance of sulfur in plant production did not receive too much attention. This was mainly due to the fact that in most parts of our continent, sulfur balance was positive(Barczak et al. 2011,Ceccotti 1996,Szulc et al. 2004).
Lowering the sulfur deposit from the atmosphere and a decline in the quantity introduced along with mineral fertilizers have led to a shortage of this nutrient in a crop production. Sulfur deficit in the environment of the plant growth was found in 73 countries of the world, including 18 countries in Europe. This problem also applies to Poland, where 53% of agricultural soils is characterized by low abundance in this element. Hence, the lack of sulfur should be expected mainly on lighter[K5], usually acidic mineral soils, located in the northern and north-eastern parts of our country(Brodowska, Kaczor 2007,Szulc et al. 2004).
In such situation, it is feared that NPK fertilization used in accordance with the nutritional requirements of plants would not be fully balanced and sulfur deficit in the environment of plant growth may limit the utilization of other ingredients, in particular nitrogen. This may cause not only the limitationin the obtained yield size, but also affect the deterioration of its quality characteristics(Barczak et al.2011,Podleśna 2005).[K6]
Therefore, the purpose of the study was to evaluate the fertilizing action of sulfur from various sources on the yield and content of this component in the crops.
MATERIAL AND METHODS
The study was carried out based on a strict three-year pot experiment using the soil material collected from the topsoil of lessive soil with a particle size of silt loam (content of size fractions:1.0-0.1mm – 9.5%, 0.1-0.05mm – 10.0%, 0.05-0.02mm – 38.0%, 0.02-0.006mm – 27.5%, 0.006-0.002mm – 7.5%, <0.002mm – 7.5%). The soil was characterized by slightly acidic reaction (pHKCl 5.56) and low level of available phosphorus (38.8 mg P kg-1), potassium (83.02 mg K kg-1), magnesium (42.0 mg Mg kg-1), and sulfate sulfur (12.0 mg S kg-1).[K7]
Variable element consisted of sulfur that was used in eight different forms. Sulfur fertilization wasapplied annually based on plant’s nutritional requirements and in accordance with the scheme:1) S0 – without sulfur fertilization; 2) RSMS – sulfate-urea solution with addition of Na2S2O3 5H2O; 3) (NH4)2SO4; 4) K2SO4; 5) Na2SO4; 6)elemental S; 7) CaSO4 2H2O; 8) H2SO4.
In the first year of study, spring wheat of Ismena cv. and white mustard of Borowska cv. were the test plant species. In the second year, spring rape of Sponsor cv. and spring barley of Rataj cv. were grown. And in the third year, the test plants were barley of Rataj cv. and orchard grass of Bepro cv. Pots filled with 3kg DMof soil were used for the experiments[K8].The plants sowing was carried out each year in the third decade of April in the amount of 10 seeds per a pot in the case of cereals and orchard, as well as 8 seeds in the case of cabbage plants. After emergence, plants werethinned leaving 6 for cereals and orchard grass and 4 for mustard and rapeseed.[K9]
In all experimentalobjects, in each year, NPKMg fertilization was used in the amount consistent with the plant’s nutritional requirements. Particular nutrients were administered in the following forms: N – NH4NO3, RSM, (NH4)2SO4; P – Ca(H2PO4) H2O; K – KCl, K2SO4; Mg – MgCl2 6H2O. [K10]During vegetation season, constant soil moisture was maintained at the level of 60% of the field water capacity[K11].
The harvest of plants was carried out at full maturity phase (wheat, barley, mustard, rape) and in 2 cuts (orchard grass).[K12]
After harvesting and extracting the plant material using 2% CH3COOH with the addition of activated carbon, the contents of sulfate sulfur was determined by means of nephelometry. Total sulfur was determined by Butters-Chenery method. Analyses of the plant material were performed in two replicates in averaged object samples. The tables show mean values.
[K13]
RESULTS AND DISCUSSION
Providing plants with the required quantities of nutrients, under proper soil conditions, is an essential element determining the achievement of expected crop yield with adequate quality(Gondeket al. 2010).Values presenting the yields of vegetative and generative parts of tested plant species are given in Table 1.[K14]
In the case of spring wheat, the yield-forming effect of sulfur on the quantity of produced straw biomass was clear. The nutritional requirements of monocots, including wheat, while being less than for oilseeds and are in the range of 15-20 kg S ha-1.Nevertheless, the shortage of this nutrient within the environmentof cerealsgrowth and development results in marked inhibition of their growth in the early stages of development and visual symptoms of malnutrition in the form of yellow surface of younger leave blades(Gondeket al. 2010,Kaczor, Zuzańska 2009). In a control object (S0), yields of vegetative parts of plants were 1.2-1.7-foldlower as compared to values recorded for crops from other experimental objects.Applying sulfur in the form of H2SO4 was the most efficient on the amount of obtained spring wheat straw yield. Sulfur applied in in the form of RSM with addition of S had the least effective impact on growth of vegetative parts of spring wheat. In the literature upon the effect of sulfur fertilization on crop yields, it is often stressed that not only the amount of sulfur, but above all, form in which this nutrient is used, is important for plant growth and development. According to a study performed by Girmaet al.(2005),calcium sulfate(VI) was more beneficial sulfur form for wheat yielding in contrast to elemental sulfur. That was also reflected in own studies. Objects, where sulfur was applied in the form of CaSO4 2H2O, like in the case of plant fertilization using sulfur as H2SO4, revealed significant increase in spring wheat straw.
Similar trends also occurred in the case of spring wheat grain. The lowest yields of generative parts of the crop were found in the object S0. This may largely affect the quality of harvested plant materials (Table 4). The wheat grain containssulfur primarily in proteins, in which it is present in the form of amino acids such as cysteine or methionine. When plants manifest insufficient level of nutritional sulfur, concentration of these amino acids is reduced and the amounts of asparagine and arginineincrease(Scherer 2001). [K15]These changes contribute to the deterioration of the protein biological value, and thus also the nutritional value and baking quality of wheat flour, which in turn is conditioned by the gluten content. Slightly higher yields were also produced by plants fertilized with sulfur in the form of RSM with addition of elemental S. In the case of spring wheat grain, besides beneficial effects of H2SO4 on this plant yields, also a clear positive effect of sulfur fertilization in the form of(NH4)2SO4was clearly observed. The literature often stresses that cereals uptake 2-4kg this component to produce 1 ton of grain, which accounts for 9-15% of the quantitative needs for nitrogen at plants (Walker, Dawson 2003,Zhaoet al.2003[K16]).
[K17]White mustard, like spring rape, is a plant with relatively high nutrition requirements with respect to sulfur. This is mainly due to the number of important physiological functions, which is met by this element, as well as the necessity for a proper growth and development of this crop (Marazzi, Städler 2004). Referring to white mustard straw, the most beneficial form of sulfur appeared to be fertilization with K2SO4and Na2SO4. Slightly lower yields of white mustard straw were also recorded after introducing the elemental S and H2SO4 into the soil.When using the elemental sulfur as a fertilizer, it should be remembered, however, that plants can take advantage of this form of fertilizer under the condition that it will undergo a process of biological oxidation. This process is determined by a number of environmental factors, including the size and activity of microbial populations in the soil as well as the degree of sulfur fragmentation. Accordingly, the use of elemental sulfur is recommended primarily on soils with significant sulfur losses associated with elution. Under such conditions, the gradual release of sulfates is no doubt their advantage(Eriksen, Mortensen 2002,Podleśna 2009).[K18]
The white mustard grain yield also significantly increased due to applied sulfur forms as fertilizer. In control object (S0), plants produced minimum yield. Unlike the straw, fertilization using RSMS appeared to be the most yield-producing form of sulfur, while the least efficient was CaSO4 2H2O application.
In the second year of the study, spring oilseed rape and spring barley were the test plant species. In order to fully exploit the yield-forming potential of rape, favorable conditions for its growth and development with the correct agricultural practices, should be created. Its main element is the appropriate fertilization using necessary nutrients, including sulfur(Wielebski 2006). It is accepted that nutritional sulfur requirements of this species are 50-70kg S ha-1(Wielebski 2011). [K19]The highest yields of spring rape straw, like that of white mustard, were recorded after sulfur applied in the forms of K2SO4and Na2SO4[K20].
In the case of generative parts of spring rape, plant’s response to sulfur fertilization marked more clearly. In the control object (S0), to which sulfur was not applied, plants did not produce seeds. The literature research (Gaj, Klikocka 2011, Malarz et al. 2011, Wielebski 2011)indicate thatsulfur deficiency in an environment for growth and development of spring rape leads to several adverse changes in the plant metabolism. Plants exposed to sulfur deficiency in the soil do not fully utilize other nutrients, including nitrogen. The effect of this can be up to 50% reduction in the size of the crop yield(Podleśna 2009, Wielebski 2011). Also object, where sulfur was applied in the form of RSM with elemental S addition,revealed the yield of generative parts by 2.0-2.7-fold lower as compared to those achieved by plants grown in other experimental objects. The highest grain yields were observed at spring rape, for cultivation of which Na2SO4and (NH4)2SO4were used. [K21]
Yield of spring barley straw ranged within 12.32-22.12g DMpot-1. Although cereals belong to a group of plants with low requirements regarding sulfur,it however should be remembered that they react with an increase in yields towards the fertilization using this component, especially under conditions of an adequate supply with nitrogen, phosphorus, and potassium(Jakubas, Toboła 2006). A significant increase in the biomass of vegetative parts of this plant species with respect to object S0 was observed only in the case of sulfur application in the form of RSM containing elemental S.[K22]
Situation for spring barley grain was slightly different. The most favorable form of sulfur appeared to be introduction of this component in the forms of Na2SO4 and RSMS.
Spring barley and orchard grass were the test plants in the subsequent year. Spring barley grown in the third year of the study gave lower yields of straw as compared with the values observed for thisspecies cultivated in the second year of the experiment. The exception was only the object, where RSMS was used. Applying K2SO4 appeared to be the least beneficial sulfur form. In the case of spring barley grain, the greatest increase in yields were observed after the introduction of RSM with elemental sulfur addition to the soil.[K23]
Fertilization of orchard grassusing analyzed forms of sulfur was also associated with an increase in the size of obtained plant biomass. Providing the grassland vegetation with a proper amount of nutrients ensures not only the yield stability during the growing season, but also a high-quality forage. Under the sulfur deficient conditions, plants accumulate nitrogen in non-protein forms, and in additionthe yield-forming effects of nitrogen gets reduced(Kaczor, Zuzańska 2010). [K24]It was confirmed by studies of other authors (Murphy et al. 2002)carried out using grasses. The literature data (Malhi et al. 2004)often underlines that grass yields, to which sulfur fertilization was used, can increase by up to 20% in reference to crops grown under sulfur deficit (Kaczor, Zuzańska 2010). In the case of the first cut of orchard grass, a significant increase in yields, as compared to object S0, was observed only after sulfur application in the form of K2SO4.In the second cut, besides positive effects of K2SO4, also beneficial contribution of elemental sulfur administration, was recorded. [K25]
Fertilization of test plants with analyzed forms of sulfur had an impact on the content of this component at plants. When determining the degree of plant nutrition with sulfur, various types of plant indicators can be helpful. Among them, the most used are following: content of total sulfur, content of S-SO4, ratio N:S, and ratio of sulfates to total sulfur(Jackson 2000, McGrathet al. 1996). It is difficult to univocally determine, which of the above indicators is the best. Its selection should be determined at first by a plant species,the sulfur supply status of whichis to be evaluated(Wielebski 2011, McGrathet al.1996).
The highest content of total S in the straw of spring wheat was recorded in object, where RSM with the addition of sulfur was used (Table2).
A similar situation developed in the case of spring wheat grain. Also, the highest content of total S characterized generative parts of the species grown in the object fertilized with sulfur in the form of RSMS. An appropriate level of spring wheat supply in sulfur is extremely important. Deficiency of this nutrient decreases the quality of wheat flour by deterioration of its “baking value”. This is due to the positive correlation between sulfur content in flour and plasticity of dough(McGrath, Zhao 1995,McGrathet al. 1996). The problem concerns especially organic products which are not allowed to contain substances that increase the baking value of flour (Girma et al. 2005, McGrathet al. 1996).[K26]
In the case of white mustard straw, like for spring wheat, fertilization with sulfur in the form of RSMS affected the most preferably the total sulfur content. Seeds revealed the highest contents of this sulfur form were recorded in objects, in which elemental sulfur and H2SO4were used during cultivation. It was also confirmed by studies carried out byBloem (1998)as well asSchnug andHaneklaus(1994). These authors emphasize that cabbage plant species accumulate much more sulfur in seeds than in straw.
McGrathet al.(1996)suggest that for winter rape harvested at the flowering stage, total S concentration is accepted as the best indicator informing about the plant’s supply in sulfur. The N:S ratio in leaves is considered less useful, because there is a linear correlation between seed yield, hence there is no possibility to set up any critical values. Under conditions of intensive nitrogen fertilization and sulfur deficiency, the N:S ratio gets clearly decreased, which results from the increase of non-protein nitrogen content at a plant. It contributes to the decrease in yields and deterioration of its qualitative parameters(Kaczor, Zuzańska 2009,Wielebski 2011). [K27]The straw from spring rape grown in the second year of experiment was characterized by the highest total S content in object, where sulfur was introduced as RSMS. Application of H2SO4 had also a beneficial effects on quantity of total S.Situation was slightly different in the case of spring rape seed. Considering the generative parts of the plant, the highest quantity of total S was recorded in object, where sulfur was introduced in the form of K2SO4.
High content of total sulfur in the straw of barley grown in the second and third year of studies was found after application of sulfur in the form of K2SO4. The grain, depending on the year of study, contained the increased total sulfur amount after introduction ofCaSO4 2H2O and H2SO4 (second year of experiment)and after introducing the sulfur as RSMS and K2SO4 (third year of study). It was also confirmed by results obtained byKaczorandŁaszcz-Zakorczmenna(2003), who underline a clear increase in total S content in straw and grain of spring barley fertilized with sulfur. MeanwhileInalet al.(2003)indicate that sulfur concentration in a plant may be an excellent reflection of sulfate availability in soil.[K28]
In the case of the first cut oforchard grass, the sharp rise in the total S was reported after fertilizing the plants with sulfur in the forms of K2SO4and H2SO4. For comparison, in the second cut,the highest content of total sulfur characterized plants from the control object (S0), where the content of that sulfur form was at the level of 3.98g S kg-1DM, while, mean sulfur concentration for Polish grasses is considered to be 2.1g S kg-1DM(Motowicka-Terelak, Terelak 2000). This may be related to the size of orchard grassyield obtained in the relevant object (Tables 1 and 4). Plants gave relatively low yield of only 1.75g DM per pot, which could have an impact on the so-called “concentration effect” of the component. Among the introduced sulfur forms, the use of this component in the form of elemental S elementary CaSO4 2H2O had the most beneficial impact on the content of S total. An adequate supply of orchard grassin sulfur is essential for the quality of harvested yields of this crop.Under conditions of insufficient plants supply in sulfur, the inhibition of protein synthesis and reduction in the content of sulfur amino acids occurs. Limiting the protein synthesis also results from the disruption in the nitrate reductase functioning. In the absence of sulfur, activity of this enzyme is considerably diminished, which in turn promotes excessive accumulation of non-protein nitrogen forms, in particular nitrates. This has a great impact on the forage value of grasses(Kaczor, Zuzańska 2009, 2010).[K29]