Effect of sulphur and silicon application on the yield and chemical composition of maize grown under saline soil conditions

INTRODUCTION

Maize (Zea mays L.) is one of the most important cereal crops growing in the Egypt. It is used as a food for human consumption as well as feeding animals (Moussa, 2001). In Egypt, the    local production still under self-sufficiency  level. Overcoming the deficiency of maize productivity is an essential national target to reduce the gap between production and consumption. Unluckily, in many regions, especially in the tropics and sub-tropics, the production of maize is markedly reduced due to environmental stresses like soil salinity or alkalinity. Egyptian soils are in general distinguished by a low to high salt content which are mainly due to its arid conditions (Abd-Alla et al., 2014).

Sulfur is the fourth major plant nutrient after nitrogen, phosphorus and potassium. It is essential for synthesis of the amino acids like cystine, cysteine and methionine, and it is a component of vitamin A and acts to activate certain enzyme systems in plants (Havlin et al.,2004). Continuous removal of S from soils through plant uptake has led to widespread S deficiency and affected soil S budget (Aulakh, 2003). In addition, continuous growing sulphur responsive crops, high intensive cropping and use of sulphur free fertilizers caused S deficiency in soils (Tandon and Tiwari, 2007).

Silicon is not listed among the higher plant essential elements, but the direct and indirect beneficial effects of Si on plant growth and development are well documented. Many studies have reported that Si may be involved in metabolic or physiological and/or structural activity in higher plants that are exposed to abiotic and biotic stresses (Liang et al., 2003 and Shen et al., 2010). Over the last two decades, numerous laboratory, greenhouse and field experiments have demonstrated that Si is able to hamper both biotic pressures caused by plant diseases and pest attacks, as well as abiotic pressures, including physical pressures such as drought, waterlogging, freezing, high temperature, and UV, and chemical pressures as salinity, nutrient deficiencies, and metal toxicity (Guntzer et al., 2012; Balakhnina and Borkowska, 2013; Marafon and Endres, 2013; Van Bockhaven et al., 2013; Zhu and Gong, 2014; Rizwan et al., 2015).Maize has been known as a Si accumulator (Liang et al., 2005) and thus it is a popular crop for studies on the useful impacts of Si under environmental pressures (Malcovska et al., 2014).

The aim of this study, therefore, was to investigate the effects of sulphur and silicon applications on the growth, yield and chemical composition of Maize (Zea mays L.) grown in saline soil.

MATERIALS AND METHODS

Field experiment was carried, out at the Experimental Station (Abis), Faculty of Agriculture, Saba Basha, Alexandria University, during the growth season of 2013/2014 to investigate the effect of sulfur and silicon applications on the yield and chemical composition of  Maize (Zea mays L.) plant grown under saline soil conditions. The seed of   individual   hybrid   352 cultivar was used in this study. Two factors were conducted in a split-plot design with three replications. The sulphur was applied to the main plots before planting at rates of 0, 200, 400 and 600 kg S/ fed. The sub- plots received silicon treatment which added before planting at rates of 0, 5, 10 and 15 kg Si/fed. as potassium silicate. The area of each plot was 10.50 m² (3.5 m length x 3 m width), with 5 ridges 60 cm apart and 25 cm between hills. The recommended doses of nitrogen (50 kg N/fed.) as ammonium sulphate fertilizer (20.5% N) and phosphorus (36 kg P₂O₅) as triple phosphate (46% P₂O₅) were applied to the soil in a single dose during land preparation. All recommended cultural practices for the maize crop were done according to the recommendations of Ministry of Agriculture and Land Reclamation (MALR). The main physical and chemical properties of the experimental soil are presented in Table (1).

The analysis of soil was carried out according to the methods outlined by Black (1965) Also, available Si was determined in soil using the method of Fox et al. (1967). The soil type is alluvial which was a naturally salt affected with electrical conductivity (EC) value of 2.55 dS/m (1:2 soil: water ratio). At maturity, plants were harvested and the corn grain yield (ton/fed) was recorded. Also, samples of leaves and grains were collected and prepared for chemical analysis according to Chapman and Pratt (1978). Samples of leaves or grains material (0.5 g) was digested with sulphuric acid and hydrogen peroxide according to Lowther (1980).  In the digested plant materials, total nitrogen, was determined by the Nessler"s method (Chapman and Pratt, 1978), Potassium by flame photometer (Jackson, 1973) and phosphorus by the vanadomolybidic acid method (Jackson,1973),respectively. Also, samples of leaves or grains materials were digested (Ali et al., 2013) .Also, total sulphurleaves material (0.5 g) was digested with Nitric acid and hydrogen peroxide (HNO₃/H₂O₂) according to (Zheljazkov and Nielson 1996) and Silicon was determined colorimetrically using the method described by Elliot and Synder (1991).Samples of soil were collected and analyzed for available Si and S using the abovementioned methods.  The obtained data were statistically analyzed for ANOVA and L.S.D. values were calculated to test the differences between the studied treatments according to Steel and Torrie (1980).

Table (1).The main physical and chemical properties of the experimental  soil

**  1:2 soil-water extract

Result and Discussion

Grain yield

Table (2) showed that sulphur application had significantly effect on the grain yield (Table 2).Increasing sulphur rate from zero to 600 kg S/fed increased grain yield from 0.349 to 1.472 ton/fed significantly. Baktash (2000) showed that using 600 kg S / fed. Produced the highest grain yield (8180 kg/ ha) which was superior than the control (6103 kg/ha) by 34%. The effect of sulphur may be due to decreasing soil pH and increasing the availability of other nutrients and their uptake besides improving soil chemical properties. Kineber et al. (2004) found that the application of sulphur to alkali soil as soil amendment, decreased soil pH value. Similar results were obtained by Szuleand Zajac (2012).

Table (3) showed that grain yield was significantly affected by different levels of silicon. The results revealed also, that applied potassium silicate in combination with sulphur levels increased the grain yield in comparison with control Table 2 and Figure 1.The data indicated that application of 600 kg S/fed with 15 kg Si/fed increased grain yield compared with 200 or 400 kg S/fed in combination with other potassium silicate rates. These increases may be due to the effect of silicon on hampering the  abiotic stresses especially soil salinity stress, by increasing the activities of tonoplast H⁺ - ATPase and H⁺- PPase (which decreased significantly in- roots under salt stress), minimize arrived damage to chloroplast and hereby it increases leaf chlorophyll and photosynthesis activity (Liang et al., 2005). Also, this might be due to combined and sustained nutrient supply by S and Si applied to plots which ultimately leads to photosynthetic activity by the crop and resulted in higher yield.     

Table (2). Grain yield of maize as affected by sulphur and silicon applications.

Table (3). Main effect of sulphur and silicon application rates on grain   yield of maize. 

Figure (1). The relationship between grain yield and silicon rates                at each sulphur rate

Elemental composition

Tables (4 and 5) showed that N, P, K, S and Si contents of maize leaves were increased significantly as sulphur rates increased from zero to 600 kg S/fed at harvest. Table (4) also showed that silicon application increased N, P, K, S and Si contents in maize leaves at harvest as compared to the control.

It was well understood that sulphur is essential for the activity of enzyme involved in nitrate reduction in plants. Therefore, it is imperative that N content increased with S application. Sinha et al. (1995) reported that increase in N content in leaves of maize due to S application seems to be associated with increase in N content with concomitant increase in grain yield. Higher P content in the presence of S could be due to the role of S in mobilizing soil P into available form. Singh et al. (2001) reported that P and K contents were stimulated in the presence of S. Significant increase in S content within S levels could be due to increased availability of S in the soil with concomitant increase in grain yield. Maximum Si content with S could be due to increase Si availability in soil and enhanced root system.

The N content was higher with Si (15kg Si/Fed.) compared to its lower levels due to its potential to raise the soil available nitrogen (Ho et al., 1980). Silicon fertilized plant gained maximum benefits of ample nitrogen availability. Increasing silicon levels increased phosphorus content due to decreased retention capacity of soil to P and consequently increased availability of phosphorus which is leading to increased efficiency of phosphatic fertilizer (Subramanian and Gopalswamy, 1990). Positive response of higher silicon application towards potassium can be linked to silicification of cell wall. This agrees with Chanchareonsook et al. (2002) who reported that application of NPK fertilizers in combination with Si significantly increased total N, P and K uptake by rice. Silicon also favorably influenced the sulphur uptake indicating its synergistic effect with silicon application.

The higher silicon content was associated with the highest rate of silicon application (15 kg /Fed.). This might be due to increase in root growth and enhanced soil silicon availability with silicon application. This finding is in agreement with those reported by Kalyan  et al. (2006). This could be due to increased root activity and enhanced the soil nutrient availability in accordance with those reported by Wani et al. (2000).

Table (4). Nitrogen, P, K, Si and S contents in leaves of maize as affected  by  sulphur and silicon applications

Table (5).The effect of soil sulphur and silicon applications on N, P, K,                 Si and S contents in leaves of maize

Nitrogen and protein contents in grain

Tables (6 and 7) showed that nitrogen concentration and protein content in grain of maize significantly increased as sulphur rate increased from 0 to 600 kg S/fed. Also, sulphur application increased significantly the protein content in grains of maize as sulphur rates increased from 0 to 600 kg S/fed. Scherer et al. (2011) reported that sulphur is an essential plant nutrient for crop production and it is required for protein and enzyme synthesis as well is a constituent of some amino acids. Data in Table 7 showed also that, silicon rates affected nitrogen concentrations and protein content in grains. Increasing silicon rate up to application of 15 kg Si/fed increased significantly nitrogen concentration and protein content in grains of maize. The highest values of nitrogen and protein contents in grains were obtained at 15 kg Si/fed. The interaction between sulphur and silicon rates had a significant effect on nitrogen or protein content in grains of maize.

Table (6). Nitrogen and protein contents in grains of maize as affected               by sulphur and silicon applications.

Table (7). The effect of sulphur and silicon applications on nitrogen and               protein contents in grains of maize

Available sulphur and Silicon in soil   

Tables (8 and 9) showed that increasing sulphur application rates from zero to 600 kg S/fed increased significantly available sulphur in soil. Available silicon was significantly increased as silicon application rate has also increased from 0 to 15 kg Si /Fed. The highest values of available silicon were attained at 15 kg S/fed. The interaction between sulphur and silicon had significant effect on available –S and available –Si (Table 8).

Havlin et al. (2004) found that the available sulphur in surface soil usually represents less than 10%  of the total sulphur in soil .Since, most of the sulphate (SO₄^--) compounds are quite soluble and not adsorbed by soil colloids, therefore sulphate ions were highly susceptible to leaching and losses (Tiwari and Gupta, 2006). Consequently, a less supply of SO₄^---S is available within the root zone of soil, and therefor sulphur fertilization is needed especially in saline soils. Nevertheless, Silicon is still relatively unknown for to be applied to agricultural soils. In many cases increased silicon availability has increased crop development and yield. Once this element can indirectly influence some photosynthetic and biochemical processes, especially in plants under biotic or abiotic stress condition. Ma et al.( 2001), Gong et al.( 2005), Ma and Yamji (2006) and Abdalla (2011) showed that silicon application is beneficial to crops such as rice, sugarcane, barley maize, sorghum and wheat which are considerable Si- accumulating species.

It can be concluded from the obtained results that the suitable conjoin application of S with   Si holds immense potentiality to boost the productivity and profitability of maize when grown under saline soil conditions.

Table (8). The amounts available sulphur and silicon in soil as   affected               by sulphur and silicon applications

Table (9). The effect of sulphur and silicon applications on the amounts of available sulphur and silicon in soil.