Use of Gypsum and Sulphur for Improving Rock P Efficiency and Their Effect on Wheat Productivity and Soil Properties

INTRODUCTION

Directly applied of phosphate rock (RP) has increased in recent years. This is principally due to RP is usually the cheapest fertilizer and it can be efficient than soluble fertilizer in term of recovery of phosphate by plants even from short-term, where soluble P readily leached in sandy soils and possibly for long-term in other soils. The effectiveness of RP depended on its properties including particle size as well as chemical properties and type of soil on which RP is applied. The rock phosphate is less effective in direct application compared with ordinary calcium superphosphate, triple-superphosphate or di-ammonium phosphate. In this connection many authors reported that direct application of RP materials may be agronomical more useful and environmentally more feasible than soluble P such as Ranawat et al. (2009),Ali et al. (2012), Chaudhary et al. (2017) and Khan et al. (2017). In addition, Zapata and Roy (2004) mentioned that rock P materials are cheaper sources of P, however, most of them are not readily available to plants because the materials released slowly and their use as fertilizer often causes insignificant yield increases of current crops. Therefore, it could be improved the efficiency of RP as P source by using some methods such as microbial solubilizing of phosphate, organic manure, sulphur or gypsum.

Gypsum has used for reclamation of saline sodic soils. Yu et al. (2003) observed that spreading gypsum on the soil surface doubled the final water infiltration rate compared to that of control. Rashid et al. (2008) indicated that gypsum improved the wheat productivity and the moisture content in soil profile at sowing of wheat. Sulphur, as a constituent of gypsum, is essential for plant growth as it is involved in protein synthesis and is a part of some amino acids. It is required for nitrogen fixation by leguminous plants.

Sulphur management is an important issue in crop nutrition. Sulphur has a role in fundamental processes such as electron transport, structure and regulation. It also associated with photosynthetic oxygen production, abiotic and biotic stress resistance and secondary metabolism. Sulphur uptake, reductive assimilation and integration into cysteine and methionine are the central processes that direct oxidized and reduced forms of organically bound S into their various functions (Capaldi et al., 2015). On the other hand, elemental S has used for the reclamation and improvement of sodic and calcareous soils (Wassif et al., 1993). Saleh (2001) reported that sulphur has a favorable effects on promoting nutrient availability in soils, use of S as a nutrient and soil acidifier under used of natural sources as RP has recently gained importance in agricultural production (Atilgan et al., 2008). Added S dropped soil pH in sodic and calcareous soil (Abbaspour et al., 2004). However, application of S with nitrogen fertilizers increased availability of phosphorus and micronutrients (Erdal et al., 2004).

The current work aims to evaluate the effects of gypsum or sulphur on enhancing the efficiency of rock phosphate as phosphorus fertilizers and its effects on wheat productivity, some soil properties and fertility after wheat harvest.

MATERIALS AND METHODS

Two field experiments were conducted at Sids Agric. Res. Station, Beni-Suef Governorate, ARC, Egypt during the two successive seasons of 2016/2017 and 2017/2018 to study the effect of application of different levels of gypsum ( 0.0, 2.5 and 5.0 ton/fed ) and sulphur  ( 0.0, 200 and 300 kg/fed ) on increasing the efficiency of rock phosphate ( at rate of 0.0 and 400 kg/fed ) as phosphorus source contain about 10.2%P and their effects on wheat (Triticum aestivum L.) growth ( plant height and dry weight/plant ), yield components, i.e., number of spikes/m², number of grains/spike and 1000-grain weight, yield (grain and straw yields) and N, P and K uptake by wheat (Triticum aestivum L.) as well as some soil properties, i.e., soil pH, EC and organic matter, soil available N, P and K. A representative soil sample was collected from the experimental site at the depth of 0.0-30 cm before planting to determine some physical and chemical properties according to Jackson (1973) and listed in Table (1) Also, at the end of each season representative soil samples were collected from each experimental plots to determine soil pH, EC and organic matter as well as soil available N, P and K according to (Jackson, 1973).

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

Some chemical attributes of rock phosphate used in the experiment according to (Jackson, 1973) are presentment in Table 2.

Table (2). Some chemical contents of rock phosphate used in the experiments

Rock phosphate, gypsum and sulphur added before wheat sowing during the land preparation. The design of the experiment was factorial (three factors), rock P ,gypsum and sulphur in  randomized complete block  design in four replication.

Wheat grains, C.V. Beni-Suef 1 variety sown during the third week of November for the two seasons at rate of 60 kg/fed. Nitrogen fertilizer applied at rate of 75 kg/fed as ammonium nitrate (33.5% N) in two equal doses, the first one before the first irrigation and the second one before the second irrigation. All other cultural practices for wheat production in district applied.

Wheat plants harvested during the first week of May for the two seasons. Representative ten wheat plants taken from each plots to determine growth parameters and yield components. Grain and straw yields were determined for each plots and converted to ardab/fed and t/fed, for grains and straw, respectively.

Samples from grains and straw were taken and analysed to determine N, P and K concentrations (according to Chapman and Pratt, 1961) and the obtained data was converted to N, P and K uptake.

The data subjected to statistical analysis according to Snedecor and Cochran (1980). Significant of differences between treatments compared using the least significant differences at 0.05, probability level.

RESULTS AND DISCUSSION

Growth parameters:

Table 3 show that, irrespective of gypsum or sulphur, added 400 kg rock P/fed had a positive effect on plant height and dry weight /plant. The relative increasing of plant height and dry weight /plant over no rock P reached to 6.4 and 15.2% in the first season and 6.7 and 14.3% in the second one, respectively. The promotive affect of natural P rock may be due its phosphorus content (about 11.5% total P). In this concern, Abou- el-Seoud and Abdel-Mageed (2012) found that plants treated with rock P minerals alone have root length higher than without P rock application, consequently take up more nutrients than those with short roots. Similar results obtained by Corretti et al. (2005) and Ahmed (2017).

With respect to the main effect of gypsum, the results in Table 3 indicate that wheat plant height and dry weight /plant significantly responded to gypsum application in both seasons. Increasing gypsum level from 0.0 up to 5.0 t/fed increased plant height and dry weight /plant by about 7.1 and 18.6 % in the first season, respectively. Same trends obtained in the second season. The positive effect of gypsum on wheat growth may be due to addition of gypsum improved the physical properties of the sodic soils (the experimental soil having pH of 8.16 and 8.21 in both seasons), consequently led to increase nutrients availability (Niazi et al., 2003). These results are in line with many authors such as AbouBakr et al. (1994) and Rashid et al. (2008).

Table(3). Growth, yields and its components of wheat as affected by rock P under different levels of gypsum and sulphur

As for sulphur, the data in Table 3 reveal that sulphur application was significantly increased wheat growth. The tallest and heaviest wheat plants recorded under added 300 kg sulphur /fed. Comparing with no sulphur application, added 300 kg S/fed, tallest and heaviest plant of wheat plants were obtained under the plants received 400 kg rock P/fed + 2.5 or 5.0 ton gypsum /fed + 300 kg S/fed. On the other hand, the plants without natural rock P + without both sulphur and gypsum exhibited the lowest plant height and dry weight /plant. It is clear from the results of the interaction that both Cooretti (1996) gypsum and sulphur had a positive effect on enhancing the efficiency of natural rock P as a phosphorus fertilizer source.  This is mainly due to added both gypsum and sulphur in wet soil produced mineral acids which affecting the dissolving rock P and decreasing the soil pH (see Table 6). Similar results were obtained by Niazi et al., (2003) and Rashid et al. (2008) for gypsum, and Ahmed (2017).

Yield attributes:

The main effect of natural rock P on yield attributes of wheat given in Table 3. The obtained results exhibited pronounced increases in number of spikes/m², number of grains/spike and 1000-grain weight due to applied 400 kg rock P. The relative increases in these studied yield attributes resulted by added rock P reached to 3.4, 2.3 and 5.6% over without rock P application in the first season, respectively. The corresponding increases in the second season were 3.3, 2.1 and 5.9% in the same respect. The positive effect of rock P on wheat yield attributes mainly explained by its effect on wheat growth as mentioned before. These results are in agreement with those obtained by Al Mamun et al. (2012) and Ahmed (2017). As for the main effect of gypsum, the results show that all studied yield attributes were gradually increased as the gypsum dose increased up to 5.0 t/fed, which mainly due to its effect on improving soil properties and plant growth as discussed former. In this connection, Yu et al. (2003) mentioned that spreading gypsum at the soil surface doubled the final water infiltration rate compared to that of control. These results are similar to those obtained by Rashid et al. (2008).

With regard to sulphur, the data reveal that sulphur application had a positive effect only on number of spikes/m² in the two studied seasons. The values of number of spikes/m² due to added 0.0, 200 and 300 kg S/fed were 324.77, 326.53 and 328.13 in the first season and 327.55, 329.28 and 331.05 in the second one, respectively. It is worthy to observe that number of grains/spike and 1000-grain weight were slightly increased but not significant due to sulphur application. These results are in harmony with these obtained by Jaggi et al. (2005) and Kacar and Katkat (2007).

Considering the effect of the interaction, the data show that both number of spikes/m² and number of grains/spikes affected by the interaction between gypsum and sulphur treatments, where the sulphur was not affected these two wheat yield components under the high dose of gypsum. In general, the maximum wheat yield attributes were produced under the treatment of 400 kg rock P + 5.0 t/fed gypsum + 300 kg S/fed. On the other hand, the lowest values of wheat yield attributes obtained at the control treatment (without rock P + zero of both gypsum and sulphur). These results support the synergistic effect of gypsum or sulphur on increasing the efficiency of natural rock P on wheat growth as mentioned before, consequently improved wheat yield components. These results are in line with those obtained by Chaudhary et al. (2015) for mixed rock P with gypsum and Besharati et al. (2007) for mixed rock P with Z increased grain and straw yield as compared with control. The increases were 9.8 and 11.8 % for grain and straw yields, respectively over without feldspar treatment in the first season. Same trends obtained in the second season. These increases might attributed to the role of phosphorus in facilitating biochemical process in plant, in turn enhanced plant growth and yield components as mentioned before. These results are in accordance with those obtained by Abou-Hussien et al. (2002) and Ahmed (2017).

As for the main effect of gypsum, the data in Table 3 reveal that both grain and straw yields of wheat significantly affected by gypsum application. Increasing gypsum dose up to 5.0 t/fed increased grain and straw yields by about 27.3 and 35.5% over control, respectively in the first season. The corresponding increases in the second season were 26.5 and 35.7% in the same order. These increases may be due to gypsum made phosphorus and micronutrient more available to plant by creating acidic condition through the formation of sulphuric acid in the presence of sufficient soil moisture, in turn reduce soil pH and improved plant growth (Melean and Ssali, 1977). Similar results reported by Chaudhary et al. (2015). With regard to the main effect of sulphur, the results in Table 3 reveal that sulphur had insignificant effect on wheat grain and straw yields, which mainly due to sulphur improved only number of spikes/m², while the two other yield components not affected by sulphur application.

Concerning the wheat yields as affected by the interaction between any two treatments or among them, the results in Table 3 clearly show that wheat yields did not affect by these interaction. The highest grain or straw yields were recorded under the wheat plants treated with 400 kg rock P/fed + 5.0 ton gypsum/fed. On the other hand, the plants without both rock P and gypsum possessed the lowest wheat yields. These results indicate that gypsum had a positive effect on improving the efficiency of natural rock P as phosphorus fertilize source. Similar results obtained by Chaudhary et al. (2015).

Nutrients uptake:

The data in Table 4  represent the effect of rock P, gypsum, sulphur, and their interaction on N, P and K concentrations and Tables (5 and 6) represent the uptake by wheat grains and/or straw. As for the main effect of natural rock P, the results clearly show that, rock P application at rate of 400 kg/fed was significantly increased N, P and K uptake in grains and straw as well as total uptake. The relative increases of total N, P and K due to rock P application reached to 12.2, 28.8 and 12.0% when compared with control, in the first season, respectively. Similar trends obtained in the second season. The positive effect of rock P on nutrients uptake is mainly due to its effect on both grain and straw yields (Table 3), since nutrient uptake calculated as multiplying yield by nutrient concentration. In this concern, Abbasi et al. (2015) mentioned that application of rock P directly to the soil had shown positive effect on root dry matter, consequently improved nutrient absorption. Similar results obtained by Correa et al. (2005) and Abd El-Hafeez et al. (2013).

Table )4(. The N, P and K concentration in wheat grains and straw as affected by rock P under different levels of gypsum and sulphur

Table )5(. The N, P and K uptake in wheat grains and straw as affected by rock P under different levels of gypsum and sulphur

Table )6(. Total N, P and K uptake as affected by rock P under different levels      of gypsum and sulphur

As for gypsum, the data in Tables (5 and 6) reveal that N, P and K uptake by grains and /or straw significantly affected by increasing the dose of applied gypsum. Added 5.0 t/fed gypsum increased total N, P and K uptake by about 30.8, 89.8 and 51.7% over the control in the first season, respectively and 29.4, 85.7 and 32.7% in the second one.

The increases in nutrient uptake due to gypsum application is mainly due to its effect on improving soil properties, especially soil pH, consequently enhanced nutrient absorption. These results are in line with those obtained by Niazi et al. (2003). Regarding sulphur effect, the data in Tables (5 and 6) reveal that nutrients uptake significantly enhanced by sulphur z values for the second season were 1.6, 19.2 and 1.8% in the above-mentioned order. It is obvious to observe that sulphur had a pronounced effect on phosphorus uptake than nitrogen or potassium. The promotive effect of sulphur on nutrient uptake may be due to its effect on improve the availability of nutrients in alkaline soil (Neilsen et al., 1993).These results are in accordance with those obtained by Kacar and Katkat (2007) and Shivay et al. (2014).

As for the interaction effect, the data clearly show that N, P and K uptake by grains and/or straw were significantly affected by the interaction between gypsum and sulphur treatments, where sulphur did not affect N, P and K uptake under the high level of gypsum (5.0 t/fed). The highest N, P and K uptake by grains and/or straw were recorded for the plants treated with 400 kg rock P + 5.0 t/fed gypsum + 300 kg/fed sulphur, while the plants without application of rock P, gypsum and sulphur achieved by the lowest nutrient uptake. The enhancement of the efficiency of rock P on nutrient (Muchovej et al., 1989). uptake by addition of gypsum and sulphur is mainly due to the effect of acid forming substances such as gypsum and sulphur on produce sulphuric acid, which lower pH near plant roots, consequently increased P availability from rock P and nutrient absorption Similar results were obtained by Chaudhary et al. (2015) and Ahmed (2017).

Soil properties:

The data of the effect of rock P, gypsum, sulphur, and their interaction on some soil properties after wheat harvest given in Table (7). As for the main effect of rock P, the results clearly show that rock P was not affected soil pH, EC and organic matter. Similar results obtained by Ali et al. (2009), El-Sheref (2012) and Ahmed (2017) for soil pH, EC and organic matter, respectively.

Concerning the main effect of gypsum, the data in Table 7 reveal that gypsum application had a promotive effect on reducing soil reaction and salinity which mainly due to gypsum consider as acid forming substance, consequently reduce soil pH (Stamford et al., 2015). Also, gypsum doubled the final water infiltration rate, in turn increased the salt leaching from the soil (Rashid et al., 2008). Soil organic matter did not respond to gypsum treatment .Similar result were obtained by Bairagi et al.(2017) and Andrade et al. (2018).

With regard to sulphur application, the data in Table (7) clearly show that sulphur was only affected soil reaction. Increasing sulphur dose from 0.0 to 300 kg/fed reduce soil pH from 8.00 to 8.01 in the first season and from 8.05 to 7.99 in the second season. In this connection, Neilsen et al. (1993) stated that oxidation of sulphur into H₂SO₄ is beneficial for alkaline soils by reducing soil reaction.

These results are in line with those obtained by Ali et al. (2009) and Ahmed (2017). Turan et al. (2013) mentioned that, the reduction in pH level due to sulphur application to increase in the solubilization of soluble compounds and microbial activities, Similar results were obtained by Ali et al. (2009), Abd El-Hafeez et al. (2013) and Kuben Kulov et al. (2013) for rock P, De and Basak (1997) and Chaudhary et al. (2015) for gypsum, and Hellal et al. (2009) and   Ahmed (2017) for sulphur.

As for the interaction effect, the data clearly show that not all the studied soil properties after wheat harvest affected by the interaction between treatments. In general added 5.0 ton gypsum/fed produced the lowest values of soil pH and EC, while added 300 kg sulphur/fed exhibited the favorable soil pH. Also, the results in Table 7 show that soil available phosphorus was significantly affected by rock P, gypsum and sulphur and their interaction, while soil available nitrogen and potassium did not affected. Application of 400 kg rock P or 5.0 t/fed or 300 kg/fed sulphur exhibited the highest values of soil available P (16.77, 14.72 and 13.05 mg/kg, respectively in the first season and 16.97, 14.90 and 13.37 mg/Kg, respectively in the second season). On the other hand, the control treatments of without each of rock P, gypsum and sulphur produced the lowest soil available P in both seasons.

The increasing of soil available P due to rock P application may be due to release phosphorus through rock P mineralization in soil (Gowda et al., 2011). On the other hand, the effect of gypsum or sulphur may be due to chemical weathering caused by gypsum or sulphur, which produced acids, consequently help in solubilizing fixed phosphorus in soil (Duponnois et al., 2005). Moreover, the data of the interaction between treatments show that soil fertility (available N, P and K) after wheat harvest did not effect by the interaction between treatments. This means that the highest values of soil available P recorded under the treatment of 400 kg rock P + 5.0 t/fed gypsum + 300 kg/fed sulphur. On the other hand, the treatment of without rock P + without gypsum + without sulphur gave the lowest soil available P.

 From the results of the interaction, it could observed that gypsum and sulphur had a positive effect on increasing the solubility of rock P and release soil available P. Similar results obtained by Badr (2006) and Chaudhary et al., (2015).

Table )7(. Soil properties after wheat harvest as affected by rock P under different levels of gypsum and sulphur

 CONCLUSION

The benefits of using natural fertilizers under gypsum and sulphur demonstrated the validity and possibility of sustained agronomic performance of wheat and reduce the cost of cultivation using cheap rock phosphate. Therefore, it could recommended to increasing wheat productivity and improving soil properties by mixed 5.0 t/fed gypsum and 300 kg/fed with 400 kg rock P under the alluvial soil of Middle Egypt.