Abstract: Background and Objective: Fertigation provide efficient method for fertilizer and irrigation of water in order to evaluate some potassium sources on wheat (Giza 168) production in sandy soil at El-Sadat City, El-Menoufia Governorate, Egypt, amid the two winter seasons 2016/2017 and 2017/2018. Materials and Methods: A split-split plot design in a randomized complete block arrangement was used with 3 replications. The main plots were allocated to the 2 potassium sources (potassium sulfate and potassium chloride) 3 potassium rates (60, 120 and 180 kg ha–1 K2O beside one treatment without potassium fertilization) were devoted to sub-plot and three patterns (1, 2 weeks and 1 month) were devoted to sub-sub plot. Results: The results showed that potassium had essentially influenced the yield and yield components of wheat and potassium fertilizers such as K2SO4 and KCl improved the quantity and quality of wheat. These results suggest that potassium application at 180 kg ha–1 associated with one pattern under fertigation can be good for obtaining an optimum yield of wheat. Conclusion: From this study can be concluded that the potassium application influence at 180 kg ha–1 K2O gave highly yield and chemical constituents under fertigation.
INTRODUCTION
Agriculture soil assets in Egypt are restricted, just 3.5% of the total areas are agricultural, while desert involves 96% of the total area, water shortage is one of the major issues for a harvest generation in Egypt, this is requirements to reduce the consumption of water in irrigation by developing new technologies and strategies that can be helpful to use this valuable contribution to a powerful way. Agriculture in Egypt is almost completely dependent on irrigation and the single main source of water is the Nile1. A study investigation directed showed that decreasing of fertigation levels from 100-50% NPK of the suggested fertilizer doses significantly decreased most studied growth characters such as yield and yield attributes protein and carbohydrate contents2. Showed that fertigation devices can be influenced by the consistency of water and fertilizer, weight differential tank decrease the consistency of water and fertilizer in a drip irrigation system3.
Fertigation plans, which are explicit for the harvest, soil and climate, are particularly significant for K, which can be provided at sufficient rates amid the reproductive stages of vegetables and fruit trees. Other advantages of fertigation are: (1) Saving of energy and labor, (2) Flexibility in the time of application: Nutrients can be applied when yield or soil conditions would some way or another forbid the utilization of wheeled application equipment, (3) There is no risk of foliar burn and development of plant pathogens, (4) Helpful utilization of compound and prepared blend nutrient solutions which can also contain small concentrations of micronutrients and (5) The supply of nutrients can be all the more deliberately controlled and checked4. While, reported that when fertilizers were connected alongside the water through the drip irrigation system, there was an impressive saving of fertilizer besides increased yields and saving of water compared to the surface technique of irrigation5. Fertigation has appeared to upgrade in general plant-root activity, improve the portability of nutritive substances, their consumption as well as reducing the contamination of surface and groundwater, says a report of Food and Agriculture Organization6. An appropriately structured drip fertigation system conveys water and nutrients at a rate, duration and frequency, to maximize crop water and nutrient uptake while minimizing leaching of nutrients and chemicals from the root zone of agricultural fields7. A valuable outcome of this is saving irrigation water, which is a critical issue in Egypt. In Egypt, as in most Middle-Eastern and North African countries, water is a restricted asset and it is very required for agriculture. The normal yearly precipitation in Egypt is very low and characterized by high variability8. Fertigation was perceived as a very effective and convenient means of maintaining optimal fertility and water supply. Found that the application of nutrients through drip irrigation improved seed cotton yield by 43.0% compared with conventional surface irrigation9.
Potassium is one of the extremely important nutrients for the plants, which directly helps in the production of the yield and decides its quality. It is characterized by high mobility in plants at all levels is the most abundant cation in the cytoplasm and along with its accompanying anions makes a high contribution to the osmotic potential of cells and tissues. Likewise, potassium involved in many physiological processes, for example, photosynthesis, enzyme stimulation of action, water relations and absorbs transport can have direct results on harvest efficiency. In this way, potassium deficiency can lead to a reduction in the number of leaves produced and the measure of individual leaves10. Fertigation likewise enables the application of soluble fertilizers and different chemicals along with irrigation water consistently and more efficiently11. The results obtained from the investigation conducted led more than 2 years showed that ideal advancement and high harvest productivity of winter wheat obtained when irrigations were planned at soil moisture levels of 60 and 75% of field capacity during the three major crop growth stages, respectively12. Reported that drip fertigation showed almost 87% more water use productivity in contrast with the treatment with furrow irrigation and conventional application of fertilizer 13.
The objective of this study was to evaluate the effect of sources, rates and patterns of some potassium fertilizers on quantity and quality of wheat gram in sandy soil under the fertigation system in Egypt.
MATERIALS AND METHODS
Experimental site: In this study, field experiments were carried out in 2 successive seasons 2016/2017 and 2017/2018 at El-Sadat city, El-Menoufia Governorate, Egypt. This experiment aimed to study the potassium fertilization of wheat (Giza 168) through fertigation in Egypt in the sandy soil by groundwater under a drip irrigation system of two lateral lines per row and emitters at 50 cm space of GR type each at 4 L h–1. Some selected properties of the soils and irrigation water collected from experimental fields determined by the standard methods are given in Table 1 and 2.
Soil samples were taken from the experimental field before conducting from soil layer (0-30 cm depth), then air-dried and ground to pass through a 2 mm sieve. Soil physical and chemical properties were carried out according to Klute and Page14 and Page et al.15. The chemical analysis of irrigation water using the method described by Cottenie et al.16.
| Table 1: | Some physico-chemical properties of the experimental site before sowing |
| Table 2: | Chemical analysis of irrigation water |
Experimental design and treatments: A split-split plot design in a randomized complete block arrangement was used with 3 replications. The main plots were allocated to the 2 potassium sources potassium sulfate, (K2SO4) 48-50% K2O and potassium chloride, (KCl) 60-62% K2O, 3 potassium rates (60, 120 and 180 kg ha–1 K2O) beside 1 treatment without potassium fertilization were devoted to sub-plot and 3 patterns (1, 2 weeks and 1 month) were devoted to sub-sub plot. In the case of fertigation treatment, K fertilizer was dissolved insufficient water and its dissolved portion was used for fertigation.
Cultural practices: The preceding crop was a tomato in both seasons. Seeds of Giza 168 wheat variety were obtained from Wheat Research Department, Field Crops Research Institute, Agricultural Research Centre, Egypt. Sowing dates were on November, 10 in 2 seasons, respectively. Seeds were drilled by hand on both sides of the ridges. Calcium superphosphate fertilizer (15.5% P2O5) at the rate of 60 kg P2O5 ha–1 was added during field preparation as a basal application. Nitrogen was added at a rate of 220 kg ha–1 N in the form of ammonium nitrate (33.5% N).
The weed control was carried out during the growing season by hoeing twice at 30 and 60 days after sowing and the pest control, if necessary, was done according to practices used at the experiment station. The other cultural practices were applied as recommended by the Ministry of Agriculture, Egypt.
Yield and its components: Samples often geared plants were taken of random from each plot to the three replications to measure growth parameters at 120 days after sowing, where, plant height and 100-grain weight were determined according to Bremner and Taha17.
At harvest date, random often guarded plants were taken from the middle rows of each plot to determine grain and straw yields ha–1 were estimated according to Abd El-Gawad et al.18.
Plant and seed, chemical analysis: Samples of 0.5 g of plant material into 100 mL beaker using 10 mL H2SO4 and digested with Perchloric on a hot plate for 30 min. The suspension was filtered on an ash-free filter paper into a 100 mL volumetric flask. The filtrate was used for nitrogen, phosphorus and potassium determinations.
Total nitrogen was determined by the Kjeldahl method using the method described by Cottenie et al.19. Phosphorus was determined spectrophotometrically using the method described by 10 potassium was determined using a flame photometer as described by Cottenie et al.19. Total N-content in seeds was determined by using the Micro-Kjeldahl method and the protein (%) were calculated by multiplying N-content by 5.75 according to the Association of Official Agricultural Chemists20,21. Total carbohydrates: were determined according to DuBois et al.22.
Statistical analysis: Statistical analysis were performed using the analysis of variance. Results presented as means of the 2 years of experimentation. The least significant differences LSD at 5% were used to compare between means23.
RESULTS
Yield and yield components
Plant height (cm): Plant height is an important component of straw yield and may likewise influence grain yield. The growth and improvement of a plant depend on the crop species being grown, the number of nutrients in the native soil, the amount of applied fertilizer, the nutrient availability in the soil, the ecological conditions during the growing season.
| Table 3: | Effect of different potassium sources, rates and pattern of application on plant height (cm) of the wheat plant under fertigation system |
The data about to yield attributes are given in Table 3 clearly show that all sources of potassium fertilizers significantly increased plant height of the wheat in both seasons. The greatest increment in the plant height in both seasons was recorded by K2SO4 being over the KCl in the 2 seasons. Greatest height of plants was 96.34 and 100.33 cm with applied 180 kg ha–1 K2O and every week with K2SO4. K2SO4 significantly surpassed the KCl in plant height in both seasons.
So also, the increase in K level increased the plant height of wheat. The K2SO4 is increasingly valuable as K fertilizer because it contains sulfur (S)24. Likewise, it enhances the activity of enzymes containing25.
100-grain weight (g): Data presented in Table 4 show that potassium fertilizer generally increased 100 grains weight of wheat during the two years. On average, K2SO4 fertilizer produced a higher 100 grains weight (7.51 and 7.82 g) as compared with KCl which produced (6.87 and 7.09 g) weight/100 grains.
It is important to point out that the increase in K level gradually increased the 100 grains weight of wheat during the 2 years. The maximum height of plants was 7.37 and 7.66 g with applied 180 kg ha–1 K2O and every week with K2SO4.
It gave the idea that the use of K increased the protein rate, which thusly expanded the grain weight26. Likewise, it reported that the 100-grain weight of wheat increased by adding potassium fertilizer to plants by Ijaz27.
Grain yield (t ha–1): Data in Table 5 revealed that all treatments significantly increased grain yield/plant in both seasons. The K2SO4 fertilizer surpassed the KCl. Such an increase due to the K2SO4 reached (7.80 and 7.83%) over the KCl in the first season and second season. The maximum height of plants was 7.84 and 8.05 t ha–1 with applied at 180 kg ha–1 K2O and one pattern with K2SO4.
Wheat grain and straw yield increased by increasing potassium fertilizers this is due to the K supply which slows plant growth and decreases biomass production, thus increasing potassium fertilization consequently causes to increase the production of grain and straw.
These interpretations matching to come out pointed to the importance of potassium due to its involvement in many physiological processes, potassium impact on water relations, photosynthesis, assimilate transport and enzyme activation can have direct consequences on crop productivity25. The results are also in line with the researcher who revealed that the grain yield of wheat increased by adding potassium fertilizer28.
Straw yield (t ha–1): Data on rates the wheat as affected by K2SO4 and KCl are given in Table 6. There were gradual increases in growth characters, i.e., plant height, grain and straw yield as fertilizer rate increased from 60, 120 or 180 kg ha–1 K2O. The increases in straw yield due to K2SO4 treatment were (0.34 and 0.40 t ha–1) over the KCl in the 1st and 2nd seasons, respectively.
| Table 4: | Effect of different potassium sources, rates and pattern of application on 100-grain weight (g) of wheat under fertigation system |
| Table 5: | Effect of different potassium sources, rates and pattern of application on yield (t ha–1) of wheat under fertigation system |
The maximum height of plants was 3.56 and 3.86 t ha–1 with applied at 180 kg ha–1 K2O and one pattern with K2SO4. Data in Table 6 indicated that K2SO4 surpassed KCl in straw yield h–1 with differences in both seasons. In this respect found that potassium fertilizer application increased the weight of straw yield28, 29.
Chemical constituents
Chlorophyll (SPAD): Data presented in Table 7 show the effects of potassium fertilizers on leaves chlorophyll content after 70 days from sowing. Results reveal that total chlorophyll content increased significantly with K2SO4 and KCl application under fertigation compared to control in chlorophyll content during the 2 seasons.
The data also clearly shows that K2SO4, types exceeded the KCl in this respect in both seasons. As for the effect of fertilizer rate on leaves wheat content from chlorophyll, results in Table 7 show that chlorophyll content significantly increased with increasing the rate of the applied K2O fertilizer with the highest increase at the highest rate of application (180 kg ha–1 K2O).
| Table 6: | Effect of different potassium sources, rates and pattern of application on straw yield (t ha–1) of wheat under fertigation system |
| Table 7: | Effect of different potassium sources, rates and pattern of application on chlorophyll (SPAD) of wheat under fertigation system |
The highest values of chlorophyll content were recorded when K2O was applied at the highest rate (180 kg ha–1 K2O) in both seasons. These results are following those obtained by Abd El-Rahman1, Abdelraouf et al.2 and Maurya et al.28.
Nitrogen (%): Data presented in Table 8 show that there were significant differences due to fertilizer type, the rate of wheat grains' nitrogen content after harvest. The data clearly shows that all potassium fertilizers under fertigation significantly exceeded the control in this regard, in both seasons.
Concerning the main effect of the applied fertilizer type, data in Table 8 show that the K2SO4 and KCl significantly increased the nitrogen content in grains compared with control in both seasons. As for potassium fertilizer rates, it is clear from the data in the same Tables that gradual significant increases of nitrogen content in wheat grains occurred as K rate increased up to 180 kg ha–1 K2O.
In this respect found that potassium fertilizer application increased the nitrogen content of grains28,29.
| Table 8: | Effect of different potassium sources, rates and pattern of application of nitrogen (%) in grains of wheat under fertigation system |
| Table 9: | Effect of different potassium sources, rates and pattern of application on phosphorus (%) in grains of wheat under fertigation system |
Phosphorus (%): Phosphorus concentration was increased by applications of different sources of potassium comparing with the control. The data in Table 9 indicate that every single received treatment of K2SO4 and KCl indicated positive, measurable consequences for the grains phosphorus percentage in the grain of wheat in both seasons. Most outrageous phosphorus with, associated with 180 kg ha–1 K2O and one pattern with K2SO4.
Wheat phosphorus rate expanded by expanding potassium fertilizers this is because the expanding potassium fertilization thus causes an increment of phosphorus percentage. In this concern, reported the utilization of potassium fertilizers increased the phosphorus percentage in the grain of wheat9,26.
Potassium (%): The presented data in Table 10 cleared that all adopted treatments of K2SO4 and KCl revealed significant statistical effects on the percentage of potassium in wheat grains in both seasons. The K2SO4 significantly surpassed KCl in K concentration in both seasons. The maximum height of plants was 1.99 and 2.16% with applied at 180 kg ha–1 K2O and 1 pattern with K2SO4.
| Table 10: | Effect of different potassium sources, rates and pattern of application of potassium (%) in grains of wheat under fertigation system |
| Table 11: | Effect of different potassium sources, rates and pattern of application of the protein (%) in grains of wheat under fertigation system |
The observed increment in the percentage of K in the grains due to increasing of K application rate can be explained based on increasing the availability of nutrients by Tahir et al.30. Moreover, mentioned that potassium is involved in the activation of more than 60 enzymes, which are necessary for essential plant processes such as energy utilization, starch synthesis, N metabolism and respiration this can explain the previous findings31.
Crude protein (%): It is realized from Table 11 that all potassium fertilizers significantly increased crude protein percentage of wheat grain under investigation in both seasons. Also, the results indicated that grains of wheat treated with K2SO4 significantly exceeded KCl in crude protein percentage in both seasons.
The highest percentage of grain, crude protein was recorded with K2SO4 in both seasons being (7.26 and 6.96%) more than the KCl treatment in the 1st and 2nd seasons, respectively. The maximum height of plants was 13.01 and 13.17% with applied at 180 kg ha–1 K2O and 1 pattern with K2SO4.
| Table 12: | Effect of different potassium sources, rates and pattern of application on carbohydrates (%) in grains of wheat under fertigation system |
In this concern, found that the application of potassium fertilizers increased the percentage of crude protein in grains of wheat12. As well as, reported that the application of potassium fertilizers increased the percentage of crude protein in grains of wheat13.
Total carbohydrates (%): The data of yield attributes are given in Table 12 clearly showed that all treatments of K2SO4 and KCl significantly increased total carbohydrates of wheat grains under investigation than the control in both seasons.
The maximum increase in the total carbohydrates in both seasons was recorded by K2SO4 being over the KCl by (3.00%) and (3.62%) in the first and second seasons, respectively. The maximum height of plants was 66.85 and 68.27% with applied at 180 kg ha–1 K2O and one pattern with K2SO4.
The data also revealed that K2SO4 surpassed KCl in this respect with a significant difference in both seasons. These results are following those obtained from Abd El-Rahman1 and Abdelraouf et al.2.
CONCLUSION
The potassium fertilizers treatments showed a higher yield and chemical constituents compared with the control under fertigation. Furthermore, results suggest that potassium application at 180 kg ha–1 associated with one pattern under fertigation can be good for obtaining an optimum yield of wheat. The results of current study revealed that potassium fertilizers such as K2SO4 and KCl improved the quantity and quality of wheat.
SIGNIFICANCE STATEMENT
This study discovered the possible effect of potassium fertilizer under fertigation that can be beneficial for the wheat producers, where a better seed yield than of the plant for K2SO4 at 180 kg ha–1 K2O. This study will help the researcher to uncover the critical areas of the potassium sources that many researchers were not able to explore. Thus a new theory on this potassium sulfate fertilizer may be arrived at.
ACKNOWLEDGMENT
The author(s) are thankful to the Director a private farm in El-Sadat city, Menoufia Governorate, Egypt for providing all the necessary facility to complete the paperwork