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© 2004 Plant Management Network.
Accepted for publication 16 April 2004. Published 9 June 2004.

Potassium Rate Effect on Plant Uptake and Forage Yield of Barley (Hordeum vulgare L.) Grown in an Arid Environment

M. Ammar Errebhi, A. Hamid AbdelGadir, and H. Ben Sarhan, Industrial Complex for Research and Technology, P.O. Box 42503, Riyadh 11551, Kingdom of Saudi Arabia; and A. A. Jaloud, King Abdulaziz City for Science and Technology, P.O. Box 28322, Riyadh 11437, Kingdom of Saudi Arabia

Corresponding author: M. A. Errebhi. merrebhi@sabic.com

Errebhi, M. A., AbdelGadir, A. H., Ben Sarhan, H., and Jaloud, A. A. 2004. Potassium Rate Effect on Plant Uptake and Forage Yield of Barley (Hordeum vulgare L.) Grown in an Arid Environment. Online. Crop Management doi:10.1094/CM-2004-0609-01-RS.

Abstract

Potassium (K) is required by field crops in high amounts to obtain maximum yield. In the arid regions of Saudi Arabia where K levels in soil and water are quite adequate, farmers and farming industries believe that there is no need for additional K fertilizer. The objective of this study was to assess the effect of various K rates on leaf K concentration and total biomass of irrigated barley (Hordeum vulgare L.) produced for use as green forage. A large-scale field experiment was conducted at two different sites: Kharj, a sandy soil with 83 ppm exchangeable K; and Makaheel, a sandy loam with 114 ppm exchangeable K. Potassium levels in irrigation water were 15 and 11 ppm for the Kharj and Makaheel sites, respectively. At both sites, potassium was applied at four rates: 0, 45, 90, and 135 lb of K₂O per acre. Barley tissue K concentration ranged from 2.0 to 3.4% at Kharj, and from 3.5 to 6.0% at Makaheel. Total forage yield ranged from 7.6 to 8.2 tons/acre at Kharj and from 10.1 to 11.9 tons/acre at Makaheel. At both locations, K rate did not statistically affect forage yield of barley. Calculations of K input-output for Kharj and similar arid environments indicate that an application of chemical K fertilizer would not be recommended. Soil salinity management and introduction of salt tolerant barley varieties are suggested. However, for Makaheel and similar regions, growers should apply chemical K fertilizer at the rate of 120 lb of K₂O per acre to sustain high forage yield and replenish soil K.

Introduction

Potassium (K) is the third macronutrient required for plant growth, after nitrogen (N) and phosphorus (P). Unlike N and P, K is not a component of cell structure. Instead, it exists in mobile ionic form, and acts primarily as a catalyst (21). Potassium has an important osmotic role in plants (7,20), a very important function in arid environments. In addition, K plays major roles in enzyme activation, energy relations, assimilate translocation, protein and starch synthesis (4,18,21).

Typically, K tissue concentration ranges between 3 and 5% (20). Leigh and Johnston (15) found significant positive correlation (r = 0.76; P < 0.001) between K concentration in leaves and the grain yield of spring barely. Potassium removal by grain and straw of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) is 99 and 179 lb of K₂O per acre, respectively (7). Habi et al. (11) reported that alfalfa (Medicago sativa L.) can remove more than 536 lb of K₂O per acre. Therefore, the soil, must supply large quantities of K for plant uptake, especially during rapid growth.

In arid regions of Saudi Arabia (20 to 35°N, 36 to 54°E), soils are normally rich in K, containing about 150 to 250 ppm in soil extracts. In addition, irrigation water from these regions contains from 5 to 20 ppm K (14). Barley is a very important crop in Saudi Arabia, and is used as food for both human and animal consumption (8). From 1990 to 1997, the world’s annual production area averaged 175 million acres. In Saudi Arabia, the annual average was 311 thousand acres (3). Farmers and farming industries from this arid environment believe that there is no need for application of K fertilizers since soil and water can supply K in quantities sufficient for plant optimum growth and yield. However, in sandy soils of some arid regions, ammonium acetate extractable K can be less than 120 ppm (2). Generally, when soil tests for K are below 75 ppm, application of K will result in a significant increase in wheat yield (12). With soil tests of K at 150 ppm and greater, wheat will probably not respond to K fertilizer application (12). Farming enterprises in arid zones cannot continue to mine soil K indefinitely by claiming that soil and water K are sufficient. Long-term, high-output practices may lead to K depletion from the soil. It would take time and investment to rebuild soil K to its original levels once soil levels drop to an insufficient range (17). A reasonable soil fertility management program would be to replenish K back to the soil at the same rate of removal by crops by taking into account both soil and water K content (14). This management program would need to consider K rates at which crops respond to K fertilization (17). However, there is very limited information on barley forage yield response to K fertilizer application under arid conditions (5). We hypothesize that farmers in the arid parts of Saudi Arabia are tapping into soil K reserve, potentially leading to its depletion over time. Therefore, the objective of this study was to assess the effect of various K rates on barley plant uptake and total forage production in an arid environment.

Large-Scale Field Experiments at Two Sites

Two large-scale field experiments were carried out during the 1999-2000 growing season at two different sites: Kharj and Makaheel (24 to 25°N, 47 to 48°E), Kingdom of Saudi Arabia. At each site, a farm was selected based on its soil type. Both farms belong to Al Safi Dairy Establishment.

Soil samples were taken from both farms prior to sowing for chemical analysis according to methods described by SSSA (19). Irrigation water samples were taken three times during the growing season and analyzed for electrical conductivity (EC), pH, and K (10). Extractable K levels in soil and K concentration in irrigation water were lower than levels typically reported for the region (2,6). Therefore, four K levels (0, 45, 90, and 135 lb of K₂O per acre) were selected for study at both sites.

At the Kharj farm, one center pivot representing sandy soils (Camborthids, calcaric cambisols) was chosen, and half of it was used for this experiment. The pivot has eight spans of equal length (144 ft) and potassium treatments were arranged in a randomized complete block design, replicated four times (Fig. 1). Inner pivot spans 1, 2, and 3 were taken as inside border; outer pivot span 8 was used as outside border. Spans 4, 5, 6, and 7 represented the four replicates. Because of the circular nature of the plots, plot sizes varied with replicates (spans). Areas of individual plots are given for each replicate in Table 1. At the Makaheel site, the center pivot chosen (164 ft) represented sandy loam soils (Calciorthids, haplic calcisols). The same experimental protocol of Kharj was followed with the exception that the randomization of treatments was different (Table 1).

Fig. 1. Experimental layout at the Kharj and Makaheel locations.

Table 1. Surface areas for treatment plots at the Kharj and Makahaeel sites.

Nitrogen and phosphorus were applied as per Al Safi Dairy farm’s usual practices, at the rates of 225 lb of N per acre and 125 lb of P₂O₅ per acre, respectively. For the various treatments, potassium sulfate (50% K₂O) was broadcast before sowing, then incorporated into the soil. Barley of the variety ‘Gusto’ was sown mechanically at both sites at a rate of 180 lb/acre. Other agricultural practices were also performed according to the normal routine used by the farm for commercial production of barley as green forage.

Above-ground whole plant samples were taken from both sites three times during the growing season, at 6, 10, and 13 weeks after sowing. Samples consisted of 20 to 30 barley plants. They were dried to constant weight at 70°C, ground to pass through a 20-mesh screen, and analyzed for K using a flame photometer (model M410, Corning Ltd., Essex, UK). The crop was grown for use as green forage, and was cut right at flowering stage, about 3 inches above soil surface. Each treatment plot was mechanically harvested, sparing 2-m border from all four sides. Barley forage yield was taken following a growing season of 92 days.

Potassium input (Kin) was estimated by the sum of K from irrigation water plus K from chemical fertilizer; organic matter was less than 0.1%, and K from plant residues and organic matter was assumed negligible. Potassium output (Kout) was defined here as K exported outside the 7-inch root zone. Kout was estimated by plant uptake (dry weight × tissue K concentration); and K leaching below the root zone was not considered because in arid environments high evaporation keeps soluble salts, including K, moving up to the top soil. Potassium balance was estimated by subtracting Kout from Kin.

Statistical analysis was performed for each site's data using analysis of variance, and for treatment comparison, least significant difference at 0.05 probability level was used.

Effect of K Rate on Uptake and Forage Yield

Results of soil and water analyses for both sites are given in Table 2. Irrigation water at the Kharj site had a higher K concentration. During the growing season, the barley crop received 100,040 ft³ of irrigation water per acre in each experimental site. This amount of water supplied 113 and 83 lb of K₂O per acre to the Kharj and Makaheel experimental plots, respectively. The irrigation water EC in Kharj experiment is approximately twice that of the EC value in Makaheel. High EC could negatively affect plant growth and yield if excess water is not applied to leach salts below the root zone (13,16).

Table 2. Electrical conductivity (EC), pH, and potassium (K) levels in soil and irrigation water at the Kharj and Makaheel sites.

 ^z Mean value ± standard deviation

Leaf analysis. Plant analysis results from both experiments (Table 3) indicate that K concentration in barley tissue fell within the adequate ranges (7). Barley tissue K concentration ranged from 2.0 to 3.4% at Kharj, and from 3.5 to 6.0% at Makaheel. This data agrees with earlier reports by Al Jaloud et al. (1) who reported that for the ‘Gusto’ variety, tissue K concentration ranged from 1.9 to 4.8%. On the first sampling date, six weeks after sowing, fertilizer K effect on leaf K varied with location (Table 3). At the Kharj site, the addition of 90 and 135 lb of K₂O per acre increased K concentration in barley tissue significantly (P < 0.05), whereas at Makahheel farm, the addition of K had no significant effect on barley tissue concentration at the 0.05 probability level. Grant (9) also found that the application of K increased K concentration in barley tissue grown on K-deficient soils, but not on soils containing high K levels.

Table 3. Effect of various levels of potassium (K) on barley tissue K concentration (% dry weight) at the Kharj and Makaheel sites.

 ^y WAS = weeks after sowing

 ^z NS = not significant at P < 0.05.

On the second sampling date, ten weeks after sowing, K tissue concentration at the Kharj site was not significantly affected by K rate at the 0.05 probability level. However, at Makahheel, application of 45 lb of K₂O per acre gave significantly (P < 0.05) higher K concentration than application of 90 and 135 lb of K₂O per acre. This effect is unusual, and could be due soil K level variability.

On the third sampling date, thirteen weeks after sowing, no statistical differences were found among treatments at either site. There was a decrease in tissue concentration at both sites, compared to the second sampling date. This drop in K concentration is probably due to a growth dilution effect. Because there were differing responses between the first and second sampling dates, and the lack of significant effect in the third sampling date, there was no consistent effect of K rate on barley tissue concentration.

Yield. Cherney and Martin (5) reported that updated and complete data on forage quality and yield of small grains crops is not available. Therefore, yield results of the trials were compared with ten years of forage yield data recorded at Al Safi Dairy. The ten-year average for barley forage yield was 10.5 tons/acre (2). While the yield at Makaheel is comparable to the average of the Al Safi data, a decline in yield at Kharj was observed (Table 4). This was attributed to very poor soil and water quality at the Kharj site, resulting from irrigation with relatively saline water. Gulam et al (8) found that increasing irrigation water salinity from 3 to 6.17 mS/cm significantly reduced ‘Gusto’ plant height, greenmatter yield, and drymatter yield. At Kharj and Makaheel, K rates did not have a statistical effect on barley forage yield. The lack of response to K application is in agreement with data reported by Halvorson et al. (12).

Table 4. Effect of various levels of potassium (K) on barley forage
production at the Kharj and Makaheel sites.

 ^z Means within a column are not significantly different (P < 0.05)

Potassium input, output, and balance. At the Kharj site, under the control rate, a K net balance of 15 lb/acre per season indicates that K is accumulating in the soil (Table 5); the fate of this net positive balance will depend largely on future K concentration of irrigation water and crop removal. The adoption of crop management practices that lead to yield increase, and hence more K export, is recommended. These practices include the application of excess water to leach down salts, and choosing high-yielding and salt-tolerant barley varieties. For Kharj and similar regions, it is not recommend to apply fertilizer K, but to routinely analyze soil and water with the objective of maintaining soil K at its current level of 83 ppm.

Table 5. Effect of various potassium levels on barley dry matter, K uptake, and K balnce.

 ^x Kout = Potassium exported outside the root zone and sampling soil depth of 7 inches.

 ^y Kin = Potassium input from chemical fertilizer and irrigation water.

 ^z K balance = Kin - Kout.

At the Makaheel site, high barley forage yield and plant uptake (Kout) resulted in a negative net K balance for the treatments of 0, 45, and 90 lb of K₂O per acre. At the control treatment, K net balance was -119 lb of K₂O per acre; while, when 90 lb of K₂O per acre was applied, the balance was -40 lb of K₂O per acre. An application of 120 lb of K₂O per acre would be required to sustain high yield and maintain soil K fertility at a level of 114 ppm. Barley removal rates of 202 to 277 lb of K₂O per acre at the Makaheel site are high compared to rates of 179 lb of K₂O per acre reported by other workers (7).

Conclusions

Under the conditions of these experiments, barley grown as a forage in an arid environment did not respond to potassium application. However, an examination of the net K balance shows that without fertilizer K application, soil K is being mined from the Makaheel site, and this could lead to K depletion in the soil.

Therefore, farmers in Kharj and similar regions can continue growing barley at moderate yields without chemical K fertilizers. For sustainable agriculture, they have to manage salt accumulation and introduce high-yielding barley varieties that can tolerate soil EC of 4.9 mS/cm. In addition, they should monitor soil K levels and add K when necessary. For Makaheel and similar regions, it is recommended that growers apply chemical fertilizer at the rate of 120 lb of K₂O per acre to sustain high forage yield and maintain soil K levels.

Acknowledgments

The authors extend their gratitude to the management and technical staff of Al Safi Dairy Establishment for providing two center pivots and assistance to carry out this study.

Literature Cited

1. Al Jaloud, A. A., Bokhari, U. G., Bashour, I. I., and Al Shanguitti, A. 1994. Mineral nutrient distribution in wheat and barley at different growth stages in calcareous soils. Biol. Sci. 3:61-78.

2. Al Safi Dairy Est. 2000. Soil and water analysis data, and crop yields. In: Annual Report: Central Region. Kharj, Kingdom of Saudi Arabia.

3. Basmail, S. M. 2002. Barley production in Saudi Arabia. Pages 20-21 in: Barley Use in Nutrition. S. M. Basmail, ed. Saudi Biological Society, Riyadh, Saudi Arabia.

4. Brag, H. 1972. The influence of potassium on the transpiration rate and stomatal opening in Triticum aestivum and Pisum sativum. Plant Physiol. 26:250-255.

5. Cherney, J. H., and Marten, G. C. 1982. Small grain crop forage potential: 1. Biological and chemical determinants of quality and yield. Crop Sci. 22:227-231.

6. Errebhi, M. A., and Jaloud, A. A. 2003. Water and soil databases. In: Database for Soil, Water, and Tissue Analyses for Saudi Arabia. SABIC Technical Report.

7. Fageria, N. K., Baligar, V. C., and Jones, C. A. 1991. Wheat and barley. Pages 125-158 in: Growth and Mineral Nutrition of Field Crops. Marcel Dekker, New York.

8. Ghulam, H., Al Jaloud, A. A., Al Shammary, S. A., Karimulla, S., and Al Aswad, S. O. 1997. Effect of saline irrigation on germination and growth parameters of barley (Hordeum vulgare L.) in a pot experiment. Agricultural Water Management. 34:125-135.

9. Grant, C. A. 1989. The effect of potassium and chlorine fertilizer additions on barley herbage yield and nutrient content in undisturbed and artificially compacted soil cores. Can. J. Plant Sci. 69:729-740.

10. Greenberg, A. E., Clesceri, L. S., and Eaton, A. D. 1992. Standard methods for the examination of water and wastewater. 18th Ed. ALPHA, AWWA, and WEF, Washington DC.

11. Habi, V. A., Russelle, M. P., and Skogley, E. O. 1990. Testing soils for potassium, calcium, and magnesium. Pages 184-221 in: Soil Testing and Plant Analysis. R. L. Westerman, ed. ASA, Madison, WI.

12. Halvorson, A. D., Alley, M. M., and Murphy, L. S. 1987. Nutrient requirements and fertilizer use. Pages 345-383 in: Wheat and Wheat Improvement: Agronomy No. 13. E. G. Hyne, ed. ASA, CSSA, SSSA. Madison, WI.

13. Heakal, M. S., Modaihash, A. S., Mashhady, A. S., and Metwally, A. I. 1990. Combined effects of leaching fraction salinity and potassium content of waters on growth and water use efficiency of wheat and barley. Plant and Soil. 125:177-184.

14. Jaloud, A. A., and Errebhi, M. A. 2001. Chemical fertilizer management and use efficiency in arid and semi-arid environment. In: 2001 Proc. Safety, Health, and the Environment. Petrotech, ed. Conf. Manamah, Bahrain, 27-31 Oct, 2001.

15. Leigh, R. A., and Johnston, A. E. 1983. Concentration of potassium in the dry matter and tissue water of field-grown spring barley and their relationship to grain yield. J. Agri Sci. 101:675-685

16. McBride, M. B. 1994. Salt affected and swelling soils. Pages 273-307 in: Environmental Soil Chemistry. Oxford Univ. Press, New York.

17. Sanchez, P. A., Shepherd, K. D., Soule, M. J., Place, F. M., Buresh, R. J., Izac, A. N., Mokwunye, A. U., Kwesiga, F. R., Ndiritu, C. G., and Woomer, P. L. 1997. Soil fertility replenishment in Africa: An investment in natural resource capital. Pages 1-46 in: Replenishing soil fertility in Africa. R. J. Buresh, P. A. Sanchez, and F. Calhoun, eds. Special Publication No. 51. SSSA, Madison, WI.

18. Smid, A. E., and Peaslee, P. E. 1976. Growth and CO₂ assimilation by corn as related to potassium nutrition and simulated canopy shading. Agron. J. 68:904-910.

19. Sparks, D. L. 1996. Methods of Soil Analysis. Part 3. Chemical Methods. SSSA Book Ser. 5, SSSA and ASA, Madison, WI.

20. Tisdale, S. L., Nelson, W. L., and Beaton, J. D. 1985. Elements required in plant nutrition. Pages 59-94 in: Soil Fertility and Fertilizers. S. L. Tisdale, W. L. Nelson, and J. D Beaton, eds. Macmillan Publish. Co., New York.

21. Wallingford, W. 1980. Function of potassium in plants. Pages 10-27 in: Potassium for Agriculture. Potash and Phosphate Inst., Atlanta, Georgia.