4 pp., 6 graphsResearch has shown that applying soluble calcium with urea, an ammonium form of nitrogen, can improve crop production. This publication reports the results of research with bermudagrass, rice and various vegetable crops. Application methods and calcium rates are discussed

Feagley, Sam E.

Fenn, Lloyd B.

Texas A&amp;M Repository

Research has shown that applying soluble calciumwith urea, an ammonium form of nitrogen, canimprove crop production. Calcium increases ammoni-um, potassium and phosphorus absorption, stimulatesphotosynthesis, and increases the size of sellable plantparts. It also makes the use of nitrogen more efficient,which improves the economics of production andreduces nitrogen contamination of the environment.How the Research Was ConductedVarious plant species grown in greenhouses were fer-tilized several times during the growing season withnutrient solutions containing various calcium-to-ammo-nium ratios, so that the value of increasing the amountof soluble calcium could be tested. Check plants weregiven nitrate fertilizer with no increased amounts of sol-uble calcium. Most field plots were planted in 40-inchrows and most greenhouse tests were accompanied byfield experiments. Greenhouse plants were grown tocertain stages and then harvested. The harvested plantswere weighed and divided into seeds, bulbs, leaves,stems and roots so the parts could be tested for nutrientconcentrations. In the field experiments, the commer-cial products were harvested and the yields recorded.Benets of CalciumWhen urea (46-0-0), anhydrous ammonia (82.5-0-0) or diammonium phosphate (18-36-0) is band-ed into the soil, an equivalent amount of calcium is precipitated. The plant roots cannot access nitrogen inan environment containing more than 32 percentammonium. Roots can be killed, but usually they growaround the fertilizer bands. After the soil microbes haveconverted much of the banded ammonium to nitrate,then the roots can begin to use the nitrogen. Whenextra soluble calcium is applied with the fertilizer itlowers the pH of the fertilizer band, thus reducing itstoxicity. If calcium is applied beyond precipitationrequirements, it stimulates ammonium absorption byplants. Adding supplemental calcium has increased therate at which plants absorb ammonium by as much as100 percent. As some of the ammonium is changed tonitrate, the previously precipitated calcium is graduallyresolubilized, adding to the available soluble calciumconcentrations that increase yield.The increased ammonium absorption caused by cal-cium has interesting results. Photosynthesis increases(Fig. 1), and greater amounts of carbon dioxide are cap-tured by the plant from the air, which increases theplant’s organic building blocks (Fig. 2). When plantsabsorb more ammonium, less nitrogen remains in thesoil and is subject to leaching. Also, surplus nitrogenabsorbed by plants is stored and is available to promotegrowth all season. In trials, both bermudagrass and rye-grass showed this effect, with denser growth and color(chlorophyll-photosynthesis) throughout the season (Fig. 3). Perhaps the most beneficial effect of applying calci-um with ammonium is that plants change their normalpattern of depositing energy stores (carbohydrates,metabolites) (Figs. 4, 5). As Figure 4 shows, rice plantshad progressively lower leaf weight and progressivelyhigher grain weight as calcium levels increased. Thisincrease continued with all calcium concentrations. Onereport showed that adding soluble calcium to ricepaddy water resulted in up to 15 percent of the flagleaf’s energy production being transported to the fillingseeds (as opposed to 5 percent without calcium). Riceweights increased 14 percent when extra calcium wasapplied at seed fill.L-52129-98Using Soluble Calcium to Stimulate Plant GrowthSam E. Feagley and Lloyd B. Fenn**Professor and Extension Soil Environmental Specialist; andProfessor, Texas Agricultural Experiment Station, The Texas A&MUniversity System.020406080100Relative dry weight increase (%)CabbageCantaloupeChileRadishSquashTomatoPlant200Figure 1. Increased photosynthesis results fromcalcium application.This same observation was made with beets, onions,wheat, oats and barley (Figs. 5, 6). Within 30 hours ofapplication, onion and beet bulbs increased in weightby up to 50 percent over bulbs grown with nitrate(without ammonium). The weight of the entire plant,however, did not increase as much as the bulb, whichmeans that calcium causes the carbonaceous com-pounds to be deposited disproportionately in the bulbs(Fig. 5).Incorporating calcium into fertilizers has secondarybenefits to crop production as well. In irrigated soils,sodium always builds up and the continuing addition ofcalcium helps improve soil structure near plant rootzones. In acid soils, where liming is practiced, the solu-ble calcium chloride will more rapidly migrate to thelower root zone, reducing the toxic effects of aluminum.Higher ratios of calcium to ammonium could be justi-fied for this reason.How to Use Calcium withNitrogen FertilizersNitrogen can be applied in several ways. It can bebroadcast on the surface of pasture land or prepared(crop) soil and watered in by rain or irrigation. It can bebanded. Or, nitrogen can be applied with irrigationwater, a method that does not stimulate plant growth asmuch as broadcast application. Each producer shouldselect the method that best fits the needs and econom-ics of his production system.20406080BeetsOnionsRadishesSquash plants1987% increase over urea alone Relative plant growth increase (%)20406080BeetsOnionsRadishesCarrots1988% increase over urea alone Relative plant growth increase (%)067892    4        6    8       10   12      14  NH4NO3 Urea+CaCa(NO3)2CheckColor96 lbs. N/creUreaWeeks after aplication067892     4 6     8 10    12 14Weeks after aplicationUrea0CaUrea, Ca(NO3)2CheckThatch density    (relative scale) NH4NO3BA102030400   100        200  300N Level (ug L-1)Grain and straw weight (g/POT) 0400800120012008004000ug L-1 CaStrawRiceFigure 2. Relative yield of vegetables grown in the field after fertilization with urea alone and with ureaplus calcium chloride (Fenn et al., 1990, 1991, 1994).Figure 3. Bermudagrass color (A) and density (B)as affected by four nitrogen sources (Horst et al.,1985).Figure 4. With increasing calcium levels, rice grainweight increases while straw weight decreases.When nitrogen (usually ammonium in the form ofurea) is applied to soils, the nitrogen can quickly con-vert to nitrate, especially in the summer (The presenceof nitrate does not hinder the plant’s use of ammoni-um.) Thus, the fertilizer application method and time ofyear could become important. The best results from thecalcium-ammonium technology are obtained in the cool-er weather of winter and spring, although nitrogen mayneed to be applied at other times. Foliar application ofthe calcium-ammonium is a good solution. In fact, foliarapplications have produced significant benefits inresearch trials, at a rate of 1 to 2 pounds of calcium peracre. Logically, plant stimulation could not be expectedunless soil nitrogen (probably nitrate) is present. Thismeans that we can use calcium-ammonium, appliedfoliarly, as a means of extracting soil nitrate, whichmakes this technology an excellent environmental andagronomic tool. Furthermore, the low rate of calciumthat can be used in foliar applications reduces the riskof leaf burn, yet seems to trigger the same beneficialeffects as soil-applied productNitrogen and Calcium RatesNitrogen needs should be determined in the tradi-tional fashion—soil testing. Take soil samples to deter-mine your nitrogen need and then calculate your calci-um addition at the desired ratios. It is possible that lessnitrogen could be required when calcium is appliedwith it, as seems to be the case in sugar cane.Research has shown that the optimum amount of cal-cium to apply is 1/2 to 1 pound of calcium chloride per1 pound of urea (Fig. 6). This rate increases yields from14 to 50 percent. However, the precise amount of calci-0501001502000     0.5:1    1:1 1.5:1 2:1OnionbulbsOniontopsCalcium–Ammonium ratioRelative nitrogen deposition (%)0501001502002500      .5:1     1:1  1.5:1           2:1BeetbulbsBeettopsCalcium–Ammonium ratioRelative nitrogen deposition (%)300AB05101520250     0.3:1   0.6:1  0.9:1         1.2:1BarleyOatsWheatCalcium–Ammonium RatioTotal plant weight (g)024680     0.3:1   0.6:1 0.9:1         1.2:1WheatOatsBarleyHead weight (g)Calcium–Ammonium ratio0481216200    0.3:1   0.6:1 0.9:1        1.2:1 BarleyOatsWheatCalcium–Ammonium ratioStalk weight (g)ABCFigure 5. Calcium stimulates growth and energydeposition patterns in onion (A) and beets (B).Figure 6. The effects on total plant weight (A),head weight (B), and stalk weight (C) of variousratios of calcium to ammonium.um needed is hard to fix because when the plantabsorbs ammonium it releases an equivalent amount ofhydrogen. This hydrogen in turn solubilizes the precipi-tated lime (calcium carbonate), if present. Urea appliedin a band will precipitate calcium even in an acid soil.Thus, there is a certain amount of this naturally occur-ring calcium that combines with supplemental calciumto stimulate plant growth.A dditional ReadingAdams, F. 1982. A comparison of the effects of monocalcium phos-phate and diammonium phosphate on phosphorus and calciumavailabilities. Soil Sci. Soc. Am. J. 46:769-771.Bailey, J. S. 1992. Effect of gypsum on the uptake, assimilation andcycling of N15-labeled ammonium and nitrate-N by perennial rye-grass. Plant and Soil. 143:19-31.Barker, A. V., R. J. Volk and W. A. Jackson. 1966. Root environmentalacidity as a regulatory factor in ammonium assimilation by thebean plant. Plant Physiol. 41: 1193-1199.Bartlett, R. J. 1965. Importance of carbon dioxide in uptake of calciumby plants receiving only a nitrate source of nitrogen. Soil Sci. Soc.Am. Proc. 29:555-558.Bastida, J.,  J. M. Llabres, F. Viladomat, R. M. Cusido and C. Codine.1988. Free amino acids and alkaloid content in snap dragon plantsgrown with nitrate, urea or ammonium nutrition. J. Plant Nutr.11:1-15.Bennett, A. C. and F. Adams. 1970a. Calcium deficiency and ammoniatoxicity as separate causal factors of (NH4)4HPO6 injury toseedlings. Soil Sci. Soc. Am. Proc. 34:255-259.Bennett, A. C. and F. Adams 1970b. Concentration of NH3 (eq)required for incipient NH3 toxicity to seedlings. Soil Sci. Soc. Am.Proc. 34:259-263.Fenn, L. B. and G. R. Gobran. 1998. Willow tree productivity on fer-tilizer solutions containing various Ca/Al ratios. Nutr. Cycling inAgroecosystems (in press).Fenn, L. B., B. Hasanein and C. M. Burks. 1995. Calcium-ammoniumeffects on growth and yield of small grains. Agron. J. 87:1041-1046.Fenn, L. B. and R. M. Taylor. 1990. Calcium stimulation of ammoni-um absorption in radish. Agron. J. 82:81.Fenn, L. B., R. M. Taylor, M. L. Binzel and C. M. Burks. 1991.Calcium stimulation of ammonium absorption in onions. Agron. J.83:840-843.Fenn, L. B., R. M. Taylor and C. J. Burks. 1994. Calcium stimulationof ammonium absorption and growth by beets. Agron. J. 86:916-920.Fenn, L. B. and L. R. Hossner. 1985. Ammonia volatilization fromammonium or ammonium- forming nitrogen fertilizers. InAdvances in Soil Sci. New York: Springer-Verlag, Inc. pp. 125-169.Fenn. L. B., R. M. Taylor and C. Pety. 1986. Calcium stimulation ofammonium absorption with some root crops. Agron Abst. p. 198.Fenn, L. B., R. J. Taylor and G. L. Horst. 1987a. Phaseolus vulgarisgrowth in an ammonium- based nutrient solution with variablecalcium. Agron. J. 79:89-91.Fenn, L. B., R. J. Taylor and C. A. Pety, Jr. 1987b. Stimulative effectsof elemental sulfur in the presence of ammonium on chile andbroccoli growth in calcareous soils. J. Plant Nutr. 10:2263- 2281.Flocker, W. J. and W. H. Fuller. 1956. Availability of calcium in cal-careous soils. Soil Sci. Soc. Am. Proc. 20:387-391.Gobran, G. R., L. B. Fenn, H. Persson and I. Al-Windi. 1993.Nutrition response of Norway spruce and willow to varying levelsof calcium and aluminum. Fert. Res. 34:181-189.Hallmark, W. B., L. P. Brown and G. L. Hawkins. 1997. Use of calci-um chloride to reduce the nitrogen requirements of sugarcane.Louisiana Agr. 40:30-31.Horst, G. L., L. B. Fenn and N. B. Beadle. 1985. Bermuda grass turfresponses to nitrogen sources. J. Amer. Soc. Hort. Sci. 110:759-761.Hunter, A. S. and W. A. Rosenau. 1966. The effects of urea, biuret,and ammonia on germination and early growth of corn. Soil Sci.Soc. Am. Proc. 30:77-81.Jacobson, L., D. P. Moore and R. J. Hannapel. 1959. Role of calciumin absorption of monovalent cations. Plant Physiol. 35:352-358.Jacobson, L. R., J. Hannapel, D. P. Moore and M. Schaedle. 1960.Influence of calcium on selectivity of ion absorption process. PlantPhysiol. 36:58-61.Krassesindhu, P. 1975. Nitrogen, potassium and calcium nutritioneffects on ion and dry matter accumulation in rice. Ph.D. diss.University of Kentucky, Lexington.Krasaesindhu, P. and J. L. Sims. 1972. Response of rice to nitrogenand calcium nutrition. Soil Sci. Soc. Am. Proc. 37:457-461.Leggett, J. E. and W. A. Gilbert. 1967. Localization of the Ca-mediatedapparent ion selectivity in the cross-sectional volume of soybeanroots. Plant Physiol. 42:1658-1664.Morre, D. J. and C. E. Brocker. 1976. Ultrastructural alteration ofplant plasma membranes induced by auxin and calcium ions. PlantPhysiol. 58:544-547.Nielsen, T. R. and R. Overstreet. 1955. A study of the role of thehydrogen ion in the mechanism of potassium absorption byexcised barley roots. Plant Physiol. 30:303-309.Sung. F. J. M. and W. S. Lo. 1990. Growth responses to rice in ammo-nium-based nutrient solution with variable calcium supply. PlantSoil. 125:239-244.Taylor, R. M., L. B. Fenn and C. Pety. 1985. The influence of calciumon growth of selected vegetable species in the presence of ammo-nium-nitrogen. J. Plant. Nutr. 8:1013-1023.Taylor, R. M., L. B. Fenn and C. A. Pety, Jr. 1984. Preliminary obser-vations of chile plant response to banded sulfur. J. Fert. Issues.1:146-149.Viets, F., Jr. 1944. Calcium and other polyvalent cations as accelera-tors of ion accumulation by excised barley roots. Plant Physiol.19:466-480.Produced by AgriLife Communications & Marketing, The Texas A&M System Extension publications can be found on the Web at: http://AgriLifebookstore.orgEducational programs of the Texas AgriLife Extension Service are open to all citizens without regard to race, color, sex, disability, religion, age or national origin. Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, incooperation with the United States Department of Agriculture. Texas AgriLife Extension Service, The  Texas A&M System.

Using Soluble Calcium to Stimulate Plant Growth

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Using Soluble Calcium to Stimulate Plant Growth

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Using Soluble Calcium to Stimulate Plant Growth

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