Soil crusting after planting is a serious problem in stand establishment
of small-seeded crops in the Southwest. When crusting occurs in a
saline, warm soil, stand establishment problems are especially severe. It
is customary to use costly irrigation water to keep seedbed surfaces moist
after planting to reduce soil crusting and to lower soil temperatures.
Phosphoric acid (24% and 12%) and sulfuric acid (95%) were evaluated
to determine their effectiveness in reducing soil crusting and reducing
the amount of water required to obtain stands of sugarbeets, alfalfa,
wheat and barley.
Phosphoric acid, applied in 4-6 cm bands over the seed row at
planting and before irrigation, reduced crusting and increased sugarbeet
and alfalfa seedling emergence. Emerged seedlings from phosphoric acid
treated plots were larger and one irrigation (10-15 ha cm/ha) was saved
in stand establishment. Sulfuric acid applied in bands reduced soil
crusting. Soluble salts in the seed zone resulting from band application
of sulfuric acid killed or damaged seedlings. Sulfuric acid, when applied
in irrigation water to saline-sodic soils, improved plant growth and water
use efficiency

Dennis, R.E.

Edmond, C.W.

Robbins, C.W.

USDA - ARS - NWISRL

111FISTEFi copr"r7PROJECT COMPLETION REPORTOWRR PROJECT No. A-034-ARIZUse of Amendments to Reduce WaterRequirements for Stand Establishmentof Small-Seeded CropsAgreement No. 14-31-0001-5003Project Dates: July 1, 1972-June 30, 1975Principal Investigators R. E. DennisC. W. EdmondC. W. RobbinsThe University of ArizonaTucson, ArizonaAugust, 1975Acknowledgement - The work upon which this project isbased was supported by funds provided by the UnitedStates Department of Interior, Office of Water Researchand Technology, as authorized under the Water ResourcesResearch Act of 1964.ABSTRACTSoil crusting after planting is a serious problem in stand establish-ment of small-seeded crops in the Southwest. When crusting occurs in asaline, warm soil, stand establishment problems are especially severe. Itis customary to use costly irrigationwater to keep seedbed surfaces moistafter planting to reduce soil crusting and to lower soil temperatures.Phosphoric acid (24% and 12%) and sulfuric acid (95%) were evaluatedto determine their effectiveness in reducing soil crusting and reducingthe amount of water required to obtain stands of sugarbeets, alfalfa,wheat and barley.Phosphoric acid, applied in 4-6 cm bands over the seed row atplanting and before irrigation, reduced crusting and increased sugarbeetand alfalfa seedling emergence. Emerged seedlings from phosphoric acidtreated plots were larger and one irrigation (10-15 ha cm/ha) was savedin stand establishment. Sulfuric acid applied in bands reduced soilcrusting. Soluble salts in the seed zone resulting from band applicationof sulfuric acid killed or damaged seedlings. Sulfuric acid, when appliedin irrigation water to saline-sodic soils, improved plant growth and wateruse efficiency.Key Words: Soil crusting, seedling emergence, water saving, wateruse efficiency, sugarbeets, alfalfa, sulfuric acid, phosphoric acid,soil amendments.INTRODUCTIONThe establishment of small-seeded crops in irrigated desert environ-ments, is seriously affected by soil crusting, high soil temperaturesand soil salinity. Saline soils, especially those with fine texture,disperse and form crusts when the surface has been wetted and then allowedto dry.Soil crusting follows the mechanical destruction of aggregates,washing of fine particles into inter-aggregate spaces, and the ruptureof soil aggregates by trapped air. Soil crusts are effective barriersto seedling emergence.Problems of soil crusting are compounded when small-seeded crops areplanted in warm, saline soil, a practice often required in irrigateddeserts. Germination percentage and vigor decrease dramatically withincreasing temperature and salinity. When soil crusting occurs additionally,stand establishment failures are common.Farmers keep the surface soil moist after planting crops such assugarbeets and alfalfa, to reduce the energy required for seedling emergence.The application of frequent, light irrigations is effective in reducingsoil crusting but it wastes water and is costly.This research evaluated phosphoric and sulfuric acids and severalother soil amendments to determine their effectiveness in reducing soilcrusting, thereby permitting a saving of irrigation water during standestablishment. Other potential uses of sulfuric acid and related culturalpractices were also investigated.OBJECTIVESThe objectives of this project were:1. To evaluate phosphoric and sulfuric acids and other amendmentsas anti-soil crustants and to determine their effect on seedlingemergence and the water requirement for stand establishment.2. To investigate the use of sulfuric acid as a soil amendment forreducing salinity in saline-alkali soils, thereby improving wateruse efficiency.3. To develop appropriate methods of applying soil crust inhibitingamendments under laboratory and field conditions.DESCRIPTIVE REPORT OF RESEARCH PROCEDURESChemicals containing sulfur have been used for years in the reclamationof saline-sodic soils. After application of sulfur containing chemicals,soluble calcium is released forming gypsum. Gypsum acts to replace adsorbedsodium and this reaction yields sodium sulfate. Other sulfates are alsoproduced. Since sulfates are soluble they may be leached to lower soildepths where they are out of the reach of roots. Sulfuric acid, asproduced in air pollution reducing procedures now used in copper and othermines, is an excellent soil amendment for saline-sodic soils.Johnson and Law (1966) applied concentrated sulfuric acid to thesoil surface in bands above the seed-row, after planting sugarbeets inUtah. In their research this practice reduced soil crusting and increasedseedling emergence 42 to 5C%. Robbins, Carter and Leggett (1972) applied657 1/ha of phosphoric acid (24%) in 6 cm bands on the soil surfaceover sugarbeet rows, simultaneous with planting, in Idaho and obtainedincreases of seedling emergence up to 80%. These and relatedencouraging results formed the basis for this research project.Other soil amendments used in this research were ferric andferrous sulfate, a commercial latex formulation and sawdust. Thesematerials were selected because of their ease of handling and availa-bility.Plan Followed for Conduct of Research First Year Experiments (1972-1973)Two laboratory and six field experiments were conducted to identifyamendments with the greatest promise of fulfilling project objectives andto lay the foundation for future studies. Laboratory experiments wereconducted in an open-air enclosure at the University of Arizona CampbellAvenue Branch Experimental Farm and field research was located on sixcentral Arizona farms.Soil from the Wade farm (pH 8.0 and ECe X 103 6.4) near Buckeye,Arizona was used for the first year laboratory studies. This silty-clay loam contained 59.8, 21.8 and 18.4% silt, clay and sand respectively.During the first year all research was with sugarbeets, Beta vulgaris L.,cultivar US-H9B.Simulated beds were established in 191, plastic lined, metal containersfor the laboratory experiments. Three rates of phosphoric and of sulfuricacid were applied to the soil surface in 7.5 cm bands immediately afterplanting and before application of the germination irrigation.Three levels of irrigation were used in each laboratory experiment.In the first laboratory experiment equal amounts of water were applied toeach side of the seed row. All irrigation water was applied to one sideof the seed row in the second laboratory experiment. Temperature andhumidity in the soil at seed depth and above the soil, were carefullymonitored during laboratory and field experiments.The field experiments during the first year were placed on six farmslocated in central Arizona. At each location one group of plots wasestablished using six different materials with anti-crustant potential.A second series of plots was established, with power equipment designedand constructed for this purpose,at each location with three rates ofphosphoric acid only. All treatments in each group of plots werereplicated four times.Appropriate seedling counts and harvests were made and beet rootswere harvested at each on-farm location in June 1973 to determine sugaryield.Second Year Experiments (1973-1974)During first year experiments phosphoric acid was found superior to othermaterials used to achieve anti-crustant objectives. Research concerning thereduction of crusting and resultant saving of water was conducted usingphosphoric acid only during the second year. Principal effort in thisregard was at the University of Arizona Mesa Branch Experimental Farmand on two farms in central Arizona.Irrigation level was a variable for the Branch Station and on-farmtests during the second year. Phosphoric acid was applied mechanicallyusing methods developed during the first year. Seedling count and weightdata were obtained at the Mesa Branch Experimental Farm and at each ofthe on-farm test locations. Additonally beet yield data were obtainedfor the on-farm plots.Sulfuric acid was used in two types of experiments during the secondyear. It was reasoned that soluble salts produced by application ofsulfuric acid would slow plant growth and that this might increase sugarstorage by sugarbeets during the period immediately preceding harvest.Sulfuric acid and several growth regulators were used in such experimentsat two locations in central Arizona. Sulfuric acid was also used at threerates and with three leaching regimes to determine its effectiveness inreducing salinity of a saline-sodic soil. This experiment also includedan evaluation of the relative salt tolerance of several spring wheatcultivars.Third Year (1974-1975)Experimentation during the third year was principally limited toexploiting first and second year findings. Phosphoric acid was appliedto the soil surface over alfalfa seedings in laboratory tests and at theUniversity of Arizona Mesa Branch Experimental Farm. Soil for thelaboratory experiment was from plots later used for field research. Thisresearch included an irrigation variable. Additionally, field researchduring the third year of this project evaluated the interaction of acidtreatment with alfalfa seeding method and seeding rate.FINDINGS AND CONCLUSIONSThe findings and conclusions for each of the three year segments ofthis project are presented in this section.First Year (1972-1973)Sugarbeet seedling emergence, seedling weight and efficiency ofwater use were greatest for plants in plots that received surface appliedphosphoric acid. Increases in these parameters were significant when 657and 1340 1/ha of 24% phosphoric acid were applied in a 7.5 cm band abovethe seed row. Surface applied sulfuric acid reduced seedling emergenceand especially seedling survival. Sulfuric acid applications increasedthe amount of soluble salt in the seed zone and this salt damaged and inmany instances killed sugarbeet seedlings. Application of phosphoricacid resulted in increased seedling emergence and weight while sulfuricacid applications significantly reduced sugarbeet seedling number andweight. Application of irrigation water to both sides of the simulatedbed increased soluble salts in the seed zone.In the second laboratory experiment, phosphoric acid was applied atthe rate of 657 and sulfuric acid 375 1/ha. Irrigation in the secondlaboratory experiment was on one side only of each of the simulated beds.The second experiment duplicated and confirmed results obtained in thefirst experiment. Phosphoric acid significantly increased seedling emer-gence and seedling size, and saved water in stand establishment. Sulfuricacid had a negative effect on each of these parameters.Field plot research during the first year confirmed beneficial effectson surface applied phosphoric acid of sugarbeet seedling emergence andimprove sugarbeet seedling emergence. Sulfuric acid reduced seedlingemergence and the size and number of emerged seedlings. Beneficialeffects of phosphoric acid on seedling emergence did not carry throughto harvest in terms of sugar yield in field tests. A successful powersprayer was developed and used in field tests during the first year.Sulfuric acid was difficult to use, because of its caustic effects,except under the most carefully controlled conditions.Second Year (1973-1974)Sulfuric acid was demonstrated to be an excellent amendment forreducing the amount of sodium in a saline-sodic soil in second yeartests. The soil for this laboratory experiment was very high in saltwith an ECe 103 of 20.2 mmhos. Application of 18,900 1/ha of sulfuricacid (95%) with 30 cm of applied water for leaching altered the makeupof the soil used so that wheat and barley seedling emergence and earlygrowth were satisfactory. This experiment also provided an opportunityto evaluate the relative salt tolerances of several spring wheats. Thecultivar Cajeme 71 was found to have salt tolerance comparable to thatof Arivat barley. Demonstration of the high salt tolerance of this wheatopens several thousand acres of saline soil of the irrigated deserts tothe production of this important crop.During the second year field plots were established in centralArizona to study further the water saving value of surface appliedphosphoric acid. Results obtained in these tests again indicated thatone irrigation could be saved in sugarbeet stand establishment by theapplication of phosphoric acid. Sugarbeet seedling emergence with oneirrigation was significantly greater than with two irrigations. Theyield of sugar was not significantly different from plants in plotsthat received two as compared to those receiving only one germinationirrigation.Third Year (1974-1975)During the third year of this study an effort was made to carry thesuccessful results with sugarbeets to alfalfa. Alfalfa seeds planted at0.7 cm depth produced 44% more seedlings than when planted at a depth of1.4 cm. The number of emerged seedlings and the weight of seedlings fromplots treated with surface applied phosphoric acid were significantlygreater than from the untreated check. Alfalfa seedlings used phosphorusfrom the phosphoric acid. This use of phosphorus played a role in increasedseedling vigor and weight of sugarbeet seedlings. It is now desirable todevelop precision equipment for the application of narrow bands of phosphoricacid over the rows when small-seeded plants are seeded.OVERALL SUMMARY AND CONCLUSIONSThis study was prompted by problems concerned with the establishmentof stands of crops having small seed and especially with the amount ofwater required to achieve stand establishment. The principal objectivewas to identify methods of using soil amendments so that water could besaved in stand establishment.In the first year of this research several soil amendment materials,especially sulfuric acid and phosphoric acid, were evaluated. Emphasisduring this period was on determination of the amendments' effect uponsoil crusting, increasing seedling emergence and most important, watersavings.Laboratory and field experiments revealed the superiority ofphosphoric acid in achieving project objectives. Phosphoric acid,while caustic, was handled with relative safety. Phosphoric acidhelped to prevent the formation of surface crusts and improved theemergence of sugarbeet and alfalfa seedlings an average of more than20%. Phosphoric acid also provided fertilizer phosphorus and thisenhanced seedling weight and vigor. This research indicates thatroutine band application of phosphoric acid for sugarbeet and alfalfaplantings made in fine-textured soils would be an economic practiceand that it would result in saving irrigationliater.Sulfuric acid, while excellent as a soil amendment for reducingsalinity, produced negative effects when applied on the surface of thesoil over planted seed. The acid was dangerous to work with and appli-cation of the acid increased the amount of soluble salt in the seedzone. The high content of soluble salts injured and often killed sugar-beet seedlings.In the next phase of this research there is a need to developcommercial models of precision equipment for the application ofphosphoric acid. These machines should be designed so as to make anapplication only one to two cm wide above the seed row. A narrow bandof precision applied phosphoric acid would increase the number, size,and vigor of emerged seedlings for crops like sugarbeets and alfalfa.Increased number and vigor of seedlings would be one important contribution.Probably more important would be the saving of at least one irrigation bysuch application.REFERENCES CITED1. Adamson, R. M., and E. F. Maas. 1971. Sawdust and other soilsubstitutes and amendments in greenhouse tomato production.Hort. Sci. 6:397-399.2. Arndt, W. 1965. The impedance of soil seals and the forces ofemerging seedlings. Aust. J. Soil Res. 3:55-67.3. Dennis, R. E., K. C. Hamilton, M. A. Massengale, and M. H.Schonhorst. 1965. Alfalfa for forage production in Arizona.The University of Arizona, Bull. A-16 p. 10-16.4. Dennis, R. E., and J. M. Nelson. 1971. Sugarbeets in Arizona.Univ. of Arizona Bull. A-71. 6 p.5. Eavis, B. W. 1972. Soil physical condition affecting seedlingroot growth. Plant and Soil 37:151-158.6. Francois, L. E., and J. R. Goodin. 1972. Interaction of temperatureand salinity on sugarbeet germination. Agron. J. 64:272-273.7. Frelich, James R., E. H. Jensen, and R. 0. Gifford. 1973. Effectof crust rigidity and osmotic potential on emergence of six grassspecies. Agron. J. 65:26-30.8. Hanks, R. G., and F. C. Thorp. 1957. Seedling emergence of wheat,grain sorghum and soybeans as influenced by soil crust strengthand moisture content. Soil Sci. Soc. Amer. Proc. 21:357-359.9. Hunter, J. R. 1951. Some factors affecting germination in sugarbeetseed (Beta vulgaris L.). Ph.D. thesis, Michigan State Univ. 95 p.10. Johnson, R. C., and G. E. Law. 1967. Controlling soil crusting insugarbeet fields by applying sulfuric acid. J. Amer. Soc. SugarBeet Technol. 14:615-618.11. Kathib, I. H., and M. A. Massengale. 1966. Effect of certain saltson germination of alfalfa and berseem clover. Progress. Agr. inArizona 18:21-23.12. Overstreet, R. J., J. C. Martin, and H. M. King. 1951. Gypsum,sulphur, sulphuric acid for reclaiming an alkali soil of the Fresnoseries. Hilgardia 21:113-127.13. Richards, L. A., ed. 1954. Diagnosis and improvement of saline andalkali soils. USDA Agricultural Handbook 60. U. S. GovernmentPrinting Orfice, Washington, D. C.14. Robbins, C. W., D. L. Carter, and G. E. Leggett. 1972. Controllingsoil crusting with phosphoric acid to enhance seedling emergence.Agron. J. 64:180-183.15. Taylor, H. M. 1962. Seedling emergence of wheat, grain sorghumand guar as affected by rigidity and thickness of surface crust.Soil Sci. Proc. 26:431-433.16. Triplett, Glover, B., Jr., and Milo B. Tesar. 1960. Effect ofcompaction, depth of planting, and soil moisture tension onseedling emergence of alfalfa. Agron. J. 52:681-684.

Use of Amendments to Reduce Water Requirements for Stand Establishment of Small-Seeded Crops

Northwest Irrigation & Soils Research Laboratory Publications

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Use of Amendments to Reduce Water Requirements for Stand Establishment of Small-Seeded Crops

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