# Nitric, phosphoric, sulfuric and citric acids in irrigation and chemigation URL: https://leafwrit.com/us/irrigation-acids-chemigation/ Reviewed: 2026-10-29 ## Nitric acid used in agriculture: nitrate input and irrigation safety **Nitric acid can neutralize irrigation-water alkalinity and adds nitrate nitrogen.** Its fumes and strong oxidizing action make handling difficult. ### Alkalinity and nitrogen Water alkalinity measures its capacity to neutralize acid. It is distinct from pH: water with high pH can have low alkalinity. Acidification decisions therefore depend on the alkalinity measurement, not pH alone. Bicarbonates, carbonates and hydroxides contribute to alkalinity. Compare acids by neutralizing capacity, nutrient contribution, hazard and cost. Nitric acid's nitrate contribution belongs in the fertilizer calculation. Calculate quantities from the acid's exact strength and specific gravity. Verify acid-service compatibility in the injector manual or with its manufacturer. ### Nitric acid hazards Nitric acid is HNO₃, CAS **7697-37-2**. Although noncombustible, it increases the flammability of combustible materials. Listed incompatibilities include metallic powders, hydrogen sulfide, carbides and alcohols. Reaction with water produces heat, and the acid corrodes metals. Exposure through inhalation or skin and eye contact can cause irritation and **delayed pulmonary edema**. ## Phosphoric acid in agriculture: irrigation alkalinity and phosphorus **Phosphoric acid can reduce irrigation-water alkalinity, but the phosphorus it supplies can limit its usefulness.** Phosphoric acid suits relatively small alkalinity reductions. Neutralizing high alkalinity with phosphoric acid can supply excessive phosphorus. ### Phosphorus limits the treatment choice For the greenhouse comparison using **75% phosphoric acid**, keep additions within **2.25 fluid ounces per 100 gallons of water** to limit added phosphorus. Calculate the requirement using exact strength and specific gravity. Measure alkalinity as well as pH when assessing treatment requirements. Resample when the water source or season changes because alkalinity can vary. ### Phosphoric acid hazards Phosphoric acid is H₃PO₄, CAS **7664-38-2**. Listed effects include skin and eye burns, dermatitis and respiratory irritation. It reacts with metals to produce flammable hydrogen. Do not mix it with solutions containing **bleach or ammonia**. ## Sulfuric acid use in agriculture: irrigation treatment and system safety **Sulfuric acid reduces irrigation-water alkalinity while adding sulfur to the nutrient supply.** Concentrated sulfuric acid presents high handling hazards. ### Sulfur and concentrated fertilizer compatibility For nutrient accounting, **one fluid ounce of 93% sulfuric acid in 100 gallons of water** contributes **43.6 ppm sulfur as sulfate**. Calculate any proposed acid addition separately from measured alkalinity, acid strength and specific gravity. Keep concentrated sulfuric acid separate from calcium-containing fertilizers, including calcium nitrate and **15-0-15 and 17-0-17** formulations. ### Sulfuric acid hazards Sulfuric acid is H₂SO₄, CAS **7664-93-9**. It reacts violently with water, releasing heat, and corrodes metals. Although noncombustible, it can ignite finely divided combustible materials. Exposure routes include inhalation and skin or eye contact. ## Citric acid in agriculture: irrigation and spray-water checks Citric acid is a weak organic solid used to reduce irrigation-water alkalinity. It is less effective than phosphoric, sulfuric or nitric acid for this purpose and therefore more expensive to use. For spray-water acidification, test the water and check the pesticide label before choosing an acidifier. Choose pH or hardness correction around the particular pesticide and target. ### Separate the water measurements Hardness measures calcium and magnesium ions. It is different from acidity or alkalinity. A hard-water result does not by itself establish the desired pH of a pesticide mixture. ### Choose the function you need An acidifier lowers pH, but other additions can still change the resulting pH. A buffer can help hold pH as materials are added. ### Understand the pH number before setting a target pH uses logarithmic units: a one-unit change represents a tenfold change in acidity or basicness. Obtain the mixture's target pH from the relevant product directions. ### Check whether acidification is allowed at all Some pesticide directions prohibit pH-adjusting agents. ### Compare suspended particles with dissolved minerals Separate floating debris, suspended solids and dissolved minerals when describing the water. Debris includes material such as leaves and seeds. Suspended silt, clay and organic matter can settle, while dissolved minerals do not simply settle out. ## Chemigation checklist: label, backflow equipment and Nebraska permits **In Nebraska, obtain the injection-location permit from the responsible Natural Resources District before chemigation.** The state requires an application for each injection location, with an exception for pumping or diverting water to or through an open discharge system. Equipment compliance and a certified chemigation applicator are conditions of approval. ### Nebraska renewal deadline Annual permits expire on June 1. Renewal applications use the district's form and list the chemicals used during the preceding year. Once a permit expires, reinstatement requires the new-permit conditions, including inspection. In Lower Elkhorn NRD, use the following local fees and inspection arrangements: | Request | Lower Elkhorn fee and condition | | --- | --- | | A new permit costs $50. | The system must pass inspection before use. | | A renewal costs $20. | The renewal must reach the district by June 1. | | A special permit costs $50. | This is a separate choice on the district form. | | An emergency permit costs $250. | The district asks applicants to allow two working days. | Lower Elkhorn inspects every new permit system and renewal systems once every three years. Complete the chemigation safety course and exam every four years. ### Complete the 2026 Lower Elkhorn application On the [2026 form](https://www.lenrd.org/sites/default/files/Water%20Resources/Chemigation/2026%20Chemigation%20Form.pdf), enter the applicant’s contact details, field name, county and legal injection location. Identify the location by quarter-quarter section, section, township and range. Select the permit type and whether the injector is portable or stationary. Enter the certified applicators' names, certification numbers, expiry dates and telephone details. The applicant signs and dates the form; a different certified applicator supplies the separate signature. For a 2026 renewal, enter names and estimated amounts of chemicals used during **2025**. List fertilizer names or formulations and totals separately from pesticide names and totals. Enter acres treated at that location. Sketch the well and access road on the reverse side, and provide vehicle access. Leave the lower permit and inspection section to the NRD. Submit the completed applicant section and fee to the district. Fees are nonrefundable and permits are not transferable. ### Backflow protections and pesticide directions Prepare the mainline check valve, vacuum relief valve, inspection port, low-pressure drain, chemical-injection check valve and electrical or mechanical interlock for inspection. For Nebraska systems, provide an inspection port or equivalent device to check the pipeline check valve under section 46-1127. The automatic low-pressure drain sits between the main check valve and irrigation pump, allowing solution to drain away from the water source. The interlock protects the supply if irrigation pumping stops. Follow any label prohibition on chemigation. Use only irrigation-system types permitted by the pesticide's chemigation instructions under PR Notice 87-1. ### Accident reporting Report actual or suspected chemigation accidents to both the NRD and Nebraska DWEE within **24 hours of discovery**. Provide the occurrence time, chemical type and quantity, location, and corrective or cleanup action under way. An emergency permit expires 45 days after issue. ## Next step Obtain a water analysis and the injector specifications. For Nebraska applications, contact the [responsible NRD](https://www.lenrd.org/i-want/chemigation-program) and check the pesticide's [chemigation instructions](https://www.epa.gov/pesticide-registration/prn-87-1-label-improvement-program-pesticides-applied-through-irrigation).