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Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil

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  • Natural soil amendment for lawns with alkaline soil
  • Loosens hard soils
  • Promotes air and water penetration for deeper rooting
  • Helps to rapidly lower soil pH to increase nutrient absorption
Real Mag-I-Cal Plus Alkaline Lawns
Product Overview
Bring balance back to your soil with Mag-I-Cal® Plus! Jonathan Green Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil lowers soil pH that is too high and loosens hard, compacted soils allowing roots to grow deeper. Healthy, lush lawns thrive in soils with slightly acidic to neutral pH levels ranging from 6.2 to 7.0. In soils with pH readings of 7.0 to 9.5, weeds thrive and the grass becomes light green and spindly.

Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil contains sulfur and gypsum which lower soil pH, is important to cell development, and is vital to many grass plant functions.

Additionally, Mag-I-Cal Plus® for Lawns in Alkaline & Hard Soil helps to break up clay and compacted soils. When soil is compacted or too alkaline, air, water, and nutrients are unable to reach the roots, making it very difficult for grass to flourish. This soil conditioner improves root penetration and promotes growth by increasing biological activity and releasing nutrients trapped in the soil.
Coverage Guide

For soils with a pH over 7.5, use the new lawns rate.


Established Lawns
New Lawns
18 lb
Up to 5,000 sq. ft.
Up to 2,500 sq. ft.
54 lb
Up to 15,000 sq. ft.
Up to 7,500 sq. ft.
How Do I Calculate My Lawn Size? First measure the length and width of your lawn. Then multiply the length by the width and deduct the square footage of any non-lawn areas (landscape bed, patio, deck, pool, etc.) from the total. Now you know how much product you need to purchase!
Shipping & Returns


  • Free ground shipping now available on orders of $75 or more! For smaller orders, shipping costs are calculated at checkout.
  • We ship orders the same day if placed by 2PM EST (later orders will be shipped the next day).
  • Orders are not shipped or delivered on weekends or holidays.
  • We offer ground and expedited shipping.


  • We offer 30-day free returns for replacement or full refund for items that are damaged or defective (shipping included). If damaged by the carrier, please file a claim with them.
  • If your items have been used or aren’t in the original packaging, we will give you a refund (minus the cost of shipping) based on the condition of the product.

View our complete shipping and return policy. If you have questions about your order, please contact our customer service team at orders@jonathangreen.com.

  • This product can be applied throughout the United States and performs well on both cool and warm-season lawns.

  • For cool and warm season lawns, apply in either spring, summer or fall when air temperatures are at least 45°F.

  • Calcium, and sulfur (Derived from: Calcium Sulfate Dihydrate(gypsum), Ammonium Sulfate, and Sulfuric Acid.


    Also contains non-plant food ingredients: humic acid (derived from humus), polyhydroxycarboxylic acids (derived from plant extracts).

  • Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil contains natural ingredients and can be applied with any of our grass seeds, weed controls, fertilizers, and insect or disease controls.

    • For a pH of 7.0 to 7.5

    Apply Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil once per year.

    • For a pH over 7.5

    Apply Mag-I-Cal Plus for Lawns in Alkaline & Hard Soil twice per year (at least one month apart).

  • Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil is a natural product, meaning it is safe for children and pets to re-enter the lawn immediately after application.

    • Carefully read all instructions prior to application.
    • Store in a cool, dry place away from children and pets.
    • Do not ingest. May cause irritation to eyes and skin.
    • Wash hands thoroughly with soap and water after handling and before eating or drinking.
    • Do not apply near water, storm drains, or drainage ditches.
    • Do not apply if heavy rain is expected.
    • Apply this product only to your lawn or garden and sweep any product that lands on the driveway, sidewalk or street back onto your lawn or garden.
  • Always read and follow the product label before use.




    Safety Data Sheets can be found at www.jonathangreen.com/safety-data-sheets-sds. If you have a specific question, do not hesitate to contact us.


spreader product


spreader product


spreader product


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Step 1/4

Who makes your spreader?

Jonathan GreenScottsAgri-FabBrinly-HardyCycloneEarthway / AmesEchoGreenViewLescoOrthoPrecision / Red DevilPrizeLAWNQuaker / Lawn CrafterRepublic / EZSearsSpykerSta-GreenViconVigoro

Don’t see your spreader here? Contact the manufacturer or review your spreader’s manual.


Step 2/4

What type of spreader are you using?

Rotary Drop Handheld


Step 3/4

What is the model of your spreader?

Agri-Fab Push Broadcast Agri-Fab Tow Broadcast Agri-Fab Drop Agri-Fab Tow Drop BS26,36 Cyclone Rotary EV-N-SPRED® Broadcast Earthway Rotary Ames Broadcast Earthway Drop Ames Drop Echo RB 60 Jet Spred III Standard Deluxe and Pro Green-Meter Hand Crank Lesco (Lettered) Lesco (Numbered) Ortho Rotary Ortho Drop Precision Rotary Red Devil Rotary Precision Drop Red Devil Drop Prizelawn CBR III Prizelawn CBR IV Prizelawn Lil\' Foot Prizelawn MPR-1 Lawn Crafter Broadcast EZ Drop All Rotary Turf Builder Classic AccuGreen 2000-3000 AccuGreen 1000 Scotts PF4 Wizz Sears Broadcast Spyker Rotary Rotary Vicon Rotary

Don’t see your spreader model here? Contact the manufacturer or review your spreader’s manual.


Step 4/4

Select the rate that best suits your lawn needs.

Depending on the type of product you selected there may only be one application rate.

Existing Lawn Rate - 3.6 lb per 1000 sq ftNew Lawn Rate - 7.2 lb per 1000 sq ftExisting Lawn Rate - 3.6 lb rate per 1000 sq ft

Note: “New lawn” indicates that you are starting a lawn from bare dirt vs overseeding or applying product to an existing lawn.


Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil

Your Spreader Setting is:

Start over
  • How do I test soil pH?

    You can test your soil’s pH by sending a soil sample to your state university cooperative extension office, who will send it off to a lab for a small fee, or by using an at-home testing kit.


    To perform a soil pH test with the Jonathan Green Soil pH Test Kit, follow these steps:


    1. Collect soil samples from your lawn

    Gather small soil samples from four different sections of your lawn by using a gardening trowel to dig four to six inches deep into the lawn’s surface. Mix all four small samples together for one, cohesive sample to use for your test. Make sure to remove all debris from your sample and proceed to the next step.

    2. Fill test container with soil sample

    Once you have your comprehensive soil sample, remove the cap off of the color comparator and take out the capsule. Make sure the pH color chart is in place, then fill the test container with your prepared soil sample. Carefully separate the two halves of the capsule and pour the contents into the test container.

    3. Add distilled water to the test container

    Using the provided dropper, add distilled water to the test container. Do not use tap water for your soil pH test, as it usually contains acidic or alkaline components.

    4. Shake test container and allow to settle

    After adding distilled water to the test container, shake thoroughly and allow the test container to settle for one to five minutes.

    5. Observe test container for results

  • Can I use your products in my garden?

  • How to take a soil sample

    Steps to take a soil sample


    • With a shovel or a spade* dig a V-shaped hole to sample depth of 4-6 inches (excluding any thatch), then cut a thin slice off to the side.
    • Do this in 4 or 5 places in the section of the lawn to be tested.
    • Mix soil samples together in a clean, plastic bucket. If the bucket has been used to hold fertilizer or other chemicals, wash it thoroughly before using it for soil samples.
    • Let the sample dry well before testing. Place it in a ziplock bag or coffee can. Approximately one quart is recommended.
    • Make sure to use distilled water for testing.


    *Tools should be either stainless steel or chrome-plated. Do not use brass, bronze, or galvanized tools because they will contaminate samples with copper and/or zinc.

Features You’ll Love

Achieve the lawn of your dreams with Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil. We understand the challenges that come with alkaline and compacted soil, from stunted growth to nutrient deficiencies and unsightly bare patches. That's why we've developed this all-in-one solution to address these issues head-on. By lowering pH levels and loosening compacted soil, our product paves the way for vibrant, healthy grass. Say goodbye to limp blades, yellow spots, and struggling lawns. With Mag-I-Cal® Plus, you'll unlock the full potential of your lawn and enjoy a lush, thriving landscape you can be proud of.

Combat Alkaline Soil

Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil effectively lowers soil pH, creating the ideal environment for your lawn to thrive. By correcting pH imbalances, this innovative product unlocks and releases vital nutrients in the soil that may have previously been unavailable to your grass.
Combat Alkaline Soil

Soften Hard & Compacted Soil

Don't waste time and money renting core aerators, apply Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil to relieve soil compaction. This one-of-a-kind formula contains gypsum to naturally aerate and loosen hard, compacted soil.
Soften Hard & Compacted Soil

Safe for Kids and Pets

Our eco-friendly formula contains only natural ingredients, making it safe for kids and pets to enjoy the lawn immediately after application.
Safe for Kids and Pets

How to Apply


Test Soil

Test your soil pH to check that it is in a healthy range for grass plants to grow. Optimal pH for cool-season lawns is 6.2 to 7.0.


For best results, rake the lawn vigorously prior to application to remove debris and thatch.



Use a spreader suitable for your specific lawn size. Set the spreader according to the recommended setting on the packaging or use our Spreader Settings Tool above. Make sure to update the setting with each product you apply.


Begin by spreading along the perimeter of your lawn. Make straight passes back and forth across the length of the lawn in a mowing pattern until the entire area is covered. Overlap slightly between passes and close the hopper when turning. Walk at a steady pace for even distribution.


To avoid staining, sweep any excess granules off of hard surfaces and back onto the lawn or garden.



Irrigate the treated area after application for 15 – 30 minutes for the best results.


Once watered, wait at least one day to mow the lawn to give the product time to activate.


For soils with pH higher than 7, repeat applications twice a year.

Mag-I-Cal® Plus for Lawns in Alkaline & Hard Soil 5,000 sq. ft.
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