Magnesium Oxide (MgO) is a highly concentrated, slow-release magnesium fertilizer specifically designed for dry soil application. With magnesium content ranging from 55% to over 85% depending on the grade, it provides one of the most economical and long-lasting sources of magnesium for correcting deficiencies and maintaining optimal soil fertility levels. For growers seeking to build soil magnesium reserves, reduce application frequency, and improve crop quality over multiple seasons, magnesium oxide is the strategic choice.

I. The Critical Role of Magnesium in Plant Health

Magnesium is the central atom of the chlorophyll molecule, making it absolutely essential for photosynthesis. Without adequate magnesium, plants cannot capture and convert the sun’s energy into growth. Magnesium also serves as an activator for more than 300 enzymes involved in energy transfer, carbohydrate metabolism, and protein synthesis. It facilitates phosphorus transport, strengthens cell walls, and improves overall plant vigor. Magnesium deficiency limits yields and cripples plant development, making adequate supply a cornerstone of productive agriculture. Magnesium (Mg2+) is pivotal for the vitality, yield, and quality of horticultural crops, powering photosynthesis as an integral component of chlorophyll, bolstering growth and biomass accumulation. Beyond basic growth, it critically affects crop quality factors, from chlorophyll synthesis to taste, texture, and shelf life.

II. Why Choose Magnesium Oxide for Soil Application

Highest Concentration of Magnesium Available
Magnesium oxide contains 55% to over 85% magnesium oxide (equivalent to 33% to over 50% actual magnesium), the highest concentration among all magnesium fertilizers. For comparison, Epsom salt (magnesium sulfate heptahydrate) contains only 9.8% magnesium, and kieserite contains approximately 17% magnesium. This high concentration means less product is required per hectare, significantly reducing transportation, storage, and application costs.

Slow-Release, Long-Lasting Nutrition
Magnesium oxide is slightly soluble in water, slowly releasing magnesium ions into the soil over an extended period. This provides a long-lasting fertilizer effect, reduces the frequency of fertilization, and prevents one-time nutrient loss through leaching. In leaching studies, 78% of extractable magnesium from MgO remained in the top 1.4 cm of soil column after rainfall equivalent, confirming that MgO is a long-lasting source of Mg in cultivated soils where leaching is a problem. In contrast, MgO has the slowest release rate and the lowest leaching rate among magnesium fertilizers, ranging from -2.4% to 3.8%.

Soil pH Management for Acidic Soils
Magnesium oxide is alkaline in nature, which can neutralize acidic soils, increase soil pH, reduce the toxic effects of aluminum and manganese, and improve the root growing environment. The alkaline character can adjust soil pH value and improve the availability of other nutrients. MgO has a pH of 10.64 in 5% solution, making it effective at raising soil pH in acidic conditions. It is most effective and reacts most quickly in acid soils with pH below 6.5.

Improves Soil Structure
Magnesium oxide promotes soil particle aggregation, increases aeration and permeability, enhances water and fertilizer retention capacity, and creates a favorable environment for crop root growth.

Cost-Effective and Economical
Compared to highly soluble magnesium alternatives, magnesium oxide is significantly more cost-effective per unit of magnesium. With a slow-release rate and the lowest leaching rate among all magnesium fertilizers, it requires fewer applications over time, reducing overall input costs and labor.

Excellent for Blending
Magnesium oxide granules are compatible with nitrogen, phosphorus, and potassium fertilizers, as well as organic fertilizers. It can be blended with NPK fertilizers for custom formulations or applied directly. However, it should not be mixed with acidic fertilizers such as superphosphate to prevent reduced fertilizer efficiency.

III. Application Methods and Recommendations

Important Note: For Dry Soil Application Only
Magnesium oxide is insoluble in water and cannot be used in fertigation programs or as a foliar spray. It is strictly for dry soil application. It is not recommended where a quick response to magnesium is required, such as in planting fertilizers for annual crops or during the growing season. When magnesium deficiency is already apparent, a water-soluble fertilizer containing magnesium in the sulfate form should be used for immediate correction. Magnesium oxide should be used to maintain soil magnesium status and build long-term reserves, not for emergency correction.

Pre-Plant Application for Annual Crops
For annual crops, magnesium oxide should be broadcast applied early in the fallow period, several months before planting. It is best to wait for a few weeks to allow the granules to weather and disperse before working the magnesium oxide into the soil. It must be applied early as it takes time to react in the soil after application and release magnesium in forms available for plant root uptake.

Application for Perennial Crops
For trees, vines, and plantation crops, broadcast in advance of the main growing season. If magnesium deficiency is evident in the foliage, supplementary magnesium will need to be applied in a more readily available water-soluble form, such as through fertigation programs or as a foliar spray, while continuing to use magnesium oxide for long-term soil building.

Application Rates
Suggested application rates for magnesium oxide, which may remain effective for several years:

• Pasture, forage, grain, and oilseed crops: 50 to 200 kg per hectare
• Sugarcane (for a crop cycle): 150 to 300 kg per hectare
• Horticulture, vegetables, tree crops, and vines: 200 to 400 kg per hectare
• General maintenance on perennial crops: 50 to 100 kg per hectare annually, often in combination with NPK programs

Dosage Based on Soil Conditions
Determine the application dosage based on soil magnesium content and crop requirements. Generally, apply 10 to 20 kg per acre (approximately 25 to 50 kg per hectare). Increase the dosage appropriately in areas with severe magnesium deficiency. For acidic soil with pH 5.0 to 6.5, apply 2 to 3 bags per 1/10 acre; for highly acidic soil with pH below 5.0, apply 4 to 5 bags per 1/10 acre.

Soil Testing Is Critical
Soil testing should be performed before application, with the ideal magnesium range being 50 to 120 ppm. Excessive magnesium oxide application can interfere with potassium and calcium uptake.

IV. Technical Specifications (Agricultural Grade, Granular)

Chemical Properties

• Chemical formula: MgO
• Magnesium oxide (MgO): 55% to 85% minimum (depending on grade)
• Magnesium equivalent (Mg): 33% to 50% minimum
• Calcium oxide (CaO): up to 2%
• Water solubility: very low (slow-release)

Physical Properties

• Appearance: White to off-white, free-flowing granules or powder
• Granule size: 1 to 5 mm (depending on grade)
• Bulk density: 900 to 1300 kg per cubic meter
• Hardness: high, resists breakage during handling
• Moisture: ≤ 0.5%
• pH of 5% solution: 10.0 to 11.0 (alkaline)

Quality Standards

• Heavy metals: Cadmium ≤ 1 ppm, Lead ≤ 10 ppm, Mercury ≤ 0.2 ppm
• Magnesium oxide content: 55% to 85% minimum
• Loss on ignition: varies by grade
• Insoluble matter: ≤ 1%

V. Crop-Specific Response and Recommendations

Acidic Soils and Soil pH Correction
Magnesium oxide is highly effective in acidic soils with pH below 6.5, where it reacts most quickly and provides both magnesium nutrition and pH adjustment. Among various magnesium sources, the effect of magnesium oxide was found superior in enhancing soil pH during flowering stage (reaching 5.38 from an initial pH of 4.90), followed by magnesium carbonate (5.31). MgO also has an alkaline character that can adjust soil pH value and improve the root growing environment.

Cereals (Wheat, Corn, Rice) and Oilseeds
Apply 100 to 200 kg per hectare pre-plant for fields with known magnesium deficiency. In the Midwest USA, magnesium oxide application has boosted corn yields by up to 15% in magnesium-deficient soils. Adequate magnesium increases grain test weight, improves stalk strength, and reduces lodging.

Fruit Trees (Citrus, Apples, Stone Fruits, Grapes)
Apply 200 to 400 kg per hectare broadcast in advance of the main growing season. For mature trees, 200 to 400 grams per square meter under the canopy or 200 to 500 grams per tree depending on size. In vineyards and tea plantations worldwide, regular use has translated into greener foliage, reduced leaf drop, and noticeably improved plant vigor. For citrus, apply twice a year: in spring with base fertilizer and again before fruit maturation.

Vegetables (Tomatoes, Potatoes, Leafy Greens)
Apply 200 to 400 kg per hectare pre-plant, incorporated into the root zone. Particularly beneficial for potatoes, tomatoes, and citrus that are highly sensitive to magnesium scarcity. Magnesium from MgO supports chlorophyll synthesis and improves overall crop vigor.

Pasture and Forage
Apply 50 to 200 kg per hectare annually or biennially. Research has shown that Mg fertilizer application increased forage yield by 41% to 946% and Mg uptake by 22% to 5407% compared to untreated controls, with the most substantial improvements occurring in strongly acidic magnesium-deficient soils. MgO has a slow-release rate and the lowest leaching rate among Mg fertilizers. Optimized Mg fertilizer application has the potential to increase annual perennial ryegrass production by 4.64 Tg in China.

Sugarcane
Apply 150 to 300 kg per hectare for a crop cycle. Magnesium oxide provides sustained magnesium release throughout the long growing season of sugarcane.

Sandy and Leached Soils
Ideal for sandy soils exposed to leaching where other magnesium sources would be quickly lost. The slow-release nature of MgO ensures that magnesium remains available to crops over an extended period, even in high-rainfall or irrigated conditions where leaching is a concern.

VI. Compatibility and Blending

Compatible with

• Most dry granular NPK fertilizers
• Urea, DAP, MAP, and potash
• Organic fertilizers and compost
• Can be blended for custom fertilizer formulations

Not Compatible With

• Superphosphate and other highly acidic fertilizers (may reduce fertilizer efficiency)
• Do not mix with acidic fertilizers in concentrated blends
• Do not use in fertigation or inject into irrigation systems (insoluble)

VII. Environmental and Safety Profile

Environmental Behavior
Magnesium oxide is a naturally occurring mineral compound that releases nutrients slowly, matching plant demand and reducing runoff and leaching. With the lowest leaching rate among magnesium fertilizers (-2.4% to 3.8%), it poses minimal risk of groundwater contamination when used at recommended rates. The product also helps reduce greenhouse gas emissions per unit of forage by 14% to 90% when optimized Mg fertilizer strategies are implemented.

Soil Health
The alkaline nature of MgO helps neutralize soil acidity, improving soil structure and the root growing environment. It also helps reduce aluminum toxicity in acidic soils, promoting beneficial microbial activity.

Worker Safety
Magnesium oxide is characteristically a dusty product. Avoid inhalation of dust and contact with eyes or skin. Wear protective clothing, eyewear, and dust masks when handling. Observe good personal hygiene, including washing hands after use.

Storage
Store in a dry place in original sealed containers. Exposure to moisture may cause caking and should be avoided. Shelf life is 24 months when properly stored. Keep away from moisture and acidic materials.

VIII. Quality Assurance and Certifications

Our magnesium oxide is manufactured in ISO 9001:2015 and ISO 14001:2015 certified facilities. Each batch is tested for magnesium content, heavy metals, particle size distribution, and solubility. We provide Certificates of Analysis with every shipment.

Heavy Metal Limits (Max)

• Cadmium (Cd): 1 mg/kg
• Lead (Pb): 10 mg/kg
• Mercury (Hg): 0.2 mg/kg

Available Grades

• Granular grade (1–5 mm): For dry bulk blending and direct soil application
• Powder grade (200 mesh): For suspension fertilizers and custom blends
• Controlled-release grade: Formulated for extended nutrient availability

IX. Why Choose Our Magnesium Oxide

• Highest magnesium concentration – Up to 85% MgO (50%+ actual Mg), reducing storage and handling costs
• Slow-release, long-lasting – Lowest leaching rate among all magnesium sources, effective for multiple seasons
• Dual-action benefit – Supplies magnesium while helping to correct acidic soil pH
• Excellent blending properties – Uniform granules compatible with all dry fertilizer programs
• Technical support – Our agronomists provide soil test interpretation, application planning, and long-term magnesium management strategies
• Flexible packaging – 25 kg bags, 1-ton FIBCs, bulk containers