There are two main types of iron supplements commonly used in agricultural production: ferrous sulfate (traditional iron fertilizer) and EDTA chelated iron, with significant differences in absorption efficiency, stability and applicable scenarios. Growers can select products according to actual needs.

In terms of existing form and soil utilization rate, iron in ferrous sulfate exists in the form of free ions. After being applied to soil, it easily combines with carbonate, phosphate and other substances to form insoluble precipitates and is fixed, with an actual crop utilization rate of only 5%-10%. In contrast, the iron ions in EDTA chelated iron are fully wrapped by chelating agent molecules to form a stable cyclic structure, which is not easily fixed by ions in the soil. The actual utilization rate by crops can reach more than 80%, 8-10 times that of ordinary iron fertilizers.

In terms of applicable soil environment, ferrous sulfate can only maintain activity in acidic soil. Once the soil pH is higher than 6.5, iron ions will quickly precipitate and fail, and basically cannot play a role in neutral and alkaline soils. EDTA chelated iron can exist stably in the pH range of 4.0-7.0, adapting to most cultivated soils from acidic to neutral, with a wider application range.

There are also obvious differences in onset speed and application methods. Ferrous sulfate has a slow effect: it usually takes 15-20 days to observe leaf greening after soil application. It is mainly applied to soil, and improper concentration of foliar spray can easily cause leaf burn. EDTA chelated iron has a fast absorption speed: leaf greening can be observed 5-7 days after foliar spray, with outstanding effect on emergency correction of chlorosis. It is also compatible with multiple application methods such as soil base application, foliar spray and drip fertigation, adapting to different planting scenarios.

Overall, ferrous sulfate is low in price but low in efficiency, and is more suitable for low-cost iron supplementation in acidic soils. Although EDTA chelated iron has a higher unit cost, it has lower dosage, faster effect and wider applicable scenarios, with lower comprehensive planting cost in the long run. It is a better choice for large-scale and high-quality planting.