Soil crusting

Soil crusting is the formation of a dense, hard layer on the soil surface following the drying of wet soil. While not a disease caused by pathogens, it is considered a severe agronomic constraint. It acts as a mechanical barrier that prevents seedling emergence, leading to reduced plant density and significantly impacting the initial development of agricultural crops.

This issue frequently affects various field crops, with soybean being particularly susceptible. Soybean emergence requires substantial upward pressure from the hypocotyl. If heavy rain occurs shortly after planting, followed by rapid drying and heating, a hard crust forms. This layer is often strong enough to break the delicate soybean cotyledons or cause them to remain trapped beneath the surface.

Symptoms include erratic emergence patterns and seedlings exhibiting stunted, twisted hypocotyls. Often, the cotyledons appear damaged or shredded because the plant spent its energy trying to break through the crust without success. Plants that do emerge are often weak, exhibit poor root development, and suffer from reduced oxygen availability within the rhizosphere.

The development of a crust depends on soil texture and structure. Silt and clay-rich soils are most vulnerable because their small particles easily disperse in water, filling pore spaces and forming a continuous, hard surface upon drying. Low soil organic matter content exacerbates the problem, as there is less aggregate stability to resist the impact of raindrops and the subsequent formation of the crust.

Effective management and prevention strategies include:

• Using rotary hoes to break the crust before the crop fully emerges.
• Incorporating organic matter to improve soil structure and porosity.
• Selecting optimal planting depths to ensure the seedling has enough energy to emerge.
• Adopting conservation tillage practices to maintain surface cover and moisture balance.