Excessive irrigation in black soils can lead to the problem of:

The correct answer is: A) Alkalinity.

Excessive irrigation in black soils can lead to the problem of alkalinity. This is because black soils are naturally alkaline, and when they are irrigated with water that contains high levels of salts, the salts can build up in the soil and make it even more alkaline. This can have a number of negative effects on plants, including stunted growth, yellowing leaves, and death.

Option B, acidity, is incorrect because black soils are naturally alkaline. Option C, erosion, is incorrect because excessive irrigation can actually help to prevent erosion by keeping the soil moist and preventing it from being blown away by the wind or washed away by rain. Option D, desertification, is incorrect because excessive irrigation can actually help to prevent desertification by keeping the soil moist and preventing it from becoming too dry.

Here is a more detailed explanation of each option:

• Option A: Alkalinity is a condition in which the pH of the soil is too high. This can cause a number of problems for plants, including stunted growth, yellowing leaves, and death. Excessive irrigation can lead to alkalinity in black soils because black soils are naturally alkaline, and when they are irrigated with water that contains high levels of salts, the salts can build up in the soil and make it even more alkaline.
• Option B: Acidity is a condition in which the pH of the soil is too low. This can also cause a number of problems for plants, including stunted growth, yellowing leaves, and death. Black soils are naturally alkaline, so they are not prone to acidity.
• Option C: Erosion is the process of soil being carried away by the wind or water. Excessive irrigation can actually help to prevent erosion by keeping the soil moist and preventing it from being blown away by the wind or washed away by rain.
• Option D: Desertification is the process of land becoming desert-like. This can be caused by a number of factors, including climate change, deforestation, and overgrazing. Excessive irrigation is not a major cause of desertification.