Arunachal Pradesh has areas with acidic soils, which affects:

The correct answer is: d) All of the above

Acidic soils are soils with a pH below 7.0. They are common in areas with high rainfall, as the rainwater dissolves minerals in the rocks and soil, making them more acidic. Acidic soils can affect crop productivity, availability of nutrients, and soil microbial activity in a number of ways.

• Crop productivity: Acidic soils can reduce crop yields by making it difficult for plants to absorb nutrients. This is because many nutrients, such as phosphorus, are less available in acidic soils. Additionally, acidic soils can make it difficult for plants to take up water, which can also reduce yields.
• Availability of nutrients: As mentioned above, acidic soils can make it difficult for plants to absorb nutrients. This is because many nutrients, such as phosphorus, are less available in acidic soils. Additionally, acidic soils can leach nutrients out of the soil, making them even less available for plants.
• Soil microbial activity: Acidic soils can also reduce soil microbial activity. This is because many soil microbes are sensitive to pH levels, and they are less active in acidic soils. Reduced soil microbial activity can lead to a number of problems, such as reduced nutrient cycling and increased soil erosion.

In conclusion, acidic soils can have a number of negative effects on crop productivity, availability of nutrients, and soil microbial activity. These effects can lead to reduced crop yields and increased soil degradation.