What happens to land in the rainforest when it is cleared for farming?

The land might degrade when it's cleared for farming.

When vegetations are cleared, the land will lost protection and become more prone to soil erosion. There would be no roots to bind the soil particles or keep the moisture in the soil, and soil particles would be eroded by transporting agencies like wind.

They would be especially easier to be carried away when they are dry and loose. Loosened soil particles will also cause it to be easily washed away by water.

Eventually, the soil will lost nutrients and the land would become no longer fertile. It might turn into badland, in worst case senarios, desertification would occur.

Hope it helps!