**1. Introduction**

Drought is a factor that leads to environmental degradation and has adverse effects on rural populations dependent on natural resources such as water and soil. Drought can eventually lead to the loss of livelihoods, promote migration in affected areas [1], and have a significant impact on the economy, society, and environment [2]. According to the IPCC, the global population exposed to extreme or exceptional total scarcity of stored water will be 3–8%. In this context, risks of drought are predicted

throughout the 21st century in many regions, increasing the probability of an economic crisis [3]. This prediction is worrying because the world population reached 8 billion inhabitants in 2022 [4], a fact that increases the demand for food. However, global climate changes can negatively affect agricultural production by altering the rainfall regime, inducing water deficiency and, consequently, reducing agricultural production [5, 6].

In tropical regions, high precipitation over time promotes the leaching of exchangeable bases and increases the levels of toxic aluminum. These two edaphic aspects result from the intense weathering of the soil. However, in tropical regions the occurrence of periods of water deficiency is normal. Thus, the sum of the factors of water deficiency and toxic aluminum potentiate the reduction of plant growth and agricultural production, because they cause disorders in gas exchange, nitrogen metabolism, and antioxidant in plants [7–10].

The chemical management of weathered tropical soils with toxic levels of aluminum can contribute to minimizing the effect of water deficit because liming reduces the toxic aluminum content and increases the surface pH and the calcium and magnesium content of the soil. In addition, gypsum contributes to the reduction of subsurface aluminum content and the increase of sulfur content in the soil.

Together, liming and plastering can minimize the effects of water deficiency, because they create an edaphic environment that improves root growth in volume and depth and, consequently, increases the absorption of nutrients and water. Therefore, the use of these two agricultural inputs can mitigate the effects of water deficiency on plants in acid soils.

This chapter will address the problem of water deficiency and aluminum toxicity in plants in the context of global climate change, emphasizing plant responses to aluminum toxicity and water deficiency, and liming and gypsum management as mitigating agents of soil chemical stress.
