The element found maximum in the soil layer is oxygen.

Explanation:
Oxygen is the most abundant element found in the Earth's crust, which includes the soil layer. It constitutes about 46.6% of the Earth's crust by weight. Here are some key points explaining why oxygen is the correct answer:

1. Abundance:
- Oxygen is the most abundant element on Earth, making up approximately 21% of the atmosphere.
- It is also a major component of the Earth's crust, comprising around 46.6% of its total mass.

2. Soil Composition:
- Soil is a complex mixture of minerals, organic matter, water, air, and various elements.
- Oxygen is a fundamental component of soil composition due to its presence in minerals and organic matter.
- It is involved in numerous chemical reactions, such as oxidation and decomposition processes, essential for soil formation and nutrient cycling.

3. Minerals:
- Oxygen is a vital component of many minerals found in soil.
- Silicates, which are the most abundant rock-forming minerals, consist of silicon and oxygen.
- Other minerals like oxides, carbonates, and sulfates also contain oxygen.

4. Organic Matter:
- Organic matter in soil, such as humus, is derived from the decomposition of plant and animal materials.
- Oxygen is present in organic compounds, including carbohydrates, proteins, and fats, which make up organic matter.

5. Biological Processes:
- Oxygen plays a crucial role in supporting soil biota, including plant roots, microorganisms, and soil fauna.
- It is required for aerobic respiration, a process utilized by plants and many soil organisms to release energy from organic matter.

Conclusion:
In conclusion, oxygen is the element found in maximum abundance in the soil layer. Its presence in minerals, organic matter, and involvement in various chemical and biological processes make it essential for soil formation and fertility.