There are several resources and websites that offer sample case studies for practice in the Agriculture Optional subject for UPSC. Here are a few of them:

1. EduRev:
EduRev is an online education platform that provides a wide range of study materials, including sample case studies for Agriculture Optional. It offers a comprehensive collection of case studies that cover various topics in agriculture, such as crop production, animal husbandry, plant breeding, and agricultural economics.

2. NABARD:
The National Bank for Agriculture and Rural Development (NABARD) website is another valuable resource for practicing case studies in agriculture. NABARD provides case studies on real-life agricultural projects and initiatives undertaken by the organization. These case studies offer insights into the practical challenges and solutions in the field of agriculture.

3. ICAR:
The Indian Council of Agricultural Research (ICAR) website is an excellent source for sample case studies in agriculture. ICAR conducts research and promotes agricultural education in India. Their website offers access to research papers, case studies, and technical reports on various aspects of agriculture. These resources can be beneficial for understanding the practical application of agricultural concepts.

4. Agricultural Universities:
Many agricultural universities have their own websites where they share case studies and research papers related to agriculture. These universities conduct research and provide educational programs in the field of agriculture. Visiting the websites of renowned agricultural universities like the Indian Agricultural Research Institute (IARI) or the Tamil Nadu Agricultural University (TNAU) can provide access to a wealth of case studies and research materials.

5. Online Forums and Discussion Boards:
Participating in online forums and discussion boards dedicated to agriculture can also be a valuable resource for finding sample case studies. Websites like Quora or Reddit have dedicated communities where experts and enthusiasts share their knowledge and experiences. Searching for specific topics or questions related to agriculture on these platforms can lead to discussions that include case studies or practical examples.

In conclusion, EduRev, NABARD, ICAR, agricultural universities' websites, and online forums are some of the recommended resources and websites that offer sample case studies for practice in Agriculture Optional for UPSC. These platforms provide a wide range of case studies that cover various aspects of agriculture and offer practical insights into the subject.