Quality Problems

The subject is nothing special.  Stock already contains millions of these:

https://stock.adobe.com/search?k=wheat

https://stock.adobe.com/search?k=foxtails

https://stock.adobe.com/search?k=tall%20grass

Whatever you submit to Stock should be unique in some way, convey a message or idea, and be commercial-ready for use in professional projects.

Stock customers expect the highest visual and technical quality.  Read your Contributor Guide for more tips.

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/how-to/tips-stock-image-acceptance.html

Hope that helps.

 Very little in focus and underexposed shadows/background.

Depth of field might be a bit too shallow, but I would also question the object in the lower left-hand corner. It doesn't add any interest to the composition.