To join scientific agricultural societies like the International Weed Science Society (IWSS) for free or at minimal cost, here are some potential approaches you can consider:

1. **Check Membership Options**: Many professional societies have different membership tiers, including student memberships, which are often discounted or even free. Visit the official IWSS website or contact them directly to inquire about any student or free membership options.

2. **University Affiliations**: If you are a student or affiliated with a university, your institution may already have a membership or partnership with such societies. Check with your department or faculty to see if they can provide access or cover membership costs.

3. **Conferences and Workshops**: Attend conferences, workshops, or webinars hosted by the society. Sometimes, attendees can receive a trial membership or discounted rates for joining after attending an event.

4. **Networking and Sponsorship**: Engage with professionals in the field through networking. Sometimes, established members or sponsors can offer sponsorships or waive fees for promising researchers or students.

5. **Volunteer Opportunities**: Some societies allow individuals to volunteer for events or committees, which can sometimes lead to free membership as a form of compensation.

6. **Open Access Resources**: Look for open-access publications or resources provided by the society. These can offer valuable information and a way to connect with the community without formal membership.

7. **Stay Informed about Promotions**: Keep an eye on the society's announcements for any promotions or special membership drives that might offer free trials or discounted rates.

For specific details and options regarding the International Weed Science Society, you can visit their [official website](https://www.iwss.org/) or reach out to them directly for personalized guidance on membership options.