My abbreviated advice would be: let the kids show you what they can do and already know. The best moments working with young learners are when they can take charge, make connections, find the evidence, defend the claims. With your agriculture background, you can certainly create opportunities for student engagement and exploration with growing plants and connections to healthy systems.
You are already here at NSTA, so be sure to take advantage of workshops, conferences, and the Science and Children journal. You will find that it is filled with classroom-tested ideas for lessons and activities. Be sure to immerse yourself in K-5 NGSS. So much to learn from reading the standards, elements, storylines, and more.
We are happy to have you join the K-5 world of teaching and learning.