Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Linear regression is shown although a log-linear relationship had slightly higher degree of explanation because of the ease of interpretation. Broad dashed line shows smoothed relationship, and small dashed line show 95% CI to the smoothed line. C refers to control plots, P to ploughed plots, R to rotavated plots, T to target plots.
