Green manure adds both nitrogen and carbon to the soil, and is getting rid of weeds too. It’s good to have a drip system in place that doesn’t water anything but your crop plants. For years I used a soak line with thousands of little holes made of a rubber foam, no control at all. The grew weeds every where. So I started to use a one hole per plant system, saved water, and grew my corn or other crops and few weeds came up. I had to plant the corn for instance like I planted beans and squash, well sort of, I used a flat tray, and then when they were four to six inches up, I transplanted them into the corn rows. That stopped the birds from digging up the seeds, and got the spacing right. So for my money and time, it’s a better way to go. Then every other day I can just rake the ground between the rows and the weeding is done. The corn grows fast and shades nearly anything else that may come up. So water is conserved work is at a minimum and the corn is exactly like I like it.