RE: Grass and weeds in my clover
did you know that the atmosphere is 97% N2. Nitrogen fixation is cynobacteria and other certain bacteria which engage with ammonia. Legumes such as clover , alfalfa, soy, and peas have these bacteria in there roots and live in a symbiotic relationship. Some bacteria convert ammonia to nitrates.
Soil samples can be sent off to your local service agent. Usually these sample can be run for around $20. This would be the first thing to do.
If fro some reasons levels are low you can---
add anhydrous ammonia to the soil as do many farmers in our area to every year. They usually apply it every in the fall here. Your soil must be very moist as to hold the gass while it goes through it chemical process.
Or more easily spray on some liqiud nitrogen fertilizer. Around 100# per acre will give you approximately 32 units of nitrogen.
Hope this helps