RE: Grass and weeds in my clover
S.Texas; The highest rates of fixation (200 lb./acre) were by alfalfa and Korean lespedeza in a Kentucky trial. Clover is an average of 100 lb./acre for sweet clover and 80 lb./acre for red clover. Alfalfa has an average of 125 lb./acre. The reason that plants won' t fix nitrogen if there is an adequite supply in the soil is that it takes energy to fix atmospheric nitrogen so the plants preferentially use the soil nitrogen if it' s abundant.
They don' t even do soil nitrogen tests in my area. They just take into account the last crop that grew on the field and give a nitrogen rate.
Dan O.