Chaw Sau Nqi Txheej txhais
Thaj chaw them nyiaj cheeb tsam tseem hu ua txheej txheej depletion. Hauv kev sib tshuam PN, vim qhov tsis txawv txav ntawm cov hluav taws xob dawb thiab txav dej txav los ntawm qhov hluav taws xob sab hauv, ib qho chaw tsim hluav taws xob tau tsim nyob nruab nrab ntawm qhov sib tshuam PN (qhov sib cuam tshuam ntawm P thiab N cheeb tsam), uas yog thaj chaw them nyiaj cheeb tsam.