autotrophic and heterotrophic respiration is the net________ productivity.Nitrogen is generally available to plants in only two forms:ammonium and ________.T.nitrateT.nitrateBiological nitrogen fixation is accomplished by symbiotic________ living in mutualistic association with plants.O.bacteriaO.bacteriaNitrogen can be returned to the atmosphere when certainbacteria convert it from nitrate into nitrogen gas, which isa process called ________.K.denitrificationK.denitrificationMicrobial decomposition of organic matter results in NH4+production through a process called ________.P.ammonificationP.ammonification
