Novel acylated hydrazinomethylphosphonic acids, hydrazinomethylphosphonates, hydrazinomethylphosphinic acids, hydrazinomethylphosphinates or hydrazinomethylphosphine oxides of formula I below are able as "antidotes" or "safeners" to protect cultivated plants from the phytotoxic action of herbicides. Suitable crops are preferably maize, sorghum, cereals, rice and soybeans and the herbicides employed are in particular chloroacetanilides.The acylated hydrazinomethylphosphonates, hydrazinomethylphosphinates or hydrazinomethylphosphine oxides have the formula I ##STR1## wherein R.sub.1 and R.sub.2 are each independently hydroxy, alkyl, aryl, phenylalkyl, alkoxy, alkenyloxy, alkynyloxy, aryl or phenylalkoxy, the radicals of which may be substituted,R.sub.3 is a halogenated alkanoyl or alkenoyl radicalR.sub.4 is hydrogen, a halogenated alkanoyl or alkenoyl radical or an alkyl, alkenyl or phenylalkyl radical, or an alkylcarbonyl, alkenylcarbonyl, alkynylcarbonyl or phenylcarbonyl radical which may be unsubstituted or substituted or is an alkoxycarbonyl or phenylalkoxycarbonyl radical which may also be unsubstituted or substituted or is an alkoxycarbonyl or phenylakoxycarbonyl radical which may also be substituted,R.sub.5 is hydrogen or an alkyl, alkenyl or alkynyl radical which may also be substituted,R.sub.9 is hydrogen, alkyl or phenyl which is unsubstituted or substituted andR.sub.10 is hydrogen or alkyl.