Accumulation Characteristics of Organic Nitrogen Fractions in Paddy Soil upon Replacement of 20%Chemical Nitrogen Fertilizer with Different Organic Fertilizers
This study aims to unveil the accumulation characteristics of soil organic nitrogen(N)fractions upon replacement of chemical fertilizer with organic fertilizer at the same proportion based on a long-term fixed-location fertilization experiment.With no N fertilizer(CK)and chemical N fertilizer(NPK)as the control groups,we measured the content and proportions of organic N fractions in total N under three replacement treatments:pig manure replacing 20%chemical N fertilizer(PM),commercial organic fertilizer replacing 20%chemical N fertilizer(OM),and Chinese milk vetch in early rice and rice straw in late rice replacing 20%chemical N fertilizer(RMS).The results indicated that the content of total N and organic N fractions presented no significant differences between NPK and CK.Compared with NPK,the three replacement treatments increased soil total N content by 5.2%-8.5%,with the highest increase in the PM treatment.The three replacement treatments increased the content of acid-hydrolyzed amino acid N,acid-hydrolyzed ammonium N,and acid-hydrolyzed amino sugar N by 11.0%-18.8%,10.8%-18.5%,and 16.7%-31.1%,respectively.Meanwhile,the three treatments increased the proportions of the three organic N fractions above in total N by 4.4%-11.1%,2.1%-12.6%,and 7.5%-24.5%,respectively.The data suggested that the replacement treatments,especially RMS,increased the available N in soil.Possible causes of these results were that organic fertilizer replacing chemical fertilizer increased the contents of microbial biomass C and N,as well as the activity of N-related enzymes,and promoted the conversion of difficultly decomposable oragnic N fractions into easily decomposable organic N fractions.In summary,replacing chemical N fertilizer with different organic fertilizers at the same proportion can effectively increase the accumulation and supply of soil N.Pig manure and straw are conducive to N accumulation and supply,respectively.
replacement at the same proportionorganic nitrogen fractionsmicrobial biomassenzyme activitypaddy soil
NETL
NSTL
万方数据
