Characteristics Of Amino Acids In Soils And Relationship Between The Characteristics And Soil Fertility

This paper deals with the effect of application of pig manure (P.M) and chemical fertilizers on the content and coaposition of total and free amino acids in soils and the dynamics of the con tent and coaposction of free amiono acids dnring the decooposition of pig aanure and corn stalks in soil, Besides ,the N-supplying potential of amino acids in soil was examined.Soil samples were collected from cultivited layers (0-20cm) of seven plots in October 1987.These plots were CK, 0₁, 0₂, NPK, ONPK, ONP and ON of the two long -tera experimental fields and the experiaents were laid out since 1978 on a brown earth ( paleudalf ) and a aeadow soil (udifluvent) belonging Shenyang Agricultural University and Liaoning Acadeay of Agricultural Scienccs respectively. Plots CK, 0₁, 0₂, NPK, ONPK, ONP and ON hase keen recieveing no fertilisers ,P.M in a low level , P. M in a high level ,NPK alone, P.M plus NPK, P.H plus NP. and P.M plus N every year respectively.Total amino acids in soils were hydrolyzed by 6N HCl at 12O'C for 12 hrs , and free amino acids were extracted by basic ethanol .The amino acid released were purified by passingthrough cation exchange resin (H+ type ) and analyzed by 835 Hitachi Amino Acid Analyzer.Results showed that the coapostion of aaino acids in soils of different plots was quits similor.Aspartis acid , glutanic acid , giveine and ataiiine, as the dominant ones , amounted to over 4C% of the total content of 1? kinds of areino acids detected . Histine , cystine and Keihioaine were present ia small amount, and their total content cemprised no score than &H of the total content, The other 10 kinds of aiaino acids made up abaut 50M of the total content of assinc acids .The total amount of amino acids in different plots varied considerably ,ranging frora 11. 02 to 26.77 ^ n>ol N/g soil, which accauiited for 26.78 to 33.10M of total soil N. It (and also the relative content , i.e. anino-acid-N as the percentage of total N) were slightly higher in NPK plots and ouch higher in 0, and 0, plots than in CK plots;and it increased as the increase of amounts of P. M. Application of chenical fertilizers and P. M togecher had the similar effect as adding P.M alcne. The content of each amino acid was also much hightr in the plots wthe P.M than CK. According to the results obtained ,it was observed that the application of P.M could increase significantly the content of aaino-acid-N and promote the the relatively accumulation of N in the form of amino acids in soils .The organic Matter in the soils investigated here derived aainely from the added P.M and the corn stubble remanining in soils, Therefore ,the ami no aicd composition of these organic materials was determined, the similarity constants ( S) and correlation coefficients (r) were calculated ,and the degree of similarity and correlation in amino-acid distribution between soil samples . soil samples and the organic amendments were evaluated .Results revealed that the vlues of s and r were all above o. 9, indicating that the correlations between pairs of samples reached a very signicant level, although .the similarity between soil sasples was higher than that between suil and organic amendments , It is suggested that in the course of huaification , when the protein in pig manure and corn stubble is transformed into the one in organic matter in soil, generally, it say not undergo the process, in which it is decomposed thoroughly and then some microbial proterns are synthersized,Instead.peptide or seme tragaents of protern molecules in these organic amendments enter soil organic matter directly to constitute amino compaunds.The N-supplying potential of amino acids (NSPAA) refers to the quantity of amino-acid-N that disappeared from sail amino acid by hydrolysis wthe IN NaOH at 40*C tor 24 hrs .It was found that about 7.4% amino-acid-N in the soils studced could be decomposed . and the NSFAA ranging from 1.10 to 1.77 uno!/g soil, accounting for Zl.t-ib.iH of the total content of hydrolysable N in soils.The NSPAA of the NPK plot was similar to that of the CK plot , and it could be increased greatly by application of pig manure. It was also revealed that different forms of amino acids detected showed differences in their resistance to hydrolysis .The acidic form of ami no acids that could be decomposed amounted to only 2.5% and or so, however , the percentage of basic fora subject to hydrolysis was over l89tf.The NSPAA of nutrial fora was similar to that of total amino acids .Ike each form of amino acids of P. M bad a sasie characteristic wir,h the corresponding cne of soils in the resistance to hydra lysis .P.usults also showed that the contents of FAAs in CK plots were about 4 |.i mcl NVlOOs seil, and adding NPK alone did nol affect the contents of FAAs ^ wh ill application of pig limiure cculd increase their cefiterits significantiy>which ^culd exceed 7 jJ. ool N/lGOg soil. Application of chemical fertilizers and P. M togecher had similar effects to that of P.M alone . Ths rato of the cc.nteni of FAAs to that ef combined amino acids was relatively stable < G. 24-0. 21H)? but ths rato cf the c oil tent of each kind of FAA to that of acorrespondhig combined amino acid varied markedly , with the lowest registering at 0.07% and the highest 0.78%.The distribution pattern of FAAs in soils of different plots was quite similar. Gluetamic acid was the predominant one.accounting for near 30^ of the total amount of FAAs. Atanine, glycine and phenylalanine came to the next . The totalcontent of above-aentioned FAAs Bade up about one halt of the total content of FAAs.It was observed that there were no significant similarity and correlation in distribution pattern between FAAs and combined aaino acids. ', Thus , it was beleived that The FAA distribution was not controlled by the combined asino acids , rather , it had much to do with the propties of soil itself > even though the release of aeino acids was rslevent to the combined amino acids , when coabinss aiaino acide were broken down becoming FAAs, which kind of FAAs could persist more than others , v acidic > autrial =S-containing fora The transforaation rate of aaiiio acids was very fast, when a â– ixture of aaino acids was added to the soils only for 3 hours, about 15jtt of aaino acids disappeared from the solution , after 12 hours,the disappearing pencentage was over 25%> and nearly all of the added aaino acids disappeared by the end of 72 hours . The transformation rate in the soils aaended was higher then that in the soils witheout aaendaents .In the middle stage of culture , the aaounts of adsorption was more than that of transformation , which would be due to the interference of the products from degraded amino acids .