| This study was conducted at the long-term location test of Red Soil Research Institute of Jiangxi (116°2024′N,28°1530′E and25to30m above mean sea level). Continuous23years experimental data of annual yield of rice under different treatments (CK, N, NP, NK, NPK, NPKM) and the tested soil samples(CK, N, NP, NPK, NPKM, OM) of different fertilization in red paddy soil for were analyzed to investigate some factors influence on the N variations in the soil.1) the influence of different fertilization on soil aggregation and its organic N forms, soil microbial activities;2) the content of soil organic C, N after23years;3) the influence of different fertilization on the nitrogen mineralization and their response to exteriorly added substrates(glucose or K2HPO4) under the waterlogged cultivation.;4) the influence of different fertilization on rice yield and soil basic fertility and relation of annual yield of rice and physiological,chernical and biochemical parameters of soil.A preliminary study was made of soil aggregates under long-term fertilization in red paddy soil. Results demonstrated that the percentage of the soil aggregates which sizes are3-5mm is increased significantly, while the size of0.05-0.25mm and<0.05mm is decreased significantly with the long-term application of organic fertilizer (OM, NPKM), but little difference in the chemical fertilizers (N, NP, NPK) in compared with that of the samples from CK. The soil aggregates formation was primarily depended on the long-term application of organic fertilizer. The correlation analysis revealed that there existed a significant positive correlation between MWD (Mean weight diameter), GMD (Geometric mean diameter), D (Fractal dimension) and the size scopes of1～2mm,0.5～1mm,0.25～0.5mm,0.05～0.25mm,<0.05mm of soil aggregates. The present results indicated that these parameters can be considered as physical indexes of soil fertility based on MWD, GMD, D.Also the current results showed that the contents of soil organic carbon(SOC) and total nitrogen(TN) in the treatments of NPKM and OM were increased by31.5-34.3%and26.5-33.7%compared to those of CK respectively(p<0.01), while increased by19.3%-21.8%and14.3-20.7%compared to those of NPK(P<0.05) after23years. However, there were a little difference between OM and NPKM. It exhibited that organic fertilizer was a sound practice to increase SOC and TN in red paddy soil. The content of oPOC (occluded Particulate Organic Carbon) and its proportion in SOC in the treatment of NPK were increased by66.0%and47.8%compared with CK respectively(P<0.05), while the content of all fractions of SOC increased significantly in the treatment of OM and NPKM. Organic fertilizer (OM, NPKM) increased contents of fPOC (free Particulate Organic Carbon) and oPOC by82.0%-270%,97.3%-97.7%respectively (P<0.01),whereas decreased the proportion of mOC (mineral Organic Carbon) in SOC by18.9%-21.3%(P<0.05) compared with CK. Moreover, organic fertilizer (OM, NPKM) increased significantly the proportion of fPOC and oPOC in SOC than NPK, but there were a little difference in the proportion of mOC in SOC between OM or NPKM and NPK and in the contents of all fractions of SOC and its proportion in SOC between OM and NPKM except for fPOC. Therefore, OM and NPKM changed composition of soil organic matter and markedly increase contents of all fractions, while NPK only significantly increased contents of oPOC and its proportion in SOC. The order of the transformation rates of all sorts of fractions in NPKM and OM was oPOC (72.8%and76.8%)> mOC (13.1%and16.7%)> fPOC (2.6%and6.1%). Moreover there were significant difference in the transformation rates of additional carbon among fPOC, oPOC and mOC. Furthermore, there were influences on transformation rate of various N fractions in the additional N, which the order of amino acid N (26.6%-38.0%)> nonhydrolizable N(27.6%-32.0%)> hydrolyzable unidentified N (HUN)(17.1%-28.5%)> ammonium N(7.0%-9.9%)> amino sugar N (5.9%-7.4%). But there a little difference in transformation rate of various C and N fractions between OM and NPKM. This indicated transformation rates of various C and N fractions maintained almost constant in red paddy soil under long-term organic fertilizer.There were also increases in the contents of TN and acid hydrolysable N in the treatment of organic fertilizer (OM, NPKM). Among various fractions of acid hydrolysable N, the increase in the contents of ammonium N, amino acid N, amino sugar N and HUN was found in the treatment of OM and NPKM, while an increase was only observed in amino acid N in NPK, but a little difference in the contents of various fractions of acid hydrolysable N in the treatments of N,NP compared to those in CK. Meantime,the organic fertilizer increased significantly the contents of acid hydrolysable N,ammonium N and amino acid N in different soil aggregates in the treatment of OM, NPKM compared to those of CK. Moreover, the significant increases were obtained in the contribution of the size of3-5mm and<0.05mm of soil aggregates to soil nutrient in the treatment of OM, NPKM compared to those of CK. These showed the organic fertilizer increased the supply of soil nitrogen in soil macro-aggregates.There were significant increases in the contents of microbial biomass-C(MBC) and microbial biomass-N (MBN) in OM and NPKM compared to those of CK and N, NP, NPK, but there were little increase in the contents of microbial biomass-C and microbial biomass-N in N,NP,NPK compared to those of CK. Furthermore, an increase of the activities of soil enzyme in OM and NPKM was found, for example, the activity of invertase(INV), cellulase(CEL), urease(URE), L-asparaginase(ASP), L-glutamin(GLU), L-histidine ammonia lyase(HIS) etc. was significantly higher than that in the treatments of N, NP and NPK and CK. And the activity of these soil enzymes in the treatment of N, NP and NPK was little higher than that in CK (p<0.05). However, little difference in the above soil enzymes was obtained between the treatment of N, NP and NPK and CK except for the increased activity of soil CEL, URE and HIS. Correlation analysis indicated that significantly positive relationship was observed among MBC, MBN soil enzyme activity, SOC and TN in red paddy soil, suggesting these physiological and biochemical parameters being as evaluation indices of soil.The net mineralization amount of N treated with organic fertilizer (OM, NPKM), either exogenously added substrate or not (carbon or phosphorus) was significantly higher than that with N, NP, NPK and CK after32days waterlogged incubation (30℃)(p<0.05) in lab. The tendency of the net mineralization amount of N treated with N, NP and NPK was NPK>NP>N>CK (p>0.05). This indicated long-term use of organic fertilizer could significantly improve N-supply capacity in red paddy soil. Minus-values in relative mineralization amount were obtained in treatments of CK, N, NP, NPK, NPKM and OM after addition of glucose, with the trends of OM<NPKM<NPK<NP<N<CK (p>0.05). This suggested biological immobilization of mineralization N exceeded than mineralization of organic N particularly in the soil (CK, N, NP and NPK) with low content of organic matter. However, positive-values of relative mineralization rate was found after addition of K2HPO4, indicating an increase in microbes number and activity by P in red paddy soil was helpful to soil mineralization especially in the higher content of organic matter (OM, NPKM). Furthermore, the relative mineralization rate in all treatments simultaneously added C and P sources was similar to single glucose, indicating inhibition of soil N mineralization by exteriorly added C (glucose) and P (K2HPO4) in the red paddy soil. After32d of waterlogged incubation, the net N mineralization amount of soil was significantly positive correlated to SOC, TN, acid hydrolysable N, MBC and MBN (p<0.01), and to ammonium N, amino acid N, HUN (p<0.05), but slight positive to amino sugar N, nonhydrolizable N (p>0.05). This is of importance to assess organic N status in red paddy soil and N requirement for rice.The yield change in different fertilizer application and the relationship between fertilizer application and soil fertility have been statistically analyzed and found based on data from continuous23years experiment. The results showed that there was46.3%～72.0%basic contribution of soil fertility. Meantime, basic contribution of soil fertility in first year decreased by9.4%compared to that of22th. With the improving of fertilization, dependence of yield on basic soil fertility increased with in the order of NPKM<NPK<NK and NP<N. Significantly increased yield has obtained from the continuous application of N element for17years and from K element for9years but little increased yield from P element. Annually increased amplitude was significantly varied with single application of N fertilizer and combined N fertilizer with P or K fertilizer. The increasing rate decreased linearly in the order of NP>N>NK. Yields treated with N, NP and NK were equivalent to or lower than those of the CK after18～21years. However, annually increased amplitude and rice yield have been raised significantly in the treatment of NPK. Furthermore, much higher increased amplitude has been observed in combination with organic fertilizer compared with other treatments. Correlation analysis indicated that significantly relationship was observed between annual yield of rice and SOC, TN, MBC, MBN, INV, CEL, URE, ASP, GLU,HIS acid hydrolysable N, ammonium N, amino acid N, amino sugar N, nonhydrolizable N, net N mineralization, size of3～5mm,0.05～0.25mm of soil aggregates and MWD, GMD, D in red paddy soil,suggesting these physiological,chemical and biochemical parameters being as evaluation indices of soil fertility. |
PDF Full Text Request