The relocation of undisturbed soil in long-term experiment impacts organo-mineral complex degree and combined humus of black soil

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1 WFL Publisher Science and Technology Meri-Rastilantie B, FI Helsinki, Finland Journal of Food, Agriculture & Environment Vol. (&): The relocation of undisturbed soil in long-term experiment impacts organo-mineral complex degree and combined humus of black soil Fengqin Chi *, Enjun Kuang, Baoku Zhou, Jiiuming Zhang, Qingrui Su and Shanshan Cai Institute of Soil Fertilizer and Environment Resource, Heilongjiang Academy of Agricultural Sciences, The Key Laboratory of Soil Environment and Plant Nutrition of Heilongjiang Province, Harbin 008, Heilongjiang, China. * zouwenxiu@hotmail.com Received 8 May 0, accepted 0 September 0. Abstract The effect of soil relocation on organo-mineral complex status and combined humus was considered to be based on the relocation of undisturbed soil in a long-term experiment in Agricultural Soil Ecological Environment Key Field Scientific Observation and Experiment Station (Harbin) of the Ministry in Northeast China. Four fertilizer treatments were selected in this study including (control, no fertilizer), M (organic fertilizer, horse manure), NPK (chemical fertilizer), (horse manure plus chemical fertilizer). Tested soils were relocated at December 8, 00 to March, 0 by the relocation of undisturbed soil columns under freezing conditions. There were no effect of soil relocation on soil organo-mineral complex degree, quantity of combined humus and the ratio of loosely and tightly combined humus. The youngest humus, the highest complex degree of organomineral complex and the highest soil fertility were observed in the combination of chemical plus organic matter (NPKM) in all tested soils. Soil organic carbon, heavy fraction of organic carbon and organo-mineral complexes contents did not change much in all tested soils. However, the soil relocation impacted significantly the content of additional organo-mineral complexes and the degree of additional organo-mineral complexes which showed the trend of increase-decrease order after two years of soil relocation. Soil relocation did not impact significantly the quantity of combined humus and the ratio of loosely and tightly combined humus in 0-0 cm soil layer in all tested soils. Key words: Long-term experiment, black soil, combined humus, organo-mineral complex degree. Introduction Long-term located fertilization experiment is the most basic and effective way to study the soil science, because it can systematically explain the evolution of soil fertility, provide a comprehensive evaluation of fertilization effect and the scientific basis for fertilization. Long-term experiment has 70 years history since Rothamsted Experimental Station in UK was established in 8. From the early 980s, more than 00 longterm experiments related to soil and fertilizer were established in typical agricultural regions in China, but finally only about 0 long-term experiments related to soil and fertilizer were preserved due to various reasons. Because the limitations of the initial trial design of long-term experiments, especially with the accelerated urbanization process in China, some long-term experiment sites must be relocated in order to protect the long-term experiment resources. Soil relocation in long-term experiment site has been recorded in a volume of literatures, but the information about the effect of soil relocation in the long-term experiment on soil humus is limited. Humus is the main resource of soil nutrients, affects the soil physical, chemical and biological properties, and controls the soil fertility. Soil humus is composed of complex components, there is much difference between humus which determines soil properties and soil fertility. Combined humus played an important role in soil fertility. Combined soil humus and minerals include forms: loosely combined humus, stably combined humus and tightly combined humus. The contribution of soil humus to soil fertility depended on the degree of the combination of humus and minerals. The effect of soil relocation on the organo-mineral complexes and combined humus of black soil were studied on the basis of undisturbed soil relocation of long-term located experiment. The objectives of this study were: () to reveal the relationship and variation of soil humus after black soil relocation, () to provide feasible basis for undisturbed soil relocation of longterm located experiment. Materials and Methods Study site: Agricultural Soil Ecological Environment Key Field Scientific Observation and Experiment Station (Harbin) of the Ministry built in 979, is the longest running long-term fertilization monitoring experiment station in the black soil region of Northeast China. Due to the expansion of urban development, the experiment station has to be relocated. The overall relocation method of the undisturbed permafrost was used. Harbin Black Soil Ecology Environment Key Field Observation Station had achieved a successful implementation of the overall relocation at December 8, 00 to March, 0 by the relocation of undisturbed soil columns under freezing conditions in order to keep soil original performance and structure. The new study site locates in Harbin Democracy Township which is away 0 km from old study site. There are similar climate conditions, soil parent material, groundwater levels, soil physical and chemistry properties between two locations. Soil sampling: The selected experiment includes four fertilizer treatments: (control, no fertilizer), M (organic fertilizer, horse manure), NPK (chemical fertilizer), (horse manure plus chemical fertilizer). Soil samples were collected in 00 (before Journal of Food, Agriculture & Environment, Vol. (&), July-October 0

2 relocation) and 0 and 0 (after relocation), respectively. The sampling depth is 0 ~ 0 cm and 0 ~ 0 cm soil depths, respectively. Soil samples collected from Harbin Democracy Township was used as a control treatment. The basic properties of the tested soil and application amount of fertilizer were shown in Tables and. Chemical analysis: Soil heavy fraction was measured using relative density fractionation method, combined humus was measured by the improved Xiongyi-Fujiping method, solid organic carbon and extracted organic carbon were measured by TOC instrument (Multi N/C 00S). Soil organic matter was measured by the potassium dichromate external heating method, alkaline hydrolysis N was measured by the alkaline hydrolysis diffusion method, available P was measured by the NaHCO extraction - Mo-Sb colorimetry method, available K was measured by the NH OAC extraction - flame photometry 7. The calculation of organo-mineral complex degree: Soil complexes (SQC) = HC HW / SW Soil complex degree (SCD) = SQC / SC 00% Quantity of additional complex (QAC) = MQC - SQC Degree of additional complex (DAC) = QAC / (MC - SC) 00% where, HC is heavy fraction of soil organic carbon, HW is heavy fraction carbon (g), SW is soil weight (g), SC is soil organic carbon content, MQC is soil added organic manure complex, MC is organic carbon content of soil added organic manure. Statistical analysis: Statistics were processed with Microsoft Excel 00 software. A correlation analysis was carried out with SPSS software. Results The effect of soil relocation on soil organic carbon and heavy fraction organic carbon contents: Heavy fraction organic carbon fractionated from soil organic carbon includes organo-mineral complex which is hard to be decomposed, thus it can be called as the real soil humus with lower C/N and longer turnover. Soil organic carbon content in 00 fluctuated from.87 to.0 g kg - (Table ), and higher values were found in 0 ~ 0 cm soil layer compared with 0 ~ 0 cm soil layer, the highest values were observed in treatment. Soil organic carbon content Table. The fertilization amount of different treatments for maize, soybean and wheat from 979 to 0. Crop N P O K O M (house (kg hm - ) (kg hm - ) (kg hm - ) manure) (t hm - ) Wheat Maize Soybean decreased and changed from.8 to.07g kg - after two years of soil relocation (0 and 0). Soil organic carbon content in 0 was decreased by.% and 7.7% for and treatments, increased.9% and.% for NPK and M treatments, respectively, compared with that in 00. Soil organic carbon content in 0 were increased 7.%,.0% and.% for, M and, decreased.% for NPK treatment, respectively, compared with that in 0. The variation of soil organic carbon in 0-0 cm soil layer was more than that in 0-0 cm soil layer. There was a significantly positive relationship between soil organic carbon content and heavy fraction organic carbon (y = 0.79x +.8, r 0.0 = 0.99, n = 8) in 00, indicating that the process of soil organic matter transformation involved gradually the formation of organo-mineral complex. This significantly positive relationship also was recorded in two years of soil relocation (0: y = 0.7x +.07, r 0.0 = 0.97, n = 8, 0: y = 0.7x +.07, r 0.0 = 0.978, n = 8), heavy fraction organic carbon showed the similar change trend with soil organic carbon in different soil layers and treatments. Heavy fraction organic carbon content in 00 was decreased.% and.% for and, increased by.9% and.8% for NPK and M, respectively, compared with that in 0. Heavy fraction organic carbon content in 0 was increased by 7.%,.7% and.% for, M and, decreased by.% for NPK, respectively, compared with that in 0. The range of change of heavy fraction organic carbon content in 0-0 cm soil layer was more than that in 0-0 cm soil layer. The effect of soil relocation on organo-mineral complex degree: The degree of organo-mineral complex and quantity of additional organo-mineral complex are used to represent complex degree of soil organic matter and minerals, and reflect the status of soil fertility, it is an important quantitative indicator to characterize complex of soil organic matter and inorganic minerals. The quantity of additional organo-mineral complex of the organic manure is the ratio of the composite organic carbon from organic manure and soil mass during the process of improving soil fertility 8. The degree of additional organo-mineral complex is the percentage of the composite organic carbon from organic manure and the increased value of total soil organic carbon. The quantity of original soil organo-mineral complex of M and treatments was higher than and NPK, and was higher in 0 ~ 0 cm soil layer than 0 ~ 0 cm soil layer in 00 (Table ). The similar trends were found in 0 and 0. The quantity of original soil organo-mineral complex in 00 was decreased by.% and.% for and, increased by.% and.9% for M and NPK, respectively, compared with that in 0. The quantity of original soil organo-mineral complex in 0 was increased by 0.9%,.7% and.% for, M and, decreased by.% for NPK, respectively, compared with that in 0. The degree of original soil organo-mineral complex was in the increasing order of > NPK > M >, and was more in 0-0 cm soil layer than that in 0-0 cm soil layer, indicating that organic manure application Table. Basic properties of the tested soils in 00. Organic carbon Total N Total P Total K Available Available Available (mg kg - ) P O (mg kg - ) K O (mg kg - ) ph NPK M Journal of Food, Agriculture & Environment, Vol. (&), July-October 0

3 Table. The difference of soil organic carbon and heavy fraction organic carbon contents in 00, 0 and 0 under different treatments. Soil organic carbon Heavy fraction organic carbon cm NPK M NPK M Table. The effect of soil relocation on the organo-mineral complex degree. (cm) SQC SDC (%) QAC DAC (%) NPK M NPK M could improve soil organo-mineral complex and more significant effect was observed in 0-0 cm soil layer. The increase of original soil organo-mineral complex degree meant the decrease of fresh soil organic carbon, soil tended to age 9, 0. There was an increasing trend for original soil organo-mineral complex degree from 00 to 0, but generally soil relocation did not affect on the original soil organo-mineral complex degree. The quantity and degree of organo-mineral complex changed much, and were increased in 0 and decreased in 0 due to that organic manure was more quickly decomposed by more active soil microbiology resulted from the change of environment conditions after soil relocation. The quantity of additional organo-mineral complex in 0 ~ 0 cm soil layer was higher than that in 0 ~ 0 cm soil layer, the degree of additional organo-mineral complex was inverse in 00. The quantity of additional organo-mineral complex of was higher than that in M, but the degree of additional organo-mineral complex was lower than that in M. Soil relocation significantly impacted the quantity and degree of additional organo-mineral complex, and were increased in 0 and decreased in 0. The carbon in out of organo-mineral complex was more quickly decomposed than that in organo-mineral complex, which resulted in the degree of additional organo-mineral complex was increased with the increase of plantation period 7. The quantity of organo-mineral complex of black soil tented to be increased by short-term application of chemical fertilizers, and decreased by long-term application of chemical fertilizer, longterm application of organic manure and chemical fertilizers could improve quantity of organo-mineral complex. The quantity of organo-mineral complex was decreased in 0 then increased in 0 for M and treatments, and was increased in 0 and then decreased in 0 for NPK treatment, which may be due to the fluctuations of the quantity of organo-mineral complex under the influence of the surrounding environment after soil relocation. The quantity of organo-mineral complex was increased in short time, but decreased in long-term for NPK treatment. The longterm application of organic manure could increase the quantity of organo-mineral complex. The effect of soil relocation on combined humus: Most of the soil humus was bound with the minerals to form organo-mineral complexes, the amount of the free humus is tiny. The combination of soil humus and minerals include three statuses: loosely combined humus, stably combined humus and tightly combined humus. Different combined humus forms had different impact on soil fertility. Loosely combined humus had the most contribution for soil fertility due to that was fresh humus and had the largest activity. Tightly combined humus was the most stable because it was tightly combined with mineral. The stability of stably combined humus was between two other forms. The content of the loosely combined humus was higher in 0 ~ 0 cm soil layer than 0 ~ 0 cm soil layer in 00 (before soil relocation), the content of the loosely combined humus of NPK, and M was decreased in 0 ~ 0 cm soil layer, and was lower than that in 0 ~ 0 cm in 0 (the first year of soil relocation), the same change trend of loosely combined humus was found in 00 and 0 (Table ). The content of loosely combined humus was increased in 0-0 cm soil layer, decreased in 0-0 cm soil layer in 0, decreased by 7.% for, increased by. -.% for NPK, and M, compared with that in 00. The content of loosely combined humus was decreased by.% for, and increased by - 8.9% for NPK, and M in 0, compared with that in 0. There was no obvious change law of stable combined humus in both 0 ~ 0 cm and 0 ~ 0 cm soil layers. Compared with the content of stable combined humus in 00, the content of stable combined humus was increased by 9.% in 0, and decreased.9% in 0 for M treatment, decreased by 7.8% in 0, increased by.8% in 0 for treatment. The content of tightly combined humus was higher in 0 ~ 0 cm soil layer than 0 ~ 0 cm soil layer in experimental three years. The content of tightly combined humus showed an order of increase-decrease in 0 and 0 for NPK, and M treatments, and an order of decrease-increase in 0 and 0 for treatment. Journal of Food, Agriculture & Environment, Vol. (&), July-October 0

4 Table. The change of combined humus after soil relocation. (cm) 0-0 cm 0-0 cm Treatment Loosely combined humus Stably combined humus Tightly combined humus NPK M NPK M Loosely combined humus has the largest activity in combined humus as fresh humus, thus it has significant contribution to soil fertility,. The effect of soil relocation on loosely combined humus was more than stable and tightly combined humus due to that loosely combined humus was more active than stable and tightly combined humus. The contents of soil nutrients and humus were higher in 0 ~ 0 cm soil layer than in 0-0 cm soil layer because soil fertility in 0 ~ 0 cm could be replenished by fertilizer application. The content of loosely combined humus of NPK, and M treatments was increased gradually for 0 ~ 0 cm soil layer and showed decrease-increase trend for 0 ~ 0 cm soil layer in 0 and 0. The effect of soil relocation on the ratio of loosely and tightly combined humus: Loosely combined humus was more active as fresh humus; tightly humus was hard to be uptake because of slow decomposition and low activity. So higher the ratio of loosely and tightly combined humus was corresponding to higher soil fertility. The highest ratio of loosely and tightly combined humus was observed in treatment, there was no obvious change of the ratio of loosely and tightly combined humus in 0 ~ 0 cm soil layer among 00, 0 and 0 (Fig. ). The ratio of loosely and tightly combined humus in 0 ~ 0 cm soil layer was decreased. ~.% in 0, and then increased in 0 compared with that in 00, but the ratio of loosely and tightly combined humus in 0-0 cm soil layer was still lower in 0 than 00. Conclusions The contents of soil organic carbon and heavy fraction of organic carbon were in an increasing order of < NPK < M < in all tested soils. The effect of soil relocation on soil organic carbon and heavy fraction of organic carbon did not be found. The quantity of organo-mineral complex showed an increasing order of < NPK < M < in 00 (before soil relocation), 0 and 0 (after soil relocation), the organo-mineral complex degree showed an inverse trend. The organo-mineral complex degree showed a decreasing order of > NPK > M >, indicating that organic manure application could improve the status of soil organo-mineral complex. The organo-mineral complex degree increased gradually in experimental three years, indicating that soil organic carbon aged with the increase of fertilization and tillage periods. The quantity of additional organo-mineral complex in was higher than in M, but the degree of additional organo-mineral complex in was less than in M. The ratio of loosely and tightly combined humus showed a higher range in 0 ~ 0 cm soil layer than in 0 ~ 0 cm soil layer, and was decreased in 0 and increased in 0 compared with that in 00. There was no significant difference of the ratio of loosely and stable combined humus, the higher change was observed in M treatment, which needs more research in the future. Generally, the properties of soil fluctuated after soil relocation, and showed that activity of soil fertility supply was decreased. However, most properties did not have significant change. Relocated soil would be suitable for new environmental conditions with the increase of experimental years. The properties of soil would be recovered to the status before soil relocation, but this needs continually observation in the future. Acknowledgements This work was supported by National Natural Science Foundation of China (7), and Key Program of the Heilongjiang Province Natural Science Fund Project, China (ZD0), the National Science and Technology Support Program of China (0BAD07B0), the Special Fund for Agro-scientific Research in the Public Interest of China (00), Soil restoration and high efficient utilization science team of Northeast Agricultural University. The ratio of loosely to tightly combined humus 0 NPK M 0-0 cm 0-0 cm Experimental year The he ratio ratio of of loosely loosely to to tightly tightly combined combined humus hum 0 NPK M 0-0 cm0-0 cm Experimental year Figure. The effect of soil relocation on ratio of loosely to tightly combined humus. Journal of Food, Agriculture & Environment, Vol. (&), July-October 0 7

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