[Study on Contents and Budgets of Cu, Zn and Cd in an Arable Soil Using AAS].

Based on a long-term experiment in Shenyang Experimental Station, the effect of manure application on the contents and budgets of Cu, Zn and Cd in the arable soil was studied. The experiment included four treatments: no mature addition (CK), mature addition 10 t · ha⁻¹ year⁻¹(M1), 25 t · ha⁻¹ year⁻¹ (M2), and 50 t · ha⁻¹ year⁻¹(M3). The result showed that Cu, Zn and Cd in soil were accumulated with manure application and prolongation of experiment, and the accumulative magnitude increased with increasing of manure application. The average annual growth rates of the heavy metals in the four treatments (CK, M1, M2, M3) were 2.83%, 6.56%, 7.54%, 8.96%; 0.03%, 3.44%, 4.53%, 6.64% and 1.51%, 8.01%, 10. 27%, 16. 08% for Cu, Zn and Cd, respectively. After six years of the experiment, the content of Cd in the M3 treatment was quite close to the threshold of Chinese Soil Quality Standard Grade III (1 mg · kg⁻¹, GB15618-1995). After 12 years of the experiment, the contents of Cu in the mature-amended treatments fell in the Chinese Soil Quality Standard Grade III, which should be paid more attention. Although the heavy metals in soil were gradually accumulated, the Cu, Zn and Cd levels in crop grain were still below the National Food Contamination Standards (GB2762-2005; GB13106-91; GB15199-94), indicating the contents of heavy metals in crop produced from contaminated soil might not exceed the corresponding standards. The contents of Cu, Zn and Cd in the straw were much greater than those in the grain. The removal of heavy metal by crop was in the order of M3 > M2 > M1 > CK. The average amounts of Cu, Zn and Cd annually removed from the soil in the four treatments (CK, M1, M2 and M3) were 35.68, 47.80, 63.65, 69.64; 249.14, 375.22, 375.16, 444.44, and 0.83, 1.39, 1.64, 1.66 g · ha⁻¹, respectively. The contents of heavy metals in organic manure varied in different years: the contents of Cu and Zn increased year by year, while Cd presented a decreasing trend. The average amounts of Cu, Zn and Cd annually remained in the soil in the treatments M1, M2 and M3 were 2 283.0, 5 763.7, 11585.4; 2 483.3, 6 771.4, 13 849.2 and 4.8, 13.9, 29.5 g · ha⁻¹, respectively. Since the heavy metals in organic manure markedly fluctuated in different years, the average residuals can only reflect the changing trend. Therefore, the residuals of heavy metals in the soil could be accurately predicted only according to status of manure in a given year.

[Study on Leaching Characteristic of Heavy Metal in the Manure-Amended Soil Using ICP-MASS].

Based on an 11-year fertilizer field trial (located at the lower liaohe river plain), the effects of different organic manure application rates on the accumulations of heavy metals (Cu, Zn, Cd and Cr) in surface soil (0-20 cm), and the leaching characteristic and vertical migration pattern of heavy metal have been investigated in this rainfed agro-ecosystem using undisturbed soil columns. The result showed that the content of heavy metal in surface soil was elevated with the increase of manure application. The increasing magnitude was in the order of Cd>Cu>Zn>Cr. According to the Chinese soil quality standard (GB15618-1995), the application of manure (not exceeding 50 t · ha⁻¹) did not result in serious heavy metal pollution in the surface soil. Chromium met the Grade I , and Cu and Zn met the Grade II; whereas, Cd was almost exceeded the threshold of Grade III. The potential risk of Cd in soil should be paid more attentions in future research. According to the National water quality standard (GB/T14848-93), the Cu and Cd concentrations in leachate samples were up to the Grade II except only a few samples that fell in Grade III. Furthermore, Cr in the leachate all matched Grade I water quality standard. These results indicated long-term application of manure (not exceeding 50 t · ha⁻¹) in our site had not induced contaminant risks of heavy metals in underground water. In addition, the Cu, Zn and Cd (except Cr) in leachate all declined with the increase of soil depth, indicating the low capacity of vertical migration of heavy metal. Among the four heavy metals, Zn and Cr tended to be leached into deep soil, whereas Cu and Cd were more prone to be accumulated in surface soil.

[The recycling rate of trace element Fe and Zn in agro-ecosystem using ICP-AES].

Input of trace elements Fe and Zn in the lower reach of Liaohe Plain under different fertilization systems was studied by long-term field experiment and ICP-AES analysis. The results showed that Fe and Zn were mainly from organic manure in agro-ecosystem. The residual rate of organic manure through a feeding-composting cycle in the absence of bedding materials was 21.84%, which was lower than that of organic matter fertilized to soil after one year. The recycling rate of Zn through a feeding-composting cycle was 71.9%, and the recycling rate of Fe was 81.0%.

[Determination of concentrations and distributions of Mn and Zn in maize under different fertilization regime using ICP-AES].

A long-term field experiment and ICP-AES analysis were conducted to study concentration and content of micronutrients Mn and Zn in maize under different fertilization systems. The results were as follows: (1) Concentrations of Mn in maize under NPKM and NPK treatments were significantly higher than those in M and control treatments. The concentration of Zn in grain of maize was similar under different treatments. The control treatment had the highest concentration of Zn in stalk, while NPKM treatment had the lowest one. (2) Contents of Mn and Zn increased with increasing yields of maize, and the regression relationship between the contents and yield of stalk was better than that between the contents and yield of grain. (3) Most of Mn and almost half of Zn were concentrated in stalk. The distribution and use efficiency of micronutrients were optimized under NPKM and NPK treatments. Returning the stalk to soil is an effective strategy for micronutrients sustainable utilization in agro-ecosystem.

[Study on the main influencing factors of black soil spectral characteristics].

To develop soil properties quick measuring methods, promote the development of quantitatively remote sensing studies relating to terrestrial ecosystem, and deepen the application of remote sensing in agriculture, the hyperspectral reflectance of black soil in Songnen Plain, northeast China, was analyzed with spectral analysis methods (continuum removal, spectral angle match and spectral feature fitting) and statistic methods to discover the reflectance spectral characteristics and its influencing factors. The results are as follows: the soil parent material determines the basic characteristics of reflectance of the black soil, which is the mixture of montmorillonite and illite, and consistent with mineral analysis result. Organic matter is the main factor determining the curve shape of black soil reflectance in the region shorter than 1 000 nm, and indirectly influencing the reflectance in the region longer than 1 000 nm because of the correlation with soil moisture and mechanical composition. The varying process of soil reflectance with changing soil moisture can be quantitatively described with cubic equation, and moisture mainly changes the reflectance value but not the curve shape. Black soil reflectance is not influenced significantly by Fe, which is different from soils of south China. Roughness mainly impacts on the soil reflectance value but not the shape feature. The spectral feature of straw reflectance is remarkably different to that of black soil, and impacts on both the value and curve shape of black soil reflectance. Different soil tillage measurements result in different moisture holding ability and the amount of straw for different farm fields, and influence the reflectance further, with the order of soil reflectance from high to low is: no tillage, moldboard tillage, combination tillage, reduced tillage, and rotary tillage.

[Effects of long-term fertilization on organic nitrogen fractions in aquic brown soil]. / 长期施肥对潮棕壤有机氮组分的影响.

The purpose of present research was to investigate how different fertilization regimes altered soil organic nitrogen fractions and their inter-annual dynamics based on a series of long-term experiment (initiated at 1990), including: CK (non-fertilization); M (recycled pig manure); NPK (chemical fertilizer NPK); NPK + M (recycled pig manure with chemical fertilizer NPK). The results showed that soil organic nitrogen components under the different fertilization treatments presented contrastive patterns from the establishment the experiments to 2015. Generally, acid hydrolysable organic nitrogen content increased year by year. The amino acid nitrogen content under CK and NPK treatments consistently declined, although amino acid nitrogen for M and NPK+M treatments showed a increasing trend. These phenomena were probably ascribed to the utilization of soil amino acids by microbes. From 1990 to 2015, NPK treatment substantially elevated the content of acid-released ammonium nitrogen by 31.1% compared with CK (mean value across the experiment), and for the treatments using organic manure (M and NPK+M), the contents of all fractions of soil organic nitrogen increased. Notably, the increase magnitudes for NPK+M were more dramatic than those of M. These results demonstrated that combined use of organic and inorganic fertilizers could more effectively elevate soil organic nitrogen, subsequently helping to improve the capacity of soil nitrogen supply and enhance the soil fertility.

[Basic features and monitoring methodologies of atmospheric nitrogen deposition].

Atmospheric nitrogen (N) deposition, including dry and wet deposition, is an important inorganic and organic N source for ecosystems, and also a key link of the N biogeochemical cycle. Recently, considerable active nitrogen has been emitted into the atmosphere due to enhanced human activities. High N emission leads to high deposition which has caused a series of environment risks, and more attentions have been focused on this issue. This article gave an overview of the basic content about the present N deposition research, such as the component, process, spatial and temporal variation, as well as ecological effect. Then the sampling methods of wet and dry deposition in the field, analysis methods in laboratory and primary techniques of N source identification were summarized. The N deposition research trend in the future was emphasized.

[Effects of long-term fertilizations on microbial biomass C and N and bacterial community structure in an aquic brown soil].

Taking a long-term field experiment on an aquic brown soil in the Shenyang Ecological Station of Chinese Academy of Sciences as a platform, the methods of traditional chloroform fumigation and modern PCR-DGGE were adopted to study the effects of different fertilizations on the changes of soil microbial biomass and bacterial community structure. During the whole period of the experiment, there was a similar trend in the dynamic changes of soil microbial biomass C and N. Long-term application of organic manure increased the soil organic C and the soil microbial biomass C and N significantly, while long-term application of chemical fertilizers had significant negative effects on the soil pH and soil microbial biomass C and N. The DGGE patterns showed that under different fertilizations, the majority of soil bacterial 16S rDNA bands were the same, 18 of the 28 bands being common, suggesting that the bacterial populations in test soil were more stable, but their numbers were affected by different fertilizations. Long-term application of organic fertilizer could promote the diversity of the bacterial community structure in aquic brown soil, while the application of chemical fertilizers was in adverse.

[Nutrient concentration and storage in different organs of Eucalyptus under effects of nitrogen topdressing].

A field experiment was conducted to study the effects of nitrogen (N) topdressing on the biomass accumulation and nutrient concentration and storage in different organs of two-year-old eucalyptus. Comparing with the control, N topdressing increased the eucalyptus biomass by 24.2%. Branch had the highest increment (38.2%), while leaf had the lowest one. The nutrient uptake under N topdressing was improved significantly, with the order of P > K > N > Mg > Ca > Si. Leaf had the highest contents of N, P, Mg, and Si; trunk had the highest storage of K; while branch had the most significant increase of nutrient concentration and storage. The N, P, and K were recycled mainly through internal flux, with 73.8% of N, 79.1% of P, and 72.9% of K in leaf transferred back to the plant before leaf fallen, and the external flux of these three nutrients only occupied 14.8%, 7.7%, and 8.6% of their total storage in the tree, respectively. The Ca, Mg and Si were the external flux elements, especially for Ca. 89.2% of Ca in leaf was cycled in external flux, accounting for 25.9% of its total storage in the tree.

[Research advances in water-fertilizer effect on dry land farmland].

Water and fertilizer are the keys in improving dry land productivity, and the main factors limiting the agricultural development in dry land regions. For our food security and agricultural sustainable development, it' s of significance to bring the effect of water and fertilizer on increasing yield into full play. This paper introduced the design principles of several commonly used methods in researching the effect of water and fertilizer, e.g., irrigation experiment, rainproof-shed experiment and long-term experiment, compared their advantages and disadvantages, and discussed the mechanisms and models of water-fertilizer interaction on dry land farmland, based on the sum-up of the achievements of related qualitative and quantitative researches. It was indicated that under appropriate conditions, there was a positive interaction between water and fertilizer on grain yield, but the effect differed with research method and natural condition. The development trend of the researches on the water-fertilizer effect on dry land farmland in light of the characteristics of agro-ecosystern was also prospected.

[Decomposition process and residual rate of organic materials C and N in soils].

By using nylon mesh bags and sand filter tubes, this paper studied the decomposition of organic materials in the soils at Shenyang and Hailun eco-experimental stations of CAS to investigate the dynamic changes of their organic C and N during decomposition. The results showed that the decomposition process could be divided into two phases, i.e., quick phase and slow phase. The organic N in the materials had an obviously lower decomposition rate than organic C, and thus, had a higher residual rate. The decline of C/N ratio could be also divided into quick and slow phases. After 3-5 years decomposition, the C/N ratio of all test materials tended to be stable. The C/N ratio of the residual organic materials with an initial lower C/N (such as pig manure) approached to that of soil humus, being about 10, which indicated that the humification process was completed, while that of the residual organic materials with an initial higher C/N was about 25, being available to the activities of soil microbes, which would benefit the increase of soil organic matter and the improvement of soil fertility.

[K fertility and K deficit index of aquic brown soil under different fertilization systems].

A 15-year fertilization experiment was conducted on an aquic brown soil to study the variations of its K fertility and the index of K deficit under different fertilization systems. The results indicated that no K application accelerated the depletion of soil K, representing a certain decrease of soil available and slow-release K. Applying K alone could not keep soil K in balance, still having a decrease of soil available and slow-release K. The application of recycled compost combined with appropriate amount of fertilizer K could compensate soil K expenditure to a certain degree, and keep the concentrations of soil available and slow-release K somewhat constant. The statistic analysis on the past years test results showed that the critical values of soil available K in corn- and soybean fields obtained by crossing method were all 73 mg x kg(-1).

[Effects of land use type on soil organic carbon storage in aquic brown soil].

The profile distribution of soil organic carbon (SOC), its storage, and carbon/nitrogen (C/N) ratio at the depth of 0-100 cm under different land use types were investigated in this paper. The results showed that the profile distribution of SOC varied significantly with land use type. The SOC contents in each soil layer in forestland, mowing land and wasteland were all higher than that in agricultural land. In all land use types, SOC was significantly correlated with soil total N. Soil C/N ratio generally decreased with depth, which was higher in forestland than in mowing land, wasteland and bare land, and was the lowest in agricultural land. At the depth of 0-100 cm, the annual sequestration of SOC in wasteland was 4.52, 4.25, 4.46 and 3.58 t x hm(-2) more than that in farmland with no fertilization, farmland with recycled manure application, farmland with N, P and K fertilization, and farmland with the application of both recycled manure and N, P and K, respectively, suggesting that wasteland had a great potential in increasing SOC storage.