Analysis and Assessment on the Heavy Metals in a Severely Degraded Subtropical Red Soil Region

5 different forests of Pinus massoniana, Schima superba, Liquidambar formosana, P. massoniana × S. superba, P. massoniana × L. formosana as the research object were set up to study the Cr, Cu and Zn content of degraded red soil region in subtropics. The soil heavy metal pollution degree was evaluated by national environmental quality standard (II class). The results showed that three soil metals of P. massoniana × S. superba were the highest, and the soil metals enrichment ability was strong. The order of single factor pollution index of metal elements was Cu (1.38) > Cr (0.81) > Zn (0.42), and moderately pollution, pollution warning and no pollution, respectively. There was no significant correlation between three soil heavy metals and soil total carbon (TC), total nitrogen (TN) and total phosphorus (TP). These results suggested that the accumulation of heavy metal elements was not derived from the parent material of soil. There was a significant positive correlation between the three metal elements which indicated that the sources of the three elements were similar. The structural equation model showed that the direct and indirect effects among the influencing factors ultimately affected the activity of heavy metals by cascade effects.

Influence of different phosphates on adsorption and leaching of Cu and Zn in red soil

Batch and soil column experiments were conducted to evaluate the influence of KH2PO4, （NH4）H2PO4and Ca（H2PO4）2on the adsorption and leaching characteristics of Cu and Zn in red soil. The results show that all the three phosphates can greatly improve the adsorption capacity of red soil for Cu and Zn, and the effect of different phosphates on Cu and Zn adsorption follows the order of Ca（H2PO4）2〉KH2PO4〉（NH4）H2PO4. The addition of phosphate has little effect on the mobility of Cu. Ca（H2PO4）2and （NH4）H2PO4 show a strong ability in immobilizing Zn while the immobilization ability of KH2PO4 is much weaker. All the three phosphates are helpful for modifying the partitioning of Cu and Zn from the non-residual phase to the residual phase; however, they could also enhance the contents of Cu and Zn associated with exchangeable and carbonates fractions.

Response of Ecosystem Service Value Based on Land Use Changes and Analysis of its Driving Factors in Typical Hilly Region with Red Soil

The contribution rate of ecosystem service value variation was used to analyze the effects of land use changes on the changes of ecosystem service value in Xingguo County during 1996-2005.Grey integrated correlation was employed to explore the contribution level of the indicators such as total population,urbanization level,proportion of primary industry and investment of social fixed assets on ecosystem service value,and the correlation analysis was also carried out.The results showed that the ecosystem service value in Xingguo County during 1996-2005 mainly was woodland,and the decrease of woodland area was the major reason for the sustained reduction of ecosystem service value.With the further increase of market demand and the incentives of local government,the garden area rapidly increased during 2001-2005,and the influence degree of garden towards the changes of ecosystem service value was only second to woodland,ranking No.2.Four socio-economic indicators had different correlation degree with ecosystem service value during the different research periods.Total population,urbanization level and proportion of primary industry had high correlation degree with ecosystem service value,whereas the influence degree of various socio-economic indicators on ecosystem service value was equal with each other day by day.Urbanization level,investment of social fixed assets and total population had significant negative correlation with ecosystem service value,while the proportion of primary industry had positive correlation with ecosystem service value.

Construction and Application of Soil Erosion Control and Circular Agriculture Mode in Hilly Red Soil of Southern China

[Objective] The paper was to construct soil erosion control and circular agriculture mode in hilly red soil of southern China, and analyze its application effort. [Method] The cause of soil erosion in hilly red soil of southern China and the reason for long-term treatment without remarkable effort were analyzed. On this basis, the key technology, economic benefit, ecological service function and carbon sequestration sink enhancement effect of various modes were further analyzed. [Result] The basic idea for comprehensive control of hilly soil erosion in southern China was as follows: the control of soil erosion was combined with modern agricultural production, in order to build "fruit(tea)-grass-livestock-methane" circular agriculture mode with comprehensive control of soil erosion; application effect analysis showed that the establishment of circular agriculture mode in southern hilly area to control soil erosion had remarkable effect, which could simultaneously meet the coordinated development of ecological, economic and social benefits. [Conclusion] This study established an effective mode suitable for soil erosion control and agricultural protection development in southern red soil mountain, which could drive the sustainable development of ecological restoration of mountainous area and rural agricultural economy.

Phosphorus Fertilizer Effect in Sugarcane Red Soil and Its Loss Risk Assessment under Different Phosphorus Application Rates

[Objectives] The soil phosphorus balance and potential risk of phosphorus loss under different phosphorus application rates in sugarcane red soil in Guangxi were evaluated to provide reference for scientific and rational application of phos- phorus fertilizer and reduction of environmental pollution. [Methods] A field trial and simulated rainfall experiment were carried out. In the field experiment, five phospho- rus levels （0, 75, 150, 300 and 600 kg P2OJhm2） were set, the yield of sugarcane stems and leaves were measured, and their phosphorus content was determined to obtain aboveground P accumulation and P surplus in soil. After sugarcane harvest- ing, calcium magnesium phosphate and potassium dihydrogen phosphate were ap- plied to soil with different levels of phosphorus to conduct the simulated rainfall ex- periment based on monthly rainfall from May to September in Guangxi during 2000-2015. The leachate was collected to analyze the concentration and total amount of phosphorus to obtain the regression equations between available phos- phorus content in soil and the increase of phosphorus concentration in leachate. [Results] Sugarcane yield increased significantly when phosphorus application rate was 150 kg P：~OJhm2. When phosphorus application rate exceeded this value, the yield of sugarcane stems and aboveground part was also significantly higher than the treatment without phosphorus application, but the increase of yield was similar to the treatment with phosphorus application rate of 150 kg P2OJhm2. According to the relationship equation between phosphorus application rate and soil Olsen-P con- tent as well as the relationship equations between the increment of P concentration in leachate and soil Olsen-P content in the treatments with calcium magnesium phosphate and KH2PO4, the increment of P concentration in leachate was 0.02-0.04 mg/L when phosphorus application rate was 75 kg P2OJhm2; the increment of P concentration in leachate was 0.07-0.10 mg/L as phosphorus application rate was 600 kg P2OJhm2. [Conclusions] The reasonable application rate of phosphorus fer- tilizer for sugarcane is 150 kg P2Or/hm2. However, long-term continuous application of phosphorus fertilizer can promote the enhancement of available phosphorus con- tent in soil and increase the risk of phosphorus loss from sugarcane fields.

Study on Liquid Special Fertilizer for Drip Irrigation of Sugarcane and Its Irrigation Mode in Guangxi Lateritic Red Soil Region

[Objective] Liquid special fertilizer for drip irrigation of sugarcane was de- veloped and the fertilizer patterns were explored in the production to provide techni- cal support for fertigation production of modern agriculture. [Method] ROC22 was selected as experimental material, two formulas of liquid special fertilizer for sugar- cane developed by the cooperation between Guangxi Academy of Agricultural Sci- ences and New Orientation （Guangxi） Chemical Industry Co.,Ltd. were selected, namely, balanced 21-21-21 ~ TE of Xinfangxiang and hyperkalemic 13-6-39-TE of Xinfangxiang. Taking conventional fertilization as the control （CK）, two modes of ap- plying base fertilizer at the earlier stage ＋ fertigation in the tillering stage and ferti- gation in the whole growth period were set. [Result] The two modes of fertilization had not significant effects on the emergence of sugarcane, but applying base fertil- izer at the earlier stage ＋ timely applying water soluble fertilizer in the tillering stage was conducive to the tillering of sugarcane. Harvest results showed that the effects of different treatments on plant height and yield were significant, in which the yield of sugarcane under the treatment of hyperkalemic water-soluble fertilizer increased by 13.04% compared with conventional treatment, and the income increased by 4 500 yuan/hm2, [Conclusion] Liquid special fertilizer for drip irrigation of sugarcane signifi- cantly promoted the growth of sugarcane, moreover, under the same condition, the effect of hyperkalemic water-soluble fertilizer was better.

Influence of Phosphorus Fertilizer Application on Available Phosphorus and Easy-loss Phosphorus Content in Red Soil

[Objective] This study was to investigate the influence of phosphorus （P） fertilizer application on available P and easy-loss P content in red soil under aerobic incubating condition, with the aim to provide theoretical basis for the management of elemental P and evaluation of elemental P loss potential. [Method] Totally six treat- ments were set to the soil samples. The Olsen-P, Bray-1 P and CaCl2-P contents of each soil sample were measured after indoor aerobic incubation. [Result] In the red soil of different P fertilizer application rates, the Olsen-P content decreased with the increasing of incubation time, while the content of Bray-1 P increased and CaCI2-P content was first increased then decreased. CaCl2-P content was linear correlated with Olsen-P content and Bray-1 P content. About 62% P fertilizers were transformed into Bray-1 P pool, and 14% into Olsen-P pool, but only 0.12% transformed into CaCl2-P pool. [Conclusion] There is little risk of P loss caused by P fertilizer application under aerobic condition, but it would increase with the increasing application dose, and the most serious time is the primeval period after P fertilizer application.

Crop Yield and Soil Responses to Long-Term Fertilization on a Red Soil in Southern China

A 15-year fertilization experiment with different applications of inorganic N,P and K fertilizers and farmyard manure (M)was conducted to study the yield and soil responses to long-term fertilization at Qiyang,Hunan Province,China. Average grain yields of wheat and corn(1 672 and 5 111 kg ha-1,respectively)for the treatment NPKM were significantly higher than those(405 and 310 kg ha-1)of the unfertilized control and single inorganic fertilizer treatments.Compared with the corresponding initial values of the experiment,all treatments showed a yield decline of 9 to 111 kg ha-1 year-1 in wheat and 35 to 260 kg ha-1 year-1 in corn,respectively,and a significant pH decline of 0.07 to 0.12 pH year?1,except for the treatments PK and NPKM.After long-term fertilization,the soil organic C,soil available P,exchangeable Ca2+ and Mg2+and available Cu2+and Zn2+contents were higher in the treatment NPKM than in the treatments applied with inorganic fertilizer only.Compared to the treatment NPK,the treatment NPKM,where manure partially replaced inorganic N,had a positive impact on arresting the decline of soil pH.This improved grain yields of wheat and corn, suggesting that application of NPK fertilizer in combination with farmyard manure is important to maintain soil fertility and buffering capacity in red soil.

Effect of Different Vegetation Systems on Soil Erosion and Soil Nutrients in Red Soil Region of Southeastern China

The effect of different vegetation systems including bamboo plantation (BP), forest ecosystem (CF),citrus orchard (Ctr) and farmland (FL) on erosion and nutrients of red soil were investigated in hilly region of southeastern China to find effective control measures for soil erosion. The results showed that all the vegetation systems could significantly reduce soil erosion and nutrient losses compared to bare land (Br).The ability of different vegetation systems to conserve soil and water was in the order of Ctr ＞ BP ＞ CF ＞ FL ＞ Br. Vegetation could also improve soil fertility. The soil organic matter, total N and total P contents were much higher in all the vegetation systems than in bare land, especially for the top soils. Vegetation systems improved soil physical properties remarkably. Compared to the bare land, soil organic matter, TP,TK and available K, especially soil microbial biomass C, N and P, increased under all the vegetation covers.However, they were still much lower than expected, thus these biological measurements are still needed to be carried out continuously.

Effects of Cadmium, Lead, and Zinc on Size of MicrobialBiomass in Red Soil

A laboratory incubation experiment was conducted to study the influence of cadmium (Cd), lead (Pb)and zinc (Zn) on the size of the microbial biomass in red soil. All the three metals were applied, separately,at five different levels that were: Cd at 5, 15, 30, 60 and 100 μg g-1; Pb at 100, 200, 300, 450 and 600 μg g-1 and Zn at 50, 100, 150, 200 and 250 μg g-1 soil. In comparison to uncontaminated soil, the microbial biomass carbon and biomass nitrogen decreased sharply in soils contaminated with Cd, Ph and Zn. A more considerable increase in the microbial biomass C: N ratio was observed in the metal contaminated soils than the non-treated control. Among the tested metals, Cd displayed the greatest biocidal effect followed by Zn and Pb, showing their relative toxicity in the order of Cd > Zn > Pb.

Long-Term Application of Organic Manure and Mineral Fertilizer on N_2O and CO_2 Emissions in a Red Soil from Cultivated Maize-Wheat Rotation in China

A long-term field experiment was established to determine the influence of mineral fertilizer and organic manure on soil fertility. A tract of red soil （Ferralic Cambisol） in Qiyang Red Soil Experimental Station （Qiyang County, Hunan Province, China） was fertilized beginning in 1990 and N20 and CO2 were examined during the maize and wheat growth season of 2007-2008. The study involved five treatments： organic manure （NPKM）, fertilizer NPK （NPK）, fertilizer NP （NP）, fertilizer NK （NK）, and control （CK）. Manured soils had higher crop biomass, organic C, and pH than soils receiving the various mineralized fertilizers indicating that long-term application of manures could efficiently prevent red soil acidification and increase crop productivity. The application of manures and fertilizers at a rate of 300 kg N ha-1 yr-1 obviously increased NzO and CO2 emissions from 0.58 kg N20-N ha-~ yr-~ and 10565 kg C ha-~ yr-~ in the CK treatment soil to 3.0l kg N20-N ha-~ yr-~ and 28 663 kg C ha-~ yr-I in the NPKM treatment. There were also obvious different effects on N20 and CO2 emissions between applying fertilizer and manure. More N20 and CO2 released during the 184-d maize growing season than the 125- d wheat growth season in the manure fertilized soils but not in mineral fertilizer treatments. N20 emission was significantly affected by soil moisture only during the wheat growing season, and CO2 emission was affected by soil temperature only in CK and NP treatment during the wheat and maize growing season. In sum, this study indicates the application of organic manure may be a preferred strategy for maintaining red emissions than treatments only with mineral fertilizer. soil productivity, but may result in greater N20 and CO2

Combined Pollution and Pollution Index of Heavy Metals in Red Soil

A field experiment was conducted to study the effects of Pb, Cd, Cu, Zn and As coexisting in red soilon growth of rice (Oryza sativa L.), mung bean (Vigna rabiata (Linn.) Wilczek), alfalfa (Medicago sativaL.), slash pine (Pinus elliottii Engelm.) and aspen (Populus L.). Results showed that rice, mung bean andalfalfa were significantly innuenced by combined pollution of the heavy metals. The contents of Pb, cd andAs in rice grains greatly exceeded the National Standards for Food Hygiene of China. Heavy metals at ahigh concentration seriously retarded growth of mung bean and alfalfa, but not so obviously with slash pineand aspen. The composite index is suggested for evaluating the relativity of combined pollution witll heavymetals in soil.

Effects of Long-Term Application of Inorganic Fertilizers on Biochemical Properties of a Rice-Planting Red Soil

A long-term experiment was set up in Yingtan of Jiangxi Province to investigate the effects of long-term application of inorganic fertilizers on the biochemical properties of a rice-planting soil derived from Quaternary red earth. Noncultivated soils are extremely eroded and characterized by a low pH and deficiencies in available nutrients, in particular P and N. After 13 years of inorganic fertilization in cultivation for double-cropped rice, the biochemical properties of the soil were changed. The nitrification potential and urease activity were higher in the treatments with N application than those without N application, Acid phosphatase activity and dehydrogenase activity were also higher in the treatments with P application than in those without P application. The dehydrogenase activity correlated well with the concentrations of both total P and hydrolysable N and with rice crop yield, suggesting that dehydrogenase activity might be a suitable indicator for improvement in soil fertility.

Impact of pH on Microbial Biomass Carbon and Microbial Biomass Phosphorus in Red Soils

The impact of pH changes on microbial biomass carbon (Cmic) and microbial biomass phosphorus (Pmic)were examined for 3 red soils under citrus production with different lengths of cultivation. Soil pH significantly affected Cmic and Pmic. The Cmic and Pmic changes, as a function of soil pH, appeared to follow a normal distribution with the original soil pH value at the apex and as pH increased or decreased compared to the original soil pH, Cmic and Pmic declined. Moreover, there were critical pH values at both extremes (3.0 on the acidic side and 8.0 to 8.5 on the alkaline side), beyond which most of microorganisms could never survive.The effect of pH on Cmic and Pmic was also related to the original soil pH. The higher the original soil pH was, the less Cmic or Pmic were affected by pH change. It is suggested that soil microorganisms that grow in a soil environment with a more neutral soil pH range (I.e. pH 5.5-7.5) may have a greater tolerance to pH changes than those growing in more acidic or more alkaline soil pH conditions.

Ecological and Economic Benefits of Vegetation Management Measures in Citrus Orchards on Red Soils

A three-year experiment was conducted to investigate and compare the economic and ecological benefits of six types of vegetation management measures in citrus orchards of the hilly red soil region of the eastern part of China.Six vegetation treatments,including tillage without herbicide(clean tillage)and no tillage without herbicide(sod culture) and with herbicide paraquat(paraquat),glyphosate(glyphosate),glyphosate-glyphosate-paraquat(G-G-P),and paraquat- paraquat-glyphosate(P-P-G),were applied in the citrus orchards on a clayey red soil with slopes of 8°and 13°and a sandy soil with slope of 25°.The results showed that the sod culture,paraquat,glyphosate,G-G-P,and P-P-G treatments reduced surface runoff by 38.8%,42.5%,18.7%,28.7%,and 37.5%,then the soil-water losses by 55.5%,51.7%,39.9%,46.8%, and 50.0%,and the N,P,and K nutrient losses by 60.3%,50.2%,37.0%,41.8%,and 45.4%,respectively,as compared with the clean tillage treatment.The weed regeneration ratios with the treatments of clean tillage without herbicide,paraquat, glyphosate,G-G-P,and P-P-G were reduced by 55.1%,67.2%,30.3%,36.8%,and 51.2%,respectively,as compared with the sod culture.The sod culture,paraquat,glyphosate,G-G-P,and P-P-G treatments could increase the soil fertility (annual accumulation of N,P,K,and OM)by 7.1%,6.9%,5.3%,6.2%,and 6.6%,respectively,whereas the clean tillage treatment without herbicide reduced soil fertility by 4.4% after the three-year experiment.The citrus fruit yields in the treatments of paraquat,glyphosate,G-G-P,and P-P-G increased by 7%-10%;the soluble solid,total sugar,total acidity,sugar-acid ratio,and single fruit weight of citrus fruits of all treatments except sod culture significantly(P>0.05) exceeded that of the clean tillage treatment.In general,the paraquat treatment showed the best economic and ecological benefits among the six treatments;therefore,it could be regarded as the best available vegetation management measure in citrus orchards of hilly red soil region to retain water and soil,enhance soil fertility,and improve the yield and quality of citrus.

GIS-Based Red Soil Resources Classification andEvaluation

A small scale red soil resources information system (RSRIS) with applied mathematical models wasdeveloped and applied in red soil resources (RSR) classification and evaluation, taking Zhejiang Province,a typical distribution area of red soil, as the study area. Computer-aided overlay was conducted to classifyRSR types. The evaluation was carried out by using three methods, i.e., index summation, square root ofindex multiplication and fuzzy comprehensive assessment, with almost identical results. The result of indexsummation could represent the basic qualitative condition of RSR, that of square root of index multiplicationreflected the real condition of RSR qualitative rank, while fuzzy comprehensive assessment could satisfactorilyhandle the relationship between the evaluation factors and the qualitative rank of RSR, and therefore it is afeasible method for RSR evaluation.

Cow manure and cow manure-derived biochar application as a soil amendment for reducing cadmium availability and accumulation by Brassica chinensis L. in acidic red soil

Organic amendment is a promising,in situ phytostabilization approach to alleviate the phytotoxic effects of heavy metal contaminated soils.The aim of this study was to evaluate the feasibility of cow manure（CM）and its derived biochar（CMB）as a soil amendment on cadmium（Cd）availability and accumulation in low and high Cd-accumulating cultivars of Brassica chinensis L.grown in an acidic red soil.CM and CMB were applied to Cd-contaminated acidic red soil at the rates of 0,3.0and 6.0%（w/w）.Application of CMB was significantly more effective than that of CM,as it reduced the availability of Cd in soil by 34.3–69.9%and its bioaccumulation in the low Cd accumulator,Aijiaoheiye 333,by 51.2 and 67.4%,respectively.The addition of CMB significantly increased the extractability and accumulation of trace metals（Zn,Mn,Fe,and Cu）by plants and improved plant biomass production.CMB application,combined with utilizing low Cd accumulating cultivars represents a new,sustainable strategy to alleviate the toxic effects on Cd and improve food safety.

Effect of Plant Roots on Penetrability and Anti-Scouri-bility of Red Soil Derived from Granite

Distribution of plant roots in a red soil derived from granite was investigated to study the effect of plantroots on intensifying soil penetrability and anti-scouribility by the double-cutting-ring and the undisturbedsoil-flume methods, respectively. The plant roots system consisting mostly of fibrils, < 1 mm in diameter,was mainly distributed in the upper surface soil 30 cm in depth. It can remarhably increase the penetrabilityand anti-scouribility of the red soil derived from granite. When the root density was > 0.35 root cm-2, theintensifying effect of roots on both the penetrability and the anti-scouribility could be described by exponentequations, △ Ks = 0.0021RD1.4826 (R2 = 0.9313) and △ As = 0.0003RD1.8478 (R2 = O.9619), where △ Ks isthe value of intensified soil penetrability, a As the value of intensified soil anti-scouribility and RD the rootdensity, especially in the top soils within 30 cm in depth where plant roots were conceotrated.

Leaching and Redistribution of Nutrients in Surface Layer of Red Soils in Southeast China

The leaching and redistribution of nutrients in the surface layer of 4 types of red soils in SoutheastChina were studied with a lysimeter experiment under field conditions. Results showed that the leachingconcentrated in the rainy season (from April to June). Generaily, the leaching of soil nutrients from thesurface layer of red soils was in the order of Ca > Mg > K > NO3-N. In fertilization treatment, the totalamount of soil nutrients leached out of the surface layer in a red soil derived from granite was the highest inall soils. The uptake by grass decreased the leaching of fertilizer ions in surface layer, particularly for NO3-N.Soil total N and exchangeable K, Ca and Mg in the surface layer decreased with leaching and grass uptakeduring the 2 years without new fertilization of urea, Ca(H2PO4)2, KCl, CaCO3 and MgCO3. Ca movedfrom the application layer (0~5 cm) of fertilizer and accumulated in the 10~30 cm depth in the soils studiedexcept that derived from Quaternary red clay. The deficiency of soil exchangeable K will become a seriousdegradation process facing the Southeast China.

Sustainable Agriculture Evaluation for Red Soil Hill Region of Southeast China

Agricultural sustainability for economic development is important and a complex issue throughout the world; however,it is difficult to synthetically evaluate its use in the policy making process. The objective of this study was to evaluate sustainable agriculture in the red soil hill region of Southeast China through a newly proposed method combining four separate sub-systems: regional population (P), resource (R), environmental (E), and socio-economic (S). This new index system was proposed to appraise synthetically the agricultural sustainability of the red soil hill region from 1988 to 1996 with a two-step method assessing: a) the agricultural sustainability in each province independently and b) the relative sustainability of each province to the whole region. The first step only provided a development trend for each province based on its original situation, while the second step provided additional information on the comparative status of each province in agricultural development to the region as a whole. Higher index scores were found for the economy and resource categories denoting improvement. However, lower scores in the environment category indicated the improvement was achieved at the cost of deteriorating ecological surroundings due to an increasing population that demanded more from the agro-ecosystem and put heavier pressures on it. Results also showed that water and soil losses in this region were the major obstacles encountered in sustainable agriculture development. The assessment results were verified when compared with results from another method. This suggested that the new assessment system was reliable and credible in evaluating agricultural sustainability on a regional scale.