Evaluation of Trace Elements in the Soil of Typical Peach Orchards in Zunyi City

[Objectives]This study was conducted to clarify the enrichment and paucity of trace elements in the soil environment of peach orchards in Zunyi City,and to provide reference for supplementary application of microelement fertilizers and high-quality peach production in peach orchards.[Methods]Taking the soil of three typical peach orchards(Taoli Renjia peach orchard,Pengrui peach orchard and Taohuadao peach orchard)in Shenxi Town,Honghuagang District,Zunyi City as the research object,the contents of trace elements in soil were analyzed through field sampling and indoor determination of trace elements.[Results]The effective contents of trace elements in the soil of peach orchard bases in the study area were at a medium level,and the soil of the peach orchards was rich in available Fe and Se.The contents of available Cu,Mo and Mn were relatively rich.The contents of available B were not high overall.The contents of available Zn were at a moderate to low level overall.The soil of Taoli Renjia peach orchard was relatively rich in trace elements.[Conclusions]The research results can provide a scientific basis for the production of high-quality crispy peaches in peach orchards.

Bioremediation of Soil Pollution in Orchard

[ Objective ] The aim was to study the bioremediation mechanism of soil pollution. [ Method ] The effects of applying biological organic fertilizers on the bioremediation of soil pollution in orchard were studid by experiment in orchard field and soil simulative experiment. [ Result] The biological organic fertilizers improved the activities of enzymes like polyphenol oxidase, urease, phosphatase, etc. in root-zone soil, promoted the passivation of heavy metals like Cd^2＋ , Pb^2＋ , Cr^3＋ , As^8＋ , etc. in root-zone soil, increased the quantities of useful active bacterium like beneficial fungi, actinomycetes, bacterium, etc. and decreased the quantities of harmful biology （like Fusarium oxysporum, Moniliophthora roreri, Ruselliniu necutrix/Helicobasidium mompa, nematode, etc. [ Conclusion] The study results provide some references for the popularization and application of biological organic fertilizers on fruit trees.

Nitrification and Denitrification Activities and N_2O Emission of Orchard Soils Cultivated for Different Periods of Time

[Objective] The aim was to investigate the differences in nitrification and denitrification activities and the N20 emission of orchard soils cultivated for different periods of time. [Method] Incubation experiment was conducted to determine the ni- trification and denitrification activities and N20 emission of three types of orchard soil samples that had been cultivated for 5, 12 and 20 years, respectively, by using the virgin soil sample as control. [Result] After 26 d of incubation, the nitrification rates of nitrogen fertilizer in the virgin soil sample and the orchard soil samples cultivated for 5, 12 and 20 years were 6.85%, 10.26%, 13.29% and 12.90%, respectively, which were positively correlated with content of soil organic matter, ammonium nitro- gen and total nitrogen （P〈0.05）, and negatively correlated with soil carbon-nitrogen ratio and pH value （P〈0.05）. The denitrification activities of these soil samples in- creased with the increase of cultivation years. The amount of nitrogen loss by deni- trification accounted for 0.01%-3.11% of the amount of fertilizer nitrogen, and had a positive correlation with the content of soil organic matter （P〈0.05）. The N20 emis- sions of orchard soil samples were higher than that of the virgin soil samples （P〈 0.05）. [Conclusion] In South China, the nitrification activity of orchard soil is relatively low, but it has a tendency to increase as the cultivation years increases; the denitri- fication activity is relatively high, and increases significantly with the increase of culti- vation years.

Variation of Potential Nitrification and Ammonia-Oxidizing Bacterial Community with Plant-Growing Period in Apple Orchard Soil

In this study, we investigated the potential nitrification and community structure of soil-based ammonia-oxidizing bacteria （AOB） in apple orchard soil during different growth periods and explored the effects of environmental factors on nitrification activity and AOB community composition in the soil of a Hanfu apple orchard, using a culture-dependent technique and denaturing gradient gel electrophoresis （DGGE）. We observed that nitrification activity and AOB abundance were the highest in November, lower in May, and the lowest in July. The results of statistical analysis indicated that total nitrogen （N） content, NH4＋-N content, NO3-N content, and pH showed significant correlations with AOB abundance and nitrification activity in soil. The Shannon-Winner diversity, as well as species richness and evenness indices （determined by PCR-DGGE banding patterns） in soil samples were the highest in September, but the lowest in July, when compared to additional sampled dates. The DGGE fingerprints of soil-based 16S rRNA genes in November were apparently distinct from those observed in May, July, and September, possessing the lowest species richness indices and the highest dominance indices among all four growth periods. Fourteen DGGE bands were excised for sequencing. The resulting analysis indicated that all AOB communities belonged to the 13-Proteobacteria phylum, with the dominant AOB showing high similarity to the Nitrosospira genus. Therefore, soil-based environmental factors, such as pH variation and content of NHa＋-N and NO3--N, can substantially influence the abundance of AOB communities in soil, and play a critical role in soil-based nitrification kinetics.

Micronutrient Contents of Citrus Orchard Soils in Southern China

Investigations were carried out on the micronutrient contents,of major citrus orchard soils (involving seven soil great groups in 8 provinces and an autonomous region of southern China),and an evaluation on the abundance and deficiency of available micronutrients in these soils was made in this paper.In southern China,citrus orchard soils derived from sandstone,sandy shale,Quaternary red clay,diluvial deposit,granite gneiss and neritic deposit were deficient in available Mo and B and low in Zn.Those developed on purple sandy shale,limestone and slope deposit were all in short supply of available Zn,B and Mo.Coastal solonchak was fairly abundant in B,but its available Fe,Zn and Mo contents were rather low.

Soil Micronutrients and Citrus Growth

By using nutritional diagnosis of citrus leaves and determining soil micronutrients,the relationship between soil micronutrients and citrus growth in southern China has been studied.Studies showed that there was a significant positive correlation between available micronutrients (such as Zn,Mo,Cu)in the soil and the corresponding nutrients in citrus leaves.Thus,one can roughly learn of the sufficiency or deficiency of certain nutrients in soils by analyzing citrus leaves.Rational spray of Zn B or Mo fertilizer not only improved citrus yields but also increased the total sugar of Satsuma mandarin and of Xinhui orange by 2.9 and 17.2% respectively compared with the control.Spraying Mo fertilizer increased the vitamin C content of Satsuma mandarin juice by 4.7%-8.4%,maturated fruits 7-10 days earlier and gave the peel a brighter color.The ultramicroscopic characteristics of Zn-deficient citrus leaves were investigated under an electron microscope.Results showed that the Zn-deficient leaf cell was characterized mainly by poor cytoplasm,endoplasmic reticula and ribosomes and by big starch grains in the chloroplast.As a result of spraying Zn fertilizer the structure of the cell returned to normal,the cytoplasm became rich and the amount of chloroplast increased.There also appeared a great deal of multiform endoplasmic reticula,thus promoting the photosynthesis of Zn-deficient plants.This provides a cytologico-theoretical basis for fertilization of high-yielding citrus trees.

The Changing Characteristics of Profile Distribution of Organic Nitrogen Components in Apple-pear Orchard Soil

In order to evaluate the effects of soil depth on the contents of soil organic nitrogen,organic nitrogen forms in apple-pear orchard soil profile were quantified using the method proposed by Bremner in 1965.The results indicated that in addition to the amino sugar-N,all the soil organic N components within the same soil layer in wasteland were more than those in apple-pear orchard soil;with the layer depth increasing,the contents of different organic nitrogen forms in apple-pear orchard soil and wasteland were decreased;and the proportion of each organic N component within total hydrolysable N was different,and the percentages of ammonia N and amino acid-N components within total hydrolysable N were higher,especially the percentage of ammonia N components within total hydrolysable N was the highest.

Free Cu^(2+) Ions,Cu Fractionation and Microbial Parameters in Soils from Apple Orchards Following Long-Term Application of Copper Fungicides

Soil samples were collected from apple orchards 5,15,20,30,and 45 years old,and one adjacent forest soil was used as reference to investigate the free Cu2+ion activity in soil solution and the soil Cu fractionation in the solid phase following long-term application of copper fungicide,Bordeaux mixture,in apple orchards and to investigate the relationships among soil free Cu2+ions,Cu fractionation and soil microbial parameters.The total Cu concentration in the orchard soils varied from 21.8 to 141 mg kg-1,increasing with the orchard age,and the value for the reference soil was 12.5 mg kg-1.The free Cu2+ion concentrations in the soil solutions extracted by 0.01 mol L-1 KNO3 ranged from 3.13×10-8(reference)to 4.08×10-6 mol L-1(45 years-old orchard).The concentration of Cu complexed in the fulvic fraction increased with orchard age from 5.16 to 52.5 mg kg-1.This was also the case for other soil Cu fractions except the residual one.The residual soil Cu remained practically constant,ranging from 4.28 to 5.66 mg kg-1,suggesting that anthropogenic soil Cu mainly existed in the more labile active fractions.Regression analyses revealed that both the free Cu2+ions in the soil solution and the humic acid-complexed Cu fraction in the solid phase were strongly related with soil microbial parameters.

Effect of lime application on microbial community in acidic tea orchard soils in comparison with those in wasteland and forest soils

Lime application is a conventional technology to control acidification in tea orchard soils. We investigated the effect of lime application on soil microbial community diversity in the soils of three tea orchards, wasteland and forest. The BIOLOG data showed that both the average well color development of all carbon sources and the functional diversity index increased with the liming rate in the tea orchards and the forest, but decreased in the wasteland. The phospholipid fatty acid （PLFA） analysis showed that the structural diversity index of soil microbial community increased with the liming rate in all the tea orchards, the wasteland and the forest. Lime application also increased the soil-bacterial PLFA content in all the soils. Soil fungal and actinomycete PLFAs in the tea orchards showed an increasing trend from 0 to 3.2 g CaCO 3 /kg application and then a decreasing trend from 3.2 to 6.4 g CaCO 3 /kg application. The principal component analysis of BIOLOG and PLFA data suggested that lime application had a significant effect on soil microbial community structure, and land use had a greater effect on soil microbial community structure compared to lime application.

Effect of orchard age on soil nitrogen transformation in subtropical China and implications

A better understanding of nitrogen transformation in soils could reveal the capacity for biological inorganic N supply and improve the efficiency of N fertilizers. In this study, a15 N tracing study was carried out to investigate the effects of converting woodland to orchard, and orchard age on the gross rates of N transformation occurring simultaneously in subtropical soils in Eastern China. The results showed that inorganic N supply rate was remained constant with soil organic C and N contents increased after converting woodland into citrus orchard and with increasing orchard age. This phenomenon was most probably due to the increase in the turnover time of recalcitrant organic-N, which increased with decreasing soil p H along with increasing orchard age significantly. The amo A gene copy numbers of both archaeal and bacterial were stimulated by orchard planting and increased with increasing orchard age. The nitrification capacity（defined as the ratio of gross rate of nitrification to total gross rate of mineralization） increased following the Michaelis–Menten equation, sharply in the first 10 years after woodland conversion to orchard, and increased continuously but much more slowly till 30 years. Due to the increase in nitrification capacity and unchanged NO3-consumption, the dominance of ammonium in inorganic N in woodland soil was shifted to nitrate dominance in orchard soils. These results indicated that the risk of NO3-loss was expected to increase and the amount of N needed from fertilizers for fruit growth did not change although soil organic N accumulated with orchard age.

Spatial interpolation of orchard soil pH using soil type and planting duration as auxiliary information

Intensified field management in orcahrds has resulted in significant and widespread acidification in the soils.However,effectively mapping the spatial patterns of soil pH aiming to support ecological management is impeded by its large variotions across soil types and planting durations.Kriging methods were used to integrate soil type and planting duration information for effective mapping of orchard soil pH in a case study in orchards of the Northeast Jiaodong Peninsula,East China.A total o f 1472 surface soil samples were collected,and the planting duration o f each sampled orchard was acquired to generate a planting duration map via Voronoi tessellations.The performance of five kriging methods was compared,namely,ordinary kriging(OK),OK combined with soil type(OK_ST),OK combined with planting duration(OK_PD),cokriging combined with soil type and planting duration(OCK_STPD),and OK combined with soil type and planting duration(OK_STPD).Results showed that soil pH declined significantly with increasing planting duration and exhibited moderate spatial variability over the study area.Soil type and planting duration both had significant influence on the spatial distribution of soil pH.The OCK_STPD and OK_STPD methods showed better prediction efficiency than OK,OK_ST,or OK_PD.With regard to the predicted maps of soil pH,the OCK_STPD and OK_STPD methods highly reflected local variations associated with soil type and planting duration,but the OK method was poorly representative.Categorical soil type and planting duration information may be used as ancillary information to improve the mapping quality o f orchard soil pH.The OCK_STPD and OK_STPD methods were practical and efficient methods for interpolating orchard soil pH in the study area.The resultant high-quality soil pH maps can contribute to improved site-specific management in the orchards.