| In this paper, we choosed the peanut as the research object to comprehensively study the effect of different planting years on agronomic characters and yields, photosynthetic and nutrition characteristic, dry matter accumulation and distribution, soil nutrient content in field conditions. Effect of different planting years on the microbial populations of rhizosphere and bulk soil were tracking studied with the pot experiments, traditional flat training and modem molecular biology technology, meanwile, the effect of different planting years on the soil enzymes were explored for the first time. The change rule of defense enzyme activity and MDA content under continuous cropping were systematically researched. Allelopathic effects of peanut plant and soil extracts on the its seed germination, plants growth were studied with the pot experiments and biological testing. Phenolic acid contents in peanuts rhizosphere soil of different planting years were targetedly detected which using the HPLC. The major findings are as follows:1. The plant height, chlorophyll relative content, Pn, Gs and Ci had been declined with the increasing length of continuous cropping system. The pods and nuts weight reached lowest at planting four years, and the yields reached lowest at planting three years. Continuous cropping influenced on the chlorophyll relative content and this influence of most evident when at matrrity. Leaf area did not show trend to decrese, but reached lowest at planting three years.When blossom stage in peanut stem and leaf, the P, K content had been reduced chage trend with the increasing length of continuous cropping system, N content changes not rule. When maturing stage in fruit, the N, P, K content were significantly the trend which reduce first and rise again.The content of medium elements at blossom stage presented certain change trend with the increasing length of continuous cropping system. Except Cu, the others had no significant differences among four treatments. Among them, the change laws of Ca, Fe were consistent which the trend had been increased. The change laws of Mg, Zn were consistent which rise first then reduce and rise again. The content of medium elements at pot-setting stage presented certain change too. Except Mg, the others had no significant differences among four treatments. Among them, the change laws of Ca, Mn, Cu were consistent which reduce first then rise and reduce again. The change laws of Mg, Fe were consistent which reduce first and rise again. The content of medium elements at maturing stage presented certain change too. Fe, Cu, Zn content had significant differences among four treatments. Among them, the change laws of Ca, Fe were consistent which the trend had been decreased. The change laws of Zn, Mn were consistent which the trend had been increased.Mo content had significant differences among four treatments at pot-setting stage. The change trend was presented that reduce first then rise and reduce again with the increasing length of continuous cropping system.At blossom and pot-setting stage, the leaf, steam, root, legume and all organs of peanut dry matter accumulation presented the change trend which reduce first and rise again with the increasing length of continuous cropping system, but its presented the change trend which rise first and reduce again at maturing stage. Under the same continuous fixed number of year, the leaf and steam of peanut dry matter accumulation presented the change trend which rise first and reduce again along with the development of growth period, peak appeared in the pot-setting stage. The legume and all organs of peanut dry matter accumulation presented the change trend which increased, peak appeared in the maturing stage.The root proportion of planting two years decreased compared planting one year, but the proportion of steam and leaf increased, and root-shoot ratio decreased at blossom stage. The root proportion of planting three and four years increased compared planting one year, but the proportion of steam and leaf decreased, and root-shoot ratio increased. At pot-setting and maturing stage, the distribution of peanut dry matter in various organs did not change obviously with the increasing length of continuous cropping system, and it would change with the growth center transferring.2. The soil microflora of peanuts significantly changed, the bacteria and actinomycete quantities obviously decreased, the fungi quantities obviously increased with the increasing of the continuous cropping years. The microbial population and variation in rhizosphere soil were significantly higher than bulk soil. Ammonifying bacteria was the predominant population in rhizosphere soil, denitrifying bacteria and aerobic nitrogen-fixing bacteria less than it, and nitrifying bacteria was the leastest. The number of ammonifying bacteria, nitrifying bacteria and aerobic nitrogen-fixing bacteria presented the change trend which decreased with the increasing of the continuous cropping years, however, the number of denitrifying bacteria presented the change trend which increased. Under the same continuous fixed number of year, the bacteria, actinomycete and fungi quantities presented the change trend which rise first and reduce again along with the development of growth period. DGGE showed that there existed some common bacteria groups in soil among four treatments, and also could appear or lack individual bacteria groups. Soil bacteria community structure similarity was highest between the seeding stage and the pot-setting stage of planting one years.3. The soil catalase and alkaline phosphatase activity presented the change trend which decreased with the increasing of the continuous cropping years. The urease and invertase activity presented the change trend which reduce first then rise and reduce again. The acid and neutral phosphatase activity presented the change trend which rise first and reduce again. Under the same continuous fixed number of year, the soil catalase activity presented the change trend which decreased along with the development of growth period, and the urease activity presented the change trend which increased, the invertase activity presented the change trend which reduce first and rise again, the neutral and alkaline phosphatase activity presented the change trend which rise first and reduce again.4. At blossom stage the content of total and available N presented the change trend which rise first then reduce and rise again in 0-20cm with the increasing of the continuous cropping years, it presented the change trend which rise first and reduce again at pot-setting stage. At blossom and pot-setting stage, the content of total K presented the change trend which reduce first and rise again in two soil strata, the content of available K presented the change trend which rise first and reduce again. At blossom stage, the content of total P presented the change trend which rise first and reduce again in two soil strata. At pot-setting stage, it presented the change trend which reduce first then rise and reduce again. At blossom and pot-setting stage, the available P presented the change trend which rise first and reduce again in 0-20cm, and it presented the change trend which reduce first then rise and reduce again in 20-40cm.At blossom and pot-setting stage, the change laws of Fe, Cu, Zn were consistent and presented the change trend which reduce first and rise again in 0-20cm with the increasing of the continuous cropping years. The change laws of Ca, Mg, Mn were consistent and presented the change trend which rise first then reduce and rise again. At blossom stage, the content of B presented the change trend which rise first and reduce again at every soil strata with the increasing of the continuous cropping years, but the change rule were different in two soil strata at pot-setting stage. It presented the change trend which rise first and reduce again in 20-40cm, and presented the change trend which reduce first and rise again in 0-20cm.5. The CAT activity of peanut leaf presented the change trend which decreased, and PPO, POD, SOD activity and MDA content presented the change trend which increased with the increasing of the continuous cropping years. The PAL activity changed not regularly. Under the same continuous fixed number of year, the CAT and POD activity presented the change trend which rise first and reduce again along with the development of growth period, the SOD activity presented the change trend which reduce first and rise again. The PPO activity of planting one year presented the change trend which rise first and reduce again, and the PPO activity of planting three years presented the change trend which rise first then reduce and rise again. The PAL activity of planting one year presented the change trend which increased, and the PAL activity of planting three years presented the change trend which rise first then reduce and rise again. As a whole, the MDA content presented the change trend which increased, but there change trend was somewhat different in two treatments. The MDA content presented the change trend which greatly increased from seedling to blossom stage, and declined at pot-setting stage, increased and achieved peak at maturing stage in planting one year. It presented the change trend which gradually increased in planting three years along with the development of growth period, peak appeared in the maturing stage.6. Different concentrations of peanut soil, steam and leaf extracts could cause the inhibition of seed germination and seedling growth of peanut. Its inhibition intensity with the increase of extracts concentration enhanced. The order of inhibition of seeds germination was: steam>leaf>soil; the order of inhibition of seedling was:steam, soil>leaf. The inhibition of seeds germination was greater than of seedling.Two kinds of phenolic acids material were detected from all treatments which were vanillic acid and coumarin, and its content both presented accumulation of trend with the increasing of the continuous cropping years. The content of vanillic acid was significantly higer than the coumarin in soil. The total content of two kinds of phenolic acids material were 0.314μg.g-1dry soil in planting six years, which higher than the total content in planting two and four years, and significantly higer than its in planting one year. |
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