| Greenhouse vegetable production, marked by rapid development and high economic benefit, has become the pillar industry for promoting peasants to increase income in many places in China. However, excessive fertilizer input and unbalanced fertilization are common in the process of greenhouse vegetable production in China. The consequent secondary salinization, the fertility degradation and the heavy mental pollution in greenhouse vegetable soils have threatened the safety of vegetable products and decreased the profit of vegetable production. Soil microorganisms play an important role in the cycling processes of many fundamental nutrients, such as carbon and nitrogen. The characteristics of soil microorganisms are sensitive to soil quality. Many studies have reported the effects of different agronomic measures on soil fertility and health by investigating the microbial characteristics in grain crop soils. Little information is available on the effects of the combined application of different organic materials with chemical fertilizers on the microbial characteristics in greenhouse vegetable soil. A fixed-site greenhouse vegetable fertilization experiment has been carried out to study the effect of different combining models of chemical fertilizers and organic materials in Xiqing District, Tianjin City. In the experiment there are eight treatments depending on the proportion of nitrogen from each type of fertilizers:(1) No nitrogen input(No nitrogen);(2) Complete chemical nitrogen fertilizer(4/4CN);(3) 3/4 N from chemical fertilizer, 1/4 N from pig manure(3/4CN+1/4PN);(4) 2/4 N from chemical fertilizer, 2/4 N from pig manure(2/4CN+2/4PN);(5) 1/4 N from chemical fertilizer, 3/4 N from pig manure(1/4CN+3/4PN);(6) 2/4 N from chemical fertilizer, 1/4 N from pig manure and 1/4 N from straw(2/4CN+1/4PN+1/4SN);(7) 2/4 N from chemical fertilizer, 2/4 N from straw(2/4CN+2/4SN); and(8) Conventional fertilization(CF). Soil samples were collected at different growth stages of the ninth-season vegetable(autumn-winter season celery) and the tenth-season vegetable(spring season tomato). The contents of microbial biomass carbon(MBC) and microbial biomass nitrogen(MBN), the enzymes activities and microbial community structure in greenhouse vegetable soil were measured to provide a scientific fertilization basis for sustainable and high-efficient greenhouse vegetable production. The main results obtained are summarized as follows:1. The combined application of chemical fertilizer with organic materials, especially corn straw were effective in increasing the microbial biomass carbon and nitrogen contentsSoil MBC and MBN contents in all the treatments in both the two tested vegetables growth period increased first and then decreased with the elongation of growth period. The relatively higher soil MBC and MBN contents appeared at 90 and 60 days after transplanting of celery, and 20-80 days for soil MBC and 60 days for soil MBN after the transplanting of tomato. In the celery season when it was in autumn-winter, the soil MBC and MBN contents were respectively 185.0~514.6 and 34.3~79.1 mg/kg, with increase of 15.1%~81.7% and 24.5%~100.0% in treatments of combined application of manure and/or straw with chemical fertilizers, compared with the 4/4CN treatment, and the highest increases for the contents of MBC and MBN in straw-amended treatments were 62.0%~81.7% and 81.1%~100.0%,respectively; In the tomato season when it was in spring, the soil MBC and MBN contents in the treatments with combined application of manure and/or straw with chemical fertilizers were respectively 120.7~338.0 and 25.5~68.8 mg/kg, with increases of 16.9%~86.9% and 12.2%~109.3%, compared with the 4/4CN treatment, and the highest increase values in straw-amended treatments were 61.4%~86.9% and 78.2%~109.3%, respectively.2. The soil enzymes activities were significantly enhanced with the combined application of chemical fertilizer with organic materials, especially corn strawThe activities of soil α-glucosidase, β-xylosidase, β-glucosidase, β-cellobiosidase and chitinase in all the treatments showed the same variation trend of increasing first and then decreasing during the growth period of vegetables, with relatively higher activity values appearing at 60~90 days after transplanting of celery and 60 days after transplanting of tomato, respectively. Soil phosphatase activities also tended to increase first and then decrease during growth period of celery and tomato, but the relatively higher activity values appeared at 60 days after transplanting of celery and 100 days after transplanting of tomato, respectively. Soil urease activities increased gradually in the celery season, but in the tomato season it increased first and then remained relatively constant, with relatively higher activity values at 60~120 days after transplanting of tomato. In the celery season, activities of soil α-glucosidase, β-xylosidase, β-glucosidase, β-cellobiosidase, chitinase, phosphatase and urease respectively increased by 22.9%~92.0%, 20.1%~152.4%, 23.1%~145.1%, 28.7%~273.8%, 9.2%~207.8%, 13.7%~86.8% and 6.5%~56.5% in treatments with combined application of manure and/or straw with chemical fertilizers, compared with the 4/4CN treatment, and the highest increases for soil α-glucosidase, β-xylosidase, β-glucosidase, β-cellobiosidase, chitinase, phosphatase and urease activities in straw-amended treatments were 59.9%~92.0%, 98.9%~152.4%, 90.3%~145.1%, 171.6%~273.8%, 106.4%~207.8%, 68.8%~86.8% and 30.7%~56.5%, respectively. In the tomato season activities of soil α-glucosidase, β-xylosidase, β-glucosidase, β-cellobiosidase, chitinase, phosphatase and urease respectively increased by 4.1%~83.4%, 7.3%~155.7%, 20.0%~ 128.3%, 23.5%~242.6%, 22.4%~248.9%, 16.2%~78.9% and 7.4%~58.0% in treatments of combined application of manure and/or straw with chemical fertilizers, compared with the 4/4CN treatment, and the highest increases for soil α-glucosidase, β-xylosidase, β-glucosidase, β-cellobiosidase, chitinase, phosphatase and urease activities in straw-amended treatments were 51.1%~83.4%, 106.5%~155.7%, 98.8%~128.3%, 186.9%~242.6%, 178.3%~248.9%, 60.5%~78.9% and 41.8%~58.0%, respectively.3. Soil total PLFA(Phospholipid Fatty Acid) contents, and contents of bacteria PLFA, fungi PLFA and actinomyces PLFA were increased by the combined application of chemical fertilizer with organic materials, especially corn strawThe total phospholipid fatty acid contents(PLFA) in treatments of combined application of manure and/or straw with chemical fertilizers were 20.5~31.2 nmol/g at the harvest stage of celery and 14.9~26.3 nmol/g at the vine removed stage of tomato. Compared with the 4/4CN treatment, the increases in the PLFA at harvest stage of celery and the vine removed stage of tomato were 34.7%~105.5% and 15.9%~103.9% in all the combined application treatments, however, those were much higher in the straw-amended treatments with values of 100.9%~105.5% and 44.0%~103.9%, respectively. In the celery season, the molar percent contents of bacteria, fungi and actinomyces PLFA were respectively 26.2~35.5, 2.60~4.09 and 9.35~13.43, with increase of 8.8%~47.4%, 20.5%~85.5% and 19.1%~77.1% in all the combined application treatments, compared with the 4/4CN treatment, and those in the straw-amended treatments were as high as 32.9%~47.4%, 71.1%~85.5% and 44.1%~71.1%, respectively. In the tomato season, the molar percent contents of bacteria, fungi and actinomyces PLFA were respectively 24.4~30.1, 1.36~2.33 and 7.36~10.29, with increase of 23.5%~52.1%, 5.4%~80.5% and 27.8%~78.6% in all the combined application treatments, and much higher increase of 45.5%~52.1%, 62.3%~80.5% and 64.1%~78.6% in straw-amended treatments, respectively.4. Close positive correlations existed among the soil microbial biomass C and N contents, the activities of soil enzymes, and total PLFA contents and contents of bacteria PLFA, fungi PLFA and actinomyces PLFA. Comprehensively considering the fertilizing soil and high yield effect, the combination application of straw, pig manure and chemical fertilizer(2/4CN+1/4PN+1/4SN)was superior to other combination patternsSignificant and positive correlations were observed among the contents of soil MBC, MBN and the contents of DOC(Dissolved Organic Carbon), DON(Dissolved Organic Nitrogen), and distinct and positive correlations were found between the soil MBC, MBN contents and the corresponding vegetable yield of current season and total yield since the start of the experiment. High soil enzyme activities were significantly and positively correlated with contents of MBC, MBN, DOC and DON during the whole growing season. Higher MBC, MBN supplies brought by the input of straw led to higher population of microorganisms, which benefited the healthy environment of vegetable soils. Comprehensively considering the favorable effects of the 5 fertilization patterns on improving the microbial characteristics of soils and the yield requirement for nutrition, combination of 2/4 chemical N plus 1/4 manure N plus 1/4 corn straw N showed priority in the practical vegetable production in greenhouse. |
PDF Full Text Request