|Alternative Title||Responses and mechanisms of rhizospheric nutrients and microbial activity to different water supply patterns in early growth stage of wheat|
|Place of Conferral||兰州|
|Keyword||壤水分 小麦 根际 微生物 养分有效性|
1.在10%、20%、30%、40%和50%（最适水分含量）田间持水量（WHC）盆栽土壤中分别种植小麦和未种植小麦，4周后，移除植物获根际土壤和非根际土壤,各设置保持在原水分梯度和均复水至50%WHC两个处理,暗室培养，在5d、10d和20d测定土壤微生物碳、氮、磷（MBC、MBN、MBP），有效氮、磷（AN和AP）和水溶性碳（WEOC）。结果表明，在10-20%WHC处理中，小麦地下生物量高于地上生物量，而在30-50%WHC处理中，地上生物量高于地下生物量。原水分土壤中，累计土壤呼吸、MBC和MBN随水分梯度降低而降低。30-50%WHC处理中，根际土壤累积土壤呼吸、MBC和MBN高于非根际土壤。根际土壤中AN含量随土壤水分降低而增高。在30-50%WHC处理中，非根际土壤AN含量较高且是根际土壤的3倍。复水提高了原水分在10-20%WHC处理的土壤呼吸和MBN。根际土壤中，50%WHC处理累积呼吸、MBC和MBN始终高于10%WHC处理。持续性干旱对根际土壤土壤微生物量、活性和有效养分含量的影响高于非根际。干旱胁迫降低了土壤养分有效性，导致植物生长受到抑制，植物的缓慢生长加剧了水分胁迫对微生物的影响。2.在20%WHC土壤中种植小麦1周，在之后的3周生长中，以1周为一个周期设置干旱期（20%WHC）和湿润期（50%WHC）随机排列组合，并以在50%WHC和20%WHC处理作为对照。结果表明，50%WHC处理下小麦地上、地下生物量、MBC和WEOC最高，但土壤AN和AP含量最低。含2个干旱期组合处理中，第二和第三周为湿润期时，小麦生物量、土壤MBC高于其他处理。含3个干旱期组合中各处理间植物生物量、微生物量和AN含量没有差异。早期干旱会降低植物对AP的吸收。说明小麦生长和土壤微生物对连续干旱更为敏感。3.补缺量模式中，在50%WHC土壤中种植小麦，生长4d后实施以4d为一个循环的3个不同的灌溉补水频率处理。处理1（1TW）：在每个循环的1d补水至50%WHC；处理2（2TW）: 每个循环的1、3d补水上一个循环失水量的50%；处理3（4TW）: 每天补水上个循环失水量的25%。补齐模式中，在50%WHC土壤中种植小麦，每当土壤水分降低到40%、30%、20%和10%WHC时，将土壤水分恢复至50%WHC。结果表明，补缺量模式中，生长24d后小麦生物量在4TW最高，而MBC含量在2TW最高，且生物量和MBC都在1TW处理最低。在4WT处理下土壤NO3-含量比在1TW和2TW处理下低30%。补齐模式中，小麦生物量和MBC随补水时土壤水分降低而降低。WEOC含量在40%WHC处理达到最大。土壤AN含量和AP含量在10%WHC补水处理中最高，在40%WHC处理下最低。NO3-含量随补水时土壤水分含量升高而降低。植物生物量比土壤微生物量对干旱胁迫更为敏感。4.在土壤水分为50%WHC条件下种植小麦4周后，收获根际和非根际土壤。将土壤水分调至50%、40%、30%、20%和10%WHC后置于暗室培养。连续测定25d土壤呼吸，并在5，10和25 d测定根际和非根际土壤MBC、MBN、MBP和AN、AP。结果表明，根际累计土壤呼吸是非根际土壤呼吸的2倍且随着土壤水分降低而降低。根际土壤中，10%WHC处理MBC含量高于50%WHC，二者的差异随时间的增加逐渐减小。MBN含量在20-50%WHC处理比10%WHC高2倍。根际土壤WEOC含量高于非根际土壤，二者之间差异随土壤水分升高而增加。根际土壤养分有效性较高，土壤水分降低对根际土壤的影响小于非根际土壤。根际土壤微生物抵御干旱能力较强且依然保持较高的活性。
As one of the most widely cultivated crop in the world, wheat has a sown area of about 220 million ha and wheat-forage rotation is also a common mode in food and grass coupling system. Drought is the most common problem in the growth of wheat, especially water stress in early growing stage will induce a series of negative effects on the later growth stage which may affect grain yield eventually. However, the mechanism of wheat and rhizosphere microbe responses to water stress is still not clear. In this research, different water gradient, dry-rewetting and watering regimes were applied during the early growing stage of wheat to study the effect of water stress on rhizosphere nutrition condition and microbial biomass and activity. Then, the response of wheat induced nutrient to water gradient was also well studied. We got the following results through the measurement of wheat biomass, microbial biomass, soil respiration and soil available nutrient:
1.Wheat was planted in pots with 10%、20%、30%、40% and 50% water holding capacity (WHC) to obtain rhizosphere soil. Pots with the same water treatments and no wheat planted were set as non-rhizosphere soil. After four weeks, plants were removed and soils were kept at the same water content as in the pots (original) or rewetted to 50% WHC (rewet). Then, soil respiration was measured continuously for 20 days, AN and AP and MBC, MBN and MBP were measured on days 5, 10 and 20. Root biomass was higher than shoot biomass at 10-20% WHC while shoot biomass was higher at 30-50% WHC. In original soil, cumulative respiration, MBC and MBN decreased with water content in planted soil and were higher in planted than unplanted soil only at 30-50% WHC. AN was up to 3-fold higher in un-planted than planted soil at 30-50% WHC. Only in planted soil, AN increased with decreasing water content. Rewetting increased cumulative respiration and MBN only in soil that had been at 10-20% WHC. In planted soil, cumulative respiration, MBC and MBN remained lower in soil that was at 10% WHC previously compared to that at 50% WHC. Consistent dry had a higher influence on rhizosphere soil than non-rhizosphere soil. It is concluded that the effect of low water content on soil microbes is exacerbated by reduced plant growth and the reduced nutrient input.2.Wheat was grown for four weeks with the soil at 20% WHC for the first week. In the following 3 weeks, dry period (20%WHC) and wet period (50%WHC) were randomly set. After four weeks, plant roots and shoots were collected and dry weight measured. AN and AP, WEOC and MBC, MBP were determined to study the effect of length and distribution of a period with low water availability on plant growth, microbial biomass and nutrient availability. The results showed that shoot and root biomass were higher in constantly moist than constantly dry soil, but the reverse was true for AN and AP. The distribution of two-week dry period had significant influence on MBC and AN. The distribution of three-week dry period had significant influence on AP. Plant and microbes were more sensitive to drought that was imposed early during growing stage.3.In loss-replenish model, wheat was grown for four days at 50%WHC, then 4-day cycles with three watering regimes were implemented: in 1TW, pots were watered on day 1 of each cycle adding 100% of water lost over 4 days, pots in 2TW were watered on day 1 and day 3 each time adding 50% of water lost. In 4TW, pots were watered daily, each time receiving 25% of water lost. In refill model, soil was rewetted to 50% WHC when soil water content reached 40%, 30%, 20% and 10% WHC. After 24 days, shoot and root biomass, soil microbial biomass C (MBC), water extractable organic carbon, available N and P were measured. In the first experiment, shoot and root biomass were higher in 4 TW than 1TW and 2TW, whereas MBC in 2TW was higher than 1TW and 4TW. NO3- concentration in 4TW was about 30% lower than 1and 2TW. In Experiment 2, shoot and root biomass and MBC decreased with soil water content at which the pots were watered. Watering treatments had a stronger effect on plant biomass than MBC. Available N and P were highest in the treatment which dried to 10% WHC before watering. NO3- concentration decreased with increasing soil water content. It can be concluded that increasing watering frequency can improve plant growth but has little effect on microbial biomass.4.Soil was maintained at 50% of water-holding capacity (WHC) for four weeks and either planted with wheat or left unplanted. After removal from the pots, soil was kept at 50% WHC or quickly dried to 40, 30, 20 or 10% of WHC. The soils were incubated four weeks during which soil respiration, microbial biomass and nutrient availability were measured. Cumulative respiration was two-fold higher in planted than unplanted soil and decreased with water content, with a smaller decrease in planted soil. MBC on days 5 and 10 was higher at 10 than at 50% WHC in planted soil, but not affected by water content in unplanted soil. MBN concentration at 20-50% WHC were more than 2-fold higher than that of 10% WHC. WEOC was higher in rhizosphere soil than non-rhizosphere soil and the difference increase with increasing of soil water content. We conclude that soil microbes in rhizosphere can maintain higher respiration in dry soil despite low biomass because activity per unit biomass is high.
In this research, synergistic relationship between plant growth, rhizosphere soil nutrient and microorganisms were clarified by comparing the responses of plant, nutrient and microbial characteristics to different water supply models. It provided a scientific basis for revealing rhizosphere regulation mechanism of soil microbial activity and nutrient availability under water stress. The mechanism of plant-induced organic matter maintaining rhizosphere soil microbial activity and nutrient availability was also clarified. This study can provide a theoretical basis for the water management during the early growing stage of wheat, which is of great significance for the effective use of water resources and the improvement of wheat production.
|薛冉. 生长早期小麦根际土壤养分及微生物对不同水分供应模式响应及其机制的研究[D]. 兰州. 兰州大学,2017.|
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