| A field experiment was conducted to Isatis indigotica under mulched drip irrigationin 2019 at hexi oasiscold irrigation area of Yimin irrigation experimental station,minle county.The effects of different water deficit treatments on different stages on growth dynamics,photosynthetic characteristics,water consumption characteristics,soil temperature changes,yield,water use efficiency and quality were studied.According to the characteristics of water demand at each growth stage of Isatis indigotica,the water deficit was set for mild(65%-75%field water capacity),moderate(55%-65%field water capacity)and severe(45%-55%field water capacity),respectively.Under the condition of ensuring adequate water supply in seedling stage,full water supply in whole growth stage(75%-85%field water capacity)was taken as the control treatment(CK).Mild(WT1),moderate(WT2)and severe(WT3)water deficit management was carried out in the vegetative stage,mild(WT4)and moderate(WT5)water deficit treatment was carried out in the fleshy root growth stage,and mild(WT6)water deficit treatment was carried out in the fleshy root maturity stage.The periodical changes in agronomic traits,dry matter accumulation and distribution,photosynthetic physiological index,water consumption rule and the change of shallow soil temperature,yield,water use efficiency and quality of Isatis indigotica were measured under different water deficit treatment.Research indicates:(1)The results showed that the plant height,taproot length,taproot diameter and leaf area index of Isatis indigotica decreased significantly(P<0.05),moderate and severe water deficit during vegetative stage and fleshy root growth stage and light water deficit during fleshy root maturity stage.There was no significant difference in plant height,taproot length,taproot diameter and leaf area index with the control treatment between the vegetative stage and fleshy root growth stage under mild water deficit treatment(P>0.05).Moderate and severe water deficit in vegetative stage and fleshy root growth stage can reduce dry matter accumulation of Isatis indigotica.The decrease ranged from 3.11%to 15.67%.Mild water deficit treatment will not significantly affect dry matter accumulation.(2)Mild water deficit during vegetative growth period did not significantly reduce transpiration rate and stomatal conductance,while moderate(WT2)and severe(WT3)water deficit significantly reduced net photosynthetic rate,transpiration rate and stomatal conductance of the leaves.The decreases of WT2 were 13.87%,18.80%and 15.94%.The decreases of WT3 were 22.08%,46.28%and 38.40%.The decrease increases with the aggravation of water deficit.When re-watering after water deficit shows a certain rehydration compensation effect.Moderate and severe water deficit management is beneficial to improve water use efficiency of Isatis indigotica leaves.WT3 leaf area duration,crop growth rate,net assimilation rate and specific leaf area in the vegetative growth period were significantly reduced compared with CK(P<0.05)30.00%,42.74%,21.26%and 10.90%,and specific leaf weight was significantly increased by 12.41%compared with CK.(3)The water consumption in the whole growth period of Isatis indigotica was influenced by the period and degree of water deficit treatments.The total water consumption of CK in full water supply treatment during the whole growth period is the largest,which is 393.85mm.The total water consumption of other treatments was significantly lower than CK treatment(P<0.05),with a decrease of 5.12%-10.78%.The variation of water consumption,daily water consumption intensity and water consumption modulus at different growth stages of Isatis indigotica rose first and then decreased.From small to large:seedling stage,fleshy root maturity stage,vegetative growth stage and fleshy root growth stage.Mild water deficit did not significantly reduce the daily water consumption strength and water consumption modulus of Isatis indigotica.Moderate and severe water deficit significantly reduced the daily water consumption intensity and water consumption modulus of Isatis indigotica.(4)Film mulching can obviously increase the temperature of the shallow soil at the early stage of growth of Isatis indigotica,which has a certain warming effect.The daily variation of soil temperature decreases with the increase of soil depth.During the whole growth period,the soil temperature at 5cm and 10cm was the highest,and the temperature fluctuation was the largest.The temperature variation was 24.6?and22.3?.The soil temperature at 20cm and 25cm was the lowest,and the temperature fluctuation was the slowest.The increase of soil moisture has the effect of heat preservation,and the more water deficit,the more drastic the change of soil temperature.(5)There was no significant difference between the economic yield of WT1 and WT4 with CK control treatment(P>0.05).Their values were 8554.18kg/hm~2 and8398.70kg/hm~2.All other treatments reduced the economic output of Isatis indigotica.The decrease ranged from 6.89%to 18.33%.Water use efficiency(WUE)and irrigation water use efficiency(IWUE)of WT4 were the highest treatment.Compared with the control treatment,it was improved by 7.91%and 7.39%.(6)The content of indigo and soluble protein in WT1 were the highest,respectively 6.83mg/kg and 69.01mg/g,which were significantly increased by 4.76%and 3.34%compared with CK(P<0.05).The contents of indiorin,(R,S)-goitrin,polysaccharide and soluble protein in WT4 were significantly increased by 1.32%,5.22%,2.57%and 3.07%,respectively,compared with CK.Other water deficit treatments can reduce the content of indirubin,(R,S)-goitrin,polysaccharide and soluble protein,with decrease of 0.77%~10.87%,2.47%~11.65%,1.53%~10.88%and 6.93%~23.29%.(7)The yield,total biomass,water use efficiency,irrigation water use efficiency and average soil moisture content of the whole growth period can be expressed by quadratic parabola.The regression equations were y=-252.54x~2+9490.4x-80547(R~2=0.8779),y=-236.46x~2+9302.6x-78405(R~2=0.846),y=-1.3649x~2+48.443x-407.4(R~2=0.7679),y=-2.0124x~2+70.589x-569.91(R~2=0.4521).The relationship between the yield and total biomass of Isatis indigotica and water consumption during the whole growth period was a quadratic parabola.The regression equation of yield,total biomass and water consumption in the whole growth period were y=-0.692x~2+544.57x-98975(R~2=0.3523),y=-0.5842x~2+480.47x-86071(R~2=0.3547).The relationship between quality indexes and water consumption during the whole growth period were quadratic parabola.With the increase of water consumption,the quality indexes of Isatis indigotica increased first and then decreased.(8)The correlation coefficients of two stage water production function models were 0.972 and 0.964 respectively,both of which could better reflect the functional relationship between yield and water consumption.The highest water sensitivity index was 1.541 and 1.764 in the growth period of the fleshy root,which was the critical period of water demand for Isatis indigotica.In order to obtain a higher yield of Isatis indigotica,sufficient soil moisture should be ensured in this growth period.Therefore,applying continuous mild water deficit during the vegetative stage and the fleshy root growth stage and providing adequate water supply during other growth stage is an optimal irrigation method with high efficiency,water saving and high yield in the irrigation area of hexi oasis cold irrigation area. |
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