Response Of Field Microclimate Characteristics And Biological Properties Of Broomcorn Millet To Fertilization Levels

To establish a good population structure and to create a suitable microclimate is the basisfor good crop growth, which is not only promote crop growth and yield but also improvequality. Broomcorn millet （Panicum miliaceum L.） is an important grain and cash crops inarid agriculture areas of Northern China, with the characteristic of drought resistance, barrentolerance, high water use efficiency. Therefore, broomcorn millet field microclimate andeco-physiological mechanism of high-yield population in dryland broomcorn millet areexplored, and good population structure are studied and established, which will be greatimportance for increasing yield and improving quality. In this paper, strong drought-resistantvarieties （DRV: Longmi8and Ning04-339） and drought-sensitive varieties （DSV: Jinmi4and Yym0965） were used as materials. The difference of field microclimate, dry matteraccumulation and transport, photosynthetic capacity, active oxygen metabolism, root vigor,yield and yield components of different broomcorn millet varieties from anthesis to maturitywere studied, and the correlation between field microclimate and physiological and ecologicalcharacteristics, yield and its components were analyzed under the low（D）, mid（Z）, high（G）fertility condition. The main results showed as follows:（1） Compared with DSV, DRV had lower canopy temperature,0²5cm soil temperature,air temperature, illumination during grain filling, higher relative humidity, which formed agood canopy microclimate, showing the characteristics of the cold wet, and thus had strongadaptability to drought. Fertility reduced canopy temperature, air temperature,0²5cm soiltemperature, illumination among broomcorn millet plants. These indexes in differentfertilization treatments showed G＜Z＜D＜CK. But relative humidity showed G＞Z＞D＞CK.（2） The contribute rate to grain dry weight of the assimilation of the DRV was17.8%higher than that of DSV after anthesis. But the contribute rate to grain dry weight of theoutput of the DRV was4.4%lower than that of DSV, and the dry matter residues of above-ground were higher those of DSV at maturity. Fertility could improve the dry matterassimilation of broomcorn millet after anthesis and output of dry matter before anthesisduring the grain filling stage. Dry matter assimilation after anthesis under D, Z, G fertilizationwere16.2%,14.9%,46.0%higher than those of CK, and output of dry matter before anthesis were13.9%,11.1%,25.6%than that of CK.（3） Net photosynthetic rate（Pn）, transpiration rate（Tr）, stomatal conductance（Gs）,intercellular CO₂concentration（Ci） of DRV were17.2%、9.4%、16.9%、15.4%higher thanthose of DSV, and soluble protein content （SP）, ASA content, GSH content, SOD activity andCAT activity of flag leaves in DRV were higher than DSV, and their decrease degree werelower than DSV. Moreover, MDA and O₂^-.content of DRV in the whole later growth stagewere18.0%、13.5%lower than those of DSV, root bleeding intensity of DRV was17.0%higher than DRV, indicating that DRV remained higher Pn, root vigor to effectively extendleaf duration, and thus produced more photosynthetic products.（4） Fertility could improve Pn, Tr, Gs, Ci, chlorophyll relative content（SPAD）, leafareas（FLA）, SOD activity, CAT activity of the flag leaves and leaf area index（LAI） ofbroomcorn millet, increase SP, ASA and GSH content, and decrease MDA and O₂^-.content.Moreover, fertility could increase effective spikes, ultimately grain higher yield. Comparedwith CK, the average Pn, Tr, Gs, Ci, SPAD, FLA, LAI of flag leaves under three fertilitytreatments were14.7%,13.3%,12.3%,6.9%,11.1%,25.9%,50.1%higher, SOD, CATactivity were13.1%,14.0%higher, and MDA and O₂^-.Content were8.3%,9.2%lower.（5） There were significant or extremely significant negative correlation between canopytemperature, air temperature and Pn, Ci, SP, SOD, CAT, ASA, GSH, root vigor, effectivespikes, grains per spike, yield in different broomcorn millet types（P＜0.05, P＜0.01）. Therewere significant or extremely significant positive correlation between canopy temperature, airtemperature and POD, MDA, O₂^-.,1000-grain weight in different broomcorn millet types（P＜0.05，P＜0.01）, indicating that field microclimatic factors were close related with strongphysiological and metabolic functions of DRV, and so they were used for screening DRV.（6） Canopy temperature, soil temperature, air temperature, illumination were significantor extremely significant negative correlated with photosynthetic capacity, SOD, CAT, ASA,GSH, root bleeding intensity, effective spikes, grains per spike, yield among differentfertilization treatments（P＜0.05, P＜0.01）. And they were significant or extremely significantpositive correlated with MDA, O₂^-.,1000-grain weight（P＜0.05, P＜0.01）. Relative humiditywas significant or extremely significant positive correlated with photosynthetic capacity, rootbleeding intensity, SOD, effective spikes, grains per spike, yield（P＜0.05, P＜0.01）.Moreover, it was significant or extremely significant negative correlated with POD, MDA,O₂^-.,1000-grain weight（P＜0.05, P＜0.01）. These results showed that excellent biologicalproperties were related with field microclimatic factors to further illustrate the cold and wetfarmland features would be associated with reasonable fertilization measures.