Dissertation > Agricultural Sciences > Crop > Cereal crops > Corn ( maize )

Effect of Agronomic Managements on Post-anthesis Leaf Photosynthetic Senescence and the Yield of Summer Maize

Author SunXueFang
Tutor ZhaoMing; DingZaiSong
School Chinese Academy of Agricultural Sciences
Course Crop Cultivation and Farming System
Keywords Varieties Density Subsoiling Yield Regulation effect
CLC S513
Type Master's thesis
Year 2013
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The main way to achieve the high-yield of maize is increasing the planting densities. But with thedensity increasing, the leaf senescence of maize was intensified, which affected the yield improvement.The photosynthtic senescence law and physiological characteristics had been researched extensively.However, the regulation technology pathways and the physiological mechanism was not clear. Thetechnical effects was conducted by the main measures of densities, varieties and subsoiling. we selectedfour different tested varieties: they were ZD958, DH661, ZD909and XY335, set up three plantingdensiti:45000(D1),67500(D2) and67500(D3) plant hm-2, used soil stripe deep loosening and directseeding, in order to research the effect of the varieties, density and soil deep loosening to leafsenescence. The dynamic process photosynthetic characteristics, Electron Transport, the content ofchlorophyll, Carbon and Nitrogen was monitored. And the group canopy photosynthetic property andyield components were also analysised. We cleared the regulation effect of different agronomicmaganements technologies on leaf senescence. The main results were as following:The Post-anthesis photosynthetic characteristics were showed, with the increase of the density, thetrent of leaf net photosynthetic rate was quadratic curve, the density from D1to D2increased by50%,the Pn decreased by9.80%, from D2to D3, the density increased by33.3%, the Pn decreased by5.08%;the Pn of ZD958and XY335were higher than the ZD909’s, the descreasing value was7.68%and5.26%less than ZD909, respectively. The teachology of subsoiling could slow down the process of the leafsenescence, and enhanced the Pn, the adjustment effect on ZD958is better than the other two varieties.The net photosynthetic rate increased by11.69%–22.59%. So the ZD958in low density (D1) combiningthe technology of subsoiling, could maintain a higher photosynthetic rate after anthesis. The releation ofthe Gsand Tr with the Pn was singnificant positive correlation. The effect of agronomic maganementson the two parameters were consistent with changes in photosynthetic rate.(2) The photosynthetic physiological mechanism in the process of leaf senescence:Firstly, the relation between the electron transfer and the photosynthetic senescence. The ΦPSⅡand Fv/Fm also decreased after anthesis. The decreasing degree was lowest in variety XY335. The twoparameters declined more markedly with the density increased. The deep loosening tillage reduced thedecreasing speed. The decline of the two parameters was43.66%and28.94%less than that in CK.Secondly, the relationship of leaf chlorophyll content with the photosynthetic senescence. Afteranthesis, the leaf chlorophyll content showed a trend of increased and then decreased. Correlationanalysis showed that photosynthetic rate and chlorophyll content no significant positive correlation in0–10d after anthesis and significant positive correlation in10–69d. The average chlorophyll content ofXY335is lowest, and which is12.78%and26.28%higher than ZD958and ZD909, respectively.Planting density had no significant effects on leaf chlorophyll content. While deep loosening tillageincreased the chlorophyll content (11.39%) and made its decline16.46%less.Thirdly, the relationship of carbon and nitrgon content with the photosynthetic senescence. Thecontent change of soluble sugar was up-down-up, while starch was down-up-down. The trent content of total N was up-down-up. There was difference between the C/N of varieties, but the C/N increased inthe whole level. The accumulation of soluble sugar and starch was less, the C/N was lower and thecontent of N was high in ZD958. As the density increased, soluble sugar and total nitrogen content wasless, the content of starch was higher In density of D2and the C/N is lowest in density of D3. By thesubsoiling, the soluble sugar and the C/N reduced, the accumulation of starch and tatal N increased.Subsoiling had delayed effect on leaf senescence.(3) The effect of agronomic management on the performance of production. The variety of XY335has higer mLAI, LAD, MNAR, and more Biomass. With planting density increasing, the dry matter,mLAI and LAD increased, while the MNAR was declined, the change of HI was hinger in D2density.By subsoiling the group dry matter, HI, LAI, mLAI, LAD were improved, the adjustment effect wasmore obviously in high density. Subsoiling could make the MNAR of ZD958and XY335higher in thedensity of D1and D2. The yield of ZD958was highest, compared with DH661, ZD909and XY335, theyield of ZD958increased by15.76%,2.98%and6.76%. The yield advantage of ZD958was highergrain weight than DH661, and more ear number than ZD909and XY335. The yield increased with theincrease of density. Subsoiling made the yield improved1.86%,4.51%and14.42%under density of D1,D2and D3. The subsoiling effect on yield more effective in high density.

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