| A study was carried out in Puding,Guizhou Province from 2019 to 2020,using two dense-tolerant spring maize varieties Xianyu 1171 and Xinzhongyu 801 as materials,and setting 3.0,4.5,6.0,7.5,9.0 and 10,5×10~4plants/ha six densities,systematically studied the effects of different planting densities on the stalk characteristics,canopy structure,photosynthetic physiological characteristics,yield formation and mechanical harvest quality of maize plants,and clarified the difference in response of two densification-tolerant varieties to densification,To find out the suitable planting density of the two varieties in Guizhou,in order to provide basis and guidance for the high-yield and mechanized high-efficiency production of spring corn in Guizhou.The main findings are as follows:1.With the increase of planting density,the plant height,ear position height and center of gravity height of the two varieties first increased and then decreased.The ear position coefficient of Xianyu 1171 first increased and then decreased,and the new Zhongyu 801 gradually increased;The inter-node length and the stem-node length-to-thickness ratio increased significantly,and the internode diameter,internode cross-sectional area,internode dry weight and dry weight per stem length decreased significantly with the increase in density.Among them,compared with 30,000plants/ha after densification,the length-to-thickness ratios of the 3rd,5th and 7th nodes of Xianyu 1171 and Xinzhongyu 801 increased by 65.66%-70.08%and68.00%-73.01%,respectively at 105,000plants/ha.the 5th node has the largest increase in the average length-to-thickness ratio(71.55%);the dry weight per unit stem length of Xianyu 1171 and Xinzhongyu 801 decreased by 49.10%-57.67%and45.40%-56.34%,respectively.The 3rd node has average decrease in dry weight per unit stem length was the largest(57.01%).For every increase of 10,000 plants/ha in density,the stem-to-node length-to-thickness ratios of Xianyu 1171 and Xinzhongyu801 increased by 0.61-0.98 and 0.41-0.64,respectively,and the dry weight per stem length decreased by 0.023-0.065g/cm,respectively.0.029-0.070g/cm,the average stem length to thickness ratio of the seventh node increased the fastest(0.81);the average dry weight per unit stem length of the third node decreased the fastest(0.067g/cm).2.With the increase of planting density,the mechanical strength,cellulose and lignin content of the two varieties gradually decreased.Among them,the decreasing range affected by density:bending strength>pushover strength>puncture strength,lignin content>cellulose content.Compared with 30,000 plants/ha after densification,the bending resistance of Xianyu 1171 and Xinzhongyu 801 at the 3rd,5th and 7th sections of Xianyu 1171 and Xinzhongyu 801 decreased by 55.09%-66.78%and57.89%-61.71%respectively at 105,000 plants/ha.The average bending strength of section 3 decreased the most(64.25%),the lignin content decreased by13.43%-20.73%,12.82%-23.87%,and the average decrease of lignin content in section 7 was the largest(22.30%).For every increase of 10,000 plants/ha in density,the bending strength of Xianyu 1171 and Xinzhongyu 801 decreased by 13.0-57.5N and 21.0-60.7N,respectively,and the average bending strength of section 3 was the fastest(59.2N).3.As the planting density increases,the lodging rates of the two varieties increase,and almost all are less than 5%.The lodging rate of Xianyu 1171 and Xinzhongyu 801 increased by 0.54%and 0.22%for every increase of 10,000plants/ha in density.Under high density,the lodging rate of Xianyu 1171 was higher than that of Xinzhongyu 801.Compared with Xianyu 1171,Xinzhongyu 801 has low plant height and ear height under high density,low center of gravity,thick and strong stalk,high mechanical strength and toughness,and high cellulose and lignin content.Strong anti-lodging ability.4.With the increase of planting density,the LAI of the two varieties increased,the angle between stem and leaf decreased,the value of leaf orientation increased,and the light transmittance decreased.Compared with 30,000 plants/ha after densification,the angle between stems and leaves of Xianyu 1171 and Xinzhongyu 801 decreased by 6.70°and 11.93°at 105,000 plants/ha,and the leaf orientation value increased by35.35%and 26.17,respectively.%;The average light transmittance of the canopy has been reduced by 48.98%and 62.40%respectively.Densification can adjust the distribution space of corn leaves to a certain extent and improve the light distribution characteristics of the population,but the influence of density is far greater than the appropriate adjustment of the plant itself.The light transmission ability of the group is still getting worse under the height.Compared with Xianyu 1171,under high density,Xinzhongyu 801 improves the population light distribution due to the smaller leaf-stem-leaf angle at the ear position and larger leaf direction value,which makes the light energy interception in the canopy higher.5.With the increase of planting density,the chlorophyll content and?PSII of the two varieties first increased and then decreased.The Fv/Fm value of Xianyu 1171 first increased and then decreased,and the Fv/Fm value of Xinzhongyu 801 showed the opposite trend.The quenching coefficient(NPQ)showed a downward trend,while the photochemical quenching coefficient(q P)had a certain increasing trend,and the net photosynthetic rate and transpiration rate decreased significantly.At a high density of105,000 plants/ha,the chlorophyll content,net photosynthetic rate and transpiration rate of Xinzhongyu 801 are 8.60%,17.75%and 17.80%higher than those of Xianyu1171,which has strong photosynthetic capacity;appropriately increasing the density can To improve the actual photochemical efficiency of PSII,corn leaves can protect themselves and promote photosynthesis by adjusting the balance of non-photochemic-al quenching(NPQ)and photochemical quenching(q P).6.With the increase of planting density,the yields of the two varieties first increased and then decreased.When Xianyu 1171 was 102,000 plants/ha,the yield was the highest(11771.0 kg/ha);when Xinzhongyu 801 was 83,000 plants/ha,the yield was The highest(10631.4kg/ha).Under the high density corresponding to the highest yield,the effective ear number and grain number per ear(87762.6 ears and557.8 grains)of Xianyu 1171 are 19.94%and 4.13%higher than that of Xinzhongyu801(73170.1 ears and 535.7 grains),but the thousand-grain weight ratio Xinzhongyu801 is 12.40%lower.For every increase of 10,000 plants/ha in density,the effective ear number of Xianyu 1171 increased by 7603.0 ears,which was 420.1 ears higher than that of Xinzhongyu 801,and the number of grains per ear decreased by 22.9,which was 7.5 ears lower than Xinzhongyu 801.The dry matter accumulation after anthesis and the contribution rate of dry matter transport have a very significant positive correlation with the yield.After the densification,the dry matter accumulation of the first jade 1171 after anthesis and its distribution to the grain dominate,and the dense planting makes the first jade 1171 yield component factors More coordinated and higher output.7.With the increase of planting density,the grain moisture content of the two varieties first decreased and then increased.Xianyu 1171 and Xinzhongyu 801 had the lowest grain moisture content at 69,000 plants/ha and 78,000 plants/ha,respectively.Density has no significant effect on the quality of machine harvest.Under the six density conditions,the average grain breakage rate is 8.39%,the average impurity rate is 3.90%,and the average ear drop rate and seed drop rate are 5.80%and 0.84%,respectively.The loss rate of machine-harvested kernels is mainly ear drop,which accounts for 87.41%of the total loss rate.Fragmentation rate and ear drop rate are extremely significantly positively correlated with grain moisture content and ear stalk length,and extremely significantly negatively correlated with bract bulkiness;impurity rate is extremely significantly positively correlated with grain moisture content,and significantly negatively correlated with bract bulkiness Related.Varieties with thinner cobs,lower cob hardness,and fluffy bracts can accelerate grain dehydration,reduce grain moisture content during machine harvest,and improve machine harvest quality.In summary,the planting density significantly affects the growth,yield formation and mechanical harvest characteristics of spring corn.The suitable density of Xianyu1171 in Guizhou is 90,000 plants/ha,and the suitable density of Xinzhongyu 801 is60,000 plants/ha. |
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