Effects Of Uniconazole Waterless-dressing Seed On Lodging Resistance Characteristics During The Vegetative Stage And Yield Of Relay-cropping Soybean

The objectives of this study were to determine the effects of Uniconazole waterless-dressing seed on growth habit in vegetative stage,lodging resistance,yield and its distribution of relay-cropping soybean.The study was conducted using two soybean cultivars,medium maturing cultivar Nandou 8 and late maturing cultivar Gongxuan 1.The results were shown as follows:1.Uniconazole treatment could postpone the vegetative growth stage of soybean.The seedling growth stage of soybean was postponed by Uniconazole treatment by 2 to 6 days.The postponement could be displayed from VE stage,and the postponement effects could be enhanced with the increase of the concentration of Uniconazole.The medium maturing cultivar could display the postponement in whole stage while the late maturing cultivar could be only postponed in vegetative stage.The whole stage of soybean could be shortened when planted in relay-cropping system,a Uniconazole treatment could counteract that shortened effect.The whole stage of late maturing cultivar had no significant differences between planting in sole cropping system and planting in relay-cropping system.2.Uniconazole treatment could regulate the growth habit of soybean.Uniconazole treatment could decrease the plant height,main stem length,cotyledonary collar,first internode length,leaf area index(LAI) and dry matter accumulation(DMA),and increase the stem diameter and SPAD value.The 10.0mg/kg treatment had the most significant effects.The soybean planted in relay-cropping system could be more slender than those planted in sole cropping system.The medium maturing cultivar had intense response when it was planted in relay-cropping system but the late maturing cultivar had little response.3.Uniconazole treatment could decrease the cellulose and lignin content of main stem of soybean.The cellulose and lignin content accumulated with the progress of vegetative stage. Uniconazole treatment decreased the cellulose and lignin content of main stem of soybean.The effects could be enhanced with the increase of the concentration of Uniconazole,but there were no significant differences between two cropping systems and between two cultivars.4.Uniconazole treatment could change the anatomical characteristics of the first internode of main stem.The cortex,phloem and xylem were thickened,and the pith area was increased with the Uniconazole treatment.The effects could be enhanced with the increase of the concentration of Uniconazole.The bark thickness of medium maturing cultivar could increase from 192.89μm (check) to 276.79～563.55μm(Uniconazole treatment).The bark area ratio could increase from 29.59%to 35.42～48.60%,and the pith area ratio could decrease from 42.48%to 28.25～40.02%. While the bark thickness of late maturing cultivar could increase from 300.13gin to 395.39～683.93μm,the bark area ratio could increase from 36.16%to 41.42～49.65%,and the pith area ratio could decrease from 39.93%to 24.75～35.07%.The cortex,phloem and xylem thickness and pith area of soybean planted in sole cropping system were higher than those planted in relay-cropping system.The bark,xylem and pith area ratio of soybean planted in sole cropping system were 35.31%,29.86%and 34.83%,respectively,but they were 35.83%,22.84%and 41.33%,respectively,when planted in relay-cropping system.5.Uniconazole treatment could avoid lodging.Uniconazole treatment could decrease the plant height/stem diameter,bending of main stem,and field lodging score.The 6.0mg/kg, 8.0mg/kg,10.0mg/kg treatments could totally avoid lodging.The plant height/stem diameter, bending of main stem,and lodging score of soybean planted in sole cropping system were lower than those planted in relay-cropping system.The lodging resistance of medium maturing cultivar with the lodging occurred primitively in 37 days after planting was weaker than late maturing cultivar with the lodging occurred primitively in 44 days after planting.6.Uniconazole treatment could increase the yield and change the yield distribution.The yield of Uniconazole treatments were higher than check.The highest yield of medium maturing cultivar was the 4.0mg/kg Uniconazole treatment,and the late maturing cultivar was 6.0mg/kg. Uniconazole treatment could increase yield through increasing the pods per plant but not through the seeds per pod and seed size.The yield of soybean planted in sole cropping system was higher than planted in relay-cropping system.In relay-cropping system,the yield of medium maturing cultivar was mainly distributed at main stem of early-stage section,and the late maturing cultivar was mainly distributed at branch of early-stage section.Uniconazole treatment could increase the yield of main stem of early-stage section of medium maturing cultivar,and increase the yield of branch of early-stage section of late maturing cultivar,and finally increase the total yield.