| In recent years,straw returning has gradually become a hot topic.Straw returning can effectively eliminate the environmental problems caused by straw burning,and it is also the most economical way to treat straw.Straw decomposition is a long process,and its early impact mechanism on crops is not clear.The purpose of this experiment is to study the influence mechanism of straw returning on seed germination and maize seedling growth,and to distinguish the physical and biochemical effects of straw returning,so as to provide a reasonable basis for straw resource utilization.This study included three groups of experiments.Experiment I:the effects of maize straw extraction solution and decomposition solution on the seed germination of maize（Zea mays L.）,wild Indian mallow（Abutilon theophrasti Medik.）and wild Barnyardgrass（Echinochloa crus-galli）.Petri dish method were used with five different gradients of extraction solution and decomposition solution.Experiment II:Effects of straw returning methods on the growth and development of maize seedlings.A pot experiment were carried out of three soils（black soil,parent soil and acid black soil）with three straw treatments（no straw,straw covering and straw mixing）,and two stone treatments（stone covering and stone mixing）were added in black soil to distinguish the physical and biochemical effects of straw returning.Experiment III:Straw decomposition experiment.A sealed culture was used to measure CO2release of three soils were treated with six different treatments（no straw,straw covering,straw mixing,straw covering+nitrogen,straw covering+sugar,straw covering+nitrogen+sugar）.The main test results are as follows:1.The maize straw extraction solution has obvious inhibitory effect on the germination and growth of maize and abutilon,but the inhibitory effect for barnyard grass is not obvious.The straw decomposition solution has the effect of promoting the germination and growth of maize and abutilon seeds at low concentration while inhibiting the growth at high concentration,the effect on radicle growth greater than that on germ.the decomposition solution has no obvious effect on the germination and growth of barnyard grass.The change of maize seed germination percentage accords with the logistic equation,and the influence of maize straw extraction solution or decomposition solution is mainly reflected in the rate of germination,which is physiologically related to amylase activity.2.Straw returning treatment promoted the growth of shoot and root parts of maize seedling,among which straw mixing treatment was better than straw mixing treatment,while stone treatment inhibited the growth of root parts;Straw returning promoted the absorption of potassium ion in maize seedling stage,while stone mixing treatment significantly reduced the potassium ion content in maize seedling stage.Straw returning treatment reduced antioxidant enzyme activity,and straw mixing treatment was better than straw covering treatment.Straw covering reduced MDA and Pro content and increased soluble sugar content.Straw mixing treatment increased the content of Pro and soluble sugar,but had no effect on MDA content.In terms of soil,straw returning treatment and stone mixing can increase soil enzyme activity,and straw mixing has the best effect;Under different soil conditions,straw mixing will change the composition of maize rhizosphere bacteria.3.Straw returning can significantly increase the accumulation of soil CO2release,and the effect of straw mixing treatment on increasing soil CO2release is greater than that of straw covering.Straw covering with nitrogen and straw covering with sugar are all significantly higher than that of straw covering treatment.Straw covering with sugar has the maximum accumulation of soil CO2release,and the soil respiration rate gradually decreases with the increase of time,indicating that straw decomposition rate was faster in the early stage and then gradually slowed down.This study found that straw returning can promote the growth and development of maize in the early stage,which is mainly due to straw decomposition has a biological and chemical impact on the growth of maize in the early stage,rather than simply changing the physical properties of soil,Moreover,under the condition of wet soil,the effect of straw mixing treatment on the growth of maize seedling was better than straw covering treatment. |
