Effects Of Straw Returning On Early Growth And Nitrogen Metabolism Of Maize

In recent years,more and more attention has been paid to the problem of straw treatment.Straw returning can increase the content of soil organic matter and avoid the environmental problems and resource waste caused by straw burning.However,the previous results of straw returning on maize growth and nitrogen application are not consistent.In order to analyze the influence mechanism of straw returning and nitrogen fertilizer application on the early growth of maize,we carried out two experiments.Experiment 1:the effect of temperature and water on the decomposition and nutrient release of maize straw.Taking maize straw as material and decomposing bacteria,the indoor 50d simulation experiment was carried out by using the quadratic saturation-d-optimal design with different temperature and water content.Experiment 2:the effects of different levels of straw returning and nitrogen fertilizer on the early growth of maize.The experiment adopts split block design with ten replications,and the main treatment was varieties（Zhengdan 958 and Xianyu 335）,the subsidiary treatment was nitrogen（urea）application rates（4.5g/pot and 2.25g/pot,equivalent to pure nitrogen 150kg/ha and 75kg/ha）and straw returning（70g/pot,35g/pot,0g/pot,equivalent to full,half and no returning）,additional no fertilization and no straw returning treatment.Five plants with uniform growth were selected at five-leaf stage and jointing stage for the determination of various indexes.The main results of the test are as follows:1.The early decomposition rate and nutrient release of maize straw can be described by logistic y=k/(1+e^（a-bx）)simulation equation.Under the condition of combined application of straw decomposition bacteria,the decomposition rate of maize straw is faster 30 days before decomposition,slower after 30 days,and the decomposition rate of maize straw is 34.4%～49.8%50 days.There is an interaction effect between temperature and water content.The maximum decomposition rate occurs under the condition of high temperature（30℃）and high water content（80%）;The fastest decomposition rate of straw increased first and then decreased with the increase of temperature or water content.It reached a high point at 25℃or 70%water content,and then the temperature and water content would inhibit the increase of the fastest decomposition rate;The release of nitrogen and phosphorus from maize straw increased with the increase of temperature（10℃～30℃）,while the release of potassium decreased slightly when it exceeded 25℃;With the increase of water content（60%～80%）,the release of nitrogen in maize straw continued to increase,the release of phosphorus reached a high point between 70%～75%water content,and the release of potassium reached a high point at 75%water content,and then decreased slightly;The release rates of nitrogen,phosphorus and potassium were 25.9%～34.9%,25.9%～34.9%and 86%～91.9%respectively.2 Sufficient nitrogen supply is needed in the early stage of maize growth,and lack of nitrogen will inhibit the growth and development of maize.In the early stage of maize growth,although a certain amount of nitrogen can be released in the early stage of straw returning,the content is too low to replace nitrogen application,and the amount of nitrogen application should not be reduced too much.In order to meet the nitrogen demand of maize growth in the early stage,the effect of high nitrogen is better.3.straw returning combined with nitrogen fertilizer improved the photosynthetic capacity of maize in the early stage.The photosynthetic capacity of maize was the highest under full straw returning combined with high nitrogen fertilizer,which significantly improved the chlorophyll content,chlorophyll fluorescence parameter value,net photosynthetic rate,transpiration rate,air pore conductivity and intercellular carbon dioxide concentration of maize leaves.3 Straw returning combined with high nitrogen fertilizer improved the related indexes of maize nitrogen metabolism,and the effect of full straw returning combined with high nitrogen fertilizer was the most significant:it increased the contents of soil total nitrogen,nitrate nitrogen,ammonium nitrogen and alkali hydrolyzable nitrogen,and increased the activities of soil urease and cellulase;The absorption of total nitrogen,nitrate nitrogen and ammonia nitrogen in maize roots was improved;The contents of total nitrogen,nitrate nitrogen,ammonia nitrogen,amide nitrogen,protein nitrogen and soluble protein in maize plants were increased,and the activities of NR and GS in leaves were increased.4 Straw returning combined with nitrogen fertilizer improved the photosynthetic capacity of Maize in the early stage.The photosynthetic capacity of maize was the highest under the condition of full straw returning combined with high nitrogen fertilizer,which significantly improved the chlorophyll content,chlorophyll fluorescence parameter value,net photosynthetic rate,transpiration rate,stomatal conductivity and intercellular carbon dioxide concentration of maize leaves.5 Straw returning combined with nitrogen fertilizer promoted the early growth of maize.The full amount of straw returning combined with high nitrogen fertilizer improved the early growth of maize the highest,significantly improved the plant height,leaf area and dry matter of maize,and provided early guarantee for the improvement of maize yield.