Effects Of Rice Straw Returning And Ni-trogen Fertilization On Soil Nutrient

Straw is an important agr icultur al resource in China.If it cannot be us ed r easonably,it w ill cause waste of r esources and env ironmental pollution.Unlike other str aws,rice str aw is not eas ily used for animal f eed and has few other uses.However,bur ning str aw will not only cause air pollution,but als o cause smog,which will also r esult in waste of resources.Returning str aw to the f ield can save r esources and reduce air pollution caus ed by burning str aw.In r ecent years,a large number of exper iments have been carr ied out on the effects of straw returning on soil enzyme activity and s oil nutr ients,but ther e are still corres pon ding problems.For example,a small amount of straw returning to the field makes the yield increas e effect not obvious,and excess ive straw returning w ill cause r educed production of r ic e,etc.Mor eover,the content of nutr ient elements in straw is relatively small,which makes the accumulation of soil nutr ients too s low.Therefor e,research on straw r eturning and fer tilizer management has important s ignif icance both in theor y and in practice.In this study,the r ice f ield soil in Heilongjiang Province was taken as the res earch object.In the field exper iment under the f ield plot in 2018,the main planting var iety Longdao 21 was used as the test mater ial,and the two-factor test of straw and nitrogen f ertilizer was set up.The straw was set at thr ee levels.They ar e: 0 kg·hm-2(S 0)?3750 kg·hm-2(S1)?7500 kg·hm-2(S2),and 6 levels of nitrogen fer tilizer.: 0 kg·hm-2(N0)?53 kg·hm-2(N53)?93 kg·hm-2(N93)?133 kg·hm-2(N133)?173 kg·hm-2(N173)?213 kg·hm-2(N213).The effects of straw application and nitr ogen applic ation on rice yield and its components,soil nutr ient,soil enzyme activity and nitrogen,phosphorus and potassium contents were studied.The test results are as follows:Under the same nitrogen applic ation level,the soil nutr ient and enzyme activities were not signif icantly diff erent with the increase of str aw returning amount.Under the tr eatment of straw returning,the nitr ogen application rate to soil available phosphorus,available potassium content,phosphor ic acid and invertase activity.The improvement eff ect was signif icant,and the eff ects on soil p H,organic matter,nitrate nitrogen,total nitrogen and total phosphorus were not significant.Under the s ame nitrogen applic ation level,the nitrogen,phosphorus and potass ium contents of rice plants were not s ignif icantly differ ent with the increase of straw returning amount.Under the different str aw retur ning treatment,the nitr ogen,potass ium and phosphorus contents of r ic e plants were applied.The difference in the increase in nitrogen is not significant.Under the same nitrogen application level,the agronomic traits and yield of r ice wer e not s ignif icantly diff erent w ith the increas e of str aw returning amount.Under the s ame straw returning amount,the increase of nitrogen applic ation r ate had a s ignif ic ant effect on the eff ective panic le number and yield of r ice.However,excess ive nitrogen applic ation resulted in a downward tr end in yield,and the highest level of yield was treated at N133 and N173,which were 8489.50 and 8858.27 kg·hm-2,respectively.Corr elation analys is showed that ther e was a signif icant negative correlation between soil phosphatase and sucr ase activity,and there was a s ignif icant pos itive correlation w ith urease activity.There was a s ignif icant pos itive correlation between soil available potass ium and available phosphorus,and a s ignif icant pos itive correlation w ith organic matter content.Ther e was no correlation between rice yield and soil nutrient and enzyme activity.