Effects Of Corn Straw Mulching On Soil Water And Heat And Weeds Occurrence

The three northeastern provinces are important grain production bases in China.the planting area of grain crops reached 23.2982 million hectares in 2018,among which the corn planting area reached 13.2613 million hectares,accounting for 56.92%of the total planting area.Although corn straw resources are abundant,the area of straw returning is small,resulting in a lot of straw burning in the open air and polluting the environment.“The Northeast Black Land Conservation Tillage Action Plan?2020-2025?”clearly proposes to strengthen the promotion of modern farming techniques with crop straw mulching and no?minimum?tillage and sowing.Therefore,it is of great theoretical and practical significance to systematically study the effects of corn straw mulching on soil water and heat conditions and weed occurrence,which promote the successful implementation of the conservation tillage for black soil in Northeast China.This experiment was carried out in Xiangyang experimental base of Northeast Agricultural University from 2017 to 2019.Continuous cultivation corn was taken as the research object,five treatments were set,including traditional tillage with straw removal?TT?,no-tillage with straw mulching?NT?,no-tillage planter with straw mulching+intertillage?NTS?,ridge subsoiling and stubbing+intertillage?SCS?,and plowing with straw returning+intertillage?DS?.Five straw mulching amounts were set in 2018 and 2019,which were 0 kg·hm^-2?SC0?,5272.8 kg·hm^-2?SC0.5?,10545.6 kg·hm^-2?SC1.0?,15818.4 kg·hm^-2?SC1.5?,21091.2 kg·hm^-2?SC2.0?,respectively.There were three herbicide application method which were no herbicide application?NH?,foliar herbicide application?FH?and soil+foliar herbicide application?SFH?.The effects of corn straw mulching on soil water and heat conditions and weeds occurrence were studied,the results showed that:Corn straw mulching increased the soil moisture content and improve soil moisture conservation ability significantly.The soil moisture content of each treatment in the spring drought year was NT>NTS>SCS>TT>DS,the differences between the first three treatments were not significant,but they were significantly higher than the latter two treatments.There is less rainfall in summer and the soil moisture content in the period of summer drought is basically consistent with that in the year of spring drought.Corn straw mulching reduced soil accumulated temperature from the sowing stage to the jointing stage.At the corn seedling stage after sowing 30 days,the soil accumulated temperature of TT treatment was 19.6?·d,26.4?·d and 35.5?·d higher than that of SCS.The soil accumulated temperature of SCS treatment was higher than the latter two treatments,but the difference was not significant.At the corn jointing stage after sowing 60 days,the trend was still maintained,and the temperature difference did not change much.The effects of different straw returning methods on soil accumulated temperature was mainly manifested in the corn seedling stage after sowing 30 days.Under the condition of no herbicide application?NH?,the increased straw mulching quantity significantly affected the weed occurrence.The SC1.5 and SC2.0 treatments reduced the quantity of weed germination by 7.75%-50.75%,decreased the density of weeds by 11.86%-43.68%,decreased the fresh weight of weeds by 6.43%-59.31%,and decreased the dry weight of weeds by4.67%-59.31%,which significantly inhibited the biomass of weeds.Under the condition of applying foliar herbicide?FH?,the increased straw mulching quantity also significantly affected the occurrence of weeds.Compared with the SC0 treatment,the SC1.0,SC1.5 and SC2.0 treatments reduced the weeds germination number by 11.91%-39.16%,and the weed density by 10.96%-34.50%,the fresh and dry weight of weeds significantly.Under the condition of soil+foliar herbicides application?SFH?,there was no significant difference in weeds occurrence among the five treatments.Under the condition of straw mulching,the comprehensive control effect of weeds in soil+foliar herbicides application?SFH?treatment was better than that in the foliar herbicide application?FH?treatment.Under the five straw mulching levels,the inhibition rate of weeds was more than69.14%in the foliar herbicide application?FH?treatment,and the inhibition rate of weeds was more than 80.22%in the soil+foliar herbicides?SFH?treatment.Both herbicide application levels had significant inhibitory effects on the fresh and dry weight of weeds.Under the two herbicide application levels?FH,SFH?,the straw was removed after 30 days of spraying the foliar herbicide,and the larger quantity of the straw mulching,the larger number of weeds germination,indicating that the straw mulching played a blocking role on the herbicides,and affected the toxic effect of herbicide on the weeds under straw,and the larger quantity of the straw mulching,the more obvious the effect was.In the three years of the experiment,the difference of corn yield was not significant under different straw returning treatments.In 2017 and 2018,the corn yields of the DS,TT and SCS treatments were higher than that of the NT treatment.In 2019,the corn yield of the NT,DS and TT treatments basically tended to be the same.