| Straw mulching is a kind of conservation tillage measure which can realize the sustainable development of agriculture.It can supplement soil nutrients,improve organic matter content and inhibit the growth of weeds.In order to explore the allelopathic effect of crop straw mulching on the growth of foxtail millet and four representative malignant weeds including Chenopodium album,Setaria viridis,Echinochloa crusgalli and Amaranthus retroflexus.This experiment adopts the method of combining biological determination of germination stage and field index determination,clarifies the allelopathic effects of three species of straws(corn,wheat and foxtail millet)with different concentrations(undiluted,10-fold dilution,50-fold dilution,100-fold dilution)on seed germination of four weeds,and clarifies the effects of four weeds occurrence and control effect,the physiological characteristics and yield of foxtail millet under different mulching amount of straw(1/4,1/2 and total straw yield per hectare).The biological control effects of different mulching amounts and crop straw mulching on weeds and millet growth were comprehensively evaluated in order to provide reference for more reasonable straw mulching technology.The results show that:(1)There were certain allelopathic effects on germination rate,germination index,root length,bud length,root fresh weight and bud fresh weight of three crops straw extract on four weeds.Under the treatment of corn straw undiluted extract,The germination rates of C.album,S.viridis,E.crusgalli and A.retroflexus were decreased by 25.55 %,23.33 %,30.00 % and 17.78 %,respectively,compared with the control.The root length,bud length,root fresh weight and bud fresh weight of S.viridis,E.crusgalli and the root length and fresh weight of A.retroflexus were inhibited,but the root length and bud length of C.album were promoted.The synthetical allelopathic effect index on the four weed seeds was 0.13,-0.44,-0.46 and-0.46.The germination rate was respectively decreased by 80.00%,24.44%,28.89% and 53.33% under the treatment of wheat straw undiluted extract.The synthetical allelopathic effect index on the four weed seeds was-0.42,-3.21,-1.07 and-1.83.The germination rate was respectively decreased by 80.00%,24.44%,28.89% and 53.33% under the treatment of foxtail millet straw undiluted extract.The synthetical allelopathic effect index on the four weed seeds was-0.65,-0.74,-0.78,and-0.52.The results shows that wheat and foxtail millet straw extract can inhibit the germination rate,root length,bud length,root fresh weight and bud fresh weight of four weed seeds.Three straw extracts which were 50-fold dilution and 100-fold dilution shows allelopathy promotion effect on four weeds.(2)The germination and growth of four weeds were inhibited by physical covering effect and allelochemicals after three crops straw mulching.After moderate rain 3 times,the average inhibition rates of four weeds densities were 59.66%,53.64%,63.87% and 77.83% with total corn straw yield mulching(12000 kg/hm~2).The density of C.album and E.crusgalli were still significantly lower than CK after the third moderate rain,which was decreased by 48.38% and 56.68%,respectively.After moderate rain 3 times,the average inhibition rates of four weeds densities were 59.01%,51.70%,71.12% and 59.44% with total wheat straw yield mulching(9000 kg/hm~2).The density of C.album and E.crusgalli were still significantly lower than CK after the third moderate rain,which were decreased by 48.38% and 63.33%,respectively.After moderate rain 3 times,the average inhibition rates of four weeds densities were 66.12%,57.62%,60.57% and 81.50% with total foxtail millet straw yield mulching(8000 kg/hm~2).The density of C.album,S.viridis and E.crusgalli were still significantly lower than CK after the third moderate rain,which were decreased by 61.66%,63.67% and 86.68%,respectively.1/4 corn straw(3000 kg/hm~2),wheat straw(2250kg/hm~2),foxtail millet straw(2000 kg/hm~2)yield and 1/2 wheat straw(4500 kg/hm~2)yield were mulched after moderate rain 3 times,the average inhibition rate of four weeds was less than 50%,but the average inhibition rate of 1/2 corn straw(6000 kg/hm~2)and foxtail millet straw(4000 kg/hm~2)yield was higher than50% after moderate rain 3 times.The average inhibition rate of C.album density was higher than 50%when 1/2 corn straw(6000 kg/hm~2)and foxtail millet straw(4000 kg/hm~2)yield mulching for moderate rain 3 times.After the second moderate rain,the total corn,wheat and foxtail millet straw yield mulchin of weeds total cover-degree decreased by 37.21%,41.98% and 33.73%,respectively.And after moderate rain3 times,the average decrease of weed total cover-degree was no more than 20% under the 1/4 and 1/2 three crops straw yield mulching,the average decrease of weed total cover-degree was more than 20% under the three crops total straw yield mulching,were 24.39%,25.50%,23.84%,respectively.The weed control efficiency was the best when three crops total straw yield mulching,the weed control effect and fresh weight with 1/2 corn straw yield returning were 74.38% and 61.03%,respectively.The weed control effect and fresh weight with 1/2 wheat straw yield mulching were 63.37% and 48.37%,respectively.The weed control effect and fresh weight with toal foxtail millet straw yield mulching were 64.51% and 52.4%,respectively.After moderate rains 3 times,the average weed control effect was 60% and the average fresh weight control effect was 40%,the average weed control efficiency and fresh weight control efficiency were lower than 40% in 1/4 and 1/2 of three crops straw yield mulching.(3)After three crops straw mulching plant height,leaf area,SPAD,leaf photosynthesis and yield of foxtail millet were increased.1/2 corn and wheat straw yield mulching had the strongest photosynthetic effect of foxtail millet,and the net photosynthetic rate and transpiration rate of foxtail millet leaves were significantly affected.1/2 Wheat straw also had a significant effect on stomatal conductance.Total foxtail millet straw yield mulching had the strongest photosynthetic effect of millet,and the net photosynthetic rate and stomatal conductance of foxtail millet leaves was significantly affected.With half corn and wheat straw,total foxtail millet straw yield mulching,the yield of foxtail millet were the highest.It was 5781.51 kg/hm~2,5931.51kg/hm~2 and 5736.51 kg/hm~2.The yield was respectively increased 10.32%,13.18% and 9.46%. |
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