| The northeast black soil area is an important agricultural production area in China.However,due to the predatory reclamation and management for many years and the reuse and light cultivation of black land,the black soil has gradually become"hard","thin","thin"and other degradation phenomena,and the soil quality has decreased and the cultivability is poor.Conservation tillage is a modern tillage model with the core of less tillage and no tillage and straw returning.It has the functions of windproof soil consolidation,improvement of soil structure,enhancement of soil fertility,stable yield and increase.However,a particular tillage measure is not suitable for all areas,but should be selected according to the local climate conditions,soil conditions and other factors.In this study,the corn soil and corn plants in the mild and sub humid agricultural climate area of the northeast black soil region were selected as the research objects.Three tillage methods were selected,namely,tilling（CT）,mulch tillage（MT）and strip tillage（ST）,to analyze the physicochemical and biological characteristics of the black soil as well as the growth and nutrient accumulation of maize under different tillage modes.In order to improve a series of problems caused by traditional tillage,such as soil structure destruction and quality reduction,black land ecological restoration and agricultural sustainable development.The results are as follows:（1）Effects of conservation tillage on soil moisture and heat effects:the average volume moisture content of 0-25 cm soil layer in the whole growth period was MT>ST>CT in order from large to small,and MT and ST were 18.17%and 9.28%higher than CT,respectively.The mean soil temperature of 0-25cm soil layer in the whole growth period was 2.12%and 9.17%higher in CT treatment than in MT treatment and ST treatment,respectively.The results showed that both mulch tillage and strip tillage could improve soil water retention,but had a certain lag effect on soil temperature change,and the effects of both tillage and cover tillage on soil water and temperature decreased with the increase of soil depth.（2）Effects of conservation tillage on black soil fertility:Compared with CT,soil total nitrogen in MT and ST increased by 15.28%and 13.32%,respectively.Soil total phosphorus increased by29.54%and 26.16%,respectively.Soil total K increased by 9.68%and 11.47%,respectively.Organic matter content increased by 11.76%and 4.98%,respectively.Both mulch tillage and strip tillage can significantly increase soil nutrient and organic matter contents,and mulch tillage has the best effect on soil fertility.（3）Effects of conservation tillage on carbon sequeering potential and aggregate stability of black soil:soluble organic carbon content under MT and ST was significantly increased by 22.02%and 13.23%compared with CT,respectively.The easily oxidized organic carbon was significantly increased by 27.23%and 16.83%,respectively.R>0.25mm（large aggregate percentage content）significantly increased by 6.89%and 7.05%,respectively.MWD（mean weight diameter）was increased by 10.13%and 8.97%,respectively.GMD（geometric mean diameter）increased by 16.08%and 14.28%,respectively.The results showed that both mulch tillage and strip tillage could significantly increase soil active organic carbon content and enhance soil aggregate stability,and mulch tillage had the best effect.（4）Effects of conservation tillage on microbial activity and diversity of black soil:MT and ST sucrose enzyme activity increased by 44.52%and 34.55%compared with CT.The urease activity was increased by 8.93%and 20.56%,respectively.Phosphatase activity increased by 15.61%and32.58%,respectively;Soil microbial biomass carbon content increased by 17.65%and 14.67%,respectively.Soil microbial nitrogen content increased by 28.47%and 14.26%,respectively.In Alpha diversity index,MT and ST increased Chao1 index（16.53%and 17.06%）,Ace index（14.09%and 16.01%）and Shannon index（4.06%and 4.49%）compared with CT.These results indicated that both mulch tillage and strip tillage could increase soil enzyme activities and microbial biomass.In general,strip tillage had a better effect on enzyme activities,while mulch tillage had a better effect on microbial biomass.In addition,the results showed that both mulch tillage and strip tillage could significantly improve soil microbial community richness,and mulch tillage could also improve soil microbial community diversity.Mulch tillage and strip tillage also had significant effects on the composition of soil microbial community.Both of them could improve the soil microecology by increasing some bacteria with degrading ability（such as Actinobacteria）and nitrogen-fixing ability（such as Bradyrhizobium）which were beneficial to crop growth and soil quality improvement.（5）Effects of conservation tillage on maize yield and nutrient accumulation:MT and ST increased maize yield（5.02%and 9.13%）,effective ear number（2.48%and 8.67%）,kernel number per ear（3.07%and 9.78%）and 100 kernel weight（12.07%and 6.17%）compared with CT.Compared with CT,MT increased grain total nitrogen content by 6.25%,while ST decreased by3.57%.Compared with CT,MT and ST increased total phosphorus content by 13.74%and 3.85%,respectively.Compared with CT,MT and ST increased total potassium content by 10.71%and7.14%,respectively,but there was no significant difference among all treatments.MT straw total nitrogen content significantly decreased by 10.53%compared with CT straw total nitrogen content,but there was no significant difference between ST and CT.The above results showed that mulch tillage could increase corn yield by increasing corn kernel weight.Band tillage can increase corn yield by increasing the number of grains per ear and the number of effective ears.Mulch tillage can also increase the absorption of total nitrogen,total phosphorus by corn grains and total phosphorus by straw.In conclusion,different conservation tillage modes have different effects on the physicochemical and biological characteristics of black soil as well as the growth and nutrient accumulation of maize,and one tillage mode is not superior to another mode in all aspects.Mulch tillage was superior to strip tillage in terms of soil moisture and heat,fertility,structure and nutrient element absorption by crops.In terms of soil microecology and crop yield,strip tillage is more suitable. |
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