Effects Of Different Tillage Depth On Soil Structure And Annual Yield Of Wheat And Maize

This experiments were carried out from 2015 to 2016 in Zhujia Bu village,Laiyang,Shandong province,where rotated with wheat-maizecropping pattern.The wheat cultivar was Yannong 24 and maize was Zhengdan 958.Straw was all filled into the fields.A completely randomized block design was used,four treatments with straw returning in which was CT-20,CT-25,CT-30 and SS-30.The effects of different tillage depth on soil structure,soil aggregates distribution and stability,soil carbon storage and wheat-maize yield were analyzed,aiming to select suitable tillage method depth for East Shandong region to achieve high and stable yield.The main results are as follows:1 Effects of different tillage depths.on soil basic structureAmong the three different tillage depths,the soil water content increased by CT-30 was significantly higher than that of the other two tillage treatments in the soil layer below 20 cm.CT-30 can break the plow bottom formed for many years,and play a role in the regulation of soil moisture.SS-30 is slightly lower than that of CT-30 in 0?60 cm soil layer.The result suggests that plowing is more beneficial to improve soil water content at the same tillage depth.However,the soil water content of SS-30 was higher than that of CT-30 after the maize Tasselling stage.This is because that the drought of maize season is serious in the Yantai area.In the sudden drought season,SS-30 can still show a higher soil moisture and have significant drought resistance.The soil compaction decreases with the increase of tillage depth in the soil layer below 30cm.Although CT-30 did not cultivate the soil layer below 30 cm,the compactness of the soil layer below 30 cm was less than that of the other two tillage treatments.This is inextricably linked with that deep tillage is beneficial to the extension of wheat root to deep layer.At the same time,subsoiling had little effect on the surface soil,but it could significantly improve the compaction of deep soil layer.In the wheat season,there were very few differences among the three plowing treatments on the bulk density at 0?20 cm soil layer,however the soil bulk density under subsoiling was higher than that under plowing,significantly.In 20?40 cm soil layer,the results was on the opposite side.In the maize season,differences in soil bulk density decreased gradually at 0?10 cm soil layer.At 20?40 cm,CT-20 showed a larger soil bulk density,while the difference in soil bulk density among other treatments was reduced.Compared with the difference in the effects of tillage on bulk density in the wheat season,which was not significantly different in the maize season.The experimental results show that the size of the bulk density depends mainly on the cultivation in the wheat season.In the maize season,the effect of tillage on the bulk density is reduced,and the bulk density is affected by more factors such as straw returning,rainwater,root and so on.2 Effects of different tillage depths on soil aggregate distribution,stability and carbon poolIn 20?40 cm soil layer,with the depth of tillage deepening,the effect of soil aggregates increased,and the stability of aggregates MWD and GMD also decreased.From the side reflects the deeper depth of farming,the more conducive to the protection of soil aggregates stability.During the process of subsoiling treatment,with the depth of soil deepened,the particle size of aggregates decreased gradually,and the number of large aggregates decreased gradually.In the growth stage of wheat,the soil micro-aggregate(Less than 0.25 mm)ratio of SS-30 was less than that of CT-30,and the stability was higher.Therefore,SS-30 is more conducive to improve the stability of soil aggregates.In this study,differences in aggregate stability among the different treatments decreased gradually with the extension of time.The soil layer with higher soil aggregate organic carbon usually has higher soil aggregate stability index.As SS-30 does not flip soil,structures of soil superficial(0-10cm)are protected,therefore soil organic matter shows the phenomenon of soil surface enrichment.While conventional tillage can improve the organic carbon content of aggregates in deep soil,it also reduces the stability of soil aggregate in this soil layer.The SOC content of soil aggregates decreased with the increase of soil depth.But soil aggregate SOC content of CT-30 at 20-40cm soil layer are significantly more than other plowing treatments,which indicates that organic carbon content of soil aggregates in the deep layer were more favorable with the increase of tillage depth.3 Effects of different tillage depths on crop yield and grain carbon costIn the wheat season,increasing the depth of tillage could effectively improve the number of spikes and grains per spike,but the impact on the 1000-grain weight was not significant.The yield of CT-30 was highest.The yield of CT-30 and that of CT-25 was respectively increased by 13.52%and 3.58%more than CT-20.Therefore,CT-30 could improve the yield of wheat significantly.There were no significant differences in spike number,grains per spike number,1000-grain weight and yield between CT-30 and SS-30.In the maize season,the number of spikes,grains per spike and 1000-grain weight of CT-30 were significantly higher than that of CT-20 and CT-25.There were no significant differences in yield between CT-30 and SS-30,but the yield was significantly better than CT-20 and CT-25.In the wheat-maize two-year system,the highest grain carbon cost was CT-20,and the lowest grain carbon cost was SS-30.The result shows that CT-20 needs to put more productive substances to maintain production in the case of the same yield.It also shows that SS-30 and CT-30 had few differences in yield,but at the same yield the input of SS-30 was less than that of CT-30,which is more suitable for the production of tillage.