Effects Of Soil Physical Environment On Crop Roots Under Mechanized Ridge Tillage Rice And Rape

Rice and rape are important food and oil crops in the world.The rice-rape rotation is the main tillage measures in southwest China.During the rape planting period,the soil was usually in a state of less than the field capacity and the rice planting period,the soil was in a nearly saturated state or flooded condition.In recent years,the mechanized rice-rape ridge planting mode has been popularized in the hilly and mountainous areas of Chongqing.The infiltration irrigation of ridge and furrow irrigation makes the soil in the near saturated state(between field capacity and saturated water content)during rice planting.This mechanized rape-rice ridge cultivation technology is the product of the combination of modern mechanical agriculture and conservation tillage,which improves the soil physical environment of rice and rape root growth and increases crop yield through mechanized field ridge cultivation.Therefore,in order to improve the sustainable utilization of tillage soil and enhance the scientific nature of modern agricultural theory,it is very important to explore the influencing mechanism of soil physical environment on crop roots under mechanized rice-rape ridge,and to distinguish the advantages and disadvantages of different tillage methods.In this study,rape and rice were taken as the objects,and four tillage methods were setup to compare and analyze the effects of soil moisture environment,aggregate stability,porosity and bulk density on the root system and yield of rape and rice,namely,conventional tillage with the rice and winter fallow(CK1),conventional tillage with the rice and rape rotation(CK2),box tillage with the rice and rape rotation(BT),and ridge tillage with the rice and rape rotation(RT).The main research results are as follows:1.BT and RT treatments could change the movement direction and distribution of water in the flat soil,making the soil moisture environment more suitable for the growth of crop roots.The water storage at the center of soil ridge was lower than that of CK1 and CK2.Water in flat cropping is gravity water,moving vertically from top to bottom,while water distribution in compartment and ridge cropping soil is capillary water flow with symmetric infiltration front,stable,and moderate.The results showed that the infiltration of BT and RT treatment could weaken the effect of soil drying and hardening under the action of water evaporation and crop absorption,and the structure was destroyed.It could also avoid the situation of soil impermeable and loose structure caused by medium and long-term flooding in flat cropping treatment,and realize the coordination and stability of water,fertilizer,gas,and heat between soil and crops to the greatest extent.The order of soil water storage of each treatment in dryland soil of rape season was CK1 > CK2 > RT > BT,and the average soil water storage of each treatment was 64.68 mm,44.01 mm,43.24 mm and 42.69 mm,respectively.The soil water storage of each treatment in paddy soil in rice season was in the order of CK1>CK2>BT>RT.The average soil water storage of each treatment was 66.57 mm,57.72 mm,56.09 mm and 53.24 mm,respectively.It can be seen that the soil water storage of some special soil ridge center sites in BT and RT treatments was always lower than that in the flat cropping treatment no matter in rape or rice season.2.With the development of rape and rice growth stages,the soil structure of BT and RT treatments became more and more stable,and finally the stability indexes at rice maturity stage were higher than those of CK1 and CK2.In the mature period of rice,the content of water-stable aggregates >5 mm particle size from high to low was RT>BT>CK2>CK1,CK2>BT> RT;PAD of CK1 treatment in 0～10 cm and 10～20 cm soil layers was significantly higher than that of CK2,BT and RT treatments;MWD in 0～10 cm soil layer,RT treatment was 85.93%,22.11%,10.12% higher than CK1,CK2,BT treatment,BT treatment was 68.84%,10.89% higher than CK1,CK2 treatment.MWD in 10～20 cm soil layer,RT treatment than CK1,CK2,and BT treatments significantly higher43.23%,22.39%,21.03%;in 0～10 cm soil layer,GMD of RT treatment was 143.69%,42.61%,16.20% higher than CK1,CK2,and BT treatments,109.71% and 22.73% higher than CK1 and CK2 treatments.GMD of RT treatment was 71.90%,38.67%,32.48% higher than CK1,CK2,and BT treatments in 10～20 cm soil layer.In all growth stages from rape season to rice season,the total porosity of CK1 treatment was always the largest among the four treatments,and the macropores of >30 μm were also the dominant pores in multiple periods.BT and RT treatments increased soil bulk density,and the soil shrinkage rate of CK1 treatment was significantly higher than that of RT treatment,which further confirmed that the soil structure of RT treatment was more stable than that of CK1.3.BT and RT treatments can promote the root development of rape and rice in varying degrees,and improve root activity.In the mature stage of rapeseed,the root dry weights of BT and RT treatments were 118.64% and 154.55% higher than those of CK2 treatment.The total root length and surface area of RT treatment were 116.66% and 111.03% higher than CK2 treatment,75.61% and70.87% higher than BT treatment.The root activity of RT treatment was 52.79% and 87.61% higher than that of CK2 and BT treatments.The total absorption area of BT and RT were 204.37% and152.84% higher than CK2.In the mature period of rice,root fresh weight,root dry weight and total root length of BT treatment were significantly higher than those of CK1,CK2,and RT treatments,in which root fresh weight was 68.97%,62.42% and 19.65% higher,root dry weight was 76.42%,50.81%,and 19.87% higher,and total root length was 65.65%,59.25%,and 16.43% higher.The root activity of BT treatment was 163.74% and 137.56% higher than CK1 and CK2.The root activity of RT treatment was 176.94% and 149.45% higher than CK1 and CK2.The total absorption area of BT treatment was significantly higher than that of CK1 and CK2 by 93.63% and 105.07%,and that of RT treatment was significantly higher than that of CK1 and CK2 by 67.77% and 77.69%.4.BT and RT treatments could increase all economic traits in a balanced way,so as to obtain high yield.In the rape season,BT and RT treatments were significantly higher than CK2 in many economic traits,including plant height 11.32%,9.30% higher,effective branch number 59.50%,32.40% higher,main inflorescence length 40.90%,25.33% higher,effective pod number 82.39%,81.96% higher,theoretical yield 12.43%,8.08% higher.In rice season,the grain number per panicle and grain number per panicle of BT treatment were significantly higher than CK1,CK2,and RT,respectively.The grain number per panicle of BT treatment was 5.75%,7.20% and 6.41% higher than CK1,CK2,and RT,respectively.The grain number per panicle of BT treatment was 12.37%,11.82%,and 5.67% higher than CK1.The theoretical yield of BT and RT treatment was 28.75% and28.16% higher than CK1.The Actual yield of BT treatment was 20.82% and 13.54% higher than CK1 and CK2.The Actual yield of RT treatment was 19.49% and 12.29% higher than CK1 and CK2.In summary,compared with the conventional tillage with the rice and winter fallow(CK1)and conventional tillage with the rice and rape rotation(CK2),the soil water environment of mechanized box ridge tillage changed,and the soil structure became more stable,and the root growth of rape and rice was more vigorous,that higher yield could be harvested.Therefore,in the selection of tillage methods,box tillage with the rice and rape rotation(BT)and ridge tillage with the rice and rape rotation(RT)are preferred.The results of this study can provide data support for rice-oil rotation and mechanized agriculture,and promote the development of modern agriculture and the sustainable utilization of cultivated land resources.