| Nutrient management measures and crop rotation systems have important implications for food production.The Yangtze River Basin has superior natural conditions and abundant water and heat resources which is an important main grain and oil producing area in China.The main crop rotation systems in the region include wet-dry rotations and dry-dry rotations.Reasonable nutrient management measures in different crop rotations play an important role in increasing crop yield and improving soil fertility.In order to clarify the effects of different nutrient management measures and crop rotation systems on soil physical properties;and explain the effects of scientific nutrient management measures and reasonable crop rotation system in fertilizing soil fertility,increasing production and efficiency from the perspective of soil physics.From 2020 to 2021,the research was carried out based on field positioning experiments that have been conducted for five years in Shayang County,Hubei Province.The study selected no fertilization(CK),conventional Fertilization(NPK),conventional fertilization + straw returning(NPK+S)of wet-dry rotations(including maize-oilseed rape(MO)and maize-wheat(MW))and dry-dry rotations(rice-oilseed rape(RO)and rice-wheat(RW)),and partial replacement of chemical fertilizers with organic fertilizers treatment(1/2NPK+M)was added in wet-dry rotations.The study investigated aboveground biomass of each crop and analyzed soil physical indicators such as soil bulk density,soil compactness,soil particle composition,soil moisture,and soil temperature.The main findings are as follows:(1)Crop biomass was not only significantly increased in different fertilization treatments,but also affected by different crop rotation systems.Compared with CK treatment,NPK,NPK+S,1/2NPK+M treatments increased the aboveground biomass by63.3%-1011.2%,64.6%-1154.6%,48.4%-234.2%,respectively,and among which NPK+S treatment had the best effect on increasing crop biomass.Compared with wheat rotations,the aboveground biomass of the summer crops in oilseed rape rotations increased by 0.2%-74.4%(rice)and 14.8%-53.5%(maize),respectively.Compared with dry-dry rotations,the wheat biomass of wet-dry rotations increased by 2.5%-69.6%;but the biomass of oilseed rape in wet-dry rotations was only increased by 63.3% in CK treatment,and decreased by22.8% and 38.1% in NPK and NPK+S treatments,respectively.(2)Fertilization could significantly reduce soil bulk density and soil compaction,and NPK+S treatment had better effect on loosing soil among fertilization treatments.There were obvious differences in soil bulk density and small differences in soil compaction among different crop rotation systems.Compared with CK treatment,soil bulk density of NPK,NPK+S and 1/2NPK+M treatments decreased by 0.4%-10.6%,0.1%-14.5%,1.0%-8.9%,respectively.Among fertilization treatments,NPK+S treatment reduced soil bulk density the most.Fertilization treatments also reduced soil compaction at the soil depth of0-45 cm,and the reduction effect was more pronounced in wet-dry rotations.Compared with wheat rotations,the soil bulk density of oilseed rape rotations decreased by 0.4%-11.1%.The soil bulk density of wet-dry rotations was 0.1%-16.8% lower than that of drydry rotations,and the difference was more obvious in 0-10 cm soil layer.Compared with dry-dry rotations,the soil compaction of wet-dry rotations was smaller at the soil depth of0-10 cm and 30-45 cm,and larger at the soil depth of 10-30 cm.(3)Different fertilization treatments and crop rotations had significant effects on soil particle composition.Compared with no fertilization treatment,the relative content of clay and silt in 0-10 cm soil layer was significantly increased,while the relative content of sand was decreased in fertilization treatments;the variation trend of soil particle composition in10-20 cm soil layer was the same as that in 0-10 cm soil layer in RO and MW rotations,and opposite to that in the 0-10 cm soil layer in RW and MO rotations.The variation trend of soil particle composition was opposite in the RO/RW and the MO/MW in oilseed rape rotations compared with wheat rotations.Compared with RW rotation,RO rotation had higher clay and silt particles and lower sand particles.Compared with MW rotation,MO rotation had lower clay and silt particles and higher sand particles.Compared with the drydry rotations,the clay and silt grains of wet-dry rotations were decreased by 3.4%-36.9%,0.1%-18.7%,and the sand grains of wet-dry rotations were increased by 0.5%-78.2%.(4)Fertilization treatments increased soil permeability,water storage and moisture retention capacity,and saturated hydraulic conductivity,field capacity and soil water content were also significantly different under different crop rotation systems.Compared with the CK treatment,the NPK,NPK+S,1/2NPK+M treatments increased saturated hydraulic conductivity of 0-10 cm soil layer by 48.6%-227.1%,37.7%-613.5%,40.9%-689.9%,respectively;increased field capacity by 0.6%-7.1%,0.9%-14.7%,2.6%-19.4%,respectively;increased soil water content of 0-20 cm soil layer in each growth period by2.6%-20.8%,3.9%-41.9%,0.5 %-34.2%,respectively.Water retention effect was more prominent when there was no precipitation and water retention and permeability of the soil treated with NPK+S were the best in fertilization treatments.Compared with wheat rotations,saturated hydraulic conductivity of oilseed rape rotations decreased by 14.0%-57.6%,and soil water content of oilseed rape rotations increased overall.Compared with wheat rotations,field capacity of oilseed rape rotations was larger in wet-dry rotations,and smaller in dry-dry rotations;in oilseed rape/wheat season,the field capacity of oilseed rape rotations was smaller in 0-10 cm soil layer,and larger in 10-20 cm soil layer.Compared with dry-dry rotations,saturated hydraulic conductivity decreased by 53.6%-99.1%,field capacity increased by 1.2%-16.7%,and soil water content increased by 1.0%-104.4%.(5)Different nutrient management measures and crop rotation systems affected the diurnal dynamics of soil temperature during overwintering.Fertilization could increase the soil temperature when it was cold,and reduced the daily range of soil temperature by increasing the daily minimum soil temperature and reducing the daily maximum soil temperature.Among fertilization treatments,the soil insulation effect of NPK+S treatment was better.Compared with wheat rotations,oilseed rape rotations had better soil thermal insulation,and the thermal insulation effect of wet-dry rotations was greater than that of dry-dry rotations.To sum up,scientific nutrient management measures in different crop rotations,such as straw returning and organic fertilizer input,can increase crop biomass and improve soil physical properties.At the same time,a reasonable crop rotation system is also conducive to increasing soil physical fertility.The research results provide scientific basis and theoretical support for scientific fertilization and rational crop rotation to improve soil productivity while fertilizing soil. |
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