| In recent years,low fertilizer efficiency and insufficient water resources have seriously restricted the development of China’s apple industry.The integrated drip irrigation and fertilization technology of water and fertilizer can efficiently improve the efficiency of water and fertilizer utilization,and has the advantages of saving water and fertilizer,increasing production and income,and has broad prospects for development.Under the condition of water and fertilizer integration,the technical parameters of drip irrigation fertilization such as capillary laying mode and fertilization cycle will affect the spatial distribution of water nutrients in the soil,thereby affecting the growth and distribution of roots.The effects of different capillary laying modes and fertilization cycles on the dynamic and spatial distribution of fine root growth in apple trees can provide a basis for regulating the root growth of apple trees through drip irrigation fertilization mode.In 2019-2021,a two-factor two-level complete combination design field experiment was carried out,and the capillary laying method was set up with one row and one tube and one row of two tubes,the fertilization cycle was set for 15 days and 30 days,and the micro-root canal in situ monitoring technology was used to divide the apple trees into three directions of south,west and northeast and 0-19 cm,19-38 cm,38-57 cm,57-76 cm soil layers at different depths.The growth and death of fine roots during the active growth period of apple trees were continuously observed,the response dynamics of fine root growth and turnover of apple trees to the layout mode and fertilization cycle of capillary were analyzed,the spatial distribution of fine roots of apple trees under different water and fertilizer integration modes was revealed,and the regulatory effects of different drip irrigation fertilization modes on the growth of fine roots of apple trees were explored.The main research results are as follows:(1)The influence dynamics of capillary laying mode and fertilization cycle on the fine root morphology of apple trees were exploredThe root length density and root surface area density of apple trees change with time to a unmoded curve,and the fine root bulk density changes with the progress of fruit tree growth in a monamodal or bimodal type,and the maximum value is in July.The diameter of apple tree fine roots is mainly concentrated in the range of 0.5-1.5 mm,and the proportion of fine roots with diameters of 0-0.5 mm and 1.5-2 mm is very small;before July(June 2021),the number of fine roots with a diameter of ≦1 mm increased,and after July,the diameter >The 1 mm fine root increases rapidly.The root root length density,root surface area density and root volume density were significantly greater than 30 days in most of the growth stages of fertilization cycle of 15days;the capillary arrangement method had a significant effect on the root length density,root surface area density and root volume density of fine roots in individual soil layers during the whole growth period,and in the middle soil(19-38 cm soil layer),one row and two tubes could increase the root length density,root surface area density and root volume density of fine roots;in deep soil(57-76 cm soil layer),one row and one tube could promote fine root root length density.Increase in root surface area density and root bulk density.Compared with the fertilization cycle of 15 days,the fertilization cycle of 30 days can increase the diameter of fine roots;in August,one row and one tube can increase the diameter of fine roots compared with one row and two tubes.(2)The influence of capillary laying mode and fertilization cycle on the spatial distribution of fine roots in apple trees was revealedIn the vertical distribution,the root length density,root surface area density and root volume density of apple trees increase with the deepening of soil depth or fluctuate,all of which have the maximum values in the soil layer of 57-76 cm.Compared with the fertilization cycle of 30 days,the fertilization cycle of 15 days can increase the root length density,root surface area density and root volume density in the vertical direction,and reduce the fine root diameter in most soil layers.Compared with one row and two tubes,the root root length density,root surface area density and root volume density under the condition of one row and one tube were significantly reduced in the middle soil and significantly increased in the deep soil.In shallow middle soils(0-38 cm soil layer),one row and two tubes tend to increase the diameter of fine roots,and in middle and deep soils(38-76 cm soil layer),one row and one tube tend to increase the diameter of fine roots.In terms of horizontal distribution,the root length density,root surface area density and root volume density of apple trees all had a due west > a south-to-east > trend at each growth period,but the difference did not reach a significant level.Compared with the fertilization cycle of 30 days,the fertilization cycle of 15 days can increase the root length density,root surface area density and root volume density,and reach a significant level in due south and west,and the fine root diameter will be reduced in 3 horizontal directions in 15 days of fertilization cycle.In the true south upwards,one row and one tube tend to increase the diameter of the fine root compared with the one-row and two-tube,and in the true west upwards,the one-line,one-tube fertilization cycle of 15 days tends to decrease the fine root diameter compared with other treatments.(3)The influence of capillary laying mode and fertilization cycle on the fine root turnover of apple trees was clarified.The amount of fine root growth and death of apple trees varies seasonally.In 2020 and2021,fine root growth was concentrated in June-July and May-July,respectively,and fine root death was concentrated in August-October and July-September,respectively.Compared with the fertilization cycle of 30 days,the fertilization cycle of 15 days can significantly increase the growth and death of fine roots in time and space.The influence of capillary arrangement on the growth and death of fine roots is more complex,and has different effects in different growth periods.When the fertilization cycle is the same,one row and one tube will reduce the growth of fine roots in the middle soil compared with one row and two tubes,and increase the growth and death of fine roots in the deep soil.The capillary laying method and fertilization cycle have a significant impact on the annual turnover rate of fine roots,and in 2020,one row and one pipe can accelerate the turnover of fine roots compared with one row and two tubes,and the fertilization cycle in 2021 can accelerate the turnover of fine roots by 15 days compared with 30 days.Spatially,the influence of fertilization cycle and capillary laying on the monthly turnover rate of fine roots is poor,and the influence is inconsistent in different years. |
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