| Facility agriculture is an important part of China's agricultural modernization,and its rapid development has greatly enriched the people's vegetable basket.In the process of facility agricultural production,unreasonable irrigation often causes waste of water resources and reduces irrigation water use efficiency,while appropriate irrigation management measures help crops to achieve high benefits of water-saving and high-yield.Micro-sprinkler irrigation under plastic film(MSPF)uses multiple groups of small micropores with hose under the plastic film to flow out to evenly distribute water in root soil with gravity and capillary suction,which has promoted crop growth.however,the mechanism of its impact on crop growth and water use efficiency is not clear.Therefore,the study on the effects of MSPF on crop soil microenvironment and crop growth can provide support for optimizing facility agricultural irrigation technology and promoting efficient utilization of water resources.This study takes the facility agricultural tomato as the research object,through the greenhouse tomato experiment and multi-objective optimization analysis.To explore the effects of different irrigation methods(micro-sprinkler irrigation under plastic film,drip irrigation under plastic film,micro-sprinkler hose irrigation),layout measures(micropore group spacing,capillary arrangement density)and irrigation scheme(irrigation frequency,irrigation quantity)on crop soil physical and chemical properties,soil microorganisms,soil enzyme activities,crop growth(crop root,plant growth and yield).The effects of soil physical and chemical properties,soil bacterial community,soil enzyme activity,crop root system,and plant growth on tomato yield under MSPF were investigated.The effect mechanism of MSPF on tomato yield and water use efficiency in the greenhouse was revealed.And the index of optimizing the irrigation technical system of MSPF is put forward.The main conclusions are as follows:(1)The MSPF can improve the uniformity of soil water distribution and promote water-saving and yield-increasing of tomato.The wetting peak of the soil profile of MSPF is banded,and the soil wetness of the tillage layer(0-40 cm)is relatively high and the irrigation uniformity is high.Suitable soil moisture promotes the root morphological development of tomato under MSPF is better than that of DIPF and MSI.The root metabolism of high-level morphological development is exuberant,which is beneficial to the increase of bacterial ACE index(population abundance)and the abundance of nitrogen and phosphorus metabolism genes in tomato soil.Metabolic vigorous roots and stable bacterial communities can increase soil enzyme activities and facilitate the activation of soil nutrients to be absorbed and utilized by tomato roots.the yield of spring and autumn tomato under MSPF was better than that of DIPF and MSI about 19.39%and 4.54%,21.03%and 58.04%;the economic benefit of spring and autumn tomato under MSPF was better than that of DIPF and MSI about 6.68%and 31.36%,19.80%and 50.31%.(2)Micropore group spacing 30 cm micro-sprinkling hose irrigation can improve soil moisture distribution,increase soil nitrogen and phosphorus metabolism gene abundance,and increase crop yield.The 30 cm micro-sprinkling pipe irrigation in the micropore group spacing not only increased the soil volume moisture content of tomato tillage layer,but also decreased the soil water-filled porosity.Suitable soil moisture and air environment are beneficial to the development of crop root morphology.Higher root development and suitable soil moisture not only increase the abundance of tomato soil bacterial amino acid transport and metabolism and nitrogen and phosphorus metabolism functional genes,but also increase soil enzyme activity,strengthen the crop roots' ability to absorb soil nutrients,increase leaf photosynthesis rate,and promote irrigation with micropore group spacing 30 cm.The yield and crop water use efficiency(WUE)of spring tomato and autumn tomato with micropore group spacing 30 cm are higher than 50cm,about 14.15%and 11.27%,12.64%and 10.35%.(3)One pipe for 3 rows(1 micro-sprinkler hose irrigation for 3 rows of tomato)capillary arrangement density irrigation increased soil water inhibition in root zone,limited crop root morphology and structure,and decreased crop WUE.The soil volume water content in the tillage layer of spring tomato and autumn tomato in one pipe for 2 rows was significantly higher than that in one pipe for 3 rows about 6.67%and 6.69%.Lower soil moisture limits the morphological development of crop roots.High-level root morphological development could increase root exudates,and increase the abundance of bacterial functional genes and soil urease activity and phosphatase activity in tomato soil with one pipe for 2 rows.The abundance of functional genes of soil bacteria and soil enzyme activity in the lower soil limit the absorption and morphological development of soil nutrients by tomato roots.As a result,the yield and WUE of spring and autumn tomatoes irrigated by one pipe for 2 rows are higher than those of 34.76%and 15.23%,31.94%and 13.91%irrigated with one pipe for 3 rows.(4)Irrigation frequency of 5 days can increase soil volume moisture content of tillage layer,accelerate soil nitrogen and phosphorus turnover,and improve crop water use efficiency.Under irrigation frequency of 3 days,the soil wetting body was smaller and the wetting duration was longer,and there were obvious wetting and drying areas in the temporal and spatial distribution of soil moisture under irrigation frequency of 7 days.As a result,the soil microorganisms of tomato roots under irrigation frequency of 3 days and irrigation frequency of 7 days are vulnerable to water and hypoxia stress,which limits the increase of functional gene abundance.The activities of urease and alkaline phosphatase in tomato soil also decreased with the lower abundance of nitrogen and phosphorus metabolism genes in soil bacteria,which was not conducive to the turnover of soil nitrogen and phosphorus,and limited the morphological development of crop roots and the accumulation of net photosynthetic dry matter in leaves.As a result,the yield and water use efficiency of spring and autumn tomatoes were better at 5 d irrigation frequency.(5)The amount of irrigation 1.00Epan every 5 days(Epan represents 5-day cumulative evapotranspiration of ? 20 evaporation pan)could enhance the positive interaction of crop root-soil bacteria-soil enzyme activity and increase crop yield.The appropriate soil water environment under 1.00Epan irrigation amount treatment promoted the total root length of spring and autumn tomatoes to be higher than that of 0.70Epan,1.20Epan treatments by about 9.98%and 11.06%,2.10%and 3.16%,respectively.Higher root morphological development could optimize soil bacterial community structure and function.The rapid development of root morphology and the metabolism of soil bacteria release more soil enzymes.Higher enzyme activity promotes the absorption of soil nutrients by crop roots,and positively promotes the high-level development of root morphology and crop dry matter accumulation.The positive interaction of crop root-soil bacterial community-soil enzyme activity promoted 1.00Epan treatment to increase tomato yield and WUE at the same time.Based on the comprehensive consideration of soil microenvironment,crop growth,and other factors,the MSPF has strong application value in facility agriculture irrigation management.Through changing irrigation management measures,the MSPF can directly or indirectly regulate soil water distribution,change crop root growth and crop activity.Changes in root morphology affect rhizosphere soil bacterial community and soil enzyme activity,thereby regulating soil nutrient turnover and affecting crop yield and water use efficiency.In the management and application of MSPF in the greenhouse,the suitable adoption of MSPF is to select micro-sprinkler pipe with micropore group spacing of 30 cm,adopt the mode of one pipe for 2 rows and the irrigation amount of 1.00Epan with irrigation frequency of 5 d can not only significantly improve the soil microenvironment,but also increase crop yield and WUE. |
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