Effects Of Biochar Application And Water-Nitrogen Interaction On Growth,Water And Nitrogen Utilization Of Greenhouse Tomato

Unreasonable water and fertilizer management will lead to serious waste of water and fertilizer resources,environmental pollution and decrease in soil fertility,which further affects crop growth,yield and quality.As a soil conditioner,biochar can improve the conversion of effective nutrients in the soil,promote crop growth and improve crop yield and quality.The water and fertilizer integration technology under mulched drip irrigation plays an important role in improving the water and fertilizer use efficiency,yield and quality of greenhouse crops.Therefore,it is of great significance for the efficient production of greenhouse tomato to study whether the combination of biochar application and mulched drip fertigation technology can improve the soil water and fertilizer status,save water and fertilizer,and improve fruit quality and resources use efficiency.The greenhouse plot experiment was conducted on the tomato variety"Jingpeng 101"during the autumn of 2021 and the spring of 2022,with two biochar application rates of 30 t ha^-1（B1,applied only in the first season before sowing）and 0 t ha^-1（B2）,two nitrogen application rates of 175 kg N ha^-1（N1）and 250 kg N ha^-1（N2）,and three irrigation levels of 100%ETc（W1,ETc is crop water requirement）,75%ETc（W2）and 50%ETc（W3）.This study was aimed to explore the effects of water and nitrogen interaction on soil physical and chemical properties,soil microbial communities,tomato growth,physiology,fruit yield,quality,water and nitrogen use efficiency under biochar application,to improve the fruit quality and save water-fertilizer resources for greenhouse tomato production.This study can provide theoretical basis and technical support for sustainable greenhouse tomato production.The main findings are as follows:（1）The effects of biochar application and water-nitrogen interaction on soil physical properties and soil inorganic nitrogen migration were clarified.Compared with non-biochar treatment,biochar application reduced the soil bulk density of the plow layer by 7%-13%,and significantly increased soil porosity by 5.5%-10%.Compared with full irrigation（W1）,deficit irrigation（W2 and W3）increased soil bulk density by 1.3%and 2.2%and decreased soil porosity by 1.3%and 2.3%in autumn,and increased soil bulk density by 0.4%and 2%and reduced soil porosity by 0.8%and 2%in spring,respectively.Nitrogen application rate had no significant effect on soil bulk density and soil porosity.Compared with that in spring 2022,the average soil ammonium nitrogen content decreased by 5.4%in autumn 2021.Biochar application reduced soil NH₄⁺-N content by 4.2%and 12.8%in autumn and spring,respectively.Increasing nitrogen rate increased soil NH₄₊-N and NO₃^--N contents by 4.5%and 8.1%in autumn,and increased soil NH₄₊-N and NO₃^--N contents by 41.7%and 8.2%in spring,respectively.Biochar application increased soil NO₃^--N content by 9.2%and 4%in autumn and spring,respectively.（2）The effects of biochar application and water-nitrogen interaction on soil microbial amount and soil respiration were explored.The number of bacteria in each treatment tripled in spring compared to that in autumn.Biochar application increased the number of bacteria by 52.7%in autumn and by 40%in spring.Compared with W1,W2 and W3 reduced soil bacterial counts by 25.7%and 53.55%in autumn,and by 4.17%and 6.3%in spring,respectively.Actinomycetes in spring decreased by 70.6%compared with that in autumn.Compared with W1,W2 and W3 reduced the number of actinomycetes by 22%and 54.5%in autumn,and by 12%and 1%in spring,respectively.The number of fungi in spring decreased by 5.3%compared with that in autumn.Biochar application in autumn increased the microbial biomass nitrogen by 4.3%compared with non-biochar treatment.Compared with W1,W2 and W3 reduced the microbial nitrogen biomass by 5.6%and 12.4%in autumn,respectively.The total soil respiratory intensity in spring increased by 3%compared with that in autumn.However,biochar application increased total soil respiration intensity by 6.7%compared with non-biochar treatment.Compared with W1,W2 and W3 reduced total soil respiration by 8.2%and 8%in autumn,respectively.Compared with that in autumn,the average soil invertase increased by 5%in spring.Although the interaction of biochar application rate,nitrogen application rate,and irrigation level was not significant,biochar application had a beneficial effect on soil microbial parameters under the same nitrogen application rates,improving the microbial measurements under the same irrigation levels.（3）The effects of biochar application and water-nitrogen interaction on the photosynthetic characteristics of tomato were revealed.Compared with non-biochar treatment,biochar application increased the transpiration rate（Tr）,photosynthetic rate（Pn）,intercellular carbon dioxide concentration（Ci）and stomatal conductance（Gs）of tomato by 22.9%,20.9%,1.5%and31.1%in autumn 2021,and by 51.5%,59.7%,1.8%and 83.6%in spring 2022,respectively.The Tr and Ci increased by 0.3%and 4.7%in autumn,and Tr,Pn,Ci and Gs increased by25.3%,3.3%,2.6%and 7.7%in spring respectively,when nitrogen application rate increased from N1 to N2.Reducing irrigation level from W1 to W2 reduced Tr,Pn,Ci,and Gs by 24.6%,10.7%,13.5%,and 37.7%in autumn,and by 4.4%,2.6%,5.2%,and 16.8%in spring,respectively.Decreasing irrigation level from W1 to W3,Tr,Pn,Ci and Gs decreased by 40.1%,22.8%,17.1%and 52%in autumn,and by 7.5%,10.7%,7.4%and 25.1%in spring,respectively.Reducing the irrigation level from W1 to W2 and W3 increased SPAD by 5.5%and 5.6%in spring,respectively.Compared with non-biochar treatment,biochar application increased LAI by 15.5%and 8.6%in autumn and spring,respectively.（4）The effects of biochar application and water-nitrogen interaction on tomato growth and nutrient uptake were clarified.Compared with non-biochar treatment,biochar application increased the plant height（PH）,stem diameter（SD）,leaf fresh weight（LF）,stem fresh weight（SF）and fruit fresh weight（FF）of tomato by 7.9%,5.9%,32.5%,23.6%and 49.0%in autumn,and by 3.5%,6.6%,15.6%,12.5%and 63.0%in spring.Compared with that under W1,the PH decreased by 10.2%and 12.6%in autumn,and by 7.8%and 19.3%in spring under W2 and W3,respectively.The SD in spring increased by 9.93%compared with that in autumn.Compared with that in autumn,the total uptake of nitrogen,phosphorus and potassium increased by 80.2%,87.7%and 85.8%in spring,respectively.Biochar application increased the plant total nitrogen,phosphorus and potassium uptake by 33.9%,17.4%and 38.8%in autumn,and by 13.1%,7%and 18.3%in spring,respectively.Increasing nitrogen rate increased total nitrogen,phosphorus and potassium uptake by 12%,6.4%and 6.6%in autumn,and by 24.7%,19.3%and 32.3%in spring,respectively.Reducing the irrigation level from W1 to W2 reduced the total uptake of N,P,and K by 12.4%,23.8%,and 19.9%in autumn,and by 25.8%,22.6%,and 8.5%in autumn.Reducing the irrigation level from W1 to W3 reduced the total plant uptake of N,P,and K by22%,31.2%,and 39.4%in autumn,and by 51.2%,49.9%,and 52%in spring,respectively.（5）The effects of biochar application and water-nitrogen interaction on tomato yield,quality,and water-nitrogen utilization were clarified.The interaction of biochar application,nitrogen application rate,and irrigation level had significant effects on tomato yield and its components,and partial productivity of nitrogen fertilizer（PFPN）in both seasons.Tomato yield in spring increased by 49.5%compared with that in autumn,and PFPN in spring increased by48.6%compared with that in autumn.Compared with non-biochar treatment,biochar application increased the tomato yield by 73.8%and 40.5%,and PFPN by 67.4%and 37.7%in autumn and spring,respectively.The tomato yield in spring increased by 20.6%when nitrogen application rate increased from N1 to N2,and PFPN decreased by 30.8%and 15.6%in autumn and spring,respectively.Reducing the irrigation level from W1 to W2 and W3 reduced the tomato yield by 15.4%and 36.4%in autumn,and by 26.7%and 43.4%in spring,respectively.Compared with that in autumn,crop water productivity（WP）increased by 47.2%in spring.Biochar application increased WP by 22.1%compared with non-biochar treatment in autumn.Increasing nitrogen application rate from N1 to N2 increased WP by 15.3%and 51.1%in autumn and spring,respectively.Decreasing irrigation level from W1 to W2 and W3,WP decreased by 6.6%and 29.3%in autumn,and by 16.6%and 33.9%in spring,respectively.Biochar application also significantly affected total soluble solids（TSS）,soluble sugars（SS）and Vitamin C in tomato fruits.Biochar application and irrigation level had significant effects on TSS and SS contents in both seasons,and nitrogen application rate only had significant effects on TSS in autumn and SS in both seasons.Compared with that in autumn,the fruit number（FN）per plant increased by 41.4%in spring.The economic benefit in spring increased by 12.9%compared with that in autumn.Compared with non-biochar treatment,biochar application increased the economic benefit by 58.2%and 22.1%in autumn and spring,respectively.Considering tomato yield,quality,water and fertilizer use efficiency and soil nutrients residue,nitrogen application rate of 250 kg N ha^-1 and drip irrigation level of 75%ETc under biochar application rate of 30 t ha^-1 is the most optimal combination in this study.Meanwhile,the biochar application significantly improved the growth of greenhouse tomato under drip fertigation with film much,and biochar application still had a positive effect on tomato growth in the next growing season.