秸秆添加对土壤微生物–根系形态介导的番茄磷吸收的影响

  【目的】  研究了添加秸秆后土壤微生物(包括解磷微生物)丰度、磷有效性的动态变化，以及作物根系的生长发育特征对作物磷吸收的影响。  【方法】  以番茄 (Solanum lycopersicum)为供试作物进行田间试验，设置添加秸秆和不添加秸秆对照两个处理，在番茄移栽后第15、30及45 天，测定了番茄地上部生物量、磷含量和根系形态，同时测定了土壤微生物数量(细菌、真菌、解磷微生物)、微生物生物量磷和速效磷含量，分析了微生物?根系–作物磷吸收的关系。  【结果】  添加秸秆提高了成熟期番茄的地上部生物量，显著提高了叶片和地上部的磷吸收量，地上部(叶+茎+果实)总磷吸收量较不加秸秆番茄增加21.8%。与无秸秆对照处理相比，添加秸秆处理提高了土壤细菌以及具phoD，phoC和pqqC功能基因的解磷微生物丰度，增加了微生物量磷。添加秸秆处理降低了移栽后15 天番茄根系生物量和组织密度，增加了根系比根长，降低了移栽后15到30 天的番茄根系生长。番茄移栽后第30 天到45 天，土壤细菌、真菌丰度下降，微生物量磷降低，丰富的解磷微生物以及微生物量磷降低介导的磷活化，驱动番茄根系生长加快，比根长增加，根系直径降低。根系生长与土壤有效磷(Olsen-P)相关性显著。  【结论】  添加秸秆初期微生物增生导致番茄根系生长缓慢，后期微生物量磷的降低和解磷微生物对磷的活化促进细根的快速伸长。秸秆还田激发微生物量磷活化协同根系高效磷吸收特征，促进成熟期番茄地上部磷吸收的增加。

Effects of straw addition on soil microbes-root morphology governing phosphorus-acquisition of Solanum lycopersicum

  【Objectives】  The interactions between microbial phosphorus (P) mobilization and root traits govern crop yield. Investigating the impacts of straw addition on dynamics of microbial abundance and microbial P mobilization as well as root traits is important to reveal the mechanism of high crop P-use efficiency underlying root-microbe interaction.   【Methods】  Tomato (Solanum lycopersicum) field experiment was conducted under addition (+straw) and no addition of straw (–straw) conditions. At 15, 30, and 45 days of transplanting, the shoot biomass, P content and root morphological traits of tomato were analyzed. The abundance of soil bacteria and fungi with phosphate-solubilizing abilities and the microbial biomass P and Olsen-P content were determined at the same time.   【Results】  The shoot P content of tomato under +straw was lower than those under –straw at 45 days of transplanting, and the P content in the aboveground part of tomato (leaves, stems, and fruits) were 21.8% higher at maturing stage. Straw addition increased abundance of bacteria and phosphate-solubilizing microbes encoding phoD, phoC and pqqC genes, and raised microbial P content in soil. At 15 days of transplanting, tomato under +straw had smaller root/shoot ratio, lower root tissue density, larger specific root length, and root traits were significantly correlated with soil Olsen-P. +Straw decreased tomato root elongation during 15–30 days of transplanting. During 30–45 days after transplanting, the abundant phosphorus-solubilizing microorganisms and the release of microbial P promoted soil P bioavailability and increased growth of thin roots with large specific length.   【Conclusions】  The proliferation of microbes caused slow growth of tomato roots initially after straw addition, whereas P mobilization mediated by the decline in microbial biomass P and phosphate-solubilizing functional microorganisms promoted rapid elongation of fine roots at the late stage. Straw return stimulated microbial P mobilization coupling with efficient root P-acquisition strategies increased crop P uptake in tomato at maturity.