生物黑炭对玉米苗期根际土壤氮素形态及相关微生物的影响

生物黑炭被作为土壤改良剂应用逐渐被认可,但其应用机制特别是生物黑炭对氮素形态和根际微生物的影响机理尚不明确,影响其推广。本文采用盆栽试验,研究了玉米和水稻秸秆烧制的生物黑炭按不同量施入土壤后,对玉米苗期株高、生物量和根际土壤氮素形态及相关微生物的影响。结果表明,施入60 g·kg-1玉米黑炭和40~60 g·kg-1水稻黑炭均对玉米苗期株高有显著(P0.05)降低作用,其中水稻黑炭的降低效果更为明显;分别施入60 g·kg-1玉米黑炭和20~60 g·kg-1水稻黑炭后,玉米植株地上部生物量均显著降低。施入60 g·kg-1玉米黑炭后根际土壤含水量和微生物量氮显著提高。随两种生物黑炭施入量的不断增加,玉米苗期根际土壤全氮、硝态氮含量以及固氮作用强度也显著增加,且均在60 g·kg-1施用量下达最大值。施用40 g·kg-1玉米黑炭可显著提高玉米苗期根际土壤氨态氮含量。同时,施用两种生物黑炭后,均不同程度地抑制了玉米根际土壤中细菌总体数量,促进了固氮菌和纤维素降解菌的生长,其中施入60 g·kg-1玉米黑炭的效果最为明显。综上,玉米和水稻秸秆生物黑炭的适量施用,可以促进玉米根际土壤氮素的循环转化,影响相关微生物的群落结构,且与水稻秸秆相比,玉米秸秆生物黑炭的施用效果更加明显。本文针对作物生长、土壤氮素形态及相关微生物数量3个方面研究生物黑炭施入土壤对氮有效性的影响,能够更全面、更准确地将生物黑炭如何影响土壤氮素转化展现出来,促进生物黑炭的深入开发利用,对黑土肥力保护具有一定意义。

Effect of biochar on nitrogen forms and related microorganisms of rhizosphere soil of seedling maize

Recent researches have noted that biochar significantly increases soil carbon storage, improves soil fertility and maintains balanced soil ecosystem. Biochar also acts as soil fertilizer or amendment to enhance plant growth and increase crop yield by supplying and retaining soil nutrients. Biochar is also widely used in agricultural soils as soil conditioner. Furthermore, there is experimental evidence that soil microbial communities/activities which sustain soil health and functions are directly affected by biochar addition to soils. The full range of the processes and consequences of the effects of biochar remains poorly documented. In a pot maize cultivation experiment, different quantities of charcoals from burnt maize and rice straws were applied and the maize seedling height, biomass and rhizosphere soil nitrogen transformation, and the related microorganisms investigated. The research results showed that 60 g·kg^-1 maize biochar and 40 60 g·kg^-1 rice biochar significantly decreased maize seedling height (P < 0.05). Rice biochar presented more apparent effects than maize biochar. Aboveground biomass of maize seedling was also significantly reduced under 60 g·kg^-1 maize biochar or 20 60 g·kg^-1 rice biochar application. Under 60 g·kg^-1 maize biochar application, rhizosphere soil water content and microbial biomass N obviously improved. As the application level of the two types of biochar increased, the content of total nitrogen/nitrate and nitrogen fixation rate also appreciably increased, reaching peak levels at 60 g·kg^-1 maize or rice biochar application. Ammonia nitrogen content significantly improved under 40 g·kg^-1 maize biochar treatment. Moreover, each application level of the two types of biochar limited total bacterial count. It also promoted at different degrees of growth of nitrogen-fixing bacteria and cellulose degrading bacteria in rhizosphere soils, with 60 g·kg^-1 maize biochar as the most effective treatment. Overall, proper biochar application enhanced nitrogen cycle and transformation by influencing community structure of related microorganisms in rhizosphere soils. The effect of maize biochar was more obvious than that of rice biochar. The effects of biochar on nitrogen efficiency in soils were investigated from three aspects-crop growth, rhizosphere soil nitrogen transformation and the related microorganisms. The results detected the mechanisms of the effects of biochar application to soils on nitrogen availability. This provided the basis for the mechanisms of increasing soil carbon sequestration and decreasing the amount of nitrogen fertilizer input under biochar application to mollisols. This was profoundly significant in terms of protecting the fertility of black soils.