Rice is an exception among cereal crops, as it tolerates a wide range of climatic, soil, and hydrological conditions. Nowadays, with the improvement of the standard of living and the tendency to increase in population and decrease in arable land, increasing rice production is becoming the important subject in China. Over time, the overuse of chemical fertilizers has not only led to deterioration in soil quality but has also led to large-scale degradation of ecosystems and long-term loss of productivity. In order to address these concerns, the substitution of chemical fertilizers with organic amendment is becoming a useful method to increase the efficiency of the use of plant resources as well as to improve the quality of agricultural products. The excessive accumulation of straw resources, the efficient use of straw, and sustainable development have received increasing attention. In the present study, the spraying of organic nitrification inhibitors and compost straw tea instead of DCD and chemical fertilizers were used in the experiment to investigate the effects on rice productivity and greenhouse gas emissions. They were associated with the rhizospere microbiome.
The effect of the dicyandiamide on greenhouse gases from rice fields showed that nitrification inhibitors significantly reduce N2O emissions compared with DCD. This finding was consistent with Wang et al. (2017), who investigated the amendment of DCD indicated no significant effect on the CO2 emissions of rice fields, but significantly reduce CH4 emissions by 20.7% and N2O emissions by 31.9%, and significantly increased rice yield by 10.0%. Overall, the biological nitrification inhibitor is the liquid secreted by the roots of sorghum, indicating more suitable for application compared to DCD. In this study, the result revealed that the paddy field’s CH4 emissions under DCD at the late stage of rice growth had the best effect on reducing CO2 and N2O. These results are confirmed by Wu et al. (2020), who investigated the use of straw compost to replace chemical fertilizers with DCD partially and found that straw compost can mitigate greenhouse gas emissions while stabilizing wheat yields and improving the wheat quality.
Concerning the effect of the return of straw to the field to replace certain chemical fertilizers on greenhouse gases from paddy fields, in this experiment, the return of straw to the field was mainly used for the composting of tea straw, which can reduce greenhouse gas emissions. The results showed that applying straw compost tea in combination with nitrification inhibitor could significantly increase rice plant height, chlorophyll content, and the number of tillers and nodes. Similar results were found by Yu et al. (2020) when combined application of inhibitors and straw (UIS) relieved the retention of urea-N in soil and decreased urea-N recovery rate by 41.29% compared with US at the tillering stage. As such, straw return stimulates immobilization and as a result changes the way fertilizer N is preserved and supplied (Yu et al 2020; Cui et al. 2021; Isabel et al. 2021). Similarly, with the addition of urease inhibitor and nitrification inhibitor, the forms of inorganic N are structured in soil, and under fooded conditions, the continuity of fertilizer NH4+ influences the retention and distribution pattern of N in soil, in particular combined with the application of straw. Therefore, biological nitrification inhibitors can be used instead of DCD, which can significantly increase rice yield, thousand-grain weight, growth, and development of the root system at the stage of rice seedlings and the height of the plant.
Proteobacteria, Germmatimonadetes, Acidobacteria, Chloroflexi Nitrospirae and Verrucomicrobia are the main phyla present in all samples (Fig. 3A), for archaea, Thaumarchaeota and Nanoarchaeota are the most abundant (Fig. 3B), in agreement with former studies, the correction organic compost increases bacterial diversity compared to conventional chemical diseases (Chaudhry et al. 2012), which could be attributed to the increased input of organic carbon substrates. Still, diversity and wealth weren't much different depending on the payment. Thus, the addition of diseases and natural nitrification impediments didn't completely impact the microbial communities of the rhizosphere in terms of diversity, richness and abundance. The results showed a high abundance of Acidobacteria in our soil with further perfection in the T3 treatment and the CK control. These results are aligned with Eichorst et al. (2018), who confirm that acid bacteria are ubiquitous in colorful agrarian lands, and argue that acid bacteria are veritably well equipped with genes that beget the metabolism of inorganic and organic sources of nitrogen. Regarding the composting biomass associated with dicyandiamide, our results don't impact the bacterial community of acidobacteria; still, we've plant that this combination plays a vital part in nitrogen obsession. According to Salam et al. (2020), acidic bacteria can effectively reduce nitrates and nitrates, and can also be nitric oxide; this is proven by genomic data which supports their active participation in nitrogenous nutrient circuits.
Numerous other bacterial diversities have been plant in our rice civilization soil, indeed if this bone is scarce because of the influence of the diseases used, it's obviously of the phylum of proteobacteria, of the class of Alphaproteobacteria of the rubric bradyrhizobium known with other rhizobias to take atmospheric nitrogen and fix it in ammonia (NH3) or ammonium (NH4), Caetanoanolles (1997); Betaproteobacteriies are known as being a more abundant class that's substantially intended to exclude organic matter and nutrients. While the Acidobacteria and the Proteobacteria are abundant, we plant the Nitrospirae, which develop in nearly all the treatments but in small amounts, these play a function of the elimination of Nitrogen (Rodríguez-Marconi 2015). Also, at the phylum position, we observed a significant reduction in the abundance of Germmatimonadetes in the soil from T3 treatments. Beseeming to say that these tend to be favored by moisture, the Germmatimonadetes accumulate the polyphosphate and reduce the vacuity of phosphate to the factory. Verrucomicrobia was another phylum present in our growing soil and lower present; it's the only phylum among numerous others, having a vastly increased soil abundance of the T3 treatment, although little is known about the physiology of these bacteria, studies have shown that Verrucomicrobia can be described as oligotrophic. Their abundance decreases when nitrogen is in excess. These bacteria play a vital part in the declination of organic carbon (Nixon et al. 2019). Chloroflexi was another phylum present in our rice growing soil; this too wasn't detected as an abundant group but was much more represented in the T1 and T4 treatment 6 (Fig. 3B). These results are aligned with other studies that showed these bacteria are acetate Oxidant Syntrophic and belong to bacteria of methanazation (Campanaro and Guivernau 2017).
The soil tested in this study exhibited another of microorganisms called Archaea, comprising the Euyarchaeota and Crenarchaeota, between which is placed the root of the phylogeny Archaea. In addition, the results revealed the presence of four phyla; hence, the most abundant was Thaumarchaeota. Spang et al. (2010) plant that the phylum of Thaumarchaeota revealed by molecular webbing of 16S rRNA genes is an Archaea able of aerobically oxidizing ammonia. The secondary phylum was Nanoarchaeota. Therefore, Nanogearchaeum isolates have only been attained from submarine hydrothermal reflections and terrestrial hot springs. The Euryarchaeota present in our soil from all the treatments were significantly less abundant; still, the phylum contained all the methanogenesis. This can be explained grounded on Garrity et al. (2001), defending that Archaea produces methane CH4 by methanogenesis. Some of the archaea phylum Euryarchaeota are aerobic and anaerobic hyperthermophiles. The last phylum were Creanarchaeota, Thermoplasmata less abundant than other that if distinguished from other Archaea on the base of their Ribosomal RNA sequence. Cubonova et al. (2005) have shown that some have an absence of Histones in their inheritable material. This cultivated contains numerous obligate anaerobic species which bear sulfur for their development.