Microorganisms are considered a genetic resource with great potential for achieving sustainable development of agricultural areas. The objective of this research was to determine the effect of microorganism application forms on the production of biomass, gas exchange, and nutrient content in upland rice. The experiment was conducted under greenhouse conditions in a completely randomized design in a factorial 7 × 3 + 1, with four replications. The treatments consisted of combining seven microorganisms with three application forms (microbiolized seed; microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS); and microbiolized seed + plant sprayed with a microorganism suspension at 7 and 15 DAS) and a control (water). Treatments with Serratia sp. (BRM32114), Bacillus sp. (BRM32110 and BRM32109), and Trichoderma asperellum pool provided, on average, the highest photosynthetic rate values and dry matter biomass of rice shoots. Plants treated with Burkolderia sp. (BRM32113), Serratia sp. (BRM32114), and Pseudomonas sp. (BRM32111 and BRM32112) led to the greatest nutrient uptake by rice shoots. Serratia sp. (BRM 32114) was the most effective for promoting an increase in the photosynthetic rate, and for the greatest accumulation of nutrients and dry matter at 84 DAS, in rice shoots, which differed from the control treatment. The use of microorganisms can bring numerous benefits of rice, such as improving physiological characteristics, nutrient uptake, biomass production, and grain yield.

No abstract

Microorganisms can promote plant growth by increasing phytomass production, nutrient uptake, photosynthesis rates, and grain yield, which can result in higher profits for farmers. However, there is limited information available about the physiological characteristics of lowland rice after treatment with beneficial microorganisms in the tropical region. This study aimed to determine the effects of different beneficial microorganisms and various application forms on phytomass production, gas exchange, and nutrient contents in the lowland rice cultivar 'BRS Catiana' in a tropical region. The experiment was performed under greenhouse conditions utilizing a completely randomized design and a 7 × 3 + 1 factorial scheme with four replications. The treatments consisted of seven microorganisms, including the rhizobacterial isolates BRM 32113, BRM 32111, BRM 32114, BRM 32112, BRM 32109, and BRM 32110 and Trichoderma asperellum pooled isolates UFRA-06, UFRA-09, UFRA-12, and UFRA-52, which were applied using three different methods (microbiolized seed, microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS), and microbiolized seed + plant spraying with a microorganism suspension at 7 and 15 DAS) with a control (water). The use of microorganisms can provide numerous benefits for rice in terms of crop growth and development. The microorganism types and methods of application positively and differentially affected the physiological characteristics evaluated in the experimental lowland rice plants. Notably, the plants treated with the bioagent BRM 32109 on the seeds and on seeds + soil produced plants with the highest dry matter biomass, gas exchange rate, and N, P, Fe, and Mg uptake. Therefore, our findings indicate strong potential for the use of microorganisms in lowland rice cultivation systems in tropical regions. Currently, an additional field experiment is in its second year to validate the beneficial result reported here and the novel input sustainability.

Upland rice can overcome major challenges through the insertion of silicate fertilization and the presence of plant growth-promoting microorganisms (PGPMs) during its cultivation, as these factors promote an increase in vigor and plant disease resistance. Two consecutive experiments were conducted to evaluate the beneficial effects of silicon fertilization combined with the PGPM, Pseudomonas fluorensces, Burkholderia pyrrocinia, and a pool of Trichoderma asperellum, in upland rice seedlings, cultivar BRS Primavera CL: (a) E1, selecting PGPM type and Si doses for rice growth promotion and leaf blast supression, and (b) E2, evaluating physiological characteristics correlated with mechanisms involved in the higher vegetative growth in highlighted treatments from E1. In E1, 2 Si t ha combined with the application of T. asperellum pool or PGPM mixture increased 54% in root dry matter biomass and 35 and 65% in shoot and root lengths, respectively; it also suppressed 99% of rice blast severity. In E2, shoot and root dry matter biomass and length, photosynthetic rate, water use efficiency, total soluble sugar, and chloroplastidic pigments were superior in BRS Primavera CL seedlings treated with 2 Si t ha and T. asperellum pool or PGPM mixture. Higher salicilic and jasmonic acid levels were found in seedlings treated with Si and T. asperellum pool, individually. These physiological characteristics may explain, in part, the higher vigor of upland rice seedlings promoted by the synergistic effect between silicate fertilization and beneficial microorganisms.

Potassium (K) is the second most uptaken nutrient by upland rice crops. Beneficial microorganisms, such as Rhizobacteria participate in different processes that affect transformation of soil nutrients, making them available to plants. However, there are no information about the use of Rhizobacteria and different rates of K fertilization in this crop. To elucidate this interaction, the objective of this study was to determine the effect of the rhizobacteria Serratia spp. strain BRM 32114 and doses of K at sowing fertilization on upland rice development. The experimental design was a complete randomized block in a factorial 4 × 2 scheme with four replications, under no-tillage systems conducted in the Brazilian Cerrado during 2015/16 and 2016/17 growing seasons. The treatments consisted of four K 2 O doses (0, 20, 40 and 60 kg ha -1 ) without or with rhizobacteria applied three times in the field (on the seeds, sprayed over the soil, seven days after sowing and sprayed on the plants, 14 days after sowing). Biomass production, gas exchange, nutrient content in leaves and grain, yield components and grain yield were evaluated. The use of BRM 32114 applied in soil with high levels of K provided increase in the contents of P, Ca, Mg, Fe and Zn in rice leaves. The results showed enhances in plant biomass (7.2%), the number of panicles per plant (10%), and the grain yield of upland rice (16.3%). Therefore, our results allow inferring that the use of microorganism BRM 32114 provided significant improvements in rice growth/development, which resulted in higher grain yield over two consecutive growing seasons under field conditions. It showed that the bioagent Serratia spp. is promising to be incorporated into crop systems.