ABSTRACT
The sustainable development of agriculture can be stimulated by the great market availability of bio-inputs, including phosphate-solubilizing microbial strains. However, these strains are currently selected using imprecise and questionable solubilization methodologies in solid or liquid media. We hypothesized that the hydroponic system could be a more efficient methodology for selecting phosphate-solubilizing strains as plant growth promoters. This methodology was tested using the plant Glycine max as a model. The growth-promoting potential of the strains was compared with that of the Biomaphos® commercial microbial mixture. The obtained calcium phosphate (CaHPO4) solubilization results using the hydroponic system were inconsistent with those observed in solid and liquid media. However, the tests in liquid medium demonstrated poor performances of Codinaeopsis sp. (328EF) and Hamigera insecticola (33EF) in reducing pH and solubilizing CaHPO4, which corroborates with the effects of biotic stress observed in G. max plants inoculated with these strains. Nevertheless, the hydroponic system allowed the characterization of Paenibacillus alvei (PA12), which is also efficient in solubilization in a liquid medium. The bacterium Lysinibacillus fusiformis (PA26) was the most effective in CaHPO4 solubilization owing to the higher phosphorus (P) absorption, growth promotion, and physiological performance observed in plants inoculated with this bacterium. The hydroponic method proved to be superior in selecting solubilizing strains, allowing the assessment of multiple patterns, such as nutritional level, growth, photosynthetic performance, and anatomical variation in plants, and even the detection of biotic stress responses to inoculation, obtaining strains with higher growth promotion potential than Biomaphos®. This study proposed a new approach to confirm the solubilizing activity of microorganisms previously selected in vitro and potentially intended for the bio-input market that are useful in P availability for important crops, such as soybeans.
ABSTRACT
Foram instalados dois experimentos independentes em solo argiloso com o objetivo de avaliar a produtividade de batata e a distribuição dos tubérculos nas diversas classes de tamanho em resposta à combinação de diferentes espaçamentos entre plantas na linha de plantio e critérios de calcular a quantidade de adubo. Um experimento foi irrigado por gotejamento e o outro por aspersão, com os mesmos tratamentos. Foram estudados seis tratamentos resultantes da combinação de três espaçamentos entre plantas na linha (29, 36 e 50 cm) e dois critérios de calcular a dose de adubo (por área ou por número de planta) no delineamento em blocos casualizados e cinco repetições. Nos dois experimentos, a produtividade comercial por área (número e massa de tubérculo) decresceu exponencialmente com o aumento do espaçamento entre plantas e não foi influenciada pelo critério de recomendação do fertilizante. A combinação de dose do adubo calculada por área com o menor espaçamento entre plantas otimizou a produtividade comercial pelo aumento de tubérculos das classes média e pequena além de aumentar a eficiência no uso do adubo. As implicações ambientais, econômicas e práticas dos resultados sobre a produção de batata são discutidas.
Two independent experiments were established in a Red Yellow Argisol Cambic soil objecting to evaluate potato yield and tuber size distribution profile in response to interplant spacing and fertilizer recommendation criteria. One experiment was sprinkler irrigated and the other one was drip-irrigated. Six treatments resulting from the combination of three interplant spacing (29, 36, and 50 cm) and two fertilizer recommendation criteria (by area or by plant number in the area) were evaluated in a completely randomized block design and five replications. In both experiments, marketable potato yield (tuber number and mass) exponentially decreased with the increase in row spacing and it was affected by recommendation criteria. The combination of fertilizer recommendation by area with narrower space optimizes marketable tuber yield by increasing medium and small tubers and aldo increases fertilizer use efficiency. Environmental, economic and practical implications of the results to potato production are discussed.
