RESUMO
Phosphate fertilization in highly weathered soils has been a major challenge for sugarcane production. The objective of this work was to evaluate the foliar levels of phosphorus (P) and nitrogen (N) and the technological quality and productivity of second ratoon cane as a function of inoculation with plant-growth-promoting bacteria (PGPBs) together with the residual effect of phosphate fertilization. The experiment was carried out at the research and extension farm of Ilha Solteira, state of São Paulo, Brazil. The experiment was designed in a randomized block with three replications in a 5 × 8 factorial scheme. The treatments consisted of five residual doses of phosphorus (0, 45, 90, 135 and 180 kg ha-1 of P2O5, 46% P) applied at planting from the source of triple superphosphate and eight inoculations from three species of PGPB (Azospirillum brasilense, Bacillus subtilis and Pseudomonas fluorescens), applied in single or co-inoculation at the base of stems of sugarcane variety RB92579. Inoculation with PGPBs influenced leaf N concentration, while inoculations with Pseudomonas fluorescens and combinations of bacteria together with the highest doses exerted a positive effect on leaf P concentration. Co-inoculation with A. brasilense + Pseudomonas fluorescens associated with a residual dose of 135 kg ha-1 of P2O5 increased stem productivity by 42%. Thus, it was concluded that inoculations with Pseudomonas fluorescens and their combinations are beneficial for the sugarcane crop, reducing phosphate fertilization and increasing productivity.
RESUMO
Biofortification of cereal crops with zinc and diazotrophic bacteria is a sustainable solution to nutrient deficiency and hidden hunger. The inoculation of staple grain crops such as maize is increased with reducing productivity losses while improving nutrition and use efficiency under climatic extremes and weathered soils of tropical savannah. Therefore, objectives of our study were to evaluate the influence of seed inoculation with diazotrophic bacteria (No inoculation-Control, Azospirillum brasilense, Bacillus subtilis, and Pseudomonas fluorescens) together with residual effect of soil Zn (absence and presence) on growth, yield, Zn nutrition, Zn use efficiencies, and intake of maize in 2019 and 2020 cropping seasons. The inoculation of B. subtilis increased hundred grain mass and yield (14.5 and 17%), while P. fluorescens under residual Zn fertilization has improved shoot and grain Zn concentration in shoot (29.5 and 30.5%). and grain (25.5 and 26.2%), while improving Zn accumulation in shoot (33.8 and 35%) and grain (37.2 and 42%) of maize. The estimated Zn intake in maize was also increased with A. brasilense inoculation and residual Zn application. The Zn use efficiencies including Zn use efficiency, agro-physiological, and utilization efficiency was increased with B. subtilis, while applied Zn recovery was increased with A. brasilense inoculations under residual Zn fertilization. Zinc use efficiency was increased by 93.3 and 397% with inoculation of B. subtilis regardless of Zn application. Therefore, inoculation with B. subtilis and P. fluorescens along residual Zn fertilization is considered the most effective and sustainable strategy for agronomic biofortification of maize under harsh tropical conditions of Brazil.
RESUMO
O cultivo de adubos verdes na entressafra altera a dinâmica e a recuperação do nitrogênio pelo milho no sistema solo-planta. O objetivo deste trabalho foi avaliar a eficiência de utilização do N da crotalária (Crotalaria juncea) e do milheto (Pennisetum americanum), marcados com 15N, pelo milho cultivado sob diferentes doses de N em plantio direto, num Latossolo Vermelho de Cerrado. O estudo foi desenvolvido na fazenda experimental da Faculdade de Engenharia de Ilha Solteira-UNESP, Selvíria-MS, nos anos agrícolas 2001/02 e 2002/03. O delineamento experimental foi o de blocos casualizados, com 15 tratamentos e quatro repetições, dispostos em esquema fatorial 5 x 3, constituídos pela combinação de cinco doses de N (0, 30, 80, 130 e 180kg ha-1), na forma de uréia, aplicadas no estádio quatro folhas, e três sistemas de cobertura do solo: crotalária, milheto e o solo em pousio entressafra. O N inorgânico promoveu um efeito sinérgico na quantidade de N absorvida e no aproveitamento pelo milho do N da crotalária e do milheto. A crotalária, na média dos dois anos agrícolas, proporcionou, no milho cultivado sem a aplicação de N, um efeito equivalente à aplicação de 56,0 e 73,0kg ha-1 de N-uréia, comparado ao do milho cultivado sobre solo em pousio e em sucessão ao milheto, respectivamente. A produtividade de grãos aumentou de forma quadrática em função das doses de N, nos dois anos agrícolas.
The cultivation of green manure in the fallow ground alter the dynamics and the recovery of the nitrogen by corn in the soil-plant system. The objective of this work was to evaluate the utilization of nitrogen (15N) from sun hemp and millet by corn grown under different N rates in no-tillage in Red Latosol of Cerrado. The research was carried in the Experimental Farm of Faculty of Engineering, Sao Paulo State University (UNESP), Ilha Solteira, located in Selvíria-MS, Brazil, during the 2001/02 and 2002/03 growing season. The experimental design was randomized complete blocks, with 15 treatments and four replications in a factorial 5 x 3, constituted by the combination of five N rates (0, 30, 80, 130 and 180kg ha-1), as urea, applied at four leaf stage; and three preceding cover crops: sun hemp, millet and fallow ground. The inorganic N promoted a synergic effect on the amount of absorbed N and utilization of sun hemp and millet N by the corn crop. The sun hemp, in average for two growing season, provided in the corn cultivated without the application of N an equivalent effect of the application of 56.0 and 73.0kg ha-1 as urea, compared to the corn grown in fallow soil and in succession to millet, respectively. The grain yield increased in a quadratic way in function of the N rates, in the two growing season.