Abstract The biological nitrogen fixation is a sustainable option to nitrogen fertilization. The objective of this study was to evaluate the effect of mineral nitrogen and N2 from the biological nitrogen fixation on nitrogen nutrition in soybean plants, six treatments resulting from combining three levels of mineral N: (0.0, 3.5 and 7 meq L-1 of NO3 -) and inoculation with the CP-2 strain of Bradhyrizobium japonicum (with and without inoculation) were evaluated, each treatment was established in triplicate, in three-liter plastic pots and agrolite as substrate, transplanting six soybean seedlings per pot. Dry matter (DM) in plant organs, number and dry weight of nodules, fixation of N2, soluble N (N-amino acid and N-ureido) and total N per organ were evaluated. The plants that received mineral N transported between 86 and 95% of the total soluble N as N amino acid, while in inoculated plants, the supply of mineral N negatively affected the number of nodules (29%) and the weight of nodules (64%), decreasing 55% the fixation of N2, in these plants between 50 and 70% of the soluble N transported was as N ureido. At the R6 stage, it was estimated that 70% of the total N accumulated in the DM came from the fixed N2, favoring the DM of leaves, stems, petioles and mainly the DM in pods. Therefore, in this study it is demonstrated that plants inoculated and supplied with mineral N obtain better effects for DM and total N.

Resumen La fijación biológica del nitrógeno, es una opción sustentable a la fertilización nitogenada. Con el objetivo de este estudio fue evaluar el efecto del nitrógeno mineral y del N2 proveniente de la fijación biológica del nitrógeno sobre la nutrición nitrogenada en plantas de soya, fueron evaluados seis tratamientos resultantes de combinar tres niveles de N mineral:(0.0, 3.5 y 7 meq L-1 de NO3 -) e inoculación con la cepa CP-2 de Bradhyrizobium japonicum (con y sin inoculación), cada tratamiento se estableció por triplicado, en macetas de plástico de tres litros de capacidad y agrolita como sustrato transplantándose seis plántulas de soya por maceta. Se evaluó la materia seca (MS) en órganos de la planta, número y peso seco de nódulos, fijación de N2, N soluble (N-aminoácido y N-ureido) y N total por órgano. Las plantas que recibieron N mineral transportaron entre 86 y 95% del N soluble total como N aminoacido, mientras que en plantas inoculadas el aporte de N mineral afectó negativamente la cantidad de nódulos (29%) y el peso de nódulos (64%), disminuyendo 55% la fijación de N2, en estas plantas entre 50 y 70% del N soluble transportado fue como N ureido. A la etapa de R6, se estimó que 70% del N total acumulado en la MS provino del N2 fijado, favoreciéndose la MS de hojas, tallos, peciolos y principalmente la MS en vainas. Por lo tanto, en este estudio demuestra que las plantas inoculadas y abastecidas con N mineral obtienen mejores efectos para la MS y el N total.

RESUMO: O objetivo foi determinar o efeito de humatas de vermicomposto como mitigador de salinidade na germinação e morfometria de mudas de variedades de manjericão, tolerantes e sensíveis à salinidade, submetidas a 0, 50 e 100 mM de NaCl e humatas de vermicomposto diluído 1/60 (v / v) em delineamento inteiramente casualizado com quatro repetições. Foram medidos a taxa e porcentagem de germinação, comprimento da radícula, altura da muda, comprimento da raiz, altura da parte aérea, raiz e biomassa fresca e seca da parte aérea. As variedades apresentaram resposta diferenciada, destacando-se o Napoletano como a mais tolerante. Humatos de vermicomposto mostraram efeitos bioestimulantes nas variáveis avaliadas, permitindo que a variedade tolerante melhorasse a germinação e o crescimento aumentando a tolerância à salinidade da variedade sensível.

ABSTRACT: This study determined the effect of vermicompost humates as salinity mitigator in germination and morphometric characteristics of basil varieties seedlings, tolerant and sensitive to salinity, subjected to vermicompost humates diluted 1/60 (v/v) and 0, 50 and 100 mM NaCl in a completely randomized design with four replications. The rate and percentage of germination, root length, shoot height, root and shoot fresh and dry-weight were measured. The varieties showed differential response, highlighting Napoletano as the most tolerant. Vermicompost humates showed biostimulant effects on variables evaluated, allowing that tolerant variety to improve germination and growth, and increasing the salinity tolerance of the sensitive variety.