NITROGEN RATES AND RESIDUAL EFFECT OF CO-INOCULATION OF SOYBEAN ON MAIZE PLANTS

Aureane Cristina Teixeira Ferreira Cândido,Adriano Maltezo Da Rocha,Ricardo Adriano Felito,Oscar Mitsuo Yamashita,Marco Antonio Camillo De Carvalho

doi:10.1590/1983-21252020v33n306rc

Abstract

ABSTRACT Co-inoculation consists of using microorganism combinations with synergic effect that surpass the results obtained with their use alone. The objective of this work was to evaluate the effect of inoculation and co-inoculation on soybean plants, and their residual effect on maize plants grown intercropped with ruzigrass (Urochloa ruziziensis), under different N fertilizer rates. The experiment was conducted at the experimental area of the Mato Grosso State University, Alta Floresta campus, in a Typic Hapludox. A randomized block design was used for the soybean crops; the treatments consisted of Bradyrhizobium japonicum inoculated single, or co-inoculated with Azospirillum brasilense, with 20 replications. A randomized block design in a strip-plot arrangement was used for the winter maize-ruzigrass intercrop (WMRI); the treatments consisted of combination of residual effect of inoculation and co-inoculation in the strips, and five N fertilizer rates (0, 50, 100, 150, and 200 kg ha-1) in plots with WMRI, with four replications. The co-inoculation of soybean seeds and its residual effect on the maize crops increased the root dry weight of plants of both crops; however, no increases were found for most vegetative and reproductive characteristics of maize plants. Yield and most characteristics evaluated had increasing linear responses to increases in N rates, indicating the plants could respond to rates above 200 kg ha-1.

Highlights

Inoculation of soybean crops with bacteria of the genus Bradyrhizobium is practiced by soybean producers because it is one of the determinant factors to reach high yields without using soil N fertilization, and biological N fixation is a sustainable source of this nutrient (FIPKE et al, 2016)
Bacteria of the genus Bradyrhizobium have been used combined with bacteria of the genus Azospirillum
Azospirillum bacteria assist in overcome environmental stresses (CHIBEBA et al, 2015) when inoculated or co-inoculated in seeds of plants, improving seed germination, plant growth, and root ramification and nodulation (JUGE et al, 2012)

Summary

Introduction

Inoculation of soybean crops with bacteria of the genus Bradyrhizobium is practiced by soybean producers because it is one of the determinant factors to reach high yields without using soil N fertilization, and biological N fixation is a sustainable source of this nutrient (FIPKE et al, 2016).In addition to the several benefits of inoculation, other alternative technologies have been studied, such as co-inoculation (ZUFFO et al, 2015).Bacteria of the genus Bradyrhizobium have been used combined with bacteria of the genus Azospirillum. Inoculation of soybean crops with bacteria of the genus Bradyrhizobium is practiced by soybean producers because it is one of the determinant factors to reach high yields without using soil N fertilization, and biological N fixation is a sustainable source of this nutrient (FIPKE et al, 2016). The residual effect of their inoculation and co-inoculation on the succeeding crops should be elucidated, since inoculation of maize seeds with Azospirillum brasilense, for example, can increase winter maize yield due to biological N fixation, and can contribute to the positive balance of N for the succeeding crop (JORDÃO et al, 2011). The N rate to be applied to winter maize is still not clear, since studies (BASTOS et al, 2008, KAPPES et al, 2009, SORATTO et al, 2010) have shown great variation in maize responses to N fertilization, with the higher yields for the rates of 70 to 180 kg ha-1 of N

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Conclusion