Interactive Effects of Nitrogen-Fixing Bacteria Inoculation and Nitrogen Fertilization on Soybean Yield in Unfavorable Edaphoclimatic Environments

Abstract

The objective of this work was to evaluate the effect of nitrogen (N) fertilization and the biological nitrogen fixation efficiency in soybean crops grown in unfavorable environments (high temperature, low fertility, and areas with sandy soil). Six field experiments were conducted between 2015 and 2018. Two experiments were performed per year. They were conducted in two separate areas. One was previously covered with degraded pasture (post-pasture area). The other was previously used to plant soybean (post-soybean crop area). The treatments consisted of inoculations with N-fixing bacteria (NFB) (0, 4, 8, and 12 doses ha−1) and N fertilization with rates of 0, 25, 50, and 100 kg ha−1. N fertilization and inoculation with NFB increased soil N, though the levels were still low. Among the tested groups, those with the application of eight doses of inoculant recorded the highest grain yields in post-soybean areas. They showed 10% (237 kg ha−1) and 15% (336 kg ha−1) higher grain yields when compared to crops treated without inoculant and crops with four doses of inoculant, respectively. N fertilization with 25 and 100 kg ha−1 decreased the root nodules of soybean plants grown in the post-soybean and post-pasture areas, respectively. Soybean crops grown on degraded pasture areas also showed good response to N fertilization (50 kg ha−1) when combined with NFB inoculation (12 doses ha−1). These showed grain yields 22% (439 kg ha−1) higher than those of plants treated with just 12 doses of inoculant and no N fertilization.

Cover crop increases soybean yield cropped after degraded pasture in sandy soil

“…In this study, N-fertilized black oats reduced soybean nodulation (Figures 3A and B). In addition, N-fertilized soybean after fallow increased nodule number by 46%, compared to fallow, probably because a small supply of N was beneficial and did not harm BNF, as previously reported (Cordeiro & Echer, 2019). Xia et al (2017) report higher nodulation of soybeans with the addition of low levels (< 50 mg L -1 ) of nitrogen due to increased nitrogenase activity in soybean roots; however, high levels of mineral N (> 50 mg L -1 ) reduce nitrogenase activity and nodulation of soybeans.…”

“…Xia et al (2017) report higher nodulation of soybeans with the addition of low levels (< 50 mg L -1 ) of nitrogen due to increased nitrogenase activity in soybean roots; however, high levels of mineral N (> 50 mg L -1 ) reduce nitrogenase activity and nodulation of soybeans. Additionally, in degraded post-pasture areas with low N stock in the soil, the application of up to 50 kg ha -1 of N does not reduce soybean nodulation (Cordeiro & Echer, 2019), as reported in this study (Figure 3A).…”

“…Due to restrictions on opening of new areas, soybean cultivation has expanded to areas with lower yield potential (Cordeiro & Echer, 2019;Silva et al, 2020). These areas include pastures that are degraded or in some stage of degradation and sandy soils, which are about 8% of Brazilian soils (Donagemma et al, 2016).…”

“…However, the studies were conducted in favorable environments for BNF activity in soybean (long-term crop rotation associated with cover crops, medium-and highfertility soils and regular rainfall pattern). Thus, in unfavorable edaphoclimatic environments for BNF, preceding cover crops (Williams et al, 2018) and mineral nitrogen fertilization can improve soybean yield (Mourtzinis et al, 2018;Cordeiro & Echer, 2019). The objective of this study was to evaluate the effect of preceding crops and nitrogen supply on soybean (Glycine max) yield.…”

Response of Soybean (Glycine max (L.) Merrill) to Mineral Nitrogen Fertilization and Bradyrhizobium japonicum Seed Inoculation

“…The greatest effects of this treatment were observed in fields without previous soybean cultivation [26]. Cordeiro and Echer [27] found that both mineral fertilization and soil inoculation increase N content in the soil, however the seed yield was clearly higher where the inoculant had been used. The lack of a clearly positive effect of seed inoculation on soybean yield can trigger some doubts as to whether the bacteria introduced proliferated, and if the inoculation was effective, or if environmental conditions and/or nitrogen fertilization did not disturb the development of symbiotic bacteria [7].…”