Inoculation and Nitrogen Fertilization Improve Nitrogen Soil Stock and Nutrition to Soybeans in Degraded Pastures with Sandy Soil

ABSTRACT

Sandy soil is typically poor in organic matter. When areas with sandy soil are used for pasture prior to soybean cultivation, the availability of nitrogen (N) for plants is limited even further. Our objective was to evaluate if inoculation combined with N fertilization increases N content in the soil and N supply to soybean plants in post-pasture and post-soybean areas. Four experiments were conducted in degraded post-pasture and post-soybean areas in a sandy soil (Rhodustult), between 2016 and 2018, in Brazil. Treatments used a combination of inoculant (zero, 4, 8 and 12 rates ha⁻¹) and mineral N (0, 25, 50, and 100 kg ha⁻¹) with four replicates. It was using the soybean cultivar TMG 7062 IPRO. The post-soybean area had higher N content in the soil than the post-pasture area; 33, 32, and 21% for total N, microbial biomass nitrogen (MBN), and inorganic nitrogen (IN), respectively. Soybean shoots from the post-soybean area also had greater accumulations of N (86 kg ha⁻¹ of N). Increased N fertilization linearly raised levels of N in the soil (total N, MBN, and IN). In both areas, the effect of inoculation was restricted by the increase of total N in the soil. Inoculation combined with moderate rates of N in soybeans (50 kg ha⁻¹) increased levels of N in the soil and N supply to plants in post-pasture areas. In post-soybean areas, inoculation alone fulfilled the N soybean need.

KEYWORDS:

• Biological nitrogen fixation
• ammonium
• nitrate
• nitrogen absorption

Additional information

For information on yield, nodulation and others, access manuscript 10.1038/s41598-019-52131-7

Acknowledgments

The authors thank the Foundation for Research Support of the State of São Paulo (FAPESP) for the support through a scholarship granted to the first author (process 2016/17232-0).

Conflicts of interest

The authors declare no conflicts of interest.

Additional information

Funding

This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo [2016/17232-0].