Seed inoculation with Azospirillum brasilense and nitrogen fertilization for no-till cereal production

Cereal crops have a high N requirement in a high-yield environment. However, N use efficiency is still low in agricultural production systems and little is known about the effects of inoculation with Azospirillum brasilense in a high-yield environment. A field experiment was conducted from 2012 to 2018 with a maize (Zea mays L.)-wheat (Triticum aestivum L.) rotation under a continuous no-till in southern Brazil. Seeds were inoculated with A. brasilense (strains Ab-V5 and Ab-V6) and different levels of N fertilization were used in top dressing. Seed inoculation provided slight changes in N, P, and K concentrations in leaves and grains of maize and wheat. Increasing N input increased the leaf and grain N concentration and the maize and wheat grain yields. Seed inoculation caused varied responses on cereals in different cropping seasons. Wheat was more affected by inoculation in response to N application than maize. Rainfall distribution during the growing seasons possibly interfered on crop responses with inoculation between years and N fertilization levels. Under a similar N input, inoculation resulted in an average increase of 454 kg ha(-1) yr(-1) of maize and 242 kg ha(-1) yr(-1) of wheat by applying a higher N rate to the maize and a lower N rate to the wheat. An additional gain of US$409.72 ha(-1) (2012-2018) was also achieved using this strategy. Although the possibility of inoculation causing economy with N fertilization in wheat was evident, for maize in rotation with wheat, A. brasilense inoculation was apparently more viable under higher N fertilizer input.

Automated summary

In a high-yield environment, inoculation with Azospirillum brasilense caused slight changes in the nitrogen, phosphorus, and potassium concentrations in cereal crops, with varying effects on maize and wheat. Wheat showed a more significant response to inoculation compared to maize, particularly in response to nitrogen application levels. Rainfall distribution during growing seasons may also impact the crop responses to inoculation and nitrogen fertilization levels. Overall, inoculation resulted in increased maize and wheat yields under similar nitrogen input, with the strategy showing potential economic gains.