Nitrogen recovery from fertilizer and use efficiency response to Bradyrhizobium sp. and Azospirillum brasilense combined with N rates in cowpea-wheat crop sequence

• Published in: Applied soil ecology : a section of Agriculture, ecosystems & environment Vol. 157; p. 103764
• Main Authors: Galindo, Fernando Shintate, da Silva, Edson Cabral, Pagliari, Paulo Humberto, Fernandes, Guilherme Carlos, Rodrigues, Willian Lima, Biagini, Antônio Leonardo Campos, Baratella, Eduardo Bianchi, da Silva Júnior, Castro Alves, Moretti Neto, Mário João, Silva, Vinicius Martins, Muraoka, Takashi, Teixeira Filho, Marcelo Carvalho Minhoto
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2021
• Subjects: Biological nitrogen fixation; Efficiency of nitrogen fertilization; Nitrogen-15; Plant growth promoting bacteria; Residual effect of N; Plant growth promoting bacteria; Nitrogen-15; Biological nitrogen fixation; Residual effect of N; Efficiency of nitrogen fertilization
• ISSN: 0929-1393; 1873-0272
• DOI: 10.1016/j.apsoil.2020.103764

A better understanding of nitrogen (N) behavior and agronomic practices is needed to improve biological nitrogen fixation (BNF) and N use efficiency under field conditions. This study aims on investigating the potential for the use of biological agents that can fix atmospheric N and are related to multiple mechanisms benefits to improve cowpea (Vigna unguiculata (L.) Walp.) development and productivity, leading to a positive residual effect on wheat (Triticum aestivum L.) development. The study was set up under a no-till system in a Rhodic Haplustox, in a randomized complete block design, with four replicates. Treatments were tested in a full factorial design and included: i) three types of inoculation (without inoculation – control; Bradyrhizobium sp. inoculation (strains SEMIA 6462 and SEMIA 6463) – the conventional inoculation of cowpea; and Bradyrhizobium sp. combined with A. brasilense (strains Ab-V5 and Ab-V6) – the co-inoculation); and ii) five N rates (0 to 160 kg N ha−1) applied as urea-15N isotope. The residual effects of inoculations and N application rates applied during the cowpea growing season were evaluated on wheat (successor crop). Co-inoculation was found to increase cowpea grain yield by 40.5% and 14.1% compared to the control and Bradyrhizobium sp. inoculation when N was omitted and up to 37.6% and 50.8% when N was applied. Co-inoculation increased N use efficiency, N recovery and N accumulation on cowpea, leading to improved crop growth. The co-inoculation also provided a positive residual effect on wheat resulting in increased plant N accumulation, crop development, and greater wheat grain yield compared to the control (increase of 7.8%) and Bradyrhizobium sp. inoculated plants (increase of 5.8%). Co-inoculation was found to increase N use efficiency on cowpea by 216.5% and 35.5% and on wheat by 159.3% and 29.5% compared to control and Bradyrhizobium sp. inoculation, respectively. The fertilizer N recovery was, on average, 22.2% by cowpea, while fertilizer N recovery by wheat was <2.3%. The percentage of N accumulated on cowpea was on average 30.8%, while the residual cowpea N contribution to wheat provided by co-inoculation was 18.6%. This study showed positive improvements in cowpea-wheat growth production parameters and N management as a result of co-inoculation, indicating that there is an opportunity to reduce N fertilizer input with the combined use of biological agents that promote plant growth and chemical fertilizers.