Does inoculation with native rhizobia enhance nitrogen fixation and yield of cowpea through legume-based intercropping in the northern mountainous areas of Vietnam?

Abstract

In the Northern mountainous region of Vietnam, cassava–cowpea intercropping system has been widely promoted with support from the local agricultural department. However, cowpea yield is often limited because of a low Biological Nitrogen Fixation (BNF) activity due to its low natural nodulation and lack of available effective Rhizobium products. The aim of this study was to identify the most effective native rhizobia isolate nodulating cowpea with the potential to increase BNF and yield of cowpea. A greenhouse experiment was initially conducted with five treatments: three native rhizobia isolates (CMBP037, CMBP054, and CMBP065); a control (no inoculation and no N application); and N+ (no inoculation, application of N as KNO3). Field inoculations were carried out and the treatments were as follows: a control (no inoculation); CMBP (037+054) – a mixture of strains from Mau Dong; CMBP065 strain from Cat Thinh. CMBP054 and CMBP065 had the highest nodulation in the greenhouse (46.4 and 60.7 nodules plant−1, respectively) and were rated as effective with symbiotic efficiency (SEF) of 54.56 and 55.73%, respectively. In the field, CMBP (037+054) recorded significantly higher nodulation (19.4 nodules plant−1) than the control (11.7 nodules plant−1). CMBP (037+054) also increased cowpea shoot dry weight, shoot N, and yield by 28.6, 4.9, and 10.5%, respectively, compared to the uninoculated control. This effect was slope dependent (statistically significant in moderate and steep slope, not with gentle slope). Besides, the high expansion rate of intercropping with cowpea showed the high adoption level of these agroecological practices by local farmers. This study reveals the potential of native rhizobia inoculation to enhance soil fertility and sustainable agriculture in the Northern mountainous region of Vietnam and proposes enhanced efforts to promote the availability and utilization of effective inoculants for cowpea.

Co-Inoculation with Azospirillum brasilense and Bradyrhizobium sp. Enhances Nitrogen Uptake and Yield in Field-Grown Cowpea and Did Not Change N-Fertilizer Recovery

“…In this process, bacteria inhabiting plant roots form nodules within the roots, and those nodules can fix atmospheric N (by converting N 2 to the usable NH 3 + form via nitrogenase enzyme complex), which is utilized by the plant in exchange for carbohydrates [ 7 , 8 ]. However, the efficiency of the N-fixing activity of the symbiotic association between plants and bacteria varies among legume species and legume-symbiont combinations, and cowpea is often characterized as a poor N-fixer compared to other legume crops [ 9 , 10 , 11 , 12 , 13 ]. It has been estimated that the amount of N fixed in different bean species, including cowpea, was low, varying between 25 and 70 kg N 2 fixed ha −1 [ 6 , 11 , 12 , 14 ], which represents a contribution between 50 and 80% of its N requirement [ 15 , 16 ].…”

Research strategies to catalyze agroecological transitions in low- and middle-income countries

“…Nguyen et al (2020) observed a tripling in the number of farmers intercropping cassava with cowpea between 2017 and 2018 in one Yen Bai commune. Cassava-cowpea intercropping provides additional income from cowpea sales at local markets, without reducing the income farmers receive from cassava, which may in part explain farmer willingness to convert Case add value to their marketed goods and be recognized for conserving traditional agricultural systems based on local agrobiodiversity, agroecological practices and traditional knowledge in harmony with the natural environment of the protected area(Fernández León 2016) (Fig.2e-f) Six farmers from Cuchillas del Toa MAB Reserve have volunteered to test the PGS guidelines.…”

Fixação biológica de nitrogênio em feijão-caupi em resposta á inoculação com bradyrhizobium e diferentes doses de molibdênio

“…Em contrapartida, os resultados deste estudo corroboram com os encontrados por Leite (2009) que também não encontrou diferença significativa para esta variável, assim como Guareschi e Perin (2009) que avaliando o efeito de doses de molibdênio em soja e feijão também não encontraram diferença significativa. Para Alcantaraet al, (2014) a influência dos inoculantes sobre o desenvolvimento do feijão-caupi também depende da variedade cultivada, podendo ser este o motivo da não diferença estatística entre os tratamentos.Quanto à massa seca da parte aérea (MSPA) também não houve significância dos tratamentos nas condições deste estudo, divergindo dos resultados obtidos por Lima Guimarães e colaboradores(2019),que estudouo efeito da inoculação com linhagens de rizóbios no crescimento inicial do feijão-caupi , cultivado em Latossolo Cerrado, encontrou maiores valores de massa seca da parte aérea para plantas inoculadas.Nos estudos feitos porSilva et al, (2009) eKaneko et al, (2010) foram identificadas estirpes nativas no solo onde foram conduzidos seus respectivos experimentos, e também não verificaram diferenças significativas na massa de matéria seca da planta com a inoculação de R.Tropici, fato este que pode ter ocorrido neste estudo acarretando a baixa eficiência das estirpes inoculadas devida a possível presença de estirpes nativas e mais adaptadas as condições edafoclimáticas da região.Os valores de nitrogênio total das plantas de feijão-caupi também não diferiram estatisticamente em função dos tratamentos, resultados estes que diferem dos obtidos porNguyen et al, (2020) que observaram influência da inoculação nos teores foliares de N no feijoeiro, assim como,Araújo et al, (2007) verificaram maior concentração de N nas folhas do feijoeiro-comum, no tratamento que recebeu o inoculante.…”