poster - International Conference of Agricultural Engineering

Biological Nitrogen Fixation In Genotypes of Cowpea Under Salt
Stress Increasing the State of Paraíba, Brazil
Ronaldo do Nascimento 1* , Jailma R. de Andrade 2 , Francisco V. da Silva 3 , Aryadne
Ellen V. de Alencar 4 , Daniele F. de Melo 4 , José Wilson Barbosa 2
1 Teacher Associate of Academic Unit of Agricultural Engineering, CTRN / UFCG, Av Aprígio
Veloso, 882, University District, Campina Grande, Paraíba, 58429-140, Brazil.
2 Graduate in Agricultural Sciences, Ms in Agricultural Engineering, Academic Unit of
Agricultural Engineering, CTRN / UFCG.
3 Agronomist Engineer, PhD, Academic Unit of Agricultural Engineering, CTRN / UFCG.
4 Graduate in Agricultural Engineering, Academic Unit of Agricultural Engineering, CTRN / UFCG.
*Corresponding author. E-mail: ronaldo@deag.ufcg.edu.br
Abstract
The symbiosis between legumes and rhizobia can supply most or all of the nitrogen needed
for growth and productivity of plant species. However, for this to occur satisfactorily, the plant
must be effectively nodulated by bacteria. Nodulation is dependent on a number of factors
involving the plant, bacteria and soil and the interaction of the three. The combined action of
these factors may limit or stimulate nodulation, which will be reflected in the amount of fixed
atmospheric nitrogen and productivity of the legume. Among the main environmental factors
that affect the potential of biological nitrogen fixation in the northeast region of Brazil, there is
the salinity of the soil, considering the use of low quality water and high evaporation due to
climate conditions in the region. The objective of the research was to evaluate the potential
for biological nitrogen fixation (BNF) for different cultivars of cowpea under conditions of
increasing salinity in irrigation water. For this we used polyethylene pots containing neolithic
regosols eutrophic fertilized as recommended for cultivation in specific vessels, except
nitrogen, and protected environment. We used a completely randomized design in a 4x5
factorial (salinity x genotype), with four repetitions. Treatments consisted of four levels of
salinity of irrigation water (1.5, 3.0, 4.5 and 6.0 dS m -1 ) and genotypes (G) were used (G1)
MNCO1-649F-1-3, (G2) BRS-Juruá, (G3) MNCO2-675F-4-9, (G4) MNCO3-736F-7 e (G5)
MNCO2-684F-5-6, inoculated with rhizobium strain BR-3267, specially developed in Brazil
for symbiosis this species legume. The FBN was estimated through the SPAD readings of
the index and weight of the dry mass of nodules, 40 days after emergence (DAE). Analysis of
variance showed that there were significant for levels of salinity on the parameters.
Regression analysis showed a negative linear response for dry weight of nodules and SPAD
index, which was negatively affected by salinity levels of irrigation water, showing a
sensitivity of the symbiosis to salt stress.
Key words: cowpea, salinity, nitrogen, nodulation.
1. Introduction
The cowpea constitutes the main subsistence crop in the north and northeast of Brazil,
especially in the semiarid northeast. Irrigation is one of the technologies applied in agriculture
that has most contributed to the increase in food production, however this practice should be
used rationally, since the weather conditions in the northeast (high temperatures, low rainfall
and high levels of salts in irrigation water), have caused problems of salinity in soils. The
salinity of the soil is particularly important in semi-arid regions, in order to lower the
precipitation rate and high evaporation. Most crop species subjected to salinity have reduced
growth and metabolism affected (Lima et al., 1997). The growing need to increase food
production, has significantly increased the expansion of cultivated areas, but this quest does
not take into account only the expansion of agricultural areas, but also considered the use of