Beneficial Effects of Nitrogen-Fixing Bacteria on the Growth and the Yield of Corn Cultivated at An Giang Province

Nitrogen is avery important nutrient source for plants. Supplying nitrogen to plants is very necessary to meet the growth and the development needs of the plants, and partially compensate for the amount of nitrogen that the plants have been absorbed. To increase productivity, farmers often used a lot of chemical nitrogen fertilizers in their fields. That causes many harmful effects on the soil, changing the physicochemical properties of the soil, reducing soil fertility, losing ecological balance, causing pollution due to nitrate loss, and adverse effects on the ecosystem. Application microbial fertilizers in crops can help improving the microenvironment of rhizosphere soil and alleviating the damage of saline stress.

That free nitrogen-fixing bacteria convert nitrogen into NHunder the normal physiological conditions due to the activity of 3 the enzyme nitrogenase [1]. Plants absorb nitrogen to synthesize plant protein. Over the past 10 years, several papers mentioned the effects of plant growth promotion of plant-associated bacteria on corn were published. Test pot and field experiments have been conducted in many countries. According to the study of Piromyou et al. (2011) of Pseudomonas sp. SUT19 and Brevibacillus sp. SUT 47 promoted the germination and the growth of corn plants grown in Leonard jars. In the field experiment, strains Pseudomonas sp. SUT 19 and Brevibacillus sp. SUT 47 mixed with compost could promote the best growth of corn among all treatments and could be applied as PGPR inoculum for forage corn [2]. Seven trains, which belonged to genera Klebsiella, Enterobacter, and Pantoea isolated from sugarcane showed abilities of nitrogen fixation and the production of IAA. These bacterial strains were tested for their abilities to promote plant growth on potted corn plants at 40 days old [3].

The study of Puneet (1998) showed that the Azotobacter sp. strain stimulated seed germinating, rooting and the yield of wheat and corn and increased by 10-15% compared to the control [4]. When applying Azospirillum lipoferum strain to corn, the results showed that it reduced 50% of the amount of N used for plants, even the corn yield was still guaranteed [5]. Bacterial Klebsiella pneumoniae bacteria fix atmospheric nitrogen to supply wheat [6]. Corn (Zea may L.)is an important food crop in the global economy. Corn needs a huge amount of fertilizer for its growth, but this cost is high. In addition, the excessive use of inorganic fertilizer will cause pollution, affect the health of humans and animal [7]. A recent trend in agricultural production is how to improve soil fertility, reduce the number of chemical fertilizers, increase bio-fertilizers and to reduce production costs, reduce environmental pollution, contribute to creating safe products, and developed sustainable ecological agriculture. In previous studies, a collection of bacteria-associated with corn, which had the abilities of nitrogen fixation and IAA production, were selected and stored in the microbiology laboratory of Can Tho University, Vietnam. In this study, two strains of well-characterized bacteria, which were selected from the collection, were continued to be evaluated for their abilities of plant growth-promoting on the host plant as corn. Bio-fertilizer, which was composed of bacterial strains and peat, was applied to the experimented corn at the greenhouse and in the field.