Soil factors exhibit greater influence than bacterial inoculation on alfalfa growth and nitrogen fixation

Abstract

In order to study the effects of soil factors and bacterial inoculation on alfalfa (Medicago sativa), plants were inoculated with Ensifer meliloti L33 and Azospirillum brasilense Sp7 in pot experiments using two different soils separately as well as in a mixture. One soil was contaminated with chemical waste products; the other was an arable soil. Soil factors, including the availability of macro- and micronutrients as well as carbon and nitrogen contents, were found to exhibit a much greater influence on the growth of alfalfa than any of the inoculations. In contaminated soil, the shoot and root growth of alfalfa was decreased and nodules were diminished and ineffective. Bacterial inoculations did not significantly improve this hostile growth environment. However, in a mixture (44% arable, 22% contaminated soil, 34% vermiculite), growth conditions for alfalfa were improved so that shoot dry weight and nodule numbers increased up to 100- and 20-fold, respectively, compared with the contaminated soil. For the strain L33, its persistence in the rhizosphere was correlated to the presence of its host plant, but its dynamics were influenced by competition with indigenous rhizobia. The strain Sp7, once provided with a suitable soil, was not dependent on the plant's rhizosphere, but it enhanced the performance of L33 and native rhizobia.

Scoping the potential uses of beneficial microorganisms for increasing productivity in cotton cropping systems

“…Soil type and farm management practices also have a great influence on rhizospheric microbe populations (Reeve et al, 2010), with nutrient availability such as N and P, different pH, moisture content varying widely across soil types, with divergent capacities to support colonisation and growth of microbes. Indeed, Neumann et al (2011) demonstrated that soil factors had a much greater influence on the growth of alfalfa than inoculation with PGP microbes. The composition of indigenous microbial communities within soils will also impact the ability of introduced microbes to effectively colonise the rhizosphere in sufficient numbers to effect plant growth (van Veen et al, 1997).…”

Differential response of kabuli and desi chickpea genotypes toward inoculation with PGPR in different soils

“…It can happily grow on marginal, poorly fertile sandy loam land, almost exclusively under rain-fed conditions in areas of low rainfall without any chemical or biological fertilizer. Soil factor exert greater influence than bacterial inoculation on plant growth, nitrogen fixation and nutrient uptake of plant (Neumann et al, 2011 ).…”

Effect of Soybean Crop Residue Incorporation, Biofertilizers on Nutrient Uptake, Yield of Chickpea (Cicer arietinum L.)

“…In supplement, being a mandatory element of human food and animal feed, chickpea also take part in a pivotal role in sustain soil productiveness up to 35 kg N ha -1 [2]. It has the probable to grow well in poor soils as well as to ameliorate them because of its systematic N fixation system [3]. Chickpea economize nitrogen utilization for succeeding cereal crop to the tune of 56-68 kg N ha -1 [4], which is one of the elevated among pulses [5].…”