Growth and survival in soil and effectiveness of plant growth promoting bacteria in lettuce (Lactuca sativa L.) grown i varying soil types

Issue Date

8-2012

Abstract

One of the constraints to the adoption of plant growth promoting bacteria (PGPB) technology is the lack of information on crop response to PGPB inoculation in different soils. This study examined the effectiveness of PGPB inoculation on yield, shoot and root dry weights, nitrogen and phosphorous uptake of lettuce variety 'Green Tower' grown in Lipa clay loam (OM 4.7; pH 6.7), Luisiana clay (OM 2.8; pH 4.5) and Binangonan clay (OM 5.7; pH 7.9) under three fertilization rates under greenhouse condition. The PGPB inoculant used belongs to the genus Bacillus and produces plant growth regulators indole acetic acid (IAA), cytokinin and gibberellin. Growth room and laboratory studies determined the effect of soil type on growth and survival of PGPB in the presence and absence of the host crop. Auxin production by PGPB inoculants in sterilized soil was also measured. In terms of yield, the response to inoculation ranged from 111-261% with the lowest increase obtained from lettuce grown in Luisiana clay and the highest increase from lettuce grown in Binangonan clay. Higher increase in fresh yield due to inoculation was attained in zero fertilization compared with half and full fertilization rates regardless of soil type. Inorganic fertilizer application significantly increased the fresh yield of lettuce grown in Binangonan clay. On the other hand, the combination of PGPB inoculation and full recommended fertilizer rate application significantly improved the N content of lettuce regardless of soil type. The 11% increase in N content was further translated into a 132% increase in N uptake of inoculated lettuce across soil type and fertilizer rate. The PGPB inoculation combined with zero and full fertilizer applications significantly enhanced plant's content. Moreover, PGPB inoculation increased P uptake by 43-300% across soil type and fertilization rates, an indication of P solubilising activity of PGPB inoculant used. The relatively poor performance of PGPB inoculant in Luisiana clay was further observed in terms of PGPB survival in sterile soil as well as poor rhizosphere competence. The significant effect of soil type on the effectiveness, growth and survival of PGPB inoculant demonstrate the importance of multilocation evaluation of microbial inoculants. The development of PGPB inoculants for specific stress environment, such as acidic soils requires selection of PGPB strains that are tolerant to acid soil conditions.

Source or Periodical Title

Philippine Journal of Crop Science

ISSN

0115-463x

Volume

37

Issue

2

Page

65-74

Document Type

Article

Frequency

tri-quarterly

Physical Description

tables, graphs

Language

English

This document is currently not available here.

Share

COinS