Use of commercial bio-inoculants to increase agricultural production through improved phosphrous acquisition

Integrated nutrient management

P deficiency is a major obstacle for crop production in subtropical red soils in South China, and the hydrolysis of organic P (Po) is of great significance in these soils due to the immobilization of P by Fe and Al. Cover cropping in orchards and symbiotic microbial inoculation are considered to improve soil quality, including P status, however, their effects on the hydrolysis of Po is little known. In this study, five soil managements were established in a guava orchard in South China for two and a half years, including clean culture (CC), cover cropping with Paspalum natatu (PN), PN with arbuscular mycorrhizal fungal inoculation (PNA), cover cropping with Stylosanthes guianensis (SG), SG with rhizobial inoculation (SGR). Soil chemical, biochemical and microbial properties were analyzed. Results indicate that soil pH and SOM content tended to increase following cover cropping alone or with microbial inoculation. Po content was significantly elevated in PNA. Po fractionation revealed that cover cropping alone or with microbial inoculation significantly affected the contents of moderately labile Po (MLPo) and moderately resistant Po (FAPo). Enzyme assay indicated that cover cropping with microbial inoculation increased the activities of acidic phosphomonoesterase (ACP), neutral phosphomonoesterase (NP) and alkaline phosphomonoesterase (ALP), with ALP the most sensitive, although ACP activity dominated in red soils. Correlation analysis suggested a significantly positive relationship between ALP activity and MLPo or FAPo. PCR-DGGE profile of the alp -harboring bacterial community showed that cover cropping with S. guianensis and mycorrhizal inoculation to P. natatu promoted the bacterial diversity and/or species richness. For almost all the measured parameters, PN and SG were comparable, however, PNA was superior to SGR, indicating the stronger additive effect of arbuscular mycorrhizal fungus than that of rhizobia. Cat-PCA indicated that MLPo was the most influential factor on phosphomonoesterase. In general, this study suggests that, in subtropical orchards with red soil, cover cropping with microbial inoculation can improve the Po hydrolysis via the promoted alp -harboring bacterial community and then ALP activity. Our results also suggest that the combination of P. natatu and arbuscular mycorrhizal fungus is better than S. guianensis and rhizobia, which possesses practical significance for sustainable production in these orchards.

The combined effects of cover crops and symbiotic microbes on phosphatase gene and organic phosphorus hydrolysis in subtropical orchard soils

Sunflower (Helianthus annuus L.) is an important ornamental plant and good source of vegetable oil, widely accepted as potential promising plant for phytoremediation. A pot experiment was conducted to evaluate the impact of cadmium on the growth and some biochemical attributes of sunflower and role of arbuscular mycorrhizal fungi (AMF) in assuaging the cadmium stress induced changes. Cadmium treatment reduced growth, chlorophyll contents and cell membrane stability. AMF inoculated plants showed increased growth, chlorophyll contents and cell membrane stability and also mitigated changes caused due to cadmium. Cadmium caused increase in lipid peroxidation, and hydrogen peroxide production. An increase in antioxidant enzyme activity was observed due to cadmium treatment which was further enhanced by inoculation of AMF. Increase in proline and total phenols due to cadmium stress was obvious. Cadmium stressed plants showed enhanced fatty acid content. AMF inoculated plants showed higher activities of acid and alkaline phosphatases which were reduced by cadmium stress. However palmitoleic acid (C16:1), oleic (C18:1), linoleic (C18:2) and linolenic acid (C18:3) reduced in cadmium treated plants and the negative impact of cadmium was mitigated by AMF.

Alleviation of adverse impact of cadmium stress in sunflower (Helianthus annuus L.) by arbuscular mycorrhizal fungi.

The effect of two arbuscular mycorrhizal fungi [G. mosseae (G) and A. laevis (A)] with P. fluorescence (Pf) in the presence of super phosphate (P) fertilization on growth and yield of bell pepper (Capsicum annuum var. California Wonder) was evaluated in pots under greenhouse conditions, in a completely randomized design with four levels of phosphorus fertilizer [F0–without P, F1–0.200g pot -1 (half of the recommended dose), F3–0.400g pot -1 (recommended dose) and F4–0.800g pot -1 (double the recommended dose)] having six different combinations of bioinoculants. Inoculation of bioinoclulants with F1 increased plant growth and nutrition to an acceptable level with AM fungi in combination with P. fluorescens. Application of higher dose of P fertilizer markedly decreased all the growth parameters. The prevalence of AM colonization was highest in G+A+Pf with F1. Similarly highest yield was recorded for the treatment involving multi inoculation of G+A+Pf in the treatment of F1 followed by dual inoculation of G+Pf in F0 plants. Thus this finding suggests the application of efficient bioinoculants (G+A+Pf) along with right dose of P fertilizer (half of the recommended P) during seedling transplantation to increase overall growth and yield performance of bell pepper and could be considered as a sustainable substitute to higher phosphorus fertilizer for bell pepper cultivation.

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Arbuscular mycorrhizal inoculation and super phosphate application influence plant growth and yield of Capsicum annuum

A pot experiment was conducted to investigate the potential effect of arbuscular mycorrhizal fungi (Glomus mosseae & Acaulospora laevis) and phosphate solubi- lizing bacteria (Pseudomonas fluorescens) with different levels of superphosphate on Chrysanthemum indicum L. After 100 days, different plant growth parameters such as mycorrhization's characteristics, phosphatase activity and phosphorus up- take were measured. The obtained results revealed that the inoculation of plants with biofertilizers and recommended dose of superphosphate significantly improved the growth parameters. Inoculation with A. laevis + P. fluorescens at medium con- centration of superphosphate showed maximum height, fresh and dry root weight, AM root colonization, AM spore count, alkaline phosphatase activity, acidic phos- phatase activity and the percent phosphorus uptake in shoot and root whereas root length was maximum in G. mosseae + A. laevis + P. fluorescens. Leaf area and fresh and dry shoot weight were maximum in the treatment (G. mosseae + A. laevis + P. fluorescens) at low concentration of superphosphate. The use of AMF increased nu- trient acquisition from an organic fertilizer source by enhancing acidic phosphatase (ACP) and alkaline phosphatase (ALP) activity, thus facilitating P acquisition and improving plant growth.

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K Prasad

Papers

Impact of different levels of superphosphate using arbuscular mycorrhizal fungi and Pseudomonasfluorescens on Chrysanthemum indicum L