AgroAzzo and AgroPhos – 2024–2025 Field Research Summary

Executive Summary

Two international field programmes conducted in Italy and the United States have evaluated microbial treatments containing the organisms used in AgroBiotech’s AgroAzzo (Azotobacter chroococcum) and AgroPhos (Pseudomonas protegens) products.

The trials were conducted independently in commercial horticultural systems and provide complementary evidence. The Italian kiwifruit study focused primarily on soil biological activity and plant physiological responses, while the University of Florida/IFAS citrus programme included commercial yield, canopy development, fruit quality and tree-health measurements in citrus affected by Huanglongbing (HLB).

The first-year results are encouraging. In Italy, treatments containing AgroAzzo and AgroPhos showed trends toward increased soil biological activity, while the microbial treatment combined with a biostimulant showed encouraging improvements in plant physiological activity. In Florida, the beneficial microbial treatment produced 19% greater harvested fruit yield and 20% greater fruit solids per tree than the untreated control at the Wauchula Valencia site.

The studies remain ongoing, and treatment effects were not consistent across all sites or statistically significant for all parameters. Nevertheless, together they provide useful independent international evidence supporting further development of AgroAzzo and AgroPhos for commercial horticultural systems.

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1. Italian Kiwifruit Trial

Trial Overview

The 2025 study was conducted by KARPOSIA srl – Innovative Agriculture in a commercial yellow-fleshed kiwifruit orchard in the Metaponto region of southern Italy.

The approximately 0.5 ha orchard contained seven-year-old vines with an expected productive potential of 30–35 t/ha. The trial used a row-strip experimental design with five replicated sampling positions.

Four treatments were evaluated:

• M – Microbial treatment: Azotobacter chroococcum (AgroAzzo) + Pseudomonas protegens (AgroPhos)
• A – Agrusaver XL: pine-resin-based fertilizer/biostimulant
• M+A: AgroAzzo + AgroPhos followed by Agrusaver XL
• CTRL: untreated control

Three applications were made through root-zone irrigation during May and June 2025. In the combined treatment, Agrusaver XL was applied approximately three days after the microbial treatment to minimise potential interference with microbial establishment.

Soil Biological Activity

Soil respiration was measured using a LI-COR 8100 infrared gas analyser, providing an objective measure of CO₂ flux associated with root and microbial activity.

Measurements were conducted in August and September, approximately two to three months after the microbial applications.

The researchers reported that the combined M+A treatment had the highest and most stable mean soil respiration, followed by the microbial treatment.

Importantly, the report states that both treatments containing the microbial inoculants showed a trend toward greater soil respiration.

The researchers concluded that:

“These results may reflect enhanced microbial metabolic activity in the rhizosphere following the application of inoculants.”

Although variability meant the treatment differences were not statistically significant in the first season, the results suggest that AgroAzzo and AgroPhos may stimulate biological processes within the kiwifruit rhizosphere.

Plant Physiological Activity

Plant physiological responses were assessed using a LI-600 porometer/fluorometer.

Measurements included:

• stomatal conductance;
• photosystem II efficiency;
• leaf temperature; and
• associated photosynthetic parameters.

The combined M+A treatment showed a tendency toward increased stomatal conductance, suggesting greater gas-exchange activity.

The same treatment also exhibited slightly lower leaf temperatures in several measurements. The researchers suggested that increased stomatal conductance could have enhanced transpirational cooling.

This response is potentially relevant to horticultural production under warm and water-limited conditions, although further seasons are required before conclusions can be drawn.

Photosystem II efficiency remained within the normal physiological range across treatments. Importantly, there was no evidence that the microbial or combined treatments negatively affected the photosynthetic apparatus.

Fruit Quality

Fruit was assessed immediately before the September 2025 harvest.

There were no significant treatment differences in fruit fresh weight or colour.

°Brix was slightly higher in untreated fruit. The researchers proposed that this could indicate that the control fruit was at a slightly more advanced stage of maturity rather than demonstrating an adverse treatment effect.

They hypothesised that treatments stimulating plant physiological activity may have maintained active vegetative metabolism for longer, potentially influencing the timing of soluble-solids accumulation.

The report appropriately notes that one year of observations is insufficient to confirm this hypothesis.

Italian Trial Conclusion

The researchers concluded that the combined application of microbial inoculants and biostimulant:

“tended to enhance plant physiological activity and soil microbial respiration, without negatively affecting photosynthetic efficiency.”

The trial is continuing into subsequent seasons to determine whether these initial trends are repeatable and to strengthen the dataset.

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2. United States Citrus Trial

Trial Overview

A separate research programme titled “Assessing therapeutic effects of CitruSaver on the productivity and health of HLB-affected citrus trees” is being conducted by the University of Florida/IFAS Citrus Research and Education Center, led by Davie Kadyampakeni.

The programme covers commercial citrus groves in Florida and Texas and includes Valencia and Hamlin sweet oranges and grapefruit.

The study evaluates CitruSaver treatments and beneficial microbes in trees affected by HLB/citrus greening.

The beneficial microbial treatment contains:

• Azotobacter chroococcum
• Pseudomonas protegens

These are the microbial species used in AgroAzzo and AgroPhos respectively.

The report describes these microorganisms as being used to promote plant growth, enhance nitrogen fixation, improve phosphorus cycling and potentially suppress harmful pathogens.

Wauchula Valencia Yield Results

The Wauchula, Florida site produced the clearest result specifically associated with the beneficial microbial treatment.

The untreated control produced 90.35 lb of fruit/tree, compared with 107.08 lb/tree from the beneficial microbial treatment.

This represented a:

+19% increase in harvested fruit yield per tree.

The effect was also apparent when commercial fruit solids were considered.

The control produced 5.52 lb solids/tree, while the beneficial microbial treatment produced 6.60 lb solids/tree.

This represented a:

+20% increase in fruit solids per tree.

Significantly, the microbial treatment performed almost identically to CitruSaver 1 at this site. CitruSaver 1 produced 107.28 lb fruit/tree and 6.63 lb solids/tree.

Therefore, at Wauchula, the treatment containing A. chroococcum and P. protegens achieved approximately the same commercial yield response as the best-performing CitruSaver treatment.

Wauchula Valencia Results

Treatment	Fruit yield/tree	Change vs Control	Fruit solids/tree	Change vs Control
Control	90.35 lb	–	5.52 lb	–
Beneficial Microbes	107.08 lb	+19%	6.60 lb	+20%
CitruSaver 1	107.28 lb	+19%	6.63 lb	+20%
CitruSaver 2	79.93 lb	-12%	4.85 lb	-12%
CitruSaver 2 + Microbes	100.63 lb	+11%	6.16 lb	+11%

These results provide particularly encouraging evidence for the AgroAzzo/AgroPhos microbial combination under commercial citrus production conditions.

Fort Meade Results

The response at the second Florida site, Fort Meade, was different.

Here, the beneficial microbes alone produced lower harvested yield and solids than the untreated control.

By comparison, CitruSaver 1 increased harvested fruit yield by approximately 36% and fruit solids/tree by 43%.

A separate 10-acre block receiving CitruSaver continuously through microjet irrigation for approximately four years produced the strongest result, with approximately 120% greater harvested yield and 109% greater fruit solids/tree than the control.

These longer-term results are noteworthy but cannot be attributed specifically to AgroAzzo and AgroPhos from the information presented in the report.

The contrasting performance of the microbial treatment between Wauchula and Fort Meade also demonstrates the importance of environmental conditions, orchard management and site-specific factors when evaluating biological products.

Canopy Development and Tree Health

Canopy development was another important component of the Florida research.

CitruSaver 1-treated trees showed approximately:

• 10% greater canopy volume at Wauchula, and
• 35% greater canopy volume at Fort Meade

compared with the respective controls.

The researchers also reported that treated trees exhibited greater canopy vigour and new flush growth, together with noticeably less branch dieback than control trees at the two Florida Valencia sites.

Given the severe decline commonly associated with HLB-affected citrus trees, these observations are encouraging and warrant continued investigation.

Fruit and Juice Quality

Juice-quality assessments included:

• soluble solids;
• titratable acidity;
• juice colour; and
• soluble solids-to-acid ratio.

The main comparison found no significant differences among treatments for these parameters.

Consequently, there was no evidence from the first harvest that the increased yields observed in the better-performing treatments were accompanied by deterioration in the measured juice-quality parameters.

HLB Pathogen Measurements

The researchers also used qPCR to measure Candidatus Liberibacter asiaticus (CLas), the bacterium associated with HLB.

Higher Ct values indicate lower bacterial loads.

At this stage, the results presented do not provide sufficient evidence to conclude that the beneficial microbial treatment suppresses CLas or controls HLB.

The current results are therefore better interpreted as evidence of potential improvements in productivity and plant health under HLB pressure rather than evidence of direct disease control.

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3. Combined Interpretation

The Italian and US trials examine the same core microbial organisms from different perspectives and consequently provide complementary information.

Italy – Evidence of Biological and Physiological Activity

The Italian kiwifruit study provides evidence that treatments containing A. chroococcum and P. protegens can influence the soil–plant system.

The principal trends were:

AgroAzzo + AgroPhos → increased rhizosphere biological activity

and, when combined with the accompanying biostimulant:

increased stomatal conductance → potentially greater physiological activity and transpirational cooling.

USA – Evidence of Commercial Crop Response

The University of Florida/IFAS programme provides a more direct measure of commercial performance.

Most notably:

AgroAzzo/AgroPhos microbial species → +19% fruit yield and +20% fruit solids/tree at Wauchula.

The absence of the same response at Fort Meade means this should not be presented as a universal yield effect. However, the Wauchula result demonstrates that a substantial agronomic response to the microbial treatment is possible under commercial production conditions.

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4. Overall Conclusions

Taken together, these two international research programmes provide encouraging independent evidence for microbial treatments based on *Azotobacter chroococcum and Pseudomonas protegens.

The key findings are:

1. Increased rhizosphere activity: The Italian kiwifruit trial showed a trend toward greater soil respiration in treatments containing AgroAzzo and AgroPhos.
2. Improved plant physiological activity: Combining the microbial inoculants with a biostimulant tended to increase stomatal conductance and was associated with slightly lower leaf temperatures.
3. Commercial yield response: At Wauchula, the beneficial microbial treatment increased Valencia harvested fruit yield by 19% and fruit solids/tree by 20% relative to the untreated control.
4. Fruit quality was maintained: Neither programme identified evidence of a material deterioration in the measured fruit-quality parameters associated with the microbial treatments.
5. Responses are site dependent: The microbial treatment did not outperform the control at the Fort Meade harvest, demonstrating the importance of soil, climate, irrigation, disease pressure and orchard management in determining biological-product performance.
6. Further research is required: Neither programme should yet be interpreted as demonstrating universal yield enhancement or disease control. Both reports support continued multi-season evaluation.

Overall Assessment

The two programmes provide different but complementary lines of evidence.

The Italian trial provides a potential biological mechanism, demonstrating trends toward increased rhizosphere activity and improved plant physiological performance.

The Florida research provides evidence of agronomic relevance, with a 19% yield and 20% fruit-solids response to the beneficial microbial treatment at one commercial Valencia site.

Together, these findings support the continued international evaluation and commercial development of AgroAzzo and AgroPhos as microbial tools for improving rhizosphere function, nutrient cycling and crop performance in high-value horticultural systems, while recognising that further replicated, multi-season research is required to establish the consistency and magnitude of these effects.

Sources: KARPOSIA srl, Report of Activity 2025 – AgroPhos, AgroAzzo and Agrusaver Application in the Kiwifruit Commercial Orchard; University of Florida/IFAS Citrus REC, Assessing Therapeutic Effects of CitruSaver on the Productivity and Health of HLB-Affected Citrus Trees – Progress Report Fall 2024–Spring 2025.