Page 19 - AJWEP-22-6

Soybean with bacteria and humics

or chemical fertilizer controls, particularly when humic impact score (scale: 1–5) was assigned to each entry
formulations lacked consistent molecular composition based on the strength of reported physiological effects,
or when application timing was suboptimal. These agronomic benefits, and frequency of field validation.
89
findings underscore the need for careful strain-genotype One major issue is formulation variability—humic
matching, robust quality control of humic products, and substances derived from different organic wastes and
site-specific management practices. extraction methods often exhibit inconsistent field
By acknowledging these non-significant outcomes, results. This lack of standardization limits reproducibility
future research can better identify the boundary and regulatory acceptance. 60,64 Future efforts should
conditions under which co-application is most effective, focus on classifying humic products based on molecular
rather than assuming universal success across contexts. properties and developing universal quality standards.
Despite these limitations, the potential of humic Host-microbe compatibility is another concern:
substances and nitrogen-fixing bacteria in sustainable soybean genotypes respond differently to microbial
agriculture remains significant. As standardization strains, leading to inconsistent nodulation and nitrogen
improves and precision delivery technologies evolve, fixation. Targeted use of genetic tools and markers (e.g.,
these inputs may play a vital role in climate-resilient, de nodulation gene Rj4) could help match rhizobial strains
facto organic farming systems and circular bioeconomy to specific cultivars. 32,55
models. There are also biological risks. Humic substances
As displayed in Figure 5, the most significant sometimes suppress plant immune responses to
limitation in applying humic-enhanced nitrogen-fixing support microbial colonization, which may increase
biotechnologies is the variable composition of humic susceptibility to pathogens if not properly dosed. This
85
products, accounting for 14.9% of the overall impact. highlights the need for optimized application rates that
This is followed by the need for comprehensive field preserve microbial benefits without compromising plant
validation (14.1%) and challenges related to microbial defense.
compatibility (13.3%). Limitations in equipment Interactions with synthetic fertilizers are complex;
and fertilization protocols contribute 12.9%, while excessive nitrogen application can reduce symbiosis
the interaction with synthetic fertilizers adds another efficiency. Studies revealed that humics can partially
12.4%. Regulatory gaps and standardization issues mitigate this effect, but the exact molecular mechanisms
score 11.6%, the risk of pathogen susceptibility due remain unclear, requiring further transcriptomic research. 86
to potential plant immunosuppression scores 10.8%, On the practical side, many farmers lack access to
and the lack of long-term field studies is represented precision tools for applying bioinoculants and humic
by 10.0%. Figure 5 highlights that technological, products, resulting in low adoption and inconsistent
biological, and institutional constraints must be outcomes. Technological solutions like coated granules
addressed simultaneously to ensure the reliable and or liquid injectors could enhance delivery accuracy and
scalable adoption of these integrated biotechnologies in microbial survival. 76,88
sustainable agriculture. Long-term soil impacts also remain under-researched.
Table 5 presents a prioritized overview of key Although short-term benefits are clear, multi-season
limitations, challenges, and promising combinations studies are needed to evaluate the sustainability of these
for integrating humic substances with nitrogen-fixing technologies across rotations and their influence on
bacteria in sustainable soybean production systems. An microbial diversity and nutrient cycling. 32,89
Finally, cost and accessibility remain significant
barriers, especially in developing regions. Formulated
humic-microbial products can be expensive or
unavailable. Local production from agricultural waste
and investment in small-scale laboratories could help
scale these solutions affordably. 60,85
Collectively, these points emphasize the need for
standardization, precision technology, and inclusive
innovation to fully realize the potential of integrated
Figure 5. Key limitations and challenges in the bio-based inputs in climate-resilient agriculture.
application of humic-enhanced nitrogen-fixing Table 6 summarizes selected field trials conducted
biotechnologies across diverse geographic and climatic conditions,

Volume 22 Issue 6 (2025) 13 doi: 10.36922/AJWEP025230190