The application of inorganic fertilizers, including NPK (nitrogen, phosphorus, and potassium) fertilizers, typically provides essential nutrients to plants, promoting their growth and development. However, there are instances where the use of fertilizers might indirectly contribute to pest problems. Here are a few reasons why this can happen:

Nutrient Imbalance: In some cases, the use of NPK fertilizers can lead to an imbalance in nutrient levels in the soil. For example, an excessive supply of nitrogen can promote rapid vegetative growth, making plants more susceptible to certain pests. Pests may be attracted to lush, tender growth that is rich in nutrients.

Plant Stress: While fertilizers provide essential nutrients, an imbalance or overapplication can stress plants. Stressed plants are more vulnerable to pest infestations. Pests are often attracted to weakened or stressed plants because they may be easier targets.

Altered Plant Chemistry: Fertilizer application can alter the chemical composition of plants. For example, high nitrogen levels can affect the concentration of certain compounds in plant tissues. Changes in plant chemistry can influence pest attraction and susceptibility.

Disruption of Natural Predators: Inorganic fertilizers can also impact the populations of beneficial organisms, including natural predators of pests. If the use of fertilizers leads to a decline in predator populations, pest populations may increase unchecked.

Impact to environment: Excessive Nitrogen will lead to run off to aquifer, which leads to algae growth in lake ponds and suffocating aquatic life

Monoculture and Fertilizer Use: Large-scale monoculture farming, where a single crop is grown over extensive areas, is often associated with the use of inorganic fertilizers. Monocultures can create ideal conditions for specific pests to thrive, as they have a continuous and abundant food source. The use of fertilizers in monocultures may exacerbate pest problems.

With growing demand and limited land availability, farmers have been increasingly using nitrogen fertilizers in order to increase crop yield. However, nitrogen fertilizers can have undesirable effects, including a decline in tea quality, soil acidification, heavy metals pollution, soil compaction, and changes in soil microbiome [2–3].

It’s important to note that the relationship between fertilizer use and pest infestations can be complex and context-specific. Integrated Pest Management (IPM) practices, which combine various strategies such as biological control, cultural practices, and judicious use of pesticides and fertilizers, are often recommended to minimize the impact of pests on crops while promoting sustainable and environmentally friendly agriculture. Monitoring the health of plants, maintaining proper nutrient balance, and adopting diverse and resilient farming systems can all contribute to reducing pest issues associated with fertilizer use.

Pesticides
Pesticides with toxicity category 1 are highly toxic, and they can have a significant impact on soil microorganisms in the rhizosphere—the region of soil around plant roots where the microorganisms interact closely with the plant. The effects of such pesticides on soil microorganisms can be detrimental, leading to both short-term and long-term consequences.

Immediate Impact: Mortality or Reduction in Population

High toxicity pesticides can directly kill or significantly reduce the population of soil microorganisms in the rhizosphere. This includes beneficial bacteria, fungi, and other microorganisms that play essential roles in nutrient cycling, disease suppression, and overall soil health.
Disruption of Microbial Diversity

Pesticides can alter the composition and diversity of soil microbial communities. A reduction in microbial diversity may lead to imbalances in the ecosystem, affecting the plant-microbe interactions that contribute to plant growth and health.
Disruption of Symbiotic Relationships

Many plants form symbiotic relationships with mycorrhizal fungi in the rhizosphere. Pesticides can disrupt these relationships, negatively impacting nutrient uptake by plants. This can result in reduced plant growth and productivity.
Impact on Nutrient Cycling

Soil microorganisms are crucial for nutrient cycling, breaking down organic matter and making nutrients available to plants. Pesticides may interfere with these processes, leading to a decline in nutrient availability for plants.
Residual Effects

Some pesticides can persist in the soil for an extended period, continuing to affect soil microorganisms long after their application. This persistence can have prolonged negative effects on the soil ecosystem.
Secondary Effects on Non-Target Organisms

Pesticides can have indirect effects on non-target organisms, such as earthworms and beneficial insects, which play important roles in maintaining soil structure and controlling pests. Disruption of these organisms can have cascading effects on the entire ecosystem.
It’s important to note that the specific effects can vary depending on the type of pesticide, its application rate, the soil type, and environmental conditions. In sustainable agriculture, there is an increasing focus on minimizing the use of highly toxic pesticides and adopting integrated pest management strategies that consider the ecological impact on soil and the broader environment.