Soil can defined as a mix of water, air, Inorganic matter, organic matter and organisms and it provide medium for plant growth on the earth and also it is a physical medium. when we consider the pesticides it help to reduce pest problem for agriculture. when we consider the fertilizer it increase the fertility of soil. But reason is overuse of both pesticides and fertilizers can be occur bad effect for the soil and environment.

Excessive use of chemical fertilizer can damage soil how it happen,

01. Soil acidification - over use of nitrogen based fertilizer can acidize the soil. (Aeonium sulfate) In here mainly reduce the soil PH . It is not suitable for the most of the plant what are we cultivated. another reason is the lower PH value affect the organisms activity. Reason is most organisms are survival is the normal pH conditions.(6-7.5 PH) Excessive use of chemical fertilizer can reduce the soil PH and therefore soil organisms activities can be reduce therefore soil damage.

02.Water pollution - All crop that we are cultivated. They have recommended fertilizer application amount. That amount based on the Crop type, what amount of fertilizer already in the soil and the what amount of fertilizer plant can absorbed. If we put over amount of fertilizer plant absorbed only what they want amount. another amount is retained in the soil and with time being it can reduce there are main three ways for that,

1. Released into atmosphere as gases like CH4 - That is the one way of excessive use of fertilizers badly affect the environment. How it happen so CH4 is the one of gas reason for the global warming. that is the main environmental problem in the world.

2.Dissolve in the soil water - That is the another way. some of excessive fertilizer dissolve in the soil water and it affect to the purity of the soil water and the plant growth because plant use this dirty water. Therefore excessive fertilizer can damage the soil because soil water is the major component of the soil.

3.Can be remove from the soil with runoff water -That is another major problem that water can be mix with the major water reservoirs like cannel and lake it can badly affect on the human and other organisms. as a example in my country srilanka the area called Nilwala occur some incidence. That is the syndrome incidence name called "BLUE BABY SYNDROME" this is a condition that occur in newborns. Reason for that is pregnant women drink the water of Nilwala river flowing from this Nilwala area. The reason for that has been found to be the presence of excessive nitrogen content in the water. Further analysis has found that the nitrogen has mixed with the water through the urea used for cultivation. Human is the main component of the environment. That is the one way of excessive use of chemical fertilizer affect the environment.

03. Salt accumulation - Over use of chemical fertilizer cause the salt accumulation in the soil. There for it affect the crop growth and the soil. High salt levels can cause soil particles to disperse rather than aggregate, leading to poor soil aeration and water infiltration. Reason for that is soil structure degradation. High salt in the soil can create an osmotic imbalance, making it difficult for plants to absorb water. This can lead to dehydration and wilting even when soil appears moist.

As example in sri lanka Mahaweli some areas cannot cultivated any kind of crop because of high salt concentrate in the soil in this area.

Therefore when you use the fertilizer please don't use over amount of fertilizer. I will upload the document about "BLUE BABY SYNDROME"

Dr Vidoosha Sandeepa thank you for your contribution to the discussion

The use of pesticides and fertilizers in agriculture has been essential for increasing crop yields and ensuring food security. However, their excessive and improper use can lead to significant harm to soil health and the broader environment. Here's a detailed overview of how pesticides and fertilizers can damage soil and the environment:

1. Effects of Pesticides on Soil

a. Impact on Soil Microorganisms

• Microbial Diversity: Pesticides can disrupt the diversity and population of soil microorganisms. Beneficial bacteria and fungi, which play crucial roles in nutrient cycling, organic matter decomposition, and plant health, can be killed or inhibited by pesticides.
• Microbial Activity: The metabolic activity of soil microorganisms can be reduced, leading to decreased soil respiration and impaired nutrient cycling processes.

b. Soil Enzyme Activity

• Enzyme Inhibition: Pesticides can inhibit the activity of soil enzymes, which are critical for organic matter decomposition and nutrient mineralization. This inhibition can lead to reduced soil fertility and nutrient availability.

c. Soil Organic Matter

• Decomposition: Pesticides can affect the decomposition of organic matter by harming decomposer organisms. This can slow down the formation of humus and other stable organic matter fractions, negatively impacting soil structure and fertility.

d. Soil Structure

• Aggregation: Pesticides can alter soil structure by affecting the microbial exudates that help bind soil particles into aggregates. Poor soil aggregation can lead to increased erosion, reduced water infiltration, and decreased soil aeration.

2. Effects of Excessive Use of Chemical Fertilizers on Soil

a. Soil Acidification

• pH Reduction: The overuse of nitrogen-based fertilizers, particularly ammonium sulfate and urea, can lead to soil acidification. This lowers soil pH, affecting nutrient availability and microbial activity.
• Aluminum Toxicity: Acidic soils can release toxic levels of aluminum, which can harm plant roots and reduce crop yields.

b. Nutrient Imbalance

• Micronutrient Deficiency: Continuous application of high doses of macronutrients (N, P, K) can lead to imbalances, causing deficiencies in essential micronutrients such as zinc, iron, and manganese.
• Nutrient Lockup: Excess phosphorus can lead to the formation of insoluble compounds with micronutrients, making them unavailable to plants.

c. Soil Salinity

• Salt Accumulation: Overuse of fertilizers can lead to the accumulation of salts in the soil, particularly in arid and semi-arid regions. High soil salinity can impair plant growth, reduce water uptake, and lead to soil degradation.

d. Soil Structure Degradation

• Compaction: Fertilizers, especially when applied in large quantities, can contribute to soil compaction by affecting soil pore structure. Compacted soils have reduced porosity, leading to poor root growth and reduced water infiltration.
• Reduced Organic Matter: Excessive use of chemical fertilizers can reduce the reliance on organic amendments, leading to a decline in soil organic matter levels and degradation of soil structure.

3. Environmental Impact of Overusing Fertilizers

a. Water Pollution

• Nutrient Runoff: Excess fertilizers can be washed off from fields into nearby water bodies, causing nutrient pollution. This leads to eutrophication, characterized by excessive growth of algae and depletion of oxygen in water bodies, harming aquatic life.
• Groundwater Contamination: Nitrates from fertilizers can leach into groundwater, contaminating drinking water sources and posing health risks to humans and animals.

b. Air Pollution

• Ammonia Volatilization: Excessive use of nitrogen fertilizers can lead to the volatilization of ammonia into the atmosphere, contributing to air pollution and the formation of fine particulate matter.
• Greenhouse Gas Emissions: The production and use of nitrogen fertilizers contribute to the release of greenhouse gases (GHGs) such as nitrous oxide (N2O), a potent GHG with a global warming potential much higher than carbon dioxide.

c. Soil and Biodiversity Loss

• Habitat Destruction: The runoff of pesticides and fertilizers into natural habitats can disrupt ecosystems, leading to the loss of biodiversity. Aquatic ecosystems, in particular, are highly vulnerable to nutrient and pesticide pollution.
• Soil Erosion: Degraded soil structure due to excessive fertilizer use can increase susceptibility to erosion. Eroded soil can further exacerbate water pollution and loss of arable land.

Dr Qasim Ali thank you for your contribution to the discussion