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— Nutrient and Pesticide FAQs

This page is a compilation of answers to the FAQs related to Nutrient and Pesticide Management.


Sources of Nutrients and Pesticides

What is point and nonpoint source?

Why is atmosphere a source of nutrient loads?

How much pesticide is used in the US?

What constituents of fertilizer are the chief pollutants of our waterways?

How does domestic water contribute to nutrient loading in water?


Nutrient Transportation

What are the general pathways of pollutants?

What is the medium of nutrient transport?

Which is the most dominant form of nitrogen found in surface waters?

What is mineralization?

What is the basic mechanics of phosphorus transport?

What are pesticide loss pathways?

What are the methods of contamination from animal wastes?

Other than organic and inorganic nutrients what contaminants are present in animal waste?


Factors Affecting Nutrient Loads

What factors affect the transport of nitrogen?

What affects sediment-loss?


Management Practices

What agricultural practices can help control nutrient loading rates to the surface waters?


Sources of Nutrients and Pesticides

What is point and nonpoint source?

When the source of pollution is identified and is stationary, such as a factory smokestack, pipe, or well, that is referred to as a point source of pollution.

When the source of pollution is from diffuse source over a relatively large area it is referred as nonpoint. Nonpoint sources depend on two use activities- land and water, including failing septic tanks, improper animal-keeping practices, forest practices, and urban and rural runoff.

Why is atmosphere a source of nutrient loads?

About 3 million tons of nitrogen is deposited in the nation from the atmosphere as described by USGS. This nitrogen results from either chemical reactions in the atmosphere or from the combustion of fossil fuels like coal and gasoline. For this reason atmosphere also is a source of pollution this is normally termed as atmospheric deposition.

How much pesticide is used in the US?

According to USGS, almost 1 billion pound of pesticides is used in the United States, 70-80 percent of which is associated to agricultural purposes. Out of this 70-80% of pesticides usage 60% usage is of herbicides.

What constituents of fertilizer are the chief pollutants of our waterways?

Nitrogen and phosphorus are the chief pollutants of our waterways, which originate from the fertilizer applications. More than 10 million tons of nitrogen and 2 million tons of phosphorus accounts for the total commercial fertilizer used. Then there is organic fertilizer that is applied in the form of manure. Nitrogen in organic fertilizer accounts for an additional 7 million tons of nitrogen application and 2 million tons of phosphorus.

How does domestic water contribute to nutrient loading in water?

Domestic use of water also adds to the nutrient loading of our waterbodies. Other than bacteria and parasitic germs wastewater from domestic sources contain high nutrients from household chemicals, detergents and organic wastes.


Nutrient Transportation

What are the general pathways of pollutants?

The general pathways of pollutants to reach the waterways are erosion, leaching, adsorption and decomposition. Subsurface flow is also responsible for transferring pollutants from the surface waters to the unsaturated zones of the soil. Within soil, the processes of adsorption, desorption, oxidation, and decomposition help in the transport of pollutants. Once pollutants reach the groundwater they can cause long-term contamination of groundwater, which may become very difficult for remediation.

What is the medium of nutrient transport?

Pollutants occurring on land undergo transformation in the presence. Thus, water is the main form of nutrient transport in the soil-water relationship.

Which is the most dominant form of nitrogen found in surface waters?

Nitrate is a highly soluble form of nitrogen, hence it is the most dominant form of nitrogen occurring in surface and ground water both.

What is mineralization?

Mineralization is the microbial activity due to which organic nitrogen is transformed to ammonium and eventually to nitrate. This is the key process which determines the uptake of mineral nitrogen by plants and also determines the loss of nitrogen-nitrate through leaching.

What is the basic mechanics of phosphorus transport?

Movement of phosphorus into surface water or ground waters is mainly associated with organic matter. Soil erosion by water and overland flow are two mechanisms through which phosphorus is removed from land. Phosphorus loss gets affected by soil structure, vulnerability to soil erosion and agricultural activities.

What are pesticide loss pathways?

The pesticide residue that remains after plant uptake is removed from the land surface by runoff, leaching, and by microbial and abiotic degradation. Abiotic transformation results from the processes like, oxidation, hydrolysis, and photolysis. When pesticides come in contact with soil, they are partitioned between organic matter of the soil and soil pore-water. Pesticides or pesticide constituents that have an affinity towards soil are lost through sedimentation loss in runoff and those which are water-affined are lost through leaching. Pesticide losses are largely result from rainfall events- intensity and frequency. Other factors affecting pesticide losses are rate and timing of application, soil types, and physical and chemical characteristics of pesticides (sorption to soil, solubility, and rate of degradation).

What are the methods of contamination from animal wastes?

Animal wastes can contaminate the surface water through one or more of the following pathways:

  • Direct leakage to drainage systems

  • Leakage of waste from waste storage facilities

  • Pathways following the application of animal waste to agricultural lands

  • Direct transport of pathogens to streams and other surface waters from deposit of feces into water or pasture lands

Other than organic and inorganic nutrients what contaminants are present in animal waste?

Contamination through pathogens like cryptosporidium, E. Coli, Salmonella, and giardia is other potential source of contamination of our surface and ground waters.


Factors Affecting Nutrient Loads

What factors affect the transport of nitrogen?

Entry of nitrogen in the surface and ground water is affected by many factors, namely, land-use, soil-type, drainage, climate, rate and timing of fertilizer application, and management practices.

What affects sediment-loss?

Sediment loss is affected by the following factors:

  • Decreased absorption capacity of the soil increases the sediment loss in runoff

  • Soil compaction and loss of soil's organic matter results in the degradation in soil structure and reduces the infiltrating capacity of the soil

  • Soil properties, topography, and location

  • Rainfall intensity and frequency

  • Sheet erosion

  • Artificial pathways like farm-tracks, ditches, and highway drainage, which are very difficult to identify

  • Freshly cultivated or lands left after tillage are very vulnerable for sediment losses


Management Practices

What agricultural practices can help control nutrient loading rates to the surface waters?

Environmental Protection Agency has described eight ways in its Agricultural Management Practices for Water Quality Protection, module  that can help control nutrient transport to surface and ground waters.

  1. Conservation Tillage- it involves leaving 30% crop residues on the soil surface after tillage. This practice can reduce soil-erosion, runoff, preserve soil moisture, hold nutrients on the applied area and improve soil structure, air and water quality.

  2. Crop Nutrient Management- this practice requires accounting and inputting nutrients in quantities that may optimize crop-growth while reducing their movements off the field where they are applied to. This practice effectively controls the nutrient build-up in soils.

  3. Pest Management- varied methods for keeping insects, weeds, disease, and other pests below economically harmful levels while protecting soil, water, and air quality.

  4. Conservation Buffers- these are simple grassed waterways that run across riparian areas, which provide buffer to capture nutrients and pollutants that may otherwise move faster to the surface water.

  5. Irrigation Water Management- this manages pollutant loadings of nonpoint nature that originate from irrigation waters.

  6. Grazing Management- managing and controlling the pollutants that may enter the surface and ground waters from grazing and pasture lands.

  7. Animal Feeding Operations Management- this involves minimizing the discharge of wastes from animal feeding operations, controlling runoff, managing waste storages, utilizing waste, and nutrient management.

  8. Erosion and Sediment Control- involves the conservation of soil and reducing the mass of sediment reaching a water body, protecting both agricultural land and water quality and habitat.


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Last Revised on: 11/20/2007