Introduction to the 4Rs

The best place for crop nutrients, like nitrogen, phosphorus and potassium, is in the soil where they can be used by the growing plants. 4R Nutrient Stewardship is a science-based approach for plant nutrient management that supports economic, social and environmental goals.


Overview of 4R Nutrient Stewardship

4R Farmers and The Lake

View these documents to get more familiar with the agricultural terms and 4R principles referenced in this section.

View 4Rs HandoutGlossary of Ag Terms

Research and Practices in the Field

Farm fields are very diverse based on the region, crop type, soil type and other geographic factors. The 4Rs provide a tool set for farmers and their agronomy advisers to make decisions on a local, field level. The following expert perspectives will share more about nutrient management decisions that support environmental sustainability.


Agricultural Use of Fertilizer and the 4R Strategies


Scientific Perspective on Phosphorus and Water Quality

Using Science to Meet Sustainability Goals

Research is key to understanding the water quality and farm impacts of implementing 4R practices. Continued research initiatives will help uncover the best management practices and generate new tools to meet important goals for reducing nutrient loading.


How Edge-of-Field Research Quantifies the Impact of Management Practices

Ontario Farm Tool Helps Farmers Manage Their Phosphorus (P)

There are two types of phosphorus (P) that can cause trouble in freshwater ecosystems. One is sediment, or particulate, P that can be washed into a ditch, stream or river by erosion. The other is soluble P, which is dissolved in the water that runs off into a stream or river. The Ontario Ministry of Agriculture, Food and Rural Affairs have developed an online farm tool to help farmers understand their phosphorus loss risk with the field management practices and other variables. This tool called PLATO (Phosphorus Loss Assessment Tool for Ontario) aids farmers in making best management practices to reduce their risk of P loss.


Managing the Risk of Phosphorus Runoff

PLATO Investigation

PLATO, (Phosphorus Loss Assessment Tool for Ontario from OMAFRA) is a calculator that can be used to estimate the risk of phosphorus loss from a farmer’s field. PLATO takes into consideration the many variables (factors) that can affect the results of the calculations.

Download materialsGo to PLATO online


Consumers and Phosphorus

Phosphorus is one of the most common elements in our environment and is essential to human, animal and plant life.

View Article

Section 04 Review

  • What are the 4Rs?

  • What are some of the management practices that can help reduce nutrient runoff and water contamination?

  • Besides agricultural practices, what are some of the other contributing factors to HABs?

Upcoming Sections

Section 05

Many people, including legislators, conservation groups and farmer organizations, are working on solutions. Which efforts will be effective?