The 4R concept (right source, right rate, right time and right place) provides a useful structure to achieve increased crop production, improved farm profitability, greater environmental protection and better sustainability. However, crop nutrient management should go beyond the 4Rs of fertilizer and manure stewardship. Other soil management factors that affect crop productivity, farm profitability, the environment, and sustainability should be considered when thinking about crop nutrient management. While fertilizer and manure applications affect nutrient availability to crops short-term (e.g., current growing season or following year), other soil management factors affect nutrient availability longterm. More specifically, factors that affect crop residues after harvest and soil structure/ aggregation affect the availability of nutrients in future years. One such soil property is soil organic matter content.
Soil Science Extension
University of Wisconsin Madison