Tile drainage phosphorus loss with long-term consistent cropping systems and fertilization

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Phosphorus (P) loss via tile drainage is a concern in agriculture.
• Short-term studies often fail to capture long-term impacts of farming practices on P loss.
• Understanding P dynamics in different cropping systems is crucial for water quality management.

Purpose of the Study:

• To evaluate the long-term effects of cropping systems and fertilization on phosphorus loss in tile drainage water.
• To identify the dominant forms of phosphorus lost and the factors influencing P loss.

Main Methods:

• A 4-year study on a clay loam soil examining long-term (≥43 yr) cropping systems: continuous corn (CC), corn-oats-alfalfa-alfalfa rotation (CR), and continuous grass (CS).
• Comparison of fertilization (F) versus no-fertilization (NF) treatments.
• Analysis of dissolved reactive P (DRP), dissolved unreactive P (DURP), and particulate P (PP) in tile drainage water.

Main Results:

• Long-term fertilization increased DRP, DURP, and total P (TP) concentrations and losses, with greater increases in CS > CR > CC.
• Dissolved P (DRP and DURP) was the dominant P form under fertilized continuous grass (72% of TP loss).
• Particulate P (PP) was dominant under other fertilized and all non-fertilized systems.
• P concentration in drainage flow was the primary factor for P loss, more so than flow volume.

Conclusions:

• Continuous grass systems, particularly with fertilization, significantly enhance P loss in tile drainage.
• Long-term grasslands receiving P inputs can become substantial P sources in tile-drained agricultural systems.
• Management practices need to consider long-term effects on P loss dynamics.