Objectives

1. To determine the effects of drainage, and water table control practices on peak outflow rates and movement and fate of nutrients and sediment from poorly drained, shallow water table soils and to determine interaction of water table control with other cultural practices such as fertilizer rate.

2. To complete development, test and document process based simulation models to predict the effects of different land and water management practices on nitrogen and phosphorus losses from poorly drained agricultural fields to coastal waters.

3. To develop recommendations for agricultural producers to minimize off site water quality degradation while allowing sustained economic yields.

---

Accomplishments

1. Controlled drainage can reduce nitrogen losses from agricultural fields to surface waters by approximately 45%, and phosphorus losses by about 40%.

2. Water management on controlled drainage systems can be utilized to reduce peak outflow rates by about 50% as compared to systems utilizing only surface drainage.

3. Controlled drainage can increase corn and soybean yields by approximately l0%.

4. Simulation models have been developed to describe the hydrology and predict losses of N,P, and sediment at the field edge so that experimental results can be extrapolated to a wide range of soils and management systems.

---

Significance

Controlled drainage has been accepted as a Best Management Practice by USDA-NRCS and water management structures for controlled drainage are cost shared by the State of North Carolina in nutrient sensitive watersheds. This practice has been accepted by farmers and by regulatory agencies because it improves both water quality and crop yields. North Carolina now has approximately 300,000 acres of farmland utilizing controlled drainage with approximately 25,000 acres being added each year. We estimate that controlled drainage has reduced nitrogen losses to surface waters from these lands by approximately 3,000,000 pounds per year. The value of the increased yields to farmers is about $5,000,000 annually and the economic value of improved water quality probably exceeds that of the increased yields.

---

Future Plans

To determine effective methods for integrating water management on agricultural land with water management on forested lands and natural wetlands to have productive watersheds with drainage water of high quality.

---