N.C. STATE UNIVERSITY

College of Agriculture and Life Sciences
N.C. Agricultural Research Service
N.C. Cooperative Extension Service

Water Management for Shallow Water Table Soils

Prepared by: Robert O. Evans

Long Term Objectives

1. Develop fertilization and water management recommendations to minimize the impact of nitrogen fertilization on water quality.

2. Evaluate and demonstrate methods for restoring wetland hydrologic, soil-water chemical, and water quality functions on prior converted, agricultural fields.

3. Implement, demonstrate, and evaluate best management practices to reduce nutrients derived from wastewater irrigation from reaching surface waters.

Short Term Objectives

1. Experimentally determine in lysimeter and field studies, nitrogen fate and movement as influenced by fertilization rate and timing, and water table management.

2. Restore hydrology and water quality functions to two prior converted wetlands then monitor and document downstream water quality improvements resulting from the wetlands restoration.

3'. Install and evaluate three W S (controlled drainage, irrigation calibration, and vegetative filter strips) on agricultural fields receiving animal wastewater and conduct a one-year irrigation scheduling service/demonstration for irrigators.

Accomplishments

1. Water table management recommendations emphasizing production efficiency, water conservation and water quality have been developed and disseminated to producers.

2. The hydrologic and treatment effectiveness of the Land-Lined Trench Septic System has been evaluated and identified for use in shallow water table soils.

3. Irrigation design workshops and training sessions promoting environmentally sound wastewater irrigation have been conducted.

Significance

Fertilizer nutrient losses in conventional drainage outflow typically exceed 20 kg N and 0.25 kg P per hectare per year. Controlled drainage had been demonstrated to reduce these losses by 30 to 50 percent. These results led to the adoption of controlled drainage as a BMP under the N. C. Agricultural cost Share Program. Controlled drainage has been adopted on over 200,000 hectares of crop and forest land resulting in an estimated crop yield increase worth 85 million annually. Current estimates are that controlled drainage is reducing agriculture's contribution of nitrogen to N. C. coastal waters by over one million kilograms annually.