Deanna Osmond, NC State University, Department of Soil Science

1. Very High Risk Low Risk 250 Medium Risk High Risk 200 150 100 50 0 0 10 20 30 40 50 60 70 80 90 100 110 120 PLAT Index value Land Use Data: Understand It Before Making Water Quality Rules Deanna Osmond, NC State University, Department of Soil Science Kathy Neas, North Carolina Department of Agriculture and Consumer Sciences, Statistics Division Nitrogen • Average Nfertilizer rates are 84 kg ha-1 (wheat); 133 kg ha-1 (corn); 94 kg ha-1 (tobacco); 87 kg ha-1 (cotton); 49 kg ha-1 (pasture/hay). • Except for tobacco and cotton, crops are generally under fertilized with N. • Only 14% of all producers used nutrient management planning. Introduction Methods and Materials Cover Crops • Used area frame sample; > 4 ha, rural, census blocks. • Selected census blocks, aggregated to 121 ha. • Random number generator selected areas to be sampled. • Fields randomly sampled for 2004 crop year per selected area. • 1,156 fields were selected representing 4,741 ha. • Agricultural data collected included current area (ha), crops, cover crops, conservation tillage, • application rates of N, P2O5 rates, and K2O, slope length, slope, and erosion rates. • Conservation practice data: buffer width, buffer type, acres affected by buffers • and water control structure and acres affected by water control structures. • Used NC Agricultural Nutrient Assessment Tool to approximate off-site P and N losses. Basin Characteristics • Wheat is the predominant cover crop in the basin. • Total cover crop acreage is 14% of all total acres. • The Tar-Pamlico River Basin empties into the Albermarle-Pamlico Sound, which was declared nutrient sensitive (Figure 1). • The Tar-Pamlico River Basin is comprised of • 17 counties • 1.2 M hectares; 323,749 hectares of farm land • 400,000 people • 290 kilometers of river length; 37,015 kilometers of streams (Figure 2). • The Tar-Pamlico River Basin was regulated in 2001 by the NC Environmental Management Commission in an attempt to reduce nutrient loading to the Albermarle-Pamlico Sound. • By 2006, agriculture was required to reduce its nitrogen contribution by 30% through the use of nutrient management, conservation practices such as riparian buffers and water control structures, and land conversion and ensure that there was no net increase in phosphorus. • No analysis of actual agricultural practices was performed prior to rule making. Conservation Tillage • Conservation tillage had a large range of use: Washington County (97.5% ) > Halifax (62.4%) > Beaufort (57.0%) = Martin (56.7%) > Granville (51.4%) > Franklin (45.1%) > Pitt (40.8%) = Hyde (39.6%) > Edgecombe (30.1%) > Nash (24.8%) > Pamlico and Wilson (0%). Figure 3. Sample locations Results and Discussion Other Agronomic Information Phosphorus • Mean erosion was 7.9 t ha-1. Mean soil loss in most counties was under “T” (11 t ha-1). • 40% of all agricultural acres were not buffered. • Mean tree buffer width = 35 m; vegetative buffer width = 9 m; 2-tiered buffer width (trees+vegetative) = 27 m. • In counties where water table management is feasible, 6 to 62% of all acres were affected by this practice. • Average P2O5 fertilizer rates are 25.8 kg ha-1 (wheat); 85 kg ha-1 (corn); 78 kg ha-1 (tobacco); 38 kg ha-1 (cotton); 10 kg ha-1 (pasture/hay). • Almost no animal agriculture was identified in this basin. • All counties, except Hyde and Washington have 1.5 to 3 times greater soil test P2O5 than the critical threshold value. • Based on soil test results, producers that needed applications of P2O5 applied 32 kg ha-1 of P2O5 ; producers that did NOT need P2O5 fertilizer (based on soil test) applied 32 of P2O5 . Producers did not discriminate P2O5 application based on soil test recommendations. Summary Wesley Childres • Soil erosion is under control, most crops are under fertilized with N, have a very low off-site loss of P, and many fields are buffered. • Efforts to reduce nutrients from agriculture should have been targeted on reducing soil test P and implementing buffers in those counties where they are lacking. Acknowledgements Figure 1. Tar-Pamlico River Basin Boundaries and position relative to the state of North Carolina Figure 2. Land use in the Tar-Pamlico River Basin The authors would like to thank NC Department of Environment and Natural Resources in supplying the pass-through USEPA 319 funds that allowed us to conduct this research. In addition, we would like to thank the NCDA&CS enumerators, who conducted the interviews, and the producers who supplied the information. Objective To obtain a statistically valid sample of crop production, including nutrient management and conservation practices in a regulated river basin in North Carolina – the Tar-Pamlico River Basin. Figure 5. Risk of P loss as derived from the Figure 4. Weighted mean, mean, and NCDA&CS mean of soil test P2O5