During crop years 1989-1992 EXNUT concepts and a version of EXNUT modified for North Carolina conditions were evaluated. This version was revised and evaluated on 20-25 peanut fields during crop years 1993, 1994, 1995, 1996, and 1997 when average yields of 4360, 4890, 4640, 4530, and 4770 kg/ha, respectively, were obtained. These yields averaged 880 kg/ha higher than average yields produced on these irrigated fields prior to 1993 and 1660 kg/ha higher than the average county yields during 1993-1997. The farmers and county agents reported that irrigation scheduled by EXNUT provided an estimated 500 kg/ha increase in yields. Costs of running EXNUT were estimated at $5.14/ha. Using these estimates, net returns from using EXNUT instead of normal irrigation scheduling by the farmer was $272.76/ha. Average compliance of farmers with EXNUT water scheduling recommendations was 85 and 75% for wet years (1994 and 1996) and dry years (1993, 1995, and 1997), respectively. On the average, a 71% or higher compliance with EXNUT recommendations on fields with sandy- and medium-type soils resulted in yields greater than 4480 kg/ha, making irrigation of peanuts feasible in these fields at a world market price as low as $350 per metric ton. Every percentage point increase in compliance with EXNUT recommendations on these fields resulted in an increase in yield of 50 and 110 kg/ha during wet and dry years, respectively. Yields from fields with heavy type soils averaged only 3850 kg/ha because of excessive disease and harvest losses. On the average, peanuts can be produced on this heavy-type soil at world market prices of $410/metric ton if compliance with EXNUT recommendations is at least 80%. This 9-yr study is an example of how expert systems can be transferred through cooperation of researchers, extension specialists, and users.

The riparian ecosystem management model (REMM) was field tested using five years (2005)(2006)(2007)(2008)(2009) of measured hydrologic and water quality data on a riparian buffer located in the Tar-Pamlico River Basin, North Carolina. The buffer site received NO 3 -N loading from an agricultural field that was fertilized with inorganic fertilizer. Field results showed the buffer reduced groundwater NO 3 -N concentration moving to the stream over a five-year period. REMM was calibrated hydrologically using daily field-measured water table depths (WTDs), and with monthly NO 3 -N concentrations in groundwater wells. Results showed simulated WTDs and NO 3 -N concentrations in good agreement with measured values. The mean absolute error and Willmott's index of agreement for WTDs varied from 13-45 cm and 0.72-0.92, respectively, while the root mean square error and Willmott's index of agreement for NO 3 -N concentrations ranged from 1.04-5.92 mg/l and 0.1-0.86, respectively, over the five-year period. REMM predicted plant nitrogen (N) uptake and denitrification were within ranges reported in other riparian buffer field studies. The calibrated and validated REMM was used to simulate 33 years of buffer performance at the site. Results showed that on average the buffer reduced NO 3 -N concentrations from 12 mg/l at the field edge to 0.7 mg/l at the stream edge over the simulation period, while the total N and NO 3 -N load reductions from the field edge to the stream were 77 and 82%, respectively.(KEY TERMS: water quality; riparian buffers; nonpoint source pollution; nutrients; riparian ecosystem management model.)Tilak, Amey S., Michael R.

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