Nitrogen management for corn production and water quality in southeastern Pennsylvania

The effect of manure and NH{dollar}sb4{dollar}NO{dollar}sb3{dollar} on corn yield and soil and soil water nitrate-N was evaluated at two sites in southeastern Pennsylvania to develop nitrogen recommendations for corn production and water quality. At Adams Co., the soil had not received long-term manure applications and did not possess a macropore structure, whereas the soil at Lancaster Co. had received manure applications for 10 to 20 years and possessed a macropore structure. Total nitrogen applications ranged from 0 to 336 and from 0 to 896 kg N/ha at Lancaster and Adams Co., respectively. Manure and NH{dollar}sb4{dollar}NO{dollar}sb3{dollar} did not affect corn yield at Lancaster Co. during the three-year study; however, a response to nitrogen was observed at Adams Co. Nitrate movement through the soil was greater at Adams than at Lancaster Co. The soil at Lancaster had higher spring residual nitrate contents than the soil at Adams Co. After the first winter, profile nitrate-N ranged from 130 to 234 kg N/ha and from 33 to 112 kg N/ha at Lancaster and Adams Co., respectively. Higher spring nitrate contents at Lancaster Co. were associated with higher nitrate concentrations in the soil matrix than in the drainage water. Average nitrate-N concentrations in the soil matrix and drainage water ranged from 5 to 60 and 0 to 20 ppm, respectively. Drainage nitrate-N concentrations did not exceed 10 ppm when fall profile nitrate-N content was less than 65 to 112 kg N/ha. Since this generally only occurred on the 112 kg N/ha manure rate and there was no response to nitrogen at Lancaster, this rate of manure would maintain water quality and maximum yields on fields with a history of high manure applications. At Adams Co., nitrogen applications should not exceed crop requirements since the profile cannot store nitrate over the winter.