Patrick R. Nash

Reducing Phosphorus Loss in Tile Water with Managed Drainage in a Claypan Soil

Installing subsurface tile drain systems in poorly drained claypan soils to improve corn ( L.) yields could potentially increase environmental phosphorus (P) loss through the tile drainage system. The objectives of the study were to quantify the average concentration and loss of ortho-P in tile drain water from a claypan soil and to determine whether managed subsurface drainage (MD) could reduce ortho-P loss in tile water compared with free subsurface drainage (FD). Flow-weighted ortho-P concentration in the tile water was significantly lower with MD (0.09 mg L) compared with that of FD (0.15 mg L). Ortho-P loss in the tile water of this study was reduced with MD (36 g ha) by 80% compared with FD (180 g ha). Contrary to previous research, reduced ortho-P loss observed over the 4-yr study was not solely due to the reduced amount of water drained annually (63%) with MD compared with FD. During the spring period, when flow was similar between MD and FD, the concentration of ortho-P in the tile water generally was lower with MD compared with FD, which resulted in significantly less ortho-P loss with MD. We speculate that MDs ability to conserve water during the dry summer months increased corns uptake of water and P, which reduced the amount of P available for leaching loss in the subsequent springs.

Reducing nitrogen loss with managed drainage and polymer-coated urea.

Continuous corn ( L.) production during dry years combined with high N fertilizer rates can have a high potential for NO-N loss through tile drainage water. Claypan soils can further increase the potential for NO-N loss through tile drainage water due to the claypan layer that restricts N leaching below the tile drains. The objective of this 4-yr study was to determine whether use of managed subsurface drainage (MD) in combination with a controlled-release N fertilizer could reduce the annual amount of NO-N loss through tile drainage water compared with free subsurface tile drainage (FD) with a noncoated urea application. Due to dry conditions over the summer and fall months, MD reduced the annual amount of water drained by at least 73% compared with FD in two of the four crop years. Low N loss and reduced corn N uptake possibly resulted in carry-over N and high soil N concentrations throughout the study, which may have limited the effect of N fertilizer source on annual NO-N loss in the tile drainage water. Use of MD reduced annual NO-N loss in the tile drainage water by 78 to 85% in two of the four years. High NO-N loss reduction with MD compared with FD was largely due to dry growing season conditions in combination with wet conditions over the noncropping period.

Simulated Soil Organic Carbon Changes in Maryland Are Affected by Tillage, Climate Change, and Crop Yield

The impact of climate change on soil organic C (SOC) stocks in no-till (NT) and conventionally tilled (CT) agricultural systems is poorly understood. The objective of this study was to simulate the impact of projected climate change on SOC to 50-cm soil depth for grain cropping systems in the southern Mid-Atlantic region of the United States. We used SOC and other data from the long-term Farming Systems Project in Beltsville, MD, and CQESTR, a process-based soil C model, to predict the impact of cropping systems and climate (air temperature and precipitation) on SOC for a 40-yr period (2012-2052). Since future crop yields are uncertain, we simulated five scenarios with differing yield levels (crop yields from 1996-2014, and at 10 or 30% greater or lesser than these yields). Without change in climate or crop yields (baseline conditions) CQESTR predicted an increase in SOC of 0.014 and 0.021 Mg ha yr in CT and NT, respectively. Predicted climate change alone resulted in an SOC increase of only 0.002 Mg ha yr in NT and a decrease of 0.017 Mg ha yr in CT. Crop yield declines of 10 and 30% led to SOC decreases between 2 and 8% compared with 2012 levels. Increasing crop yield by 10 and 30% was sufficient to raise SOC 2 and 7%, respectively, above the climate-only scenario under both CT and NT between 2012 and 2052. Results indicate that under these simulated conditions, the negative impact of climate change on SOC levels could be mitigated by crop yield increases.