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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #207302
Title: Nitrogen and phosphorus concentrations of runoff as affected by moldboard plowing

Author
item Gilley, John
item EGHBALL, BAHMAN - DECEASED USDA ARS
item MARX, D - PROF/STATS/U OF NE

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2007
Publication Date: 10/15/2007
Citation: Gilley, J.E., Eghball, B., Marx, D.B. 2007. Nitrogen and phosphorus concentrations of runoff as affected by moldboard plowing. Transactions of the ASABE 50:1543-1548.

Interpretive Summary: The repeated excessive application of manure on cropland areas can cause nutrients to accumulate near the soil surface and increase nutrient transport by overland flow. Inverting soils with high surface nutrient content could reduce runoff nutrient transport. This study was conducted to measure the effects of plowing on: a) the redistribution of nutrients within the soil profile; and b) nutrient transport by overland flow. Composted beef cattle manure was applied at five rates to selected areas and then incorporated by disking. Selected plots were plowed 244 days later to a depth of approximately 23 cm, and then disked. Soil samples for analysis of nutrient contend were collected at depths of 0-5, 5-15, and 15-30 cm both before and after plowing. Three 30-min simulated rainfall events, separated by 24-hour intervals, were applied at an intensity of approximately 70 mm hr-1. Nutrient content of runoff was measured from 0.75 x 2.0 m long plots. Phosphorus and nitrogen content at the 0 – 5 cm soil depth were reduced significantly as a result of plowing. Consequently, concentrations of phosphorus and nitrogen in runoff decreased significantly on the plowed plots. However, it is recommended that plowing only occur when appropriate measures have been taken to control soil erosion. Cropping and management practices should also be implemented to extract excess nutrients inverted during the plowing operation.

Technical Abstract: The repeated excessive application of manure on cropland areas can cause nutrients to accumulate near the soil surface and increase nutrient transport by overland flow. Inverting soils with high surface nutrient content could reduce runoff nutrient transport. This study was conducted to measure the effects of plowing on: a) the redistribution of nutrients within the soil profile; and b) nutrient transport by overland flow. Composted beef cattle manure was applied at five rates to selected areas and then incorporated by disking. Selected plots were plowed 244 days later to a depth of approximately 23 cm, and then disked. Soil samples for analysis of water-soluble phosphorus, Bray and Kurtz No. 1 phosphorus (Bray-1 P), NO3-N and NH4-N were collected at depths of 0-5, 5-15, and 15-30 cm both before and after plowing. Three 30-min simulated rainfall events, separated by 24-hour intervals, were applied at an intensity of approximately 70 mm hr-1. Dissolved phosphorus (DP), total phosphorus (TP), NO3-N, NH4-N, and total nitrogen (TN) content of runoff were measured from 0.75 x 2.0 m long plots. Bray-1 P and NO3-N content at the 0 – 5 cm soil depth were reduced significantly as a result of plowing. Consequently, concentrations of DP, TP, NO3-N, and TN in runoff decreased significantly on the plowed plots. However, it is recommended that plowing only occur when appropriate measures have been taken to control soil erosion. Cropping and management practices should also be implemented to extract excess nutrients inverted during the plowing operation.