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United States Department of Agriculture

Agricultural Research Service

Research Project: Soil and Water Conservation for Northwestern Irrigated Agriculture

Location: Northwest Irrigation and Soils Research

Title: Nutrient loads and sediment losses in sprinkler irrigation runoff affected by compost and manure

Authors
item Lehrsch, Gary
item Lentz, Rodrick
item Westermann, D -
item Kincaid, D -

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2014
Publication Date: N/A

Interpretive Summary: High water application rates beneath the outer spans of center pivot sprinkler systems can cause runoff, erosion, and nutrient losses, particularly from sloping fields. This study determined runoff, as well as losses of sediment and nutrients (including nitrate-nitrogen, ammonium-nitrogen, total phosphorus [P], dissolved P, calcium, and sodium) in sprinkler runoff for two years after a single application of either stockpiled or composted dairy manure. The two-year field investigation studied two rates of manure and two rates of compost applied in fall of 1999 to a silt loam soil with slopes from 0.8% to 4.4%. In spring of 2000 and 2001 before irrigating, we collected surface soil from furrows to determine soil test phosphorus (STP). We applied 21 to 46 mm of water using a moving-lateral sprinkler system (essentially a center pivot simulator) to field plots six times in 2000 and twice in 2001. We measured runoff rates and collected runoff samples to determine sediment and constituent losses for each monitored irrigation. None of the amendment treatments significantly affected runoff or losses of sediment, ammonium-nitrogen, or total P. Without exception, runoff and losses of sediment and every measured constituent varied among irrigations, after accounting for differences in water applied. Treatments affected dissolved P, with those losses being 5 to 6 times greater from manured than untreated plots. Losses of nitrate-nitrogen, dissolved P, and sodium were 2- to 4-fold greater from plots amended with manure rather than compost.

Technical Abstract: High water application rates beneath the outer spans of center pivot sprinkler systems can cause runoff, erosion, and nutrient losses, particularly from sloping fields. This study determined runoff, sediment losses, and loads of nutrients (dissolved organic C, Nitrate-N, ammonium-N, total phosphorus [TP], ferric-oxide strip phosphorus [FeO P], dissolved reactive phosphorus [DRP], K, Ca, Mg, and Na) in sprinkler runoff for two years after a single application of either stockpiled or composted dairy manure. The two-year field investigation studied five treatments, including a non-amended control, in each of six blocks, with each block situated under a different span of a moving-lateral sprinkler system. In October 1999, we incorporated 29.1 or 71.7 Mg/ha of dry manure or 22.4 or 47.0 Mg/ha of dry compost into a calcareous silt loam soil on slopes from 0.8% to 4.4%. In spring of 2000 and 2001, we collected surface soil (0 to 5 mm) from bed tops to determine aggregate stability by wet-sieving field-moist aggregates and surface soil (0 to 30 mm) from furrows to determine soil test phosphorus (STP). We applied 21 to 46 mm of water at an average application intensity of 28 mm/h (peak intensity of 40 mm/h) to 6.4- x 36.6-m field plots six times in 2000 and twice in 2001. Additional non-monitored irrigations were made as needed to produce corn (Zea mays L.) silage each year. We measured runoff rates and collected 1-L runoff samples at 15- to 30-minute intervals to determine sediment and constituent losses for each monitored irrigation. None of the amendment treatments significantly affected runoff, sediment losses, or loads of dissolved organic C, ammonium-N, or TP. Without exception, runoff, sediment losses, and loads of every measured constituent varied among irrigations, after accounting for differences in water applied. Treatments influenced DRP, K, and Ca runoff loads, with DRP loads being 5 to 6 times greater from the manure treatments than the control. Loads of Nitrate-N, DRP, and Na were 2- to 4-fold greater from plots amended with manure rather than compost.

Last Modified: 7/25/2014
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