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United States Department of Agriculture

Agricultural Research Service

Title: Seedbed Surface Geometry Effects on Soil Crusting and Seedling Emergence

Authors
item Baumhardt, Roland
item Dao, Thanh
item Unger, Paul

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2004
Publication Date: July 1, 2004
Citation: Baumhardt, R.L., Dao, T.H., Unger, P.W. 2004. Seedbed surface geometry effects on soil crusting and seedling emergence. Agronomy Journal. 96:1112-1117.

Interpretive Summary: Seedling emergence is crucial for crop establishment, but rainstorms form thin, dense, soil crusts that seedlings must penetrate to emerge. To increase seedling emergence, small soil-ridges or caps can be formed above the seed for removal after rain. We hypothesized that soil caps may promote fractures and reduce the force needed to break through the crust without being removed. Our objectives were to quantify crust formation and strength, seed zone soil temperature, and seedling emergence of selected crops through a 1 inch-high x 2 inch-wide cap formed above the seed compared with a flat seedbed. Sieved Pullman clay loam soil was packed into boxes (12 inches wide x 18 inches long x 6 inches deep) and planted with grain sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) in rows beneath a flat or capped soil surface. Boxes were placed under a rain simulator for one h at a rainfall intensity of 2 inches per hour with normal or intercepted drop impact energy. We measured cumulative infiltration, crust thickness and penetration resistance, seed zone temperature, and seedling emergence. Compared with no drop impact conditions, normal drop impact reduced infiltration 22% and formed a thicker crust that prevented seedling emergence. Surface caps did not reduce crust thickness, penetration resistance, or seedling emergence. Mean seed zone soil temperature increased with no drop impact, but was unchanged by surface caps. Under the conditions of our test, we conclude that soil capping would not improve seedling emergence when not removed.

Technical Abstract: Seedling emergence is the crucial first step in crop establishment; however, crops frequently must penetrate or lift a thin, dense, soil crust formed during rainstorms. Shaping the soil surface into a small ridge or cap above the seed may promote crust fractures and improve seedling emergence and vigor. Our objectives were to quantify crust formation and strength, seed zone soil temperature, and seedling emergence of selected crops through a 25-mm-high x 50-mm-wide hill, or cap, formed above the seed compared with a flat seedbed. Sieved (<12 mm) Pullman clay loam soil (Torrertic Paleustoll) was packed into columns (0.30 m wide x 0.45 m long x 0.15 m deep) and planted with grain sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) in rows beneath a flat or capped soil surface. Columns were mounted at a 5% slope on a turntable beneath a rotating disk type rain simulator that applied water treated by reverse osmosis for one h at a rainfall intensity of 48 mm h-1 with normal or intercepted drop impact energy. We measured cumulative infiltration, crust thickness and penetration resistance, seed zone temperature, and seedling emergence. Compared with intercepted drop impact conditions, normal drop impact reduced infiltration 22% and formed 4.9 mm thicker crusts that prevented seedling emergence. Surface caps did not affect crust thickness, penetration resistance, or seedling emergence. Mean seed zone soil temperatures increased when drop impact was intercepted, but was unaffected by surface geometry. Under the conditions of our test, we conclude that soil capping would not improve seedling emergence when not removed.

Last Modified: 10/1/2014
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