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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED WATER RESOURCES MANAGEMENT FOR IRRIGATED AGRICULTURE IN THE PACIFIC NORTHWEST Title: Oilseed Radish (Raphanus Sativus) Effects on Soil Structure and Soil Water Relations

Authors
item Lehrsch, Gary
item Gallian, J -

Submitted to: Journal of Sugar Beet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2009
Publication Date: May 12, 2010
Citation: Lehrsch, G.A., Gallian, J.J. 2010. Oilseed Radish (Raphanus Sativus) Effects on Soil Structure and Soil Water Relations. Journal of Sugarbeet Research. 47(1&2):1-21.

Interpretive Summary: Oilseed radish (Raphanus sativus spp. oleifera) reduces nematode populations. Fall-incorporated radish biomass may also improve soil properties to increase the yield and quality of subsequently grown sugarbeet (Beta vulgaris L.). This field study determined radish effects on the sizes and stability of near-surface soil aggregates (naturally occurring clusters of sand, silt, and clay), soil density, and the water content of near-surface soil when all pores (or openings) were filled with water, termed the field-saturated water content. We also studied radish effects on rates of infiltration (the downward entry of water into soil) and hydraulic conductivity (the movement of water through soil) when all soil pores were conducting water and when only relatively small pores were conducting water. In 2003 and 2004 in Twin Falls, ID, radish were grown in a Portneuf silt loam for about 10 weeks in the fall, then incorporated later that fall by disking, followed by moldboard plowing. In early May of the following year, sugarbeet were planted in 0.56-m rows, irrigated with hand-lines, then harvested for yield and quality. In the spring and fall of each sugarbeet growing season, soil samples were collected from two depths, 0-5 and 5-50 mm, on which we measured aggregate stability and various aggregate sizes by wet sieving. Soil cores were collected from 0-34 mm to measure soil density. Also in Spring and Fall, we used infiltrometers to measure infiltration rates and, from those rates, to calculate hydraulic conductivities. Radish had either few or inconsistent effects on soil structure or hydraulic properties, with but two exceptions. Fall-incorporated radish increased field-saturated water contents by 10% in Spring 2003 but had no effect in Spring 2004, compared to controls. Most importantly, compared to controls, radish as a fall-incorporated green manure consistently increased the proportion of flow-conducting soil pores less than or equal to 0.75 mm in diameter, likely increasing the amount of water a soil could hold within it without the water draining from it.

Technical Abstract: Oilseed radish (Raphanus sativus spp. oleifera) reduces nematode populations. Fall-incorporated radish biomass may also improve soil physical and hydraulic properties to increase the yield and quality of subsequently grown sugarbeet (Beta vulgaris L.). This field study determined radish effects on near-surface soil aggregate stability, water-stable aggregate size distribution, bulk density, and field-saturated water content, as well as infiltration and hydraulic conductivity measured at water supply potentials of -40, -20, and +0 mm water. In 2003 and 2004 in Twin Falls, ID, radish were grown in a Portneuf silt loam (Durinodic Xeric Haplocalcid) for about 10 weeks in the fall, then incorporated later that fall by disking, followed by moldboard plowing. In early May of the following year, sugarbeet were planted to stand in 0.56-m rows, irrigated with hand-lines, then harvested for yield and quality. In the spring and fall of each sugarbeet growing season, soil samples were collected from two depths, 0-5 and 5-50 mm, on which we measured aggregate stability and size distribution by wet sieving. Soil cores were collected from 0-34 mm to measure bulk density. Also in Spring and Fall, we used ponded and tension infiltrometers with 0.11-m bases placed in the row to measure steady-state, unconfined infiltration rates and, from those rates, to calculate near-surface hydraulic conductivities at each supply potential. Radish had either few or inconsistent effects on soil structure or hydraulic properties at potentials greater than -20 mm water, with but two exceptions. Fall-incorporated radish increased the field-saturated water content by 10% to 0.446 cubic meters per cubic meter in Spring 2003 but had no effect in Spring 2004, compared to controls. Most importantly, compared to controls, radish as a fall-incorporated green manure consistently increased the proportion of flow-conducting soil pores less than or equal to 0.75 mm in diameter, likely increasing water retention.

Last Modified: 11/23/2014
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