Soil Water Dynamics under Winter Rye Cover Crop in Central Iowa

Abstract

UƟ lizaƟ on of cereal rye (Secale cereale L. ssp. cereal) as a winter cover crop has potenƟ al benefi ts for subsurface drainage and NO 3 loss reducƟ on. The objecƟ ve of this study was to quanƟ fy the soil water balance components and impacts of a rye cover crop on subsurface drainage in central Iowa. Rye was planted in lysimeters in mid-October and terminated in early June in 3 yr and the lysimeters were leŌ fallow during the summer months. Subsurface drainage water was generally pumped out weekly along with taking soil moisture measurements; however, mulƟ ple appreciable rain events in a given week required more frequent pumping. During May through July of the 3 yr, monthly subsurface drainage was signifi cantly reduced by 21% when comparing the rye system to bare soil (P < 0.1). Drainage of individual pumping events was signifi cantly lower in the rye lysimeters than the bare lysimeters when averaged across 3 yr (P < 0.05). Soil water storage in the rye treatment was also signifi cantly lower than the bare treatment (P < 0.05) in all 3 yr. The winter cover crop eff ecƟ vely reduced subsurface drainage, which would then be expected to decrease the NO 3 load, which is essenƟ al to water quality improvement. During the main growing month, May, esƟ mated evapotranspiraƟ on of rye was 2.4 mm d −1 , signifi cantly higher than evaporaƟ on from the bare treatment (1.5 mm d −1 , P < 0.1). Soil water depleƟ on by rye in May could reduce the drainage volume and may also help facilitate traffi cability, but it is sƟ ll unknown what impact there may be on crop producƟ on in dry years.