DEEP SOIL NITROGEN CAPTURE AND RECYCLING BY EARLY-PLANTED, DEEP-ROOTED COVER CROPS

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dc.contributor.advisorWeil, Ray Ren_US
dc.contributor.authorHirsh, Sarah Marieen_US
dc.contributor.departmentEnvironmental Science and Technologyen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2018-09-13T05:31:19Z
dc.date.available2018-09-13T05:31:19Z
dc.date.issued2018en_US
dc.description.abstractThe overall purpose of this study was to improve the efficiency of nitrogen (N) cycling in Mid-Atlantic cropping systems through the use of cover crops. Our focus was on describing soil inorganic N pools (0-210 cm deep) and investigating the potential for cover crops to scavenge and recycle deep soil N. Few agronomic studies consider soil properties and processes deeper than the upper 20 to 30 cm, as the majority of roots, amendments, and practices such as fertilizer application or tillage occur on the soil surface or in the topsoil. We 1) assessed amounts of deep soil N on 29 farms in the Mid-Atlantic region, 2) used 15N tracer to investigate the capacity of various cover crops with early- or late-planting dates to capture and recycle deep soil N, and 3) investigated early-planted cover crop systems on 19 farm trials to assess their performance on farms with various soils with diverse management practices. We found that on average 253 kg N ha-1 of inorganic N remained in the soil following summer crops, 55% from 90-210 cm deep. Soil following soybean had the same amount or more of inorganic N than soil following corn throughout the soil profile. Using 15N isotopic tracer, we determined that radish, rye, and radish/rye mixes with and without crimson clover all could capture N from deep soil (60+ cm), but in order for cover crops to capture agronomically meaningful amounts of nitrate-nitrogen (NO3-N) from deep soil, they had to be planted by early-September. Cover crop trials on 19 farms indicated that, while variable site-by-site, early-planted cover crops tended to accumulate substantial N in the fall and reduce residual soil NO3-N levels substantially in the fall and spring. Cover crops also impacted subsequent corn growth and yield, with winter cereal tending to cause lower yields or increased corn N fertilizer needs compared to a no cover crop control, and forage radish sometimes leading to higher yields compared to the control. Overall, cover crops are effective at scavenging deep soil N in the fall, before winter leaching occurs, and under certain conditions, can release N for subsequent crops.en_US
dc.identifierhttps://doi.org/10.13016/M20R9M745
dc.identifier.urihttp://hdl.handle.net/1903/21318
dc.language.isoenen_US
dc.subject.pqcontrolledSoil sciencesen_US
dc.subject.pqcontrolledAgricultureen_US
dc.subject.pquncontrolledCover cropsen_US
dc.subject.pquncontrolledDeep-rooteden_US
dc.subject.pquncontrolledDeep soilen_US
dc.subject.pquncontrolledNitrogenen_US
dc.subject.pquncontrolledRadishen_US
dc.subject.pquncontrolledRyeen_US
dc.titleDEEP SOIL NITROGEN CAPTURE AND RECYCLING BY EARLY-PLANTED, DEEP-ROOTED COVER CROPSen_US
dc.typeDissertationen_US

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