Semester of Graduation

Fall 2021

Degree

Master of Science (MS)

Department

School of Plant, Environmental and Soil Sciences

Document Type

Thesis

Abstract

Adoption of no-tillage (NT) and cover crops (CC) significantly effect soil physicochemical properties and nutrient cycling that necessitates modified nutrient management to maximize crop yields. Two field experiments were conducted to evaluate N-sources Urea Ammonium Nitrate (UAN), urea, and urea+ N-stabilizer (urea+ stab) and N-split applications 100%N at V2 (S1), 25%N at V2+75%N at V6 (S2), 25%N at V2+ 50%N at V6+ 25%N at VT (S3) in a sandy loam soil and three CC wheat (Triticum aestivum), hairy vetch (Vicia villosa) , and radish (Raphanus sativus) and their combinations along with three N-rates ( 67, 135 and 202 kg N ha-1) in a silt loam soil on corn (Zea mays) growth and yield in the NT compared to conventional tillage (CT). Among the N-sources urea+ stab produced the highest corn growth and yield compared to UAN and urea under NT while no appreciable differences were observed in CT. Though N-split applications improved yield under both tillage systems, response was higher under NT. Interactions of N-source and N-split applications showed, urea+ stab and UAN improved corn grain yield by both S2 and S3 while only by S2 for urea under NT. Under CT, urea+ stab improved yield by both S2 and S3, while UAN did not show increase in yield from S3, and urea did not improve yield from split application. Overall, in compaction prone light textured soils with NT, urea+ stab along with up to 3-split applications were observed to be beneficial compared to UAN and urea and single N-application. Cover crop study showed that regardless of the tillage system, the hairy vetch increased corn growth and yield, whereas wheat decreased yields. The decrease in corn yield from wheat CC was relatively lower in the NT than CT, and it is attributed to the slower decomposition of residue caused by poor soil contact. No-tillage generally showed lower yields than CT under all CC treatments; however, the gap became insignificant at higher N-rate application. The higher bulk density, surface residue, weed pressure in the NT than the CT attributed to the differential corn response to N-source, N-split, and CC treatments between the tillage systems.

Committee Chair

Syam Dodla

Available for download on Tuesday, November 01, 2022

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