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Title:Irrigation and nitrogen management of soybean in highly productive soils
Author(s):Vonk, Joshua Paul
Director of Research:Nafziger, Emerson D
Doctoral Committee Chair(s):Nafziger, Emerson D
Doctoral Committee Member(s):Davidson, Paul C; Diers, Brian W; Lee, DoKyoung
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):soybean
irrigation
nitrogen
seeding rate
fungicide
insecticide
foliar fertilization
Abstract:“Intensively managed” is a phrase becoming more common and describes an approach in which soybean [Glycine max (L.) Merrill] producers try to increase soybean yields through various applications of in-season inputs or other alterations of typical production practices. Two areas of interest include water limitations of soybean yield under rainfed conditions in highly productive Illinois soils and use of fertilizer nitrogen (N) to supplement soybean when mineralized soil N and biologically fixed N may be insufficient. Three studies on productive soil in Urbana, IL over six years (2008, 2009-2010, 2012-2014) tested irrigation’s impact seeding rate or seed treatment and different in-season products (fungicide, insecticide, nitrogen fertilizer, and foliar macro and micro-nutrients) with and without irrigation. Additionally, nine site-years from a combination of years (2014-2017) and locations (Brownstown, Chillicothe, Monmouth, and Urbana) examined the impact of N applied at different timings (planting, R1, R3, R5, and planting+R1+R3+R5) over a range of Illinois soils. Soybean yield was increased by irrigation at Urbana, IL by an average of 685 kg ha-1 (15.8%) in three years with moderate precipitation deficits (2008, 2012, and 2013), but not in three years (2009, 2010, and 2014) with more consistent rainfall. Across all six years, irrigation increased soybean yield by an average of 295 kg ha-1 (6.2%). Three applications of foliar fungicide (2009-2010) or two applications of fungicide plus insecticide (2012-2014) consistently increased yield, by 311 kg ha-1 (6.2%) and 269 kg ha-1 (5.5%), respectively. Seeding rate and seed treatment had no effect on yield. Irrigation interacted with other management factors only in 2008, when separate treatments of fungicide and nitrogen fertilizer increased yield only under irrigation. Fertilizer N applied four times (at planting, R1, R3, and R5) increased yield at four of nine sites, but yield increases were insufficient to pay for repeated applications of N fertilizer. Applying N at planting on coarser-textured soils at Chillicothe increased yield by 1,830 kg ha-1 (16%) in 2015 and by 1,351 kg ha-1 (26%) in 2016 but had no effect in 2017. Managing soybean with irrigation, fungicide and/or insecticide, and nitrogen fertilizer increased yields, but responses were typically modest and not consistent. Moderate yield benefits combined with considerable costs make these practices unprofitable at current soybean prices for most Illinois producers.
Issue Date:2018-04-19
Type:Thesis
URI:http://hdl.handle.net/2142/101020
Rights Information:Copyright 2018 Joshua Vonk
Date Available in IDEALS:2018-09-04
Date Deposited:2018-05


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