Location: Cropping Systems and Water Quality Research
Title: Losing control: What happens when we exclude the control treatment in nitrogen fertilizer rate trials?Author
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CLEVERINGA, ALEX - Iowa State University |
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Ransom, Curtis |
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MIGUEZ, FERNANDO - Iowa State University |
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 11/12/2024 Publication Date: 11/12/2024 Citation: Cleveringa, A., Ransom, C.J., Miguez, F. 2024. Losing control: What happens when we exclude the control treatment in nitrogen fertilizer rate trials? [abstract]. ASA,CSSA,SSA International Annual Meeting, November 10-13, 2024, San Antonio, Texas. Paper No. 157192. Available: https://scisoc.confex.com/scisoc/2024am/meetingapp.cgi/Paper/157192 Interpretive Summary: Technical Abstract: One of the most significant challenges facing agronomists is providing producers with the most precise and accurate nitrogen fertilizer application rate recommendations. The premier tool for creating fertilizer recommendations is the fertility trial, field experiments in which different fertilizer rates are applied and a statistical model is fit that captures the relationship between yield and fertilizer amount applied. The agronomic optimum nitrogen rate (AONR) is the rate of nitrogen fertilizer above which an increase in yield is not expected and is a common outcome of interest from fertility trials. With the proliferation of on-farm trials, there is increasing pressure to exclude the control treatment, experimental units that do not receive fertilizer. We evaluated the impact of excluding individual fertilizer rates on the AONR estimate and its uncertainty on a mixed effects quadratic-plateau model on a previously published large dataset of plot scale maize fertility trials. Our first finding is that excluding the control treatment does not meaningfully affect the bias of the AONR. Our second finding is that excluding the control treatment caused the most significant increase in uncertainty of the AONR. The results demonstrate the importance of including the control treatment in on-farm fertility trials. |