Evaluation of a Mechanistic Approach for Determining N Rates in Dryland Precision Farming

Authors: Vigil, Merle; Calderon, Francisco; Poss, David; Nielsen, David

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/26/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: n/a

Technical Abstract: Determining the correct Fertilizer N rate in different field-management zones is central to variable rate N management in Precision farming systems. Our objective, is to test a mechanistic approach to predict fertilizer N rate for different field-management zones in no-till dryland winter-wheat based systems in the Central Great Plains region. A simple mechanistic model that employs both a target for wheat grain protein and wheat grain yield will be tested for its ability to match actual crop N requirements. Protein as a grain quality goal must be included because wheat protein is an important economic quality indicator for bread wheats grown in the region. Inputs to the model include residual inorganic N in the top 60 cm of the soil profile, soil organic matter, an efficiency factor for both residual inorganic N and fertilizer N, and estimates of N mineralized from native soil organic matter, crop residues and/or organic amendments. Because final amounts of N made available through mineralization and because expected grain yields are both highly dependent on weather (primarily rainfall in semi-arid systems), probability distributions of expected weather are used to provide some estimates of risk for both predicted N and expected grain yield.