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Colorado State University (2013)

ENHANCEMENT OF AGRICULTURAL SYSTEMS MODELS FOR LIMITED IRRIGATED CROPPING SYSTEMS RESEARCH

Anapalli Saseendran S.

Titre : ENHANCEMENT OF AGRICULTURAL SYSTEMS MODELS FOR LIMITED IRRIGATED CROPPING SYSTEMS RESEARCH

Auteur : Anapalli Saseendran S.

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 2013

Résumé partiel
Dwindling water supplies for irrigated crop production is the most limiting factor facing agriculture in the world today. In the evolving scenario, there is a need for making agricultural water use more efficient by bringing in up-to-date science based technologies in the irrigation field. In this context, crop water production functions (CWPFs, expressed as crop yield vs. consumptive water use or water applied) are helpful for optimal management of limited water resources for irrigation. However, they are site specific and vary from year to year, therefore for planning and managing limited irrigation, the CWPFs should be based on long-term field experiments to take into account the variations in precipitation and other climatic variables at the location. These problems can be addressed by using data from short term irrigation trials to calibrate and evaluate agricultural systems models that can subsequently be used for developing various irrigation water management strategies and thus extend the results across temporal and spatial dimensions. The primary objective this dissertation was to develop a methodology and use it to develop location (soil and climate) specific long-term averaged CWPFs for corn (Zea mays L) using available experimental data, long-term climate data, and a cropping system model, Root Zone Water Quality Model (RZWQM2), for various locations in the Great Plains of USA. A paramount prerequisite for a system model to be qualified for such applications is its ability to accurately simulate crop responses to water deficit stresses (WS). In the RZWQM2, WS were calculated as the ratio of potential plant water uptake to potential transpiration to modify carbon assimilation (SWFAC) and leaf expansion (TURFAC) processes. Nonetheless, inadequate simulations of crop responses to limited irrigations using these WS factors were reported. To begin with, several ways of quantifying WS based on soil water measurements and their relationship with grain yield, biomass and canopy cover of corn, winter wheat (Triticum aestivium L.) and dry (pinto) bean (Phaseolus vulgaris L. ) were investigated. There were six irrigation treatments for each crop, designed to meet 100 to 40% of potential crop ET (ETc) requirements during the growing season. Experiments were conducted from 2008 to 2011 near Greeley, Colorado in a sandy loam soil (LIRF, Limited irrigation Research Farm experiments). Water available for plant uptake (PAW, plant available water) and the maximum PAW (MAW) in the soil profile over the growing season were estimated from the soil water measurements. Daily tall reference crop ET (ETr) was calculated using Allen et al. (2005) method. Daily water deficit stress (WS) factors were calculated as ratios of (1) PAW to ETr (WSF1), (2) PAW to MAW (WSF2), and (3) WSF2 to ETr (WSF3). Average WSF1, WSF2 and WSF3 over the growing season were related to grain yield, biomass, and fraction canopy cover measurements. Results showed that in both experiments and simulations using RZWQM2 the responses of yield, biomass and canopy cover were explained most by WSF3, followed by WSF2 and WSF1.

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Page publiée le 29 novembre 2013, mise à jour le 18 novembre 2018