Nutrient Management Guide for Dryland and Irrigated Alfalfa in the Inland Northwest

Nutrient Management Guide for Dryland and Irrigated Alfalfa in the Inland Northwest

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Richard Koenig, Washington State University Department of crop and soil sciences, Donald Horneck, Oregon State University extension, hermiston, Phil Peterson, Washington State University Extension, Ephrata, Robert Stevens, Washington State University, Prosser, Steve Fransen, Washington State University, Prosser, Brad Bowen, University of Idaho, Parma
This full-color illustrated guide for optimizing alfalfa production according to the growing conditions common throughout Idaho and east of the Cascades in Oregon and Washington provides specific recommendations for all critical nutrients.
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Nutrient management is necessary to produce high-yielding, high-quality alfalfa economically, while at the same time preserving soil, air, and water quality. As the term implies, nutrient management includes activities such as sampling to monitor soil and plant tissue nutrient levels, adjusting nutrient application rates based on soil and tissue test results, and varying the placement, timing, and source of nutrients to optimize plant availability and uptake.

The information presented here is applicable to alfalfa grown throughout Idaho and east of the Cascade mountain range in Oregon and Washington. Different climates, soils, and topography result in considerable variation  in alfalfa yields across a region, an individual farm, and even within a field on the same farm. Due to this inherent variability, a one-size-fits-all recommendation for the management of any one nutrient is of little value. Nutrient management choices should be based on individual grower practices, realistic yield expectations, and current soil and tissue test information.

This document summarizes locally-based guidelines for managing major nutrients in alfalfa, emphasizes how producers can tailor recommendations to their production system, and identifies opportunities where information such as soil and tissue test results can help

refine and improve nutrient management practices to optimize alfalfa yield, quality, and economic returns. The recommendations are based on existing Extension bulletins, recent research data, field experiences, and estimates of nutrient removal and efficiency.

Nutrient removal by alfalfa

Growing alfalfa removes large quantities of nutrients from soil (Table 1). In fact, high- yielding stands of alfalfa hay remove as much or more nutrients than any other intensive forage managed for hay or silage. Growers have historically relied on phosphorus and potassium as the main nutrients added for optimal alfalfa production. Areas with a long history of alfalfa and other intensive crops have commonly mined soil nutrient reserves. This, coupled with modern, higher-yielding varieties and production systems, means that many alfalfa fields now require supplementation with multiple nutrients.

Soil pH and alfalfa

Optimum alfalfa yields occur when soil pH is near 7.0; however, alfalfa can tolerate soil in the pH range 6.0–8.2 and still produce high yields. Northern Idaho and western Oregon and Washington, where rainfall is high, have lower soil pH than more arid regions of the inland



Copyright 2009 Washington State University

Published April, 2009

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