Evaluating Winter Annual/Summer Annual Forage Rotation in NE Iowa
Agronomy & Pest Management
Denise Schwab
Extension Beef Specialist
Iowa State University
Vinton
Abstract
Interest in grazing cover crops and winter annuals has increased in recent years. Research on grazing winter and summer annuals in Iowa has been concentrated in southern Iowa, but because of differences in growing conditions, data on growth potential from the northern half of the state is needed. Similar interest has been developing on utilizing summer annuals to maximize production during the summer slump of Iowa pastures. The research component of this project is designed to measure and demonstrate the applicability of a winter annual - summer annual forage rotation in northern Iowa at the Northeast Research and Demonstration Farm at Nashua. The educational component focused on the synergy of incorporating annual forages into the farming operation to manage production risk associated with weather extremes, diversify the cropping system, control cow grazing costs, and improve soil health. A winter annual- summer annual forage rotation can be used to break up the traditional corn - soybean rotation and produce 7-11 tons per acre of forage biomass on a dry matter basis per year. On-farm demonstration field days were held at 15 locations and information was presented at 15 other meetings directly reaching 732 producers. An additional 8800 social media contacts were made through YouTube, FaceBook, blogs, and podcasts. Dry conditions in the fall of 2020 and again in the fall of 2022 through 2023, limited germination and early growth. The drought in the spring of 2023 prevented germination of the summer annual so only a single harvest was taken on September 5, 2023. The 47-year average rainfall for the farm for April – November is 30.8 inches but from April – November 2023 there was only 13.8 inches of rainfall significantly reducing summer annual yields. The variation between years indicates a double cropping system is very dependent on adequate rainfall for forage establishment and growth, as seen by the loss of the August harvest in 2023 where only half the average rainfall was received compared to 2021 and 2022.
Authors: Denise Schwab
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Denise Schwab Extension Beef Specialist, Iowa State University Extension, Iowa, 52349