S. Maxwell

Fallow Replacement Crop (Cover Crops, Annual Forages, and Short-Season Grain Crops) Effects on Wheat and Grain Sorghum Yields

Producers are interested in growing cover crops and reducing fallow. Growing a crop during the fallow period would increase profitability if crop benefits exceeded expenses. Benefits of growing a cover crop were shown in high rainfall areas, but limited information is available on growing cover crops in place of fallow in the semiarid Great Plains. A study was conducted from 2007–2017 that evaluated cover crops, annual forages, and short season grain crops grown in place of fallow. In the first experiment (2007-2012), the rotation was no-tillage wheat-fallow. The second experiment (2012-2017) rotation was no-tillage wheat-grain sorghum-fallow. This report presents results from the second experiment. Wheat yield was affected by the previous crop, but growing a previous crop, such as hay or cover, did not affect wheat yield. Wheat yield following the previous crop was dependent on precipitation during fallow and the growing season. In dry years (2011-2014), growing a crop during the fallow period reduced wheat yields, while growing a crop during the fallow period had little impact on wheat yield in wet years (2008-2010). The length of the fallow period also affected yields of the following wheat crop. Growing a cover or hay crop until June 1 affected wheat less than if a winter or spring crop were grown for grain, which utilized the land approximately the first week of July. Cover crops did not improve wheat or grain sorghum yields compared to fallow. To be successful, the benefits of growing a cover crop during the fallow period must be greater than the expense of growing it and must compensate for any negative yield impacts on the subsequent crop. Cover crops always resulted in less profit than fallow, while annual forages often increased profit compared to fallow. The negative effects on wheat yields might be minimized with flexfallow, which is the concept of only growing a crop in place of fallow in years when soil moisture at planting and precipitation outlook are favorable at the time of making the decision to plant.

Determining Profitable Forage Rotations

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2017 Kansas Summer Annual Forage Hay and Silage Variety Trial

The 2017 summer annual forage variety trials were conducted across Kansas near Garden City, Hays, Mound Valley, and Scandia. All sites evaluated included hay and silage entries. Companies were able to enter varieties into any possible combinations of research sites, so not all sites had all varieties. Across the sites, a total of 61 hay varieties and 66 silage varieties were evaluated. The objectives of the Kansas Summer Annual Forage Variety Trial are to evaluate the performance of released and experimental varieties, determine where these varieties are best adapted, and increase the visibility of summer annual forages in Kansas. Breeders, marketers, and producers use data collected from the trials to make informed variety selections. The Summer Annual Forage Trial is planted at locations across Kansas based on the interest of those entering varieties into the test.

Effects of Fallow Replacement Crops on Wheat and Grain Sorghum Yields

Interest in replacing fallow with a cash crop or cover crop has necessitated research on soil, water, and wheat yields following a shortened fallow period. Fallow stores moisture, which helps stabilize crop yields and reduces the risk of crop failure; however, only 25 to 30% of the precipitation received during the fallow period of a no-till wheat-fallow rotation is stored. The remaining 75 to 70% of precipitation is lost, primarily due to evaporation. Moisture storage in fallow is more efficient earlier in the fallow period, when the soil is dry, and during the winter months when the evaporation rate is lower. It may be possible to increase cropping intensity without reducing winter wheat yield. This study evaluated replacing part of the fallow period with a cover, annual forage, or short-season grain crop. Plant available water at wheat and grain sorghum planting and winter wheat and grain sorghum yields were measured.

Forage Type and Maturity Effects on Yield and Nutritive Value

Forage sorghum (Sorghum bicolor L.) and sorghum × sudan (Sorghum bicolor sssp. Drummondii) are important annual forages in the High Plains. Advancements in brown mid-rib (BMR) cultivars will likely affect forage yield and nutritive values. A study was initiated in 2017 at the Southwest ResearchExtension Center near Garden City, KS, comparing one variety each of BMR and non-BMR forage sorghum and sorghum × sudan cultivars. Forage type and growth stage affected yield and nutritive value, and occasionally there was an interaction between forage type and maturity.

Integrated Grain and Forage Rotations

Forage production is important for the western Kansas region’s livestock and dairy industries and has become increasingly important as irrigation-well capacity declines. Forages require less water than grain crops and may allow for increased cropping intensity and opportunistic cropping. Being able to estimate forage production is important for determining forage availability versus forage needs. Data from several studies were used to quantify annual forage yield response to plant available water (PAW) at planting and growing season precipitation (GSP). In addition, water use efficiency was quantified. Forages evaluated included winter triticale, spring triticale, and forage sorghum. Preliminary results showed PAW and GSP explained 26% of the variability in forage sorghum yield. Winter triticale yield increased by 640 lb/a for every inch of water use (PAW plus GSP). However, spring triticale produced only 193 lb/a for every inch of water use. The low correlation with water use and spring triticale yield suggests other factors, such as temperature, affect spring forage production more than soil moisture.

2015 Kansas Spring Annual Forage Variety Trial

A total of 3 spring annual forage varieties were tested for performance at the Southwest Research-Extension Center near Garden City, KS and the Western Kansas Agriculture Research Center near Hays, KS, in 2015. Spring crops evaluated included oat and triticale.

2015 Kansas Winter Annual Forage Variety Trial

A total of 16 winter annual forage varieties were tested for performance near Garden City, KS, at the Southwest Research-Extension Center in 2014-2015. Winter crops evaluated included wheat, triticale, and cereal rye.

Teff Grass Response to Nitrogen Fertilization

Teff, a warm season annual grass native to Africa, is gaining popularity as a forage crop in the United States. Little information regarding nitrogen fertilization is available for teff grass production. This field experiment was conducted to evaluate teff grass response to varying nitrogen fertilization rates under dryland conditions. There was no yield response to increasing nitrogen rate or nitrogen source applied.

Determining Profitable Annual Forage Rotations

Producers are interested in growing forages, yet the southwest region of Kansas lacks proven recommended crop rotations such as those for grain crops. Forage production is important to the region’s livestock and dairy industries and is becoming increasingly important as irrigation well capacity declines. Forages require less water than grain crops and may allow for increased cropping intensity and opportunistic cropping. A study was initiated in 2013 comparing several 1-, 3-, and 4-year forage rotations with no-till and minimum-till (mintill). Data presented are from 2013 through 2014. Winter triticale yields were not affected by tillage in 2013 but were increased by tillage in 2014. Double-crop forage sorghum yielded 30% of full-season forage sorghum in 2013, which was a drought year, but across years yielded 70% of full-season sorghum. Oats failed to make a crop during the drought year and do not appear to be as drought tolerant as spring triticale or forage sorghum. Subsequent years will be used to compare forage rotations and profitability.