2020 Forage Sorghum Silage Trial Report

Greetings all,

Dr. Jourdan Bell has completed the 2020 Forage Sorghum Silage Trial Report.  If you don’t already have a copy, here is some good result information for you.

Thanks,

Blayne

 The  2020  Texas  A&M  AgriLife  Research  and  Extension  Forage  Sorghum  Silage  Trial  
consisted  of  71 sorghum  hybrids  including  forage  sorghums,  sorghum-sudangrasses,  and  grain
 sorghum  hybrids. Evaluated hybrids included brown midrib and brachytic variants (Table 1).  Two
grain sorghum hybrids (DKS  37-07  and  P84G62)  serve  as  long-term  grain  production  checks.  
Grain  yields  are  requested  by companies at the time of entry. Requested grain yields are
reported to the USDA Farm Service Agency to annually update the Loan Deficiency Payment tables for
forage sorghum hybrids. Corn checks provide a comparison between the forage production potential in
a water limited production environment (Table 2).

The summer cropping season was marked by hot, dry, and windy conditions as well as a September cold front (low 35°F). Lower than average yields were a function of compounded environmental stress, which resulted in reduced biomass production and poor grain development. In-season precipitation totaled 6.24 inches. There was not any precipitation after September 9 (Fig. 1). The average forage yield was 18.2 tons/acre with yields ranging from 25.3 to 12.3 tons/acre (65% Moisture). Although sorghum is a heat tolerant crop that can withstand temperatures as high as 104°F (Peacock, 1982), the crop water demand increases with elevated temperatures. In 2020, a limited crop water supply (soil moisture, precipitation, and irrigation) compounded plant physiological responses to heat stress resulting in curling leaves, poor panicle exertion, stunted height, and reduced biomass production in some hybrids. Cold temperatures on September 9 further impacted sorghum grain development. It has been previously documented that temperatures below 40 °F reduce pollen viability and the number of
grains per panicle. The September 9 cold front resulted in temperatures less than 40°F for 19 hours with
the low temperature reaching 35°F when early hybrids were at the milk stage and later hybrids were at
vegetative, heading, and bloom stages. As a result, pollination was variable for hybrids that bloomed
after early September (Fig. 2). Because grain yield can be a significant component of forage tonnage, yields for many hybrids were reduced because of poor pollination. The 2020 starch levels are also an
indication of lower grain yields. During grain fill, assimilated carbohydrates are translocated to the
developing grain and converted to starch. If grain does not develop, starch levels will remain low. The
impact of the 2020 season is evident when comparing starch concentrations between the 2019 and 2020
trials. In 2019, the average starch concentration for sorghum hybrids was 15.1%. In comparison, the average starch concentration for sorghum hybrids in the 2020 trial was 8.6% with values ranging from
0.1 to 27.6% (Table 3).

The trial was located near Bushland, TX under center pivot irrigation within a production forage
sorghum field that was irrigated at approximately 50% ET (evapotranspiration demand of the crop).
Seed companies submitted forage sorghum hybrids on a per fee basis except for the grain sorghum
checks and corn hybrids. Extended windy conditions in early June 2020 delayed planting.

Agronomic Information
Cooperator: Michael Menke
Previous Crop: Wheat hay
Planting Date: June 18, 2020
Plot size: Four, 30‐inch rows by 25 ft. (30ft planted)
Forage Sorghum Seeding Rate: 75,000 seeds/acre
Corn Silage Seeding Rate: 32,000 seeds/acre

Herbicide: Pre‐plant application of Bicep (Atrazine + S‐metolachlor) 1.5 pts/acre
Post-emergent application Facet-L (quinclorac) 2.0 pts/acre
Fertilizer: 215 lbs. N/acre as 46-0-0 preplant
Insecticide: 1 aerial application of Sivanto on August 15, 2020 (6 oz/ac at 3 GPA)
In-season Irrigation: 9.5 inches from planting to 9/24 for early hybrids
10.3 inches from planting to 9/28 for medium, late, and PS hybrids
In-season precipitation: 6.24 inches 

Hybrids were blocked according to their marketed maturity class so that forages within each block
could be mechanically harvested for yield when grain reached soft dough. Planting date,
water stress, and latitude can affect the duration of the vegetative phase resulting in forages deviating
from the marketed hybrid maturity. Hybrids that reached soft-dough before the average stage of the
predefined maturity block were harvested by hand. Consequently, forage yields were obtained from a
25 ft2 area (1 row by 10 ft.) for Dyna Gro’s Dynagraze II and F75FS13 plots on October 1, 2020. In all
other plots, the center 2 rows were mechanically chopped (sample size: 2 rows by 25 feet).
Photoperiod sensitive hybrids were all harvested on the last sampling date (October 16, 2020).
Uniform sub-samples were collected for dry matter and nutritional composition from all plots. A subsample of the chopped forage was dried at 221°F (105°C) to determine harvest moisture. All reported yields are corrected to 65% moisture. A 600-gram sample was submitted to Dairyland Laboratories, Arcadia, WI via Servi-Tech Laboratory, Amarillo, TX for forage nutritional analyses using near infrared reflectance spectroscopy (NIR). Forage constituents are reported on a dry matter (DM) basis (Table 3). Sugarcane aphids (SCA) were identified on August 7, 2020. All plots were scouted for SCA infestation upon initial identification. In response to infestation, the entire field including our test plots was sprayed on August 15, 2020. Due to the timely insecticide application, there was no significant damage from SCAs in the 2020 trial.

Grain yield was collected on October 19 following forage harvest for select hybrids. Statistical analyses
were completed for sorghum hybrids using SAS 9.4. Adjusted least significant differences for multiple
comparisons were determined using Tukey’s HSD. Effects and comparisons were determined significant at the 0.05 probability level. The discussion addresses broad averages for types of forage sorghums, grain sorghums evaluated as silage, and sorghum/sudangrass hybrids evaluated in the 2020 test. It is not recommended that hybrid selection be made based on marketed forage type. While the marketed forage types provide an indication of potential quality, actual quality parameters vary for hybrids of the same forage type, and there is often an overlap among hybrids in these type categories. Because forage quality requirements vary between livestock class and ration formulation, evaluated parameters provide a broad comparison of forage quality in the respective production environment.