Deficit Irrigation Influence on Forage Sorghum Biomass Production and Silage Quality.

A two-year study was initiated in 2016 at the UNR Main Station Field Lab to evaluate the effects of deficit irrigation on forage sorghum (Sorghum bicolor L. Moench) and sorghum × sudangrass hybrid (Sorghum bicolor × S. bicolor var. Sudanese) biomass production and silage quality. One deficit level irrigation application rate of 75% of reference ET was selected and used based on the previous year’s data of forage sorghum production at full irrigation in Reno and Fallon locations of Nevada. Four sorghum entries (‘CW 7700’, ‘SilageKing’, ‘DwarfKing’, and ‘Canex BMR’) and one hybrid sorghum × sudangrass entry (‘HayKing II’) were selected and used in a randomized complete block design experiment with four replications of each entry. Plot size was 7.62 m long × 1.5 m wide and plots were seeded on 17 June 2016 and harvested on 05 October 2016 (growing cycle of 110 d). Seeding rates for each entry were 22.4, 11.2, 13.5, 22.4, and 67.3 kg PLS ha^-1 respectively. Biomass production was similar for entries CW7700 (12.5 Mg DM ha^-1) and Canex BMR (11.8 Mg DM ha^-1). However, CW 7700 had greater biomass than HayKing II (8.3 Mg DM ha^-1), SilageKing (9.2 Mg DM ha^-1), and DwarfKing (8.5 Mg DM ha^‑1). Canex BMR entry had greater biomass than HayKing II and DwarfKing but similar to SilageKing. Entries HayKing II, SilageKing, and DwarfKing were not different in biomass production. Silage pH was not different (P = 0.3880; SEM 0.09) among entries (average pH = 4.6) and duration of ensilage had no effect (P = 0.7267; SEM 0.05) on silage pH (average pH = 4.62). Forage sorghum’s ability to use less water and still sustained high production makes it a valuable feed option for cattle producers in Nevada either as a green chop or silage.