Seeding and nitrogen fertilization effects on the yield and quality of brachytic dwarf brown midrib forage sorghum hybrids

Abstract

AbstractBrown midrib (BMR) forage sorghum [Sorghum bicolor (L.) Moench] silage is an alternative to corn (Zea mays L.) silage for areas with limited soil moisture. Traditional forage varieties are tall and prone to lodging, with low forage quality. Brachtyic dwarf BMR lines are shorter and lodging‐resistant and have higher forage quality. Newer earlier‐maturing hybrids have expanded the potential adaptation of forage sorghums to northern latitudes. A 2‐yr study was conducted during the 2014 and 2015 growing seasons with brachytic dwarf BMR forage hybrids to determine the effects of different seeding and N fertilization rates on forage dry matter yield and quality. The experimental design was a split‐split‐plot with four replications. The main plots were two hybrids (‘AF7202’ and ‘AF7401’), the subplots were two seeding rates (80,000 and 120,000 seeds acre−1), and the sub‐subplots were two N rates (110 and 150 lb acre−1). Significant differences were observed between hybrids for all parameters except neutral detergent fiber digestibility (NDFD) in 2015. The early hybrid, AF7202, had higher yields and higher starch content and net energy for lactation levels than dwarf hybrid AF7401 and was more responsive to higher N. AF7401 had higher crude protein content and NDFD. Crude protein increased as N level increased for both hybrids but other forage quality traits were unaffected. Neither variety responded to an increased seeding rate. The earlier brachytic dwarf forage sorghums, such as AF7202, managed with recommended seeding rates and possibly higher N rates, have potential for high forage yield and quality in central Pennsylvania.