Shoot Growth and Development of Alamo Switchgrass as Influenced by Mowing and Fertilization

Abstract

The response of shoot development and forage yield of a 2-year old 'Alamo' switchgrass stand to mowing and fertilization was evaluated to provide information needed for effective management of this variety. Mowing to a 20-cm stubble height in mid-spring removed only a few apical me&ems and had little impact on shoot development. Late spring and early summer mowing were done when apical meristems of primary compound shoots were elevated to near the 20-cm cutting height in May and over 20 cm in June. Secondary nonrooted shoot and aerial shoot numbers were increased and plant vigor, measured by spring growth in 1980, was decreased slightly the following spring. Mowing in mid-summer removed apical meristems from essentially all primary compound shoots and many secondary compound shoots. Regrowth was slight during the remainder of the summer, but the number of secondary and tertiary nonroqted shoots and aerial shoots in- creased. The number of proaxis buds decreased, and plant vigor was severely decreased the following spring. Mowing twice includ- ing early fall, removed apical me&ems from secondary com- pound shoots and some primary and secondary nonrooted shoots. Numbers of secondary, tertiary, and quarternary nonrooted shoots increased, but proaxis bud numbers were reduced. Plant vigor was very low the following spring, possibly due to exposure of mowed plants to cold winter temperatures. Fertilization increas- ed the rate of development of compound and nonrooted shoots, the number of secondary and compound shoots in spring, the number of proaxis buds in fall and the weight of primary and secondary compound shoots. Fertilized stands mowed during summer and early fall were more productive than all other mowed stands. Fertilized plants mowed in mid-summer were vigorous and productive the following spring. However, fertilization did not overcome the loss of vigor caused by fall mowing.