Interactions between Forage Sorghum Cultivars and Defoliation Managements¹

Abstract

Yield and plant constituent responses of forage sorghum (Sorghum bicolor (L.) Moench) cultivars have usually been compared in uniform defoliation management tests. However, the influence of time of harvest and stubble height on differential response of cultivars needs more precise definition. The extent of cultivar × management interaction was studied for ‘Sweet Sioux III’3 (a leafy high‐producing cultivar similar to many others available), ‘FS‐531’ (a silage‐forage cultivar) and ‘Super‐Chowmaker 235’ (several weeks later in maturity than most other forage sorghum cultivars) for 2 years. The soil was a Sequatchie sandy loam (fine‐loamy, siliceous, thermic Humic Hapludults). Stubble height and defoliation managements designed to simulate grazing, greenchop, hay or silage harvests, in various combinations, were used with each cultivar. Chowmaker plants yielded more, had the same or higher N percent, and the same in vitro dry matter digestibility (IVDMD) when cut to a 15‐cm than when cut to an 8‐cm stubble. Sweet Sioux plants yielded more when cut back to 8 cm than to 15 cm, but their N percent and IVDMD were not affected by stubble height. Cutting when forage reached 50 cm previous to the boot (B) or early bloom (EB) cuts delayed subsequent development, and hence harvest, of FS‐531. The other two cultivars reached the B or EB stages at the same time, regardless of whether that harvest was preceded by a prior harvest or not, but the B or EB stages occurred at shorter heights if preceded by a harvest. Harvesting when forage reached 90 cm before the B or EB cut delayed harvest for all cultivars, probably because all regrowth had to originate from axillary meristems. The delay in B or EB harvests may be beneficial in situations where dry matter production later in the season is more desirable. The results suggested that, if the three different cultivars used here had been entered in a yield trial where all entries were managed uniformly, the information on the potential performance of these forage sorghum cultivars could have been misleading. Harvests at early stages of growth would have penalized Super‐Chowmaker 235 in comparison to Sweet Sioux III, and the reverse would have occurred if later stages of growth had been used to determine harvest time.

Effect of Nitrogen Rates and Method of Nitrogen Application on Dry Matter Yield and some Characters of Sorghum-Sudangrass Hybrid

“…The stubble height (Beuerlein et al, 1968;Creel & Fribourg, 1981) and N fertilizer rates (Jung et al, 1964) are very important factors affecting the tillering capacity of Effect of N on sorghum -sudangrass hybrid sorghum varieties. An increase in tillering from 2 plant ¼ 1 (0 kg N ha ¼ 1 ) to 20 plant ¼ 1 with increasing rates of N fertilizer was also reported by Jung et al (1964).…”

“…Sorghum, sudangrass and the sorghum -sudangrass hybrid are capable of producing high-quality forage in mid to late summer when cool-season perennials have low production (Creel & Fribourg, 1981;Undersander et al, 1990). These crops are generally rapid growing and produce high-quality forage, if managed properly.…”

“…The amount of N to be applied and the method of application depends on climate, soil fertility, plant variety and the utilization purposes, i.e. whether these crops are used for grazing, silage or hay (Beuerlein et al, 1968;Harms & Tucker, 1973;Creel & Fribourg, 1981;Singh et al, 1988;Rahman et al, 2001).…”

Response of growth and forage yield of pearl millet (Pennisetum galucum) to nitrogen fertilization rates and cutting height

“…Forage yield (green or dry) of some summer crops influenced by cutting height above the soil surface (Creel and Fribourg, 1981) in sorghum (Koraiem et al, 1983 andEl-Houssini andNasser, 1998) and in pearl millet.…”

Quality Traits in Forage Sorghum Harvested at Early Head Emergence and at Physiological Maturity1

“…[Sorghum bicolor (L.) Moench 1 sampled at various stages of development or under different management regimes are well documented (1,3,5,6,9). Much less information is available, however, on possible differences among plants of the same genotype and within the same field plot that reach a given developmental stage at different ages in terms cf O:3.ys after planting.…”