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ABSTRACT
Five warm-season annual grasses were compared for dry matter (DM) yield and nutrient uptake alongside bermudagrass [Cynodon dactylon (L.) Pers.] on a Brooksville silty clay (fine, montmorillonitic, thermic Aquic Chromuderts) in a field that had swine (Sus scrofa) effluent applied through a center pivot sprinkler system. Annuals were browntop millet [Panicum ramosum (L.) Stapf in Prain], pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench], sorghum-sudan, [Sorghum bicolor (L.) Moench], and crabgrass [Digitaria sanguinalis (L.) Scop.]. Grasses were tested in 3 yr (1999-2001), but results in 2000 were incomplete due to poor growing conditions. In 1999 (establishment year for bermudagrass) sorghum-sudan had the highest DM yield (18.9 Mg ha-1) and P uptake (50.3 kg ha-1). In 2001, sorghum-sudan DM yield (20.6 Mg ha^sup -1^) and P uptake (56.3 kg ha^sup -1^) were equivalent to established bermudagrass (21.3 Mg ha^sup -1^ and 56.1 kg ha^sup -1^, respectively). In 2001 sudangrass and pearl millet DM yields (17.4 and 15.7 Mg ha^sup -1^, respectively) were equal to and lower than sorghum-sudan, but P uptake of pearl millet (49.5 kg ha^sup -1^) did not differ from sorghum-sudan, due to the high P concentration (3.2 g kg^sup -1^) in pearl millet. Browntop millet and crabgrass DM yields and P uptake were less than those of sorghum-sudan in both years. Sorghum-sudan and pearl millet were higher in DM yield and P uptake than the other annuals in both years, equal to established bermudagrass, and therefore should be the most useful in nutrient management hay systems in the southeastern USA.
Abbreviations: BMG, bermudagrass; BTM, browntop millet; CEC, cation exchange capacity; CRB, crabgrass; DM, dry matter; OM, organic matter; PRL, pearl millet; SSH, sorghum-sudan hybrid; SUD, sudangrass.
SINCE THE 1980s, swine production in the USA has shifted away from large numbers of independent growers toward fewer and larger farm operations and contract growers (Welsh and Hubbell, 1999). This industrial shift resulted in concentrating larger numbers of hogs per hectare and spreading their manure as fertilizer over smaller areas. The value of swine effluent as fertilizer is in its nutrient content, especially N. Even with good utilization of N, however, other manure nutrients, especially P, can build up in manured soils. Accumulation of excess P to the point of...