Submitted to: Bay Area Scientific Information Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 1/2/2004
Publication Date: 1/3/2004
Citation: Sigua, G.C., Adjei, M.B., Rechcigl, J.E. Residual assessment of forage yield and soil chemical status in subtropical beef cattle pastures following repeated biosolids application. Bay Area Scientific Information Symposium. Lake Buena Vista, FL. Abstract p.81. Interpretive Summary:
Technical Abstract: The objectives of this study were to compare: (a) the chemical status of soil that received annual application of biosolid materials (1997-2000) with test values of soils in 2002 (no biosolid application); and (b) the yield of bahiagrass pastures over years with and without biosolids application in South Florida. Bahiagrass plots received biosolids to supply 90 or 180 kg total N ha-1 yr-1 from 1997 to 2000. Land application of biosolids ceased in 2001 season. The experimental design was three randomized complete blocks with nine N-source treatments: ammonium nitrate (AM), slurry biosolids of pH 7 (SB7) or pH 11 (SB11), lime-stabilized cake biosolids (CB), and a nonfertilized control. Soil samples were taken from each plot in June 1997, Jan 1999, June 1999 and in June 2002. There was no treatment by year interaction (P > 0.05), but significant effects (P< 0.01) of applied biosolids on soil levels of K, Zn, Mn, and Cu. Average soil test values in June 2002 exhibited: a) decrease in TN (-0.73 mg kg-1), pH (-0.5 pH unit), P (-10 mg kg-1), K (-18.8 mg kg-1), Ca (-178.1 mg kg-1), Mg (-37.7 mg kg-1), Mn (-0.07 mg kg-1), and Fe (-7.0 mg kg-1); b) slight increase in Zn (+0.1 mg kg-1), Cu (+0.12 mg kg-1), and Na (+6.8 mg kg-1) when compared with the June 1997 soil test results. Although the average bahiagrass forage yield in 2002 (2.3 ± 0.7 Mg ha-1) was slightly lower than in 2000 (3.5 ± 1.2 Mg ha-1), yield differences in 2002 between the control (1.2 ± 0.2 Mg ha-1) and treated plots (2.3 ± 0.5' 3.3 ± 0.6 Mg ha-1) were indicative of a positive carry over effect of applied biosolids. This study has shown that excessive build up of plant nutrients may not occur in beef cattle pastures that repeatedly receive biosolids while favoring increased forage yield of bahiagrass.