Residual Effects of Composted and Fresh Solid Swine (Sus scrofa L.) Manure on Soybean [Glycine max (L.) Merr.] Growth and Yield

Applying livestock manure to soil can enhance soil fertility and crop growth; however, little information is available on the residual effects of manure on crop growth. The objective of this study was to investigate the residual effect of fresh or composted hoop house swine manure on the growth and yield of soybean [Glycine max (L.) Merr.]. During 2000 and 2001 near Boone, IA, research plots received applications of composted or fresh solid swine manure from hoop structures or one of four levels of urea (0, 60, 120, and 180 kg N ha-1) before planting maize (Zea mays L.). During the growing season following maize harvest, we evaluated the responses of soybean to the eight treatments applied the previous year. During both years, soybean plants from manure-amended plots were significantly taller and had a thicker stem diameter than plants from the other plots. The manure-treated plots produced 39% greater soybean leaf area than the control in 2001 and 11% greater leaf area than the urea-amended plots in 2002. There was a 21 to 34% greater K concentration in soybean plants grown in the manure-amended sites than in the other plots. Soybean grain yield was 0.2 to 0.5 Mg ha-1 greater in the manure-treated plots than the control or urea-fertilized plots. Responses to manure were unaffected by the time of application (fall or spring) or the form of manure (composted or fresh). We have shown that fresh and composted swine manure application before growing maize resulted in detectable, positive residual effects on soybean growth and yield.