Effect of manure on accumulation of dry matter, nitrogen, and phosphorus by soybean

Manure application for soybean [Glycine max (L.) Merr.] production is being considered by livestock producers, but the manure's influence on dry matte r (DM), nitrogen (N), and phosphorus (P) accumulation is not well documente d. The objectives of this study were to measure N, P, and DM accumulation p atterns and quantities by three genetically-different soybean varieties. Tw o preplant, sweep-injected manure application rates and a control were main plot treatments and three soybean varieties were subplots at seven experim ental sites in 1996 and 1997. Starting in mid-June and continuing on a 15-d schedule until maturity, whole-plant samples were collected, dried, weighe d, and analyzed for N and P. Plant DM increased with increasing manure rate s at each sampling after mid-June. Nitrogen concentration differences among manure rates were greatest early in the season and diminished with time, w hereas P concentration differences were consistent throughout the sampling period. Compared to the control treatment, manure resulted in an average of 25% more N accumulation at the first sampling date, 35% more at the second sampling, 42% at the third sampling, and then steadily decreased to a 10% increase at the final sampling date. Similar to N accumulation, mean P accu mulation differences between the control and the manure treatments increase d to 27% at the third sampling and then gradually decreased to 14% by the f inal sampling date. The overall effect of variety was minimal, yet statisti cally significant, and interactions between manure rate and variety were no t found. Applying manure for soybean increased end-of-season accumulation o f DM, N, and P by 9, 10, and 14%, respectively, compared to the non-manure treatment.