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 matter (DM), nitrogen (N), and phosphorus (P) accumulation is not well documented. The objectives of this study were to measure N, P, and DM accumulation patterns and quantities by three genetically-different soybean varieties. Two preplant, sweep-injected manure application rates and a control were main plot treatments and three soybean varieties were subplots at seven experimental sites in 1996 and 1997. Starting in mid-June and continuing on a 15-d schedule until maturity, whole-plant samples were collected, dried, weighed, and analyzed for N and P. Plant DM increased with increasing manure rates at each sampling after mid-June. Nitrogen concentration differences among manure rates were greatest early in the season and diminished with time, whereas 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 accumulation differences between the control and the manure treatments increased to 27% at the third sampling and then gradually decreased to 14% by the final sampling date. The overall effect of variety was minimal, yet statistically significant, and interactions between manure rate and variety were not found. Applying manure for soybean increased end-of-season accumulation of DM, N, and P by 9, 10, and 14%, respectively, compared to the non-manure treatment.