Rapid on-farm nutrient determination and land management of swine slurries

Government regulatory agencies recommend a nutrient management plan (NMP) for animal operations. These plans require manure analysis for total nitrogen (TN) and total phosphorus (TP), and use indices to determine nutrient availability. This study determined if manure solid content (TS), storage facility, animal growth stage, and season could be used to predict TN and TP concentrations. Manure samples used to develop rapid on-farm models were collected from agitated holding pits via the distribution pipe used to load tankers, and from unagitated holding pits prior to loading using a discrete level sampler. A liquid ratio (liquid volume/filtrate volume) was generated by sieving a known manure volume. Liquid ratios correlated well with TS for manure samples collected from integrated swine growth facilities. Regression analysis demonstrated that the liquid ratio and historical TN and TP manure sample results could be used to predict TN and TP. Validation samples collected from loaded tankers were used to develop regressions of actual versus predicted values, which indicated that the procedure and models had good predictive value for determining TN and TP. This study showed that liquid ratio is a rapid method for predicting TP concentrations of swine slurries whereas animal growth stage is a better predictor of TN. This study also demonstrated that sampling unagitated holding pits at discrete depths characterized manure TN and TP concentrations, and could be used by producers using vacuum loading tankers to develop individualized nutrient prediction models for NMPs, different manure storage structures, and animal growth stages. A field investigation based on this rapid assessment procedure was used to evaluate the effect of a NMP on corn yield and soil fertility. The corn was grown on two phosphorus (P) soil test levels (medium and excessive). The rapid model manure application rate produced grain yields that were significantly higher than inorganic-N fertilization treatments. Potassium chloride extractable P and ammonium were not significantly different in manure treatments compared with the inorganic-N treatment. Analysis of ear leaf N, P, and K using the diagnosis and recommendation integrated system (DRIS) demonstrated that the rapid model manure application developed by a NMP met crop requirements.