Rapid analysis of hog manure and manure-amended soils using near-infrared spectroscopy

Application of hog (Sus domesticus) manure to agricultural land converts waste to fertilizer. Nevertheless, matching nutrients in highly variable manure to soil or crop needs requires analytical capability that is ideally field portable and cost-effective. This study explored using rapid nondestructive near-infrared spectroscopy (NIRS) to analyze nutrients in hog manure and receiving soil. Spectral data in the visible and near-infrared (NIR) region (400-2500 nm) from manure samples were correlated with chemical analytical data from the same samples using multiple linear regression statistics to develop calibrations for the prediction of future unknown samples. For 64 manure samples from seven manure storage facilities, r(2) between NIR-predicted values and chemically measured values was 0.93 to 0.99 for NH4-N, total dissolved N (TDN), suspended N, soluble reactive P (SRP), total dissolved P (TDP), suspended P, suspended C, Na, and Mg. For K, Ca, conductivity, and pH, r(2) was >0.80. Subsequent analysis of 75 samples from 25 facilities gave similar or slightly less successful results. Soil samples collected before and following application of manure were scanned in a field-moist state and after drying. For field-moist soil, r(2) for N, organic matter, Mg+ and moisture was >0.84; for SO4-S was 0.7. For dry soil, results were similar for N and better for Mg SO4-S, Ca, and K. Near-infrared spectroscopy has potential to predict sonic nutrient and salt concentrations in manure rapidly and without sample preparation. It can determine moisture, organic matter, total N, and Mg in field-moist or dry soil and SO4-S, Ca, and possibly K in dry soil.