EFFECT OF DRYING ON THE PLANT NUTRIENT CONTENT OF HEN MANURE

The nutrient content of animal manure must be characterized before it can be used efficiently as a soil amendment. The purposes of this study were to assess the nutrient content and measure the effect of sample preparation on variability of selected plant nutrients in hen (Gallus gallus domesticus) manure. Analyses for total nitrogen (TN), inorganic N (N(i)), P, K, Ca, Mg, and S were compared in wet and dry hen manure for changes induced by drying at 150-degrees-F (66-degrees-C). Twelve truckloads of hen manure produced from the same commercial operation were sampled. Approximately 5 lb (2.27 kg) of fresh manure from each truck was collected, frozen, transported to the lab, thawed, and homogenized. Subsamples were taken for wet and dry analyses. Nitrogen analyses were conducted with semimicro-Kjeldahl methods, and analyses of other elements were determined by inductively coupled plasma emission spectroscopy after digestion. Values for all analyses of wet and dry samples were reported on a dry weight basis. Drying reduced estimates of TN from 5.65 to 4.01% in wet and dry manure, respectively. The N(i) in the manure was in the ammoniacal form with means of 1.93 and 0.20% for wet and dry analyses, respectively. Volatilization of NH3-N was responsible for the N decrease in the dried manure. In the wet and dry samples, the P and K contents were not different with mean levels of 2.41 and 2.05%, respectively, and the dry samples were less variable than the wet ones. Results from this study indicate that, for value estimates of the N content of hen manure, samples should not be dried prior to analysis. Although a reduction in the variability of the lab analyses was noted with drying, the mean values for elements other than N were not significantly different between the wet and dry samples.