MANURE Mineralizable Carbon, Nitrogen, and Water-Extractable Phosphorus Release from Stockpiled and Composted Manure and Manure-Amended Soils

Much of land-applied manure is surface-broadcast or incorporated to a shallow depth of fields under crop Dissolved N and P transfer to runoff water may increase with residue and conservation tillage management because of surface applications and shallow soil incorporation of animal manure. Information is needed regarding water-extractable nutrient release the need to conserve stored soil water for crop producduring manure decomposition to quantify that potential transfer to tion (Unger and Parker, 1976; Dao and Nguyen, 1989; runoff in permanent pastures and conservation tillage systems. ReDao, 1993; Schwartz et al., 2002). Incorporating manure lease of net mineralizable C (MIN_C), net mineralizable N (MIN_N), using inversion or disk tillage may improve the effiand dissolved reactive P (DRP) was determined in stockpiled and ciency of manure nutrient utilization by crops, but intencomposted cattle (Bos taurus) manure and manure-amended soils at sive tillage often eliminates the benefits associated with 4, 20, and 35 C for 322 d at about 60% water-filled pore space. Flushes conservation tillage practices such as reduced soil water of CO2–C exceeding 100 mg kg 1 d 1, inorganic N, and DRP were evaporation, erosion and runoff control, and soil C storreleased rapidly from both manures when incubated alone or as soil age (Jones et al., 1985; Gilley et al., 1997; Dao, 1993, amendments. Dissolved P release varied inversely with sorption ca1998; Allmaras et al., 2000). Large quantities of stockpacity and degree of P saturation in an Aridic Paleustalf and Torrertic Paleustoll. Net mineralizable C, MIN_N, and DRP flux densities were piled cattle and poultry manure or manure mixed with lognormally distributed during the 322-d incubation. Results from the bedding materials are also applied to Conservation Relognormal modeling approach suggest that incubations needed to be serve Program grasslands and pastures (Marshall et al., performed only for as long as needed to attain the 50% maximal flux 2001). As a result, manure particulates remain on the density beyond the maximum to predict MIN_C, MIN_N, and DRP soil surface, causing elevated flow-weighted NH4–N and release flux density distributions. Significant nonlinear relationships DRP concentrations in runoff after manure applications exist between ln(cumulative CO2–C) and inorganic N or DRP and (Pierson et al., 2001). Water-extractable manure nutrihave an inflexion point between 14 and 20 d. The nonlinearity of the ents may directly discharge to surface waters or build C-to-N and C-to-DRP relationships indicates multiple substrate pools up at the soil surface and increase the potential for N and supports the use of lognormal distributions to describe MIN_C, and P losses and contamination of surface and ground MIN_N, and DRP release from manures and manure-amended soils and to shorten laborious incubations. water via surface and subsurface transport mechanisms (Liebhardt et al., 1979; Sharpley et al., 1993; James et al., 1996; Jansen et al., 2000; Zhang et al., 2002). Information regarding decomposition and particulate L production in the United States increasnutrient mineralization in manures at the soil surface is ingly occurs in confined animal feeding operations needed. Insights into the decomposition process may (CAFOs). Large numbers of animals are gathered in a be gained from the knowledge of transformations that relatively small land area where huge quantities of nutrioccur during the composting of animal manure to which ents in feeds are imported to support the operations of no additional materials (i.e., crop residues, wood chips, dairies and poultry (Gallus gallus domesticus), swine saw dust, etc.) have been added. The N fraction has been (Sus scrofa domesticus), and beef cattle production facilextensively studied to predict the N-supplying capacity ities (CAST, 1996). Large-scale CAFOs faced with inof composts (Gale and Gilmour, 1986; Hadas and Portcreasing pollution potential are managing manure as a noy, 1994; Thomsen and Olesen, 2000). Manure and waste product (Natl. Res. Counc., 1993; CAST, 1996). manure compost MIN_N is associated with proteins and This results in intensive land applications of manure in is thus strongly correlated with N released by digestion the immediate vicinity of the feedlots because of the with pepsin (Castellanos and Pratt, 1981). Composihigh cost of transporting manure for distances greater tional differences, primarily in total C and N between than about 30 km. Such management practices have manures and composts, result in significant differences resulted in nutrient-loaded soils in agricultural fields in manure and compost MIN_N. A linear relationship near CAFOs (Zhang et al., 2002). was observed between MIN_N and MIN-C as percentAnimal manure has long been used as an organic age of added total N and C during the first 4 wk of source of plant nutrients and organic matter to improve incubation of 10 manures and composts added to a Typic the physical and fertility conditions of agricultural lands. Abbreviations: CAFO, confined animal feeding operation; CM, comT.H. Dao, USDA-ARS, AMBL, BARC-East, Beltsville, MD 20705posted manure; DRP, dissolved reactive phosphorus; flux densitymax, 2350; and M.A. Cavigelli, USDA-ARS, SASL, 10300 Baltimore Ave., maximal flux density; MIN_C, net carbon mineralized; MIN_N, net Beltsville, MD 20705-2350. Received 14 June 2002. *Corresponding nitrogen mineralized; PDF, probability density function; S-1, first firstauthor ([email protected]). order reaction; S-2, second first-order reaction; SM, stockpiled manure; WFPS, water-filled pore space. Published in Agron. J. 95:405–413 (2003).