The quality of water draining fields fertilized with liquid swine (Sus scrofa) manure (LSM) sidedressed into standing corn (Zea mays L.) at rates ranging from 0 to 94 m(3) ha(-1), either topdressed (TD) onto the surface, or injected (INJ) into the soil once annually for each of three consecutive years was evaluated. Liquid swine manure application rate was a critical driver of preferential flow of LSM to tile as detected by turbidity, concentrations of NH(4)(+)-N, dissolved reactive phosphorus (DRP), and the presence of enteric bacteria (Escherichia coli). Contaminant movement to drains occurred immediately after 75 and 94 m(3) LSM ha(-1) were injected (e.g., 2.5 mg DRP L(-1), 3-yr average). With injection of 56 m(3) ha(-1) or less, drainage water was not turbid and concentrations of NH(4)(+)-N, DRP, and enteric bacteria were dramatically lower than with the higher rates, even when tiles flowed freely during manure application. Application method also affected tile water quality. With TD applications (37 and 56 m(3) ha(-1)), nutrients and bacteria did not move to tiles at the time of application, but with rains that fell within 3 d after application, concentrations increased (e.g., 0.1 mg DRP L(-1)), although less than with INJ. Overall, sidedress injection rates that supplied adequate crop nutrients did not compromise drainage water quality.

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[1] A scarcity of information exists on how physical processes govern the movement of liquid manure, or other viscous fluids, through layered macroporous soils. To elucidate these complex flow and transport phenomena, a viscosity dependent, two-dimensional dual-permeability model that considers macropore anisotropy is employed to simulate field experiments where liquid swine manure (LSM) was applied to silt loam with both a soil crust and plowpan layer present. Using data from the field experiment as a benchmark, the model was used to predict nutrient (NH 4 -N and total P) breakthrough to tile drains; and to assess the influence of reduced permeability crust and plowpan layers, and fluid viscosity, on solute movement within 48 h of LSM application. Results demonstrate the importance of viscosity on flow and transport in macroporous soils. By increasing LSM viscosity, nutrient breakthrough to tile drains can be greatly reduced, and near surface nutrient retention can increase. The presence of a nonmacroporous soil crust layer can also lead to reduced nutrient concentrations in tile discharge by reducing pressure heads in the underlying A-horizon soil matrix, resulting in reduced macropore flow; whereas a low permeability plowpan layer at the base of the A horizon can increase pressure heads in the A-horizon soil matrix and lead to increased macropore flow. Multiple target point parameter sensitivity analysis revealed that relative parameter sensitivity can be a transient characteristic, and that hydraulic properties of the A and B horizon tend to exhibit their greatest influence over the respective early and late time solute breakthrough characteristics.

Animal manure is an important source of N for crops in areas with intensive livestock production. Variable manure N availability can incite over‐application of manure or supplemental fertilizer leading to low N recovery and possible negative environmental and economic impacts. To improve manure N use efficiency, the effects of rate and method of sidedress application of liquid swine (Sus scrofa) manure (LSM) on N recovery by corn (Zea mays L.) were determined. We used in‐row injection (INJ) or topdressing (TD) to sidedress LSM from 1999 to 2002 at rates ranging from 0 to 93.5 m3 ha−1, and measured grain N uptake and NO3–N in drainage tile water, stalks, and topsoil postharvest. Apparent recovery of manure total N (LSM‐N) ranged from 0 to 57% and was greatest with injection of 37.4 m3 ha−1 (194 kg LSM‐N ha−1). Injection rate to achieve 95% of maximum grain yield averaged 216 kg LSM‐N ha−1 over 4 yr. Transport of LSM‐N to ground‐ and surface waters was minimized when sidedressed at or below rates for optimal yield. When injected N exceeded crop demand, NO3–N increased to over 10 mg kg−1 in topsoil, 20 mg L−1 in drainage water, and to excessive (3.6 g kg−1) levels in stalks. Due to greater LSM‐N recovery, injection (59%) is recommended rather than topdress (41%) for sidedress application of manure.

Sidedressing may provide a better window of opportunity for land application of liquid swine (Sus scrofa) manure than early spring or fall application. Rates could be fine‐tuned to match crop N demand using the presidedress nitrate test (PSNT) if: (i) the yield response function to sidedress rate is consistent and (ii) yield and PSNT are positively correlated. To optimize application rate and method, we measured corn (Zea mays L.) grain yield response to in‐row injection (INJ) and topdress (TD) of liquid swine manure (LSM) sidedressed at different rates on clay loam (51‐cm rows in 1999) and silt loam (75‐cm rows from 2000–2002). Yields exceeded local long‐term averages with INJ in all but the wettest year, were variable with TD, and were 2 Mg ha−1 greater with INJ than TD at 37.4 m3 LSM ha−1. From the quadratic yield response to sidedress injection rate, optimal rate (to achieve 95% maximum yield) ranged from 38 to 63 m3 ha−1 (plot‐scale data; four 6‐m sections per plot) and 37 to 49 m3 ha−1 (field‐scale data; 0.2‐ha plots). Yields were correlated with the PSNT (r = 0.75 for no LSM sidedress; r = 0.24 for all treatments). Given the consistent yield response to sidedress INJ rate and accurate (correct 88% of the time) PSNT‐based predictions of additional N requirements (from comparisons of N fertilizer recommendation and relative yield), sidedress injection of LSM using the PSNT to fine‐tune rates according to crop N requirements can be considered as a best management practice.