Optimization of Liquid Swine Manure Sidedress Rate and Method for Grain Corn

such as on-the-go sensors (Scotford et al., 1999; Stombaugh and Shearer, 2000) and images (Schnug et al., Sidedressing may provide a better window of opportunity for land 1998) to adjust sidedress rates on a site-specific basis application of liquid swine (Sus scrofa) manure than early spring or fall application. Rates could be fine-tuned to match crop N demand according to soil properties or crop response. In Quebec, using the presidedress nitrate test (PSNT) if: (i) the yield response sidedressing was found to be more economically and agfunction to sidedress rate is consistent and (ii) yield and PSNT are ronomically sound than fall spreading (Cote et al., 1999). positively correlated. To optimize application rate and method, we meaThe variable-rate manure application method is relasured corn (Zea mays L.) grain yield response to in-row injection tively new, and tools have not yet been developed on (INJ) and topdress (TD) of liquid swine manure (LSM) sidedressed which to base application rates. The PSNT (NO3 conat different rates on clay loam (51-cm rows in 1999) and silt loam centration in the top 30 cm of soil when corn is 15 to (75-cm rows from 2000–2002). Yields exceeded local long-term aver30 cm tall) is used in a number of U.S. states and in ages with INJ in all but the wettest year, were variable with TD, and Ontario to refine fertilizer N recommendations for corn were 2 Mg ha 1 greater with INJ than TD at 37.4 m3 LSM ha 1. From (Randall et al., 1999; OMAF, 1999). With adoption of the quadratic yield response to sidedress injection rate, optimal rate (to achieve 95% maximum yield) ranged from 38 to 63 m3 ha 1 (plotthe late PSNT, surface water quality was improved relascale data; four 6-m sections per plot) and 37 to 49 m3 ha 1 (fieldtive to a control subwatershed in a recent study (N scale data; 0.2-ha plots). Yields were correlated with the PSNT (r requirements were supplied predominantly by fertilizer 0.75 for no LSM sidedress; r 0.24 for all treatments). Given the N in both subwatersheds; Jaynes et al., 2004). Critical consistent yield response to sidedress INJ rate and accurate (correct PSNT values determined originally for fertilizer rates 88% of the time) PSNT-based predictions of additional N require(20 to 30 mg kg 1) may differ in systems where manure ments (from comparisons of N fertilizer recommendation and relative is the primary nutrient source, however, according to yield), sidedress injection of LSM using the PSNT to fine-tune rates results from the U.S. northern Corn Belt (Randall et al., according to crop N requirements can be considered as a best manage1999). To use the PSNT to accurately adjust sidedress ment practice. manure rates to meet crop N requirements, there must be a consistent relation between crop yield and sidedress manure rate that can be described mathematically, as I nutrient use efficiency of land-applied well as a correlation between yield response and the manure, possibly through better placement and timPSNT in manured soils. ing, could reduce supplemental fertilizer requirements, Information regarding crop response to sidedressed improve profitability, and minimize environmental immanure gathered using modern application equipment pacts. Sidedressing (mid-June) provides a good window of under field-scale conditions is limited. For example, opportunity for application of liquid manure from swine there are few comparisons of the effects of different apoperations for several reasons. At sidedressing time, plication methods on the response to sidedress manure there is uptake by developing roots, and soil water conrate. Injection rather than in-lay or TD presents a comtent is typically lower than in fall or spring. As a result, promise between damage to roots by injectors and imthe potential for soil compaction is reduced, and drainproved nutrient availability due to placement in the age tiles are less likely to be flowing. Active roots couroot zone and reduced NH3 volatilization. Injection can pled with minimal tile flow can lead to increased nutrient reduce volatilization by 90% without concurrently inuptake and decreased transfer of material to ground or creasing denitrification N loss (Dendooven et al., 1998). surface waters. Contaminant movement to surface waters Surface application of manure without incorporation is is particularly a concern on tiled land (Dean and Foran, further susceptible to runoff losses of NH4 and P (Egh1992; Shipitalo and Gibbs, 2000). Furthermore, applicaball and Gilley, 1999), especially when rain falls soon tion rates for corn can be determined more precisely at after application (Cote et al., 1999). Besides reducing sidedress than in fall or spring because potential exists runoff and volatilization, injection has the added benefit to use the PSNT [more accurate than the preplant nitrate of solving application-related odor problems. test (Grove, 1992; Ball-Coelho et al., 2004)] or other tools Field-scale comparisons are needed to determine crop yield responses across varying soil and landscape conB.R. Ball Coelho and A.J. Bruin, Agric. & Agri-Food Canada, Southditions due to concerns regarding the validity of scalingern Crop Protection & Food Res. Cent., 1391 Sandford St., London, up from small plots (Kachanoski and Fairchild, 1996) ON, Canada N5V 4T3; and R.C. Roy (deceased), Agric. & Agri-Food and to assess and calibrate rate-determining methodoloCanada, Southern Crop Protection & Food Res. Cent., Delhi, ON, Canada, N4B 2W9. Received 6 Jan. 2005. *Corresponding author gies. Large-scale plots also allow the use of commercial([email protected]). sized equipment, which coupled with the potential to Published in Agron. J. 97:1322–1332 (2005). Corn Abbreviations: bicarb-P, sodium bicarbonate extractable phosphorus; CEC, cation exchange capacity; INJ, inject; LSM, liquid swine manure; doi:10.2134/agronj2005.0008 © American Society of Agronomy Ninorg, inorganic nitrogen; PSNT, presidedress nitrate test; SOM, soil organic matter; TD, topdress; UAN, urea ammonium nitrate. 677 S. Segoe Rd., Madison, WI 53711 USA 1322 Published online August 17, 2005