Antonio P. Mallarino

Crop rotation effects on soil quality at three northern corn/soybean belt locations

This paper examines how three different rotations effect on soil quality and profitability.

Efficacy of Grid and Zone Soil Sampling Approaches for Site-Specific Assessment of Phosphorus, Potassium, pH, and Organic Matter

Within-field variability of plant-available nutrients often results in different fertilizer requirements across a field. There is uncertainty concerning the efficacy of alternative sampling strategies suitable for site-specific management. This study compared various soil sampling approaches for P, K, pH, and organic matter (OM) in eight agricultural fields. Soil samples were collected using an intensive 0.2-ha grid-point procedure, and were used to compare less intensive sampling approaches. The approaches were based on 1.2–1.6-ha grid cells (Grid), soil series of digitized soil survey maps (SSM), soil series of detailed soil survey (1:12,000 scale) maps, elevation zones, and management zones based on various information layers (ZS). The approaches varied in reducing the within-unit soil-test variability and maximizing mean soil-test values across sampling units, but none was superior across all fields and nutrients. All approaches were less efficient for P and K than for pH or OM. The Grid and ZS approach were the most effective across all nutrients and fields. However, the Grid approach was more effective for P, the Grid and ZS approaches were better for K and pH, and the SSM and ZS approaches were better for OM. The ZS approach often resulted in fewer sampling zones than the Grid approach, which implies lower soil testing costs for producers, but required more knowledge and subjective judgement than a Grid approach to adapt it to field-specific conditions.

Effect of liquid swine manure rate, incorporation, and timing of rainfall on phosphorus loss with surface runoff.

Excessive manure phosphorus (P) application increases risk of P loss from fields. This study assessed total runoff P (TPR), bioavailable P (BAP), and dissolved reactive P (DRP) concentrations and loads in surface runoff after liquid swine (Sus scrofa domesticus) manure application with or without incorporation into soil and different timing of rainfall. Four replicated manure P treatments were applied in 2002 and in 2003 to two Iowa soils testing low in P managed with corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotations. Total P applied each time was 0 to 80 kg P ha(-1) at one site and 0 to 108 kg P ha(-1) at the other. Simulated rainfall was applied within 24 h of P application or after 10 to 16 d and 5 to 6 mo. Nonincorporated manure P increased DRP, BAP, and TPR concentrations and loads linearly or exponentially for 24-h and 10- to 16-d runoff events. On average for the 24-h events, DRP, BAP, and TPR concentrations were 5.4, 4.7, and 2.2 times higher, respectively, for nonincorporated manure than for incorporated manure; P loads were 3.8, 7.7, and 3.6 times higher; and DRP and BAP concentrations were 54% of TPR for nonincorporated manure and 22 to 25% for incorporated manure. A 10- to 16-d rainfall delay resulted in DRP, BAP, and TPR concentrations that were 3.1, 2.7, and 1.1 times lower, respectively, than for 24-h events across all nonincorporated P rates, sites, and years, whereas runoff P loads were 3.8, 3.6, and 1.6 times lower, respectively. A 5- to 6-mo simulated rainfall delay reduced runoff P to levels similar to control plots. Incorporating swine manure when the probability of immediate rainfall is high reduces the risk of P loss in surface runoff; however, this benefit sharply decreases with time.

Drought impact on crop production and the soil environment: 2012 experiences from Iowa

Enormous challenges were presented by the 2012 drought. Poor water availability and high temperatures resulted in significant stress during critical phases of corn (Zea mays L.) and soybean (Glycine max L.) development. These stress factors lead to management challenges with insects, diseases, and reduced nutrient availability and uptake by plants. The drought triggered soil changes, particularly in conventional tillage systems, such as increased fracturing, crusting, and deterioration of soil structure and aggregation. All this reinforced the need for soil conservation planning, especially its necessary role in buffering against unpredictable conditions and the impacts of dry and wet events on production and soil quality. In 2011, the USDAs National Drought Mitigation Center reported that 43% of Iowa experienced moderate-drought conditions and nearly 10% experienced severe-drought conditions. In 2012, 100% of Iowa experienced severe-drought conditions, while 65% experienced extreme-drought conditions by October. This article addresses several effects of drought on soil and crop production and lessons learned that will help develop appropriate drought mitigation strategies for future soil and crop management practices. The 2012 drought created unfavorable soil conditions for plant development and growth and changes in soil structure in many areas in the Midwest. These changes in soil structure included fracturing…

Runoff phosphorus loss immediately after poultry manure application as influenced by the application rate and tillage.

Excessive or N-based application of poultry manure for crops may result in significant risk of P loss with surface runoff. This study assessed P loss immediately after poultry manure application to soybean [Glycine max (L.) Merr.] residue with and without tillage at eight Iowa fields. Manure from chickens (Gallus gallus domesticus) or turkeys (Melleagris gollopavo) was applied at intended rates of 0, 84, or 168 kg total N ha(-1) (total P was 0, 21-63, 50-123 kg P ha(-1), respectively) with three replications. Simulated rainfall (76 mm h(-1)) was applied to 3-m2 sections of larger field plots with 2 to 7% slope, usually within 2 d of application, to collect runoff during 30 min. Runoff was analyzed for concentrations of sediment, dissolved reactive P (DRPC), bioavailable P (BAPC), and total P (TPRC). Non-incorporated manure consistently increased (P < or = 0.10) concentrations of all runoff P fractions in five sites, but there were increasing trends at all sites, and on average manure increased DRPC, BAPC, and TPRC 32, 23, and 12 times, respectively, over the control. Tillage to incorporate manure reduced DRPC, BAPC, and TPRC by 88, 89, and 77% on average, respectively, although in non-manured plots tillage seldom affected DRPC or BAPC and often increased TPRC. Tillage increased sediment concentration in runoff but not enough to offset the benefits of manure P incorporation. Runoff P loads generally followed trends of runoff P concentrations but were more variable, and significant treatment effects were less frequent. Overall, incorporation of manure by tillage was very effective at reducing P loss during runoff events shortly after poultry manure application under the conditions of this study.

Performance-based evaluations of guidelines for nitrogen fertilizer application after animal manure

guidelines that estimate amounts of N needed by the crop and amounts of N supplied by the manure and the Nitrogen fertilizer needs for corn (Zea mays L.) in fields already soil (Midwest Planning Service Livestock Waste Subtreated with animal manure can be estimated by using general guidecommittee, 1985; Miller, 1986; Killorn, 1995; Schmitt et al., lines or soil testing for inorganic N. Although the soil-testing approach has been extensively evaluated for ability to predict yield responses 1997; Killorn and Lorimor, 1999; USDA Nat. Resour. to applied N under field conditions, the general-guideline approach Conserv. Serv., 1999, 2001; Iowa Dep. of Nat. Resour., has not been subjected to comparable performance-based evaluations. 2000; Jackson et al., 2000). Estimates of N need by the Fertilizer response trials were conducted in 205 manured fields to (i) crop are based on expected N removal by the crop, compare the two approaches for ability to predict corn yield responses which is based on expected yield level or published yield to fertilizer N applied after animal manure, (ii) identify reasons for potentials of soil map units. Amounts of N supplied by differences in predictive ability, and (iii) explore the benefits of perforthe manure are estimated by analyzing the manure for mance-based comparisons of the alternative approaches. Analyses N content and adjusting for expected losses of N by showed that 34% of the observed variability in response could be NH3 volatilization soon after application and for perexplained by inorganic N concentrations whereas less than 5% of this centages of organic N expected to be mineralized. variability could be explained by the general-guideline approach. The soil-testing approach, therefore, had greater ability to integrate the Soil testing for inorganic N when plants are 15 to effects of all factors affecting yield responses across the range of 30 cm tall (i.e., in late spring) offers an alternative apconditions studied. Mean yield responses (0.55 Mg ha 1) were smaller proach for selecting rates of N fertilization (Magdoff et than are usually detectable in individual trials, but they were great al., 1984; Blackmer et al., 1989; Fox et al., 1989; Magdoff, enough to prompt farmers to fertilize. Results of this study indicate 1990; Binford et al., 1992; Bundy and Meisinger, 1994). that the most commonly accepted approach to estimating N fertilizer Such testing gives site-specific estimates of the suffineeds is less reliable than generally believed and, therefore, that ciency of N for plant growth where sufficiency indicates superior approaches are likely to remain unrecognized unless the supply relative to needs of the plants on a scale ranging performance of the commonly accepted approach is objectively evalufrom below to above optimal (Blackmer, 2000). Balkated under realistic field conditions. com et al. (2003) recently showed that testing soils for inorganic N after fertilization offers an effective way to evaluate N management practices and guidelines given L application of animal manure provides N needed to farmers. for corn production, but there is great uncertainty Performance of the soil-testing approach to estimating in the amount of N a given application of animal manure fertilizer need is usually evaluated by considering ability will supply for plant growth (Bouldin et al., 1984; Boulto predict yield responses (often expressed as relative din and Klausner, 1998; Sharpley et al., 1998; Klausner yields) to fertilizer N under field conditions. Such evaluet al., 1994; Blackmer, 2000). Schepers and Fox (1989) ations are reasonable because fertilizers are applied to attributed this uncertainty to (i) inaccurate and vague increase yields. The problem addressed in this paper estimates by farmers concerning amounts of manure is that we can find no published studies that provide applied, (ii) extreme variation in N concentrations in comparable evaluations of the performance of the genmanure, (iii) variable amounts of N lost by NH3 volatileral-guideline approach (i.e., estimating N fertilizer needs ization following unincorporated surface applications, by following general guidelines that do not include soil (iv) uncertainty concerning the proportion of the matesting for NO3). There is need for such evaluations benure N that will become available for plant uptake, and cause reports indicate that most farmers make little or (v) the possibility that manure additions will increase no downward adjustment in rates of N fertilization for N losses due to denitrification. N already applied as animal manure (Duffy and White, This uncertainty causes problems when selecting rates 1998; Nowak et al., 1998; Balkcom et al., 2003). Balkat which commercially prepared fertilizer N should be com et al. (2003) found that farmers may have valid applied after the manure. These problems usually are reasons for not making these adjustments. The reliabiladdressed by encouraging farmers to follow general ity of methods for estimating N fertilizer needs is more important than ever before because land application of D.J. Hansen, Dep. of Plant and Soil Sci., Univ. of Delaware Res. and animal manure and fertilizer N has been identified as Educ. Cent., 16684 County Seat Hwy., Georgetown, DE 19947; and a major source of NO3 in rivers, and therefore, many A.M. Blackmer, A.P. Mallarino, and M.A. Wuebker, Dep. of Agron., farmers are now being required to develop nutrient Iowa State Univ., Ames, IA 50011. Journal paper of the Iowa Agric. management plans (Jackson et al., 2000; Kalkhoff et al., and Home Econ. Exp. Stn., Ames, Project no. 4003. Received 10 July 2003. *Corresponding author (ablackmr@iastate.edu). 2000; USEPA, 2001). Our objectives in this paper are (i) to compare the soilPublished in Agron. J. 96:34–41 (2004). testing and the general-guideline approaches for ability  American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA to predict corn yield responses to fertilizer N applied af-

Multisite Evaluation of APEX for Water Quality: II. Regional Parameterization

Phosphorus (P) Index assessment requires independent estimates of long-term average annual P loss from fields, representing multiple climatic scenarios, management practices, and landscape positions. Because currently available measured data are insufficient to evaluate P Index performance, calibrated and validated process-based models have been proposed as tools to generate the required data. The objectives of this research were to develop a regional parameterization for the Agricultural Policy Environmental eXtender (APEX) model to estimate edge-of-field runoff, sediment, and P losses in restricted-layer soils of Missouri and Kansas and to assess the performance of this parameterization using monitoring data from multiple sites in this region. Five site-specific calibrated models (SSCM) from within the region were used to develop a regionally calibrated model (RCM), which was further calibrated and validated with measured data. Performance of the RCM was similar to that of the SSCMs for runoff simulation and had Nash-Sutcliffe efficiency (NSE) > 0.72 and absolute percent bias (|PBIAS|) < 18% for both calibration and validation. The RCM could not simulate sediment loss (NSE < 0, |PBIAS| > 90%) and was particularly ineffective at simulating sediment loss from locations with small sediment loads. The RCM had acceptable performance for simulation of total P loss (NSE > 0.74, |PBIAS| < 30%) but underperformed the SSCMs. Total P-loss estimates should be used with caution due to poor simulation of sediment loss. Although we did not attain our goal of a robust regional parameterization of APEX for estimating sediment and total P losses, runoff estimates with the RCM were acceptable for P Index evaluation.

Multisite Evaluation of APEX for Water Quality: I. Best Professional Judgment Parameterization

The Agricultural Policy Environmental eXtender (APEX) model is capable of estimating edge-of-field water, nutrient, and sediment transport and is used to assess the environmental impacts of management practices. The current practice is to fully calibrate the model for each site simulation, a task that requires resources and data not always available. The objective of this study was to compare model performance for flow, sediment, and phosphorus transport under two parameterization schemes: a best professional judgment (BPJ) parameterization based on readily available data and a fully calibrated parameterization based on site-specific soil, weather, event flow, and water quality data. The analysis was conducted using 12 datasets at four locations representing poorly drained soils and row-crop production under different tillage systems. Model performance was based on the Nash-Sutcliffe efficiency (NSE), the coefficient of determination () and the regression slope between simulated and measured annualized loads across all site years. Although the BPJ model performance for flow was acceptable (NSE = 0.7) at the annual time step, calibration improved it (NSE = 0.9). Acceptable simulation of sediment and total phosphorus transport (NSE = 0.5 and 0.9, respectively) was obtained only after full calibration at each site. Given the unacceptable performance of the BPJ approach, uncalibrated use of APEX for planning or management purposes may be misleading. Model calibration with water quality data prior to using APEX for simulating sediment and total phosphorus loss is essential.

Runoff Phosphorus Loss as Affected by Tillage, Fertilizer, and Swine Manure Phosphorus Management in Corn-Soybean Production Systems

Introduction Information on phosphorus (P) loss from surface runoff in fields managed with different cropping and P management systems is scarce. Swine manure can supply nitrogen (N), P, and K (potassium) for crops. Continued use of N-based manure rates can result in P buildup in the soil, mainly in continuous corn or when manure is applied for both corn and soybean production. Excessive soil P and P applications increase the risk of P loss from fields and of water quality impairment.

Drainage Water Quality Impacts of Agricultural Management Practices: Effectof Manure Application Timing and Cover Crops

The primary objective of this study is to evaluate the impact of various cropping and nutrient management systems on drainage water quality and crop yields. Treatment comparisons evaluate the impact of liquid swine manure application timing, nitrification inhibitor with late fall swine manure application, cereal rye cover crop, and gypsum application. These comparisons will be conducted for multiple years and used to develop appropriate manure and nutrient management practices in order to minimize water contamination potential and enhance the use of swine manure as a nutrient resource.