Subsurface drainage improves row crop production but also short circuits nitrate-nitrogen (NO 3-N) pathways in the soil with significant losses to surface waters. The objective of this study was to evaluate the effect of shallow, controlled, conventional, and undrained drainage treatments on depth to water table, drainage volume and NO 3-N loads, soil water content and storage in the soil profile, and crop yields. This research was conducted at the Iowa State University Southeast Research Farm near Crawfordsville, Iowa, from 2007 to 2015. We report on years five through nine here. The site consisted of eight large field plots with each of the four drainage treatments replicated twice. One-half of each plot was planted with corn (Zea mays L.) and the other half with soybeans (Glycine max [L.] Merr.). The corn and soybean halves were rotated every year in accordance with a typical corn-soybean rotation. The undrained treatment had a shallower water table than the other treatments and had a significantly higher number of days during the growing season when the water table was within 30 cm (12 in) of the ground surface than the other treatments. However, there was no difference in soil water contents in the top 80 cm (31.5 in) of the soil profile during the growing season between drainage treatments. Over the five-year study, controlled and shallow drainage reduced annual subsurface flows by 60% and 58%, respectively, while also reducing NO 3-N loads by 61% and 49%, respectively, as compared to the conventional drainage design. Crop yields were similar along the drainage designs but significantly lower in the undrained treatment. This study highlights the effectiveness of shallow and controlled drainage to reduce NO 3-N loads.

CHAPTER 1. GENERAL INTRODUCTION Background Thesis Organization References CHAPTER 2. EFFECTS OF DRAINAGE WATER MANAGEMENT ON YIELD, DRAINAGE, WATER TABLE, AND SOIL WATER STORAGE Abstract Introduction Materials and Methods Site location and design Data collection Data analysis Results and Discussion Precipitation Soils data Water table Volumetric water content Drainage Nitrate-N loss Crop yield Conclusions Acknowledgements References CHAPTER 3. EFFECT OF DRAINAGE WATER MANAGEMENT ON THE PLANTING DATE OF CORN Abstract Introduction Materials and Methods Site location and design Data collection Data analysis Results and Discussion Climate Volumetric water content iii Soil temperature Water table Drainage effect on plating date Conclusions Acknowledgements References CHAPTER 4. EFFECT OF DRAINAGE WATER MANAGEMENT ON PEAK DRAINAGE AND WATER TABLE RECESSION Abstract Introduction Materials and Methods Site location and design Data collection Event definition Data analysis Results and Discussion Event description Time to peak discharge Peak discharge Water table recession time Conclusions Acknowledgements References CHAPTER 5. CONCLUSIONS General Discussion Recommendations for Future Research References CHAPTER 1. GENERAL INTRODUCTION Background In 2011, a five-year grant from the United States Department of Agriculture National Institute of Food and Agriculture (USDA-NIFA) began funding a transdisciplinary project: Climate Change, Mitigation, and Adaptation in Corn-Based Cropping Systems (CSCAP). This project included 11 Midwestern institutions:

Soil arthropods play an important role in nutrient cycling and maintenance of soil structure, and their abundance and diversity provide an indication of the biological quality of soil. Land application of livestock manure provides crop nutrients and may also impact the soil arthropod community. This study was conducted to quantify soil arthropod abundance and diversity for a period of one year following swine manure application via broadcast or injection. Arthropods were extracted from plot soil samples using Berlese funnels, identified and counted, and the QBS index (Qualità Biologica del Suolo) was calculated for each soil sample. Collembola (Hypogastruridae and Isotomidae) populations were greater (p < 0.05) in the broadcast plots than the injection or control plots. Pseudoscorpiones were more abundant (p < 0.05) in the injection treatment compared to the broadcast and control treatments. Acari populations and the QBS index were not significantly impacted by manure application.

ABSTRACT. Developing drainage water management (DWM) systems in the Midwest to reduce nitrogen (N) transport to the northern Gulf of Mexico hypoxic zone requires understanding of the long

A comprehensive review of research data on the effects of swine manure on soil health properties that is applicable to agricultural producers is lacking. The objectives of this review were (a) to synthesize literature describing effects of swine manure on soil properties that affect “soil health” and (b) to identify knowledge gaps and research needs to further our understanding of this topic. We reviewed papers from two databases and extracted soil property and swine manure data based on a set of criteria. For a paper to be included, (a) the studies were replicated field experiments, (b) manure was the only differing factor between or among treatments, and (c) data means of swine manure amended treatments and controls were included. In total, 40 papers met the criteria and were included. Based on this review, swine manure has the potential to significantly increase soil organic carbon. Soil organic carbon, soil organic matter, and microbial biomass carbon increased when swine manure was applied to crop fields, whereas bulk density tended to decrease. To conclude, previous literature reviews failed to account for differences in methodologies between individual research studies and whether research is applicable to producers utilizing swine manure as amendments to improve soil health. Future research studies should measure and report a standard set of metrics for both soil and manure properties and should investigate the effects of application frequency on short‐ and long‐term soil health properties.