Drainage water management effects over five years on water tables, drainage, and yields in southeast Iowa

Abstract

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.

Drainage water management effect on corn planting date in southeast Iowa

“…Additionally, corn hybrids can be selected that have greater resilience to early season suboptimal temperatures (Gupta 1985). At this site, drainage volumes and NO 3 loss were reduced by 60% and 61% for the controlled drainage treatment and 58% and 49% for the shallow drainage treatment, respectively, when compared to conventional drainage for the five-year period from 2011 to 2015 (Schott et al 2017). Thus, at this site, drainage water management substantially reduced NO 3 loss without delaying planting or reducing yields.…”

“…All drainage treatments were planted on the same day due to plot layout, and the field manager decided when field conditions were suitable for planting. Yield methodology was outlined in Helmers et al (2012) and reported in Schott et al (2017). When necessary, the boards in the controlled drainage treatments were removed in mid-to late April for approximately two weeks prior to planting to allow free drainage and replaced in late May to early June after planting.…”

“…Shallow drainage reduced drainage volume and NO 3 -N loss by 20% to 58% and 18% to 49%, respectively, whenMidwest and Canada, Skaggs et al (2012) reported an 18% to 80% reduction in annual drainage volume and an 18% to 79% reduction in NO 3 -N loads when compared to conventional drainage. Additionally, Schott et al (2017) reported an average 60% and 61% reduction in drainage volume and NO 3 , respectively. However, corn yields from these same sites ranged from a mild yield reduction to an increase of 19% (Helmers et al 2012;Skaggs et al 2012;Schott et al 2017).…”

“…Additionally, Schott et al (2017) reported an average 60% and 61% reduction in drainage volume and NO 3 , respectively. However, corn yields from these same sites ranged from a mild yield reduction to an increase of 19% (Helmers et al 2012;Skaggs et al 2012;Schott et al 2017).…”

“…(https://sustainablecorn.org/). Four drainage treatments of no drainage, conventional drainage, shallow drainage, and controlled drainage were replicated twice across eight large research plots (i.e., 1.2 to 2.4 ha each) whose site map is presented by Schott et al (2017). The plots were blocked by soil type: a silty clay loam Kalona series (fine, smectitic, mesic Vertic Endoaquolls) on the northern plots and a silty clay loam Taintor series (fine, smectitic, mesic Vertic Argiaquolls) on the southern plots.…”