T. W. Welacky

Managing tile drainage, subirrigation, and nitrogen fertilization to enhance crop yields and reduce nitrate loss.

Improving field-crop use of fertilizer nitrogen is essential for protecting water quality and increasing crop yields. The objective of this study was to determine the effectiveness of controlled tile drainage (CD) and controlled tile drainage with subsurface irrigation (CDS) for mitigating off-field nitrate losses and enhancing crop yields. The CD and CDS systems were compared on a clay loam soil to traditional unrestricted tile drainage (UTD) under a corn (Zea Mays L.)-soybean (Glycine Max. (L.) Merr.) rotation at two nitrogen (N) fertilization rates (N1: 150 kg N ha(-1) applied to corn, no N applied to soybean; N2: 200 kg N ha(-1) applied to corn, 50 kg N ha(-1) applied to soybean). The N concentrations in tile flow events with the UTD treatment exceeded the provisional long-term aquatic life limit (LT-ALL) for freshwater (4.7 mg N L(-1)) 72% of the time at the N1 rate and 78% at the N2 rate, whereas only 24% of tile flow events at N1 and 40% at N2 exceeded the LT-ALL for the CDS treatment. Exceedances in N concentration for surface runoff and tile drainage were greater during the growing season than the non-growing season. At the N1 rate, CD and CDS reduced average annual N losses via tile drainage by 44 and 66%, respectively, relative to UTD. At the N2 rate, the average annual decreases in N loss were 31 and 68%, respectively. Crop yields from CDS were increased by an average of 2.8% relative to UTD at the N2 rate but were reduced by an average of 6.5% at the N1 rate. Hence, CD and CDS were effective for reducing average nitrate losses in tile drainage, but CDS increased average crop yields only when additional N fertilizer was applied.

Impacts of Zone Tillage and Red Clover on Corn Performance and Soil Physical Quality

benefits of conservation tillage with the yield benefits of conventional moldboard plow tillage (e.g., Pierce et Despite extensive research, reduced corn (Zea mays L.) performance is still encountered using conservation tillage on fine-textured al., 1992) for cool humid climatic zones. Here, a narrow soils in cool humid temperate climates. These problems are intensified zone 10 to 20 cm wide by 10 to 30 cm deep is conventionwhen corn is planted into residue from a previous crop such as winter ally tilled in the crop row while the rest of the soil surface wheat (Triticum aestivum L.). The objective of this 4-yr study was is left in an untouched no-till state. This supposedly to determine the influence of fall zone tillage (ZT), no tillage (NT), encourages the more favorable soil temperature, moisand conventional moldboard plow tillage (CT) (fall plowing) on corn ture, aeration, density, and strength conditions associperformance and soil physical quality under a winter wheat–corn– ated with conventional tillage in the narrow seedbed soybean (Glycine max L. Merr.) rotation with and without red clover (Trifolium pratense L.) (RC) underseeded in the wheat phase of the zones, while retaining the increased erosion resistance, rotation. A randomized complete block design (3 2 factorial, 4 organic matter protection and reduced energy inputs of replicates) was established on three adjacent fields in the fall of 1996 no tillage between the zones. Although there is much on a Brookston clay loam soil (fine loamy, mixed, mesic, Typic Argiainterest in the zone-till system, it has not yet been tested quoll) at Woodslee, ON Canada, and measurements were collected extensively in cool humid temperate climates, nor on during 1997 to 2000. Over both wet and dry growing seasons from the agriculturally important clay and clay loam soils of 1998-2000, zone tillage following underseeded RC produced average southern Ontario. In nearby Michigan, ZT on sandy corn grain yields (7.23 Mg ha 1) that were within 1% of those obtained using conventional tillage (7.33 Mg ha 1), and 36% higher than those loam soils did indeed improve potato (Solanum tuberoobtained using no tillage and RC (5.33 Mg ha 1). Zone tillage also sum L.) yields and soil physical conditions relative to improved soil quality as evidenced by generally lower soil strength conventional tillage in most years of a 4-yr study (Pierce than no tillage, and near-surface soil physical quality parameters that and Burpee, 1995); however, corn yields were not inwere equivalent to, or more favorable than, those of the other treatcreased by zone tillage in a similar 3-yr study, despite ments. It was concluded that corn production using zone tillage and substantially reduced soil strength (penetration resisRC underseeding is a viable option in Brookston clay loam soil, as it retains much of the soil quality benefit of conventional tillage but tance) within the 0to 30-cm depth range (Pierce et still achieves most of the yield benefit of conventional moldboard al., 1992). plow tillage. Red clover underseeded in cereals can produce large quantities of plant biomass and it fixes N in the nodules, which can in turn provide the equivalent of 90 to 125 C systems, such as no-till, have kg N ha 1 to the following crop (Bruulsema and Christie, been demonstrated to have several advantages 1987). In addition, RC can be effective in cool-temperover conventional moldboard plow systems, including ate climates for increasing microbial biomass, improving reduced soil erosion and surface runoff, slower loss of the structure of fine-textured soils (Drury et al., 1991), soil organic matter, and lower production costs. Howand for accelerating the decomposition of surface crop ever, there are many reports of reduced corn emergence residues (Drury et al., 1999). It was consequently hyand yields under no-till relative to conventional till on pothesized that including RC underseeding in a crop fine-textured soils in humid and cool temperate clirotation might further improve the potential yield and mates. This appears to be primarily a result of spring soil quality benefits of zone tillage on fine-textured soils. soil conditions that are cooler (Graven and Carter, 1991; The objective of this study was to determine, for a Fortin and Pierce, 1990; Fortin and Pierce, 1991) and clay loam soil in southern Ontario, if zone tillage and wetter (Fortin, 1993) relative to conventional tillage, RC underseeding could achieve corn yields comparable plus other factors such as increased soil bulk density with conventional moldboard plow tillage, but still reand strength (e.g., Hill, 1990; Pierce et al., 1992), detain most of the soil quality, environmental, and reduced creased soil air-filled porosity and saturated hydraulic energy inputs of no tillage. To accomplish this, convenconductivity (e.g., Pierce et al., 1992), and desiccation of seeds or seedlings through reopening of the planting tional moldboard plow tillage, no tillage, and zone-tillage slot produced by the no-till planter (Drury et al., 1999). systems were applied to a winter wheat–corn–soybean Zone tillage has been proposed as a possible alternarotation, with and without RC underseeded in the wintive tillage system that may combine the soil quality ter wheat. Evaluations were made on the basis of corn emergence, corn yield, and near-surface soil physical C.F. Drury, C.S. Tan, W.D. Reynolds, T.W. Welacky, S.E. Weaver, quality. and A.S. Hamill, Greenhouse & Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, ON, Canada N0R 1G0. T.J. Vyn, Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907Abbreviations: CHU, corn heat unit; CT, conventional moldboard 1150. Received 22 Jan. 2002. *Corresponding author (druryc@agr. plow tillage; FC, field capacity; NT, no tillage; PR, penetration resisgc.ca). tance; PWP, permanent wilting point; RC, red clover; WAS, wet aggregate stability; ZT, zone tillage. Published in Soil Sci. Soc. Am. J. 67:867–877 (2003).

Effect of tillage and water table control on evapotranspiration, surface runoff, tile drainage and soil water content under maize on a clay loam soil

Two tillage and two water table control treatments under continuous maize cropping were evaluated over a 3-year period (1992–1994) for their effects on evapotranspiration, surface runoff (SR), tile drainage (TD) and soil water content in the root-zone on a clay loam soil in southern Ontario. The tillage treatments included soil saver (SS, reduced tillage) and moldboard plow (MP, conventional tillage). The water table control treatments included controlled drainage-subirrigation (CDS) and regular tile drainage (DR). There was no significant difference (P<0.05) in evapotranspiration estimates between the SS and MP tillage treatments. The SS tillage increased SR compared with MP tillage during the non-cropping periods in 1993 and 1994, but not in 1992. Relative to MP, the SS tillage increased soil profile water content during the cropping period but decreased soil profile water content during the non-cropping period in 1992. The CDS treatment produced significantly higher (P<0.05) evapotranspiration and soil water content than the drainage treatment during the dry 1993 and 1994 years, but not during the wet 1992 year. The CDS treatment also had significantly lower (P<0.05) TD and higher SR than the drainage treatment. For all the treatments, over 65% of SR and TD occurred in the 5 month non-cropping period from November to March. Of the total annual water input (precipitation and/or subirrigation) to the field site, 8% was partitioned to SR, 30% was partitioned to TD, 55% was removed by crop and soil evapotranspiration and 7% was accounted for by changes in soil profile water content.

Reducing Nitrate Loss in Tile Drainage Water with Cover Crops and Water-Table Management Systems

Nitrate lost from agricultural soils is an economic cost to producers, an environmental concern when it enters rivers and lakes, and a health risk when it enters wells and aquifers used for drinking water. Planting a winter wheat cover crop (CC) and/or use of controlled tile drainage-subirrigation (CDS) may reduce losses of nitrate (NO) relative to no cover crop (NCC) and/or traditional unrestricted tile drainage (UTD). A 6-yr (1999-2005) corn-soybean study was conducted to determine the effectiveness of CC+CDS, CC+UTD, NCC+CDS, and NCC+UTD treatments for reducing NO loss. Flow volume and NO concentration in surface runoff and tile drainage were measured continuously, and CC reduced the 5-yr flow-weighted mean (FWM) NO concentration in tile drainage water by 21 to 38% and cumulative NO loss by 14 to 16% relative to NCC. Controlled tile drainage-subirrigation reduced FWM NO concentration by 15 to 33% and cumulative NO loss by 38 to 39% relative to UTD. When CC and CDS were combined, 5-yr cumulative FWM NO concentrations and loss in tile drainage were decreased by 47% (from 9.45 to 4.99 mg N L and from 102 to 53.6 kg N ha) relative to NCC+UTD. The reductions in runoff and concomitant increases in tile drainage under CC occurred primarily because of increases in near-surface soil hydraulic conductivity. Cover crops increased corn grain yields by 4 to 7% in 2004 increased 3-yr average soybean yields by 8 to 15%, whereas CDS did not affect corn or soybean yields over the 6 yr. The combined use of a cover crop and water-table management system was highly effective for reducing NO loss from cool, humid agricultural soils.

Identification of the full-length Hs1pro-1 coding sequence and preliminary evaluation of soybean cyst nematode resistance in soybean transformed with Hs1pro-1 cDNA

The Hs1pro-1 gene reportedly confers resistance to the beet cyst nematode in wild beet and sugar beet. Here, we tested the hypothesis that Hs1pro-1 confers resistance in soybean against the soybean cyst nematode (SCN). The full-length Hs1pro-1 coding sequence, which encodes a predicted polypeptide of 490 amino acids, was first acquired then expressed in ‘Westag’ soybean using a constitutive octopine synthase – mannopine synthase promoter. Thirty T0 lines that successfully expressed the Hs1pro-1 gene, as indicated by both polymerase chain reaction and reverse transcriptase – polymerase chain reaction analyses, were generated. Bioassay of the T1 progeny from these lines revealed that only five T0 lines grew normally and exhibited a high degree of SCN resistance. On average, these T1 transgenic progeny were about 70% more resistant to SCN than susceptible control cultivars. These preliminary data suggest that Hs1pro-1 is a promising candidate for genetically engineering SCN resistance in elite, locally adapt...

Solute dynamics and the Ontario nitrogen index: II. Nitrate leaching 1

Abstract: Nitrogen (N) leaching from soil into surface and ground waters is a concern in humid areas of Canada. As a result, N management protocols, including the Ontario N Index, are widely used to identify N leaching risk, although field assessment remains limited. Nitrogen fertilizer and chloride (Cl) tracer were fall-applied to five agricultural soils in Ontario with different textures and hydrologic soil groups (HSG) to assess the Ontario N Index and characterize inorganic N movement over 1 yr. The treatments included three N rates (0, 100, and 200 kg N ha-1) plus Cl tracer and 200 kg N ha-1 rate without Cl. After spring thaw, N loss from the crop root zone (top 60 cm) ranged from 68% for Brookston clay loam to 99% for Harrow sandy loam. A strong linear relationship between apparent N recovery and apparent Cl recovery indicated that N loss from the root zone occurred primarily by downward leaching. Leaching was controlled by the minimum measured saturated hydraulic conductivity (Ksat), and good estimates of N leaching were obtained using a quasi-theoretical relationship between N loss and Ksat. We concluded that Ontario N Index estimates of N leaching risk might be improved by including site-specific measurements of Ksat.

Solute dynamics and the Ontario nitrogen index: I. Chloride leaching1

Abstract: The nitrogen (N) index for humid temperate southern Ontario, Canada (Ontario N index) incorporates previous and current crop type, fertilizer and (or) manure management, and hydrologic soil group (HSG) to estimate risk for contamination of tile drainage water and groundwater by nitrate leached below the primary crop root zone (top 60 cm of soil). The Ontario N index has received limited ground-truthing, and the leaching component was assessed using chloride tracer (ClTR) on five soils (one sandy loam, two loams, and two clay loams) representing four HSG-based risk levels (HSG-A, high risk; HSG-B, medium risk; HSG-C, low risk; HSG-D, very low risk). A square-wave pulse of ClTR was applied to the soil surfaces in fall 2007 as KCl, and movement and loss of ClTR was tracked over 1-1.2 years using monthly soil core samples collected from the top 60-80 cm. For all five soils, 60-96% of ClTR was leached out of the primary crop root zone (below 60 cm depth) during the noncropping period (October 2007 to March 2008 inclusive), and >80% was leached out of the root zone within 1 year. The percentage of ClTR that leached did not correlate with precipitation or HSG designation, but produced significant (P < 0.05) power function regressions with minimum and harmonic mean saturated soil hydraulic conductivity (Ksat) measured in the top 50-60 cm. ClTR leaching rate appeared to be controlled primarily by Ksat in a manner consistent with infiltration and solute transport theory. It was consequently proposed that solute leaching loss versus Ksat relationships may improve N index risk estimates for both southern Ontario and other humid temperate regions.

Soil phosphorus loss in tile drainage water from long-term conventional- and non-tillage soils of Ontario with and without compost addition.

Recent ascertainment of tile drainage a predominant pathway of soil phosphorus (P) loss, along with the rise in concentration of soluble P in the Lake Erie, has led to a need to re-examine the impacts of agricultural practices. A three-year on-farm study was conducted to assess P loss in tile drainage water under long-term conventional- (CT) and non-tillage (NT) as influenced by yard waste leaf compost (LC) application in a Brookston clay loam soil. The effects of LC addition on soil P loss in tile drainage water varied depending on P forms and tillage systems. Under CT, dissolved reactive P (DRP) loss with LC addition over the study period was 765g P ha-1, 2.9 times higher than CT without LC application, due to both a 50% increase in tile drainage flow volume and a 165% increase in DRP concentration. Under NT, DRP loss in tile drainage water with LC addition was 1447gPha-1, 5.3 times greater than that for NT without LC application; this was solely caused by a 564% increase in DRP concentration. However, particulate P loads in tile drainage water with LC application remained unchanged, relative to non-LC application, regardless of tillage systems. Consequently, LC addition led to an increase in total P loads in tile drainage water by 57 and 69% under CT and NT, respectively. The results indicate that LC application may become an environmental concern due to increased DRP loss, particularly under NT.

Solid Cattle Manure Less Prone to Phosphorus Loss in Tile Drainage Water

Forms (e.g., liquid and solid) of manure influence the risk of P loss after land application. The objective of this study was to investigate the effects of P-based application of various forms of cattle manure (liquid, LCM; or solid, SCM) or inorganic P as triple superphosphate (IP) on soil P losses in tile drainage water. A 4-yr field experiment was conducted in a clay loam soil with a corn ( L.)-soybean [ (L.) Merr.] rotation in the Lake Erie basin. Over the 4 yr, the dissolved reactive P (DRP) flow-weighted mean concentration (FWMC) in tile drainage water was greater under SCM fertilization than under either IP or LCM fertilization. Despite its lower value on an annual basis, DRP FWMC rose dramatically immediately after LCM application. However, the differences in DRP FWMC did not result in detectable differences in DRP loads. Regarding particulate P and total P losses during the 4 yr, they were 68 and 47%, respectively, lower in the soils amended with SCM than in those with IP, whereas both values were similar between IP and LCM treatments. Overall, the P contained in solid cattle manure was less prone to P loss after land application. Accordingly, the present results can provide a basis for manure storage and application of best management practices designed to reduce P losses and improve crop growth.