Illinois Fertilizer
Conference Proceedings
January 26-28, 1998
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K.D. Smiciklas and A.S. Moore1
Lake Bloomington is a major source of drinking water for area residents of Bloomington, IL, and has a history of nitrate (NO3-N) concentrations that exceed 10 ppm. Drinking water with greater than 10 ppm NO3-N consumed by infants under the age of six months can induce a fatal disorder known as methemoglobinemia (blue baby syndrome). Lake Bloomington was created in 1929 with surface area of 572 acres, and depends primarily on surface water from two tributaries (Money and Hickory creeks) and rainwater to maintain water volume. The Lake Bloomington watershed consists of approximately 43,100 acres, of which 86% is row cropped with corn or soybean, 4% is pasture, 5% is wooded, and 5% is contained in water or urban areas. The McLean County Extension Service, McLean County Soil and Water Conservation District, the Natural Resource Conservation Service of McLean County, Illinois State University, and the City of Bloomington, IL have formed a cooperative work group to address the water quality problems of Lake Bloomington.
Nitrogen (N) fertilizers are necessary for profitable corn production, but there is concern that excessive rates of N fertilizer may have adverse effects on groundwater quality (Schepers et al., 1991). As environmental and human health concerns about N fertilizer use intensify, the importance of proper N management is becoming more critical. Keeney and DeLuca (1993) noted that relatively high NO3-N concentrations of certain surface waters of Iowa can be attributed to N fertilizers (both synthetic and organic sources) and intensive agricultural practices such as the installation of tiles to drain farmland. Of particular concern is the agricultural producers who over-apply N fertilizer in excess of what the crop can utilize, thus increasing the potential of N leaching into groundwater supplies (Schepers et al., 1991). The rate of N application, and not the source (as synthetic fertilizer or manure), was the most important determinant of the potential for NO3-N leaching in corn (Patni and Culley, 1989). Other non-agricultural sources of NO3-N include suburban land use via septic system effluent (Gold et al., 1990), or naturally occurring N release from soil organic matter in the spring (mineralization). Thus, many researchers have investigated means to reduce the potential of N loss from agricultural production systems, such as winter cover crops and lower fertilizer N rates (Staver and Brinsfield, 1990; Hubbard et al., 1991). A 1993-96 survey of people actively engaged in agricultural field crop production in the Lake Bloomington watershed found that the median N fertilizer application rate was 151-180 lbs N/acre, with an expected mean corn grain yield of 156 bu/acre (Smiciklas and Moore, 1997). Although lowering the application rate of N may help to alleviate NO3-N leaching, agricultural producers may risk substantial economic loss from lowered productivity (Roberts and Lighthall, 1991). It has long been recognized that NO3-N may leach beneath the rooting zone of corn, and move into shallow groundwater supplies (Wagner et al., 1976). The majority of the NO3-N may leach within 1.5 months after application, if rainfall exceeds 200 mm during this period (Hubbard et al., 1991). Nitrate-nitrogen may also leach in significant amounts during the winter and early spring periods, when plant growth and uptake of N is minimal (Owens, 1990). Thus, delaying fertilizer N application until the corn crop can efficiently utilize the N is one option that may help to reduce NO3-N leaching. Agricultural producers that apply fertilizer N after crop emergence may be able to decrease the potential of NO3-N leaching. Post-emergence N applications entail a higher degree of risk, because the weather may prevent the timely application during the critical stages of corn growth. Therefore, many agricultural producers have chosen to apply fertilizer N in the spring before planting. This increases the likelihood of NO3-N leaching, particularly in seasons with excessive moisture.
One objective of this study is to quantify sources of NO3-N
in water that enters Lake Bloomington. Beginning in 1993, 36 sites within the
Lake Bloomington watershed have been monitored for NO3-N
concentration on a weekly basis. The second phase of this study is to elucidate
the influence of fertilizer N management upon subsequent water quality. Six
agricultural fertilizer N management techniques will be monitored for NO3-N
release via tile and surface drainage. The knowledge gained from this study
will aid in developing recommendations that deal with fertility and cultural
practices that promote the safe stewardship of Illinois farmland, while maintaining
high quality drinking water.
To elucidate the impact of fertilizer N practices upon water quality, a 30
acre site has been selected with the assistance of Mr. James Rutherford, a
NRCS soil conservationist from McLean County, IL (Hoffman farm, Hudson, IL;
farmed by Mr. Larry Troyer, Hudson, IL). The site has been subdivided into
six equal parcels of approximately 5acres. Within each 5 acre parcel, 4" tile
was installed in April 1997 on a 75 ft grid with interceptor access to collect
tile water on a weekly basis for NO3-N concentration.
Six agricultural fertilizer N practices for corn will be evaluated:
Soil sampling to a depth of 12 inches will also be conducted as needed to supplement tile NO3-N data. A corn/soybean rotation will be employed. Soybean was grown in the first year of this experiment (1997), to allow the establishment of fertilizer N treatments in the fall of 1997. The second year (1998) will be devoted to corn production, utilizing the six treatments listed above. In 1999, soybean will be grown in all six plots. Utilizing data collected from this experiment will help to elucidate when excessive NO3 is released from corn and soybean production, and if the timing or method of fertilizer N application can minimize NO3 leaching into Lake Bloomington.
Beginning in 1993, various sites within the Lake Bloomington watershed have been monitored for NO3-N concentration on a weekly basis. These sites include tiles that drain native woodland/pastures, agricultural production fields, and organic production fields. In addition, surface water runoff, rainwater, and creek water has also been sampled at 3 mile increments. A yearly survey to ascertain the productivity, timing, rate, and form of N fertilizers by agricultural producers in the watershed has also been conducted.
The field N study was initiated in 1997, with the installation of tile in the six separate parcels. After the tile was installed in April 1997, all six parcels were planted into soybean in early May. The first year of this study will provide a "baseline" to evaluate the uniformity of the six parcels before the application of fertilizer N treatments in the Fall 1997. The 1997 soybean yield for the six parcels was very similar, with an average yield of 56 bu/A (data not shown). There are some differences in soil pH, P, K, and organic matter for the six parcels (Table 1). However, these differences were based on a single soil sampling, and were not reflected in the soybean seed yield. The parcels that are potentially low in fertility will be monitored, and if needed, supplemental fertilizer will be added to ensure uniformity between parcels. Weekly sampling of tile water from these six parcels contained high concentrations of NO3-N (Figure 1). It is possible that the disturbance of the soil during tile installation and subsequent tillage may have stimulated NO3-N losses into tile water, or that high levels of NO3-N were in the soil from previous cropping patterns. These parcels will continue to be monitored for NO3-N leaching patterns. In the Fall of 1997, the fall agricultural N treatments were applied utilizing a N rate monitor to ensure accurate application. In the Spring of 1998, the other N treatments will be applied, and corn will be planted in the six parcels.
During 1993-97, various sites within the Lake Bloomington watershed have been monitored for NO3-N concentration on a weekly basis. These sites include tiles that drain native woodland/pastures, agricultural production fields, and organic production fields (Table 2). In addition, surface water runoff, rainwater, and creek water have also been sampled at 3 mile increments (Table 2 and Figure 2). The data indicates that row-crop agriculture releases excessive NO3-N into tile lines that drain into Money Creek, and subsequently Lake Bloomington. Based on the comparison of water from a wooded pasture tile and water from row crop agricultural tiles (organic and "conventional"), it would appear that agriculture plays a major role in the release of NO3-N into water that feeds into Lake Bloomington, IL (Table 2). The 2nd phase of the study (field N tile study at the Hoffman farm) will determine if the release of excessive NO3-N from agriculture can be minimized. At the Hoffman site, NO3-N released from mineralization (no fertilizer N parcel) can be compared to that of several fertilizer N treatments. Utilizing data collected from this study will help to elucidate when excessive NO3-N is released from corn and soybean production, and if the timing or method of fertilizer N application can minimize NO3-N leaching into Lake Bloomington.
A yearly survey to ascertain N management practices of agricultural producers in the watershed has also been conducted. The survey was sent to all landowners and tenants that farmed within the watershed, and the average response rate over the 4-year period was 35%. The 1993-96 mean expected corn yield was 156 bu/acre, and a median N fertilizer application rate was 151-180 lbs N/acre, which is within current University recommendations. In addition to N rate, the timing of N fertilizer application may have an impact on NO3-N leaching. On average, 47% of fertilizer N in the watershed was applied in the fall, 36% in the spring before planting, and 17% after planting in the spring. Our data indicates that a large majority of the NO3-N leached into Lake Bloomington in the spring (March - June), thus fall applications of fertilizer N may be partially responsible for the elevated NO3-N levels in spring tilewater. These results need to be verified over a number of years to assess seasonal variability patterns. It is hoped that the knowledge gained from this cooperative work group will aid in developing strategies that protect the quality of water in Lake Bloomington.
The use of N fertilizer in Illinois corn production is widespread because it is required for plant growth, and most soils do not have sufficient capacity to supply N. The importance of proper N management as it relates to yield is becoming more critical as environmental concerns about excessive N fertilization intensify. One objective of this study is to quantify sources of NO3-N in water that enters Lake Bloomington. Beginning in 1993, 36 sites within the Lake Bloomington watershed have been monitored for NO3-N concentration on a weekly basis. The 1993-97 average NO3-N concentration for the following sources within the watershed was: water from rain (1.1 ppm), surface water runoff (6.5 ppm), wooded pasture tile (1.4 ppm), organic production tile (10.2 ppm), agricultural production tiles (17.1 ppm), and subsequent creek water (12.1 ppm). In addition, as creek water passed through small municipalities, its NO3-N concentration dropped an average of 0.9 ppm. A yearly survey to ascertain N management practices of agricultural producers in the watershed has also been conducted. The 1993-96 mean expected corn yield was 156 bu/acre, and a median N fertilizer application rate was 151-180 lbs N/acre. In addition to N rate, the timing of N fertilizer application may have an impact on NO3-N leaching. On average, 47% of fertilizer N in the watershed was applied in the fall, 36% in the spring before planting, and 17% after planting in the spring. The second phase of this study is to elucidate the influence of fertilizer N management upon subsequent water quality. Six agricultural fertilizer N management techniques will be monitored for NO3-N release via tile and surface drainage. The knowledge gained from this study will aid in developing recommendations that deal with fertility and cultural practices that promote the safe stewardship of Illinois farmland, while maintaining high quality drinking water.
1Lloyd Burling is President, Lisa Muirheid
Martin is Communications Director, and Jean Trobec is Government Relations
Director, Illinois Fertilizer & Chemical Association.
