Illinois Fertilizer
Conference Proceedings
January 24-26, 2005
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S. A. Ebelhar, E. C. Varsa, J. D. Hernandez, C. D. Hart, and T. D. Wyciskalla1
Tile drainage provides many benefits to growing crops. Draining wet fields allows fields to warm up faster and be planted earlier, provides better aeration to plant roots, and reduces problems with denitrification losses of N (IL Agronomy Handbook). Earlier planting and better growth associated with drainage leads to increased yields and perhaps even a more efficient use of applied fertilizer N. Tile drainage of claypan and poorly drained soils in southern Illinois is increasing at a rapid rate, even though the effects on yield and environmental issues have yet to be demonstrated. There is little information as to the effects of tile drainage on nitrogen use efficiency and subsequently the impact on nitrates leaving through tile lines. This study should help to determine if N use efficiency is affected by drainage and at what spacings tile should be placed to optimize this efficiency.
The current nitrogen use efficiency numbers for corn in Illinois ranges from 0.8 to 1.2 lb N/bu based on yield goal, previous crop, manure credits and other incidentals. The efficiency for wheat is about 1.0 lb N/bu or higher. But there is little information as to the effects of tile drainage on nitrogen use efficiency and subsequently the impact on nitrates leaving through tile lines. This study should help to determine if N use efficiency is affected by drainage and at what spacings tile should be placed to optimize this efficiency.
Potassium (K) fixation and availability may also be affected by tile drainage. Work by Stucki and Huo (1997) indicated that oxidation and reduction (redox) may play a significant role in the ability of clays (especially smectitic clays) to fix K. In poorly drained soils, one would expect soil near tile lines to be significantly drier that soil between lines, especially if tile lines are greater than 50 ft apart on centers. This would suggest that soil test K levels may be different above or near tile lines versus between tile lines, but to what magnitude. Periodic sampling over tiles and between tiles would provide information on K fixation and availability as related to tiling.
The objectives of this study are to
A tile drainage study was established in the Spring 2003 on a 52 acre field in Franklin Co., IL. The field was broken into six replications (Reps) of tile spacings of 30 ft, 60 ft and 120 ft randomly assigned within Reps forming a randomized complete block (RCB) design. Treatments were broken into five classes:
Soybeans were grown in 2003 with wheat planted in the fall of 2003. Nitrogen rate plots were established for wheat in spring 2004 within each of the five basic drainage treatments replicated five times. Nitrogen rates for wheat were 0, 30, 60, 90 and 120 lb N/acre spring applied treatments. Plot size was based on the width of the farmer’s equipment (currently 10 ft for the wheat drill and 15 ft for the corn planter) x 30 ft with the center 5 ft x 30 ft harvested for yield. The optimum N rate and yield at optimum N for each crop were determined and compared among the five drainage treatments. Nitrogen use efficiency will be calculated as the lb N per bu of crop produced.
To address the issue of K fixation, sampling points were identified with GPS markers for each of the 5 drainage treatments. Monthly samples (as possible) were collected to measure soil test P and K levels, soil moisture, and soil temperature. Grain yields and nutrient removal will be monitored along with fertilizer additions to determine nutrient balances and effects on changes in soil test levels over time.
The soil type for this field is almost exclusively Hoyleton silt loam (Fine, smectitic, mesic, Aquertic Hapludalfs), a flat, somewhat poorly drained soil high in shrink-swell type clays with K-fixing potential.
Small plots. Wheat yields were very good for this location in 2004. Increasing N rates had a highly significant effect on increasing wheat yields (Table 1). However, there was no significant differences among tile treatments. Flag-leaf N concentrations were also significantly increased with increasing N rates, but test weights were actually reduced slightly with increasing N rates. There was a significant interaction between tile spacings and N rates for flag-leaf N (Figure 2). The 120' foot tile spacing had the lower N concentration with the 30' tile spacing had the higher N concentration. This was an indication of better N availability with closer tile spacings, although there was no difference between the "over tile" versus the "between tile" treatments, and there was no effect on grain yields.
The rainfall after N was applied on March 19 was very sparse with less than four inches of rainfall over an eight week period. Although there were differences among tile spacing for flag-leaf N, these differences were very small and the rainfall pattern would suggest that there was little N loss experienced by the wheat crop after the time of N application until well into grain fill. This would account for the little difference in yields among the tile treatments. The optimum economic N rate was 84.5 lb N/acre producing an optimum economic yield of 81.9 bu/acre (Figure 4) and a nitrogen use efficiency of 1.03 lb N/bu wheat, which is very close to the published efficiency of 1.0 lb N/bu.
Whole field. Yields within 5' on either side of the tile treatments were determined across the whole field and compared to the center 10' between tile treatments. There was a highly significant difference between the 30' tile treatments and the 60' tile treatments (Table 2). The 60' tile treatments had about a three bu/acre yield advantage over the 30' tile spacings. We can offer no explanation for this effect at this time.
When the field conditions are adequate (not too wet or too dry or frozen), soil samples are taken on a monthly basis on a transect across tile treatments and replications. Samples are taken within a five foot radius around known (GPS marked) points. Soil moisture and soil temperatures are also determined. March and November were the only two months where soil moisture was lower over tile lines than between tile lines (Figure 5). There is little difference between soil test nutrients and pH associated with tile treatments, except that here appears to be higher soil test K values for the between 120' tile treatment (Figure 6) compared to the other treatments.
With only one year's data, there is little to conclude at this juncture. Conditions were probably too dry in 2004 for there to be significant effects of tile treatments on wheat.
Table 2. Effects tile treatments (based on 5' buffers) on wheat yields, Benton, 2004
Figure 1. Map of tile lines for field in Franklin Co., Illinois
Figure 2. Effects of N rates and tile treatments on wheat flag-leaf N concentrations, 2004.
Figure 3. Rainfall accumulation after N application to wheat, 2004.
Figure 4. Effects of N rates on wheat yields, 2004.
Figure 5. Effects of tile treatments on soil moisture as measured by TDR, Benton, 2004.
Figure 6. Effects of tile treatments on soil test K over time, Benton, 2004.
1 S. A. Ebelhar is an agronomist, Department of Crop Sciences, Univ. of Illinois.
E. C. Varsa is a professor and J. D. Hernandez is an assist. professor,
Dept. of Plant, Soil, and Gen. Ag., Southern Illinois Univ.
C. D. Hart is senior research specialist, Dept. of Crop Sciences, Univ. of Illinois.
T. D. Wyciskalla is a research specialist, Dept. of Plant, Soil, and Gen. Ag., Southern Illinois Univ.
Stucki, J. W. and D. Huo. 1997. Continued studies on the behavior of potassium in soils. In R. G. Hoeft (ed.) IL Fert. Conf. Proc. pp 1-10.
