Illinois Fertilizer
Conference Proceedings
January 23-25, 1995
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R.G. Hoeft, E.D. Nafziger, K.B. Ritchie, W.L. Banwart, L.C. Gonzini, and J.J. Warren1
Rapid adoption, both voluntary and mandatory, of 0-till planting systems has spurred considerable interest in fertility management programs. In particular, producers are concerned about the use of starter fertilizer for 0-till corn production with different nitrogen management systems. Both research and farmer experience have shown that these concerns are not unfounded.
The increased residue cover associated with 0-till has many advantages, but unless one manages fertilizer N programs carefully, this increased residue may increase N loss potential. Reactions that need to be considered in the development of an N management program include:
Immobilization: Surface application of N into the high residue zone will result in an increase in immobilization as the residue decomposes. Ultimately, most of the N that is tied up by this reaction will be released, but it frequently is not released soon enough for the following crop. One solution to avoid this problem is to inject the N below the zone of residue accumulation.
Denitrification and leaching: One of the benefits of 0-till is conservation of moisture. The heavy residue holds water from runoff, thus it increasing infiltration. In addition, the surface residue reduces the rate of evaporation. The net of these two actions is an increase in soil moisture, which is positive unless soil water increases to the point where denitrification or leaching become a problem. Leaching will be of greatest concern on sandy soils, whereas denitrification will be the primary loss mechanism on medium to heavy textured soils. Delaying application until near the time of crop need or inclusion of nitrification inhibitors will help minimize these losses. If application is delayed until sidedressing, there is some indication that there is more advantage to the use of a starter fertilizer that contains N.
Volatilization: Surface application of urea based fertilizers when temperatures are warm (greater than 50° F) will result in volatilization of ammonia unless the materials are incorporated with a tillage tool or by precipitation. Under 0-till conditions, losses of 30 or more of the N have been observed when no precipitation is received within 10 days to two weeks after urea application. In 1996, a new product will be available that will reduce the potential for volatilization losses from urea containing material. The product, called AgrotaiN, is a urease inhibitor. It has been shown to increase yield when combined with surface applied, urea based materials on 0-till corn.
To minimize N loss problems in 0-till systems, agronomists generally agree that it is best to minimize the fertilizer-residue contact. In priority order, the choices for nitrogen management programs would be : sub-surface injection of anhydrous ammonia or urea-ammonium nitrate solutions > surface application of urea based materials with a urease inhibitor= ammonium sulfate > surface application of ammonium nitrate > surface application of urea based materials.
The fact that 0-till soils are generally cooler in the early part of the growing season combined with the knowledge that surface application of immobile nutrients like P and K will result in an accumulation of these elements near the soil surface has prompted the concern about the need for starter fertilizer on 0-till fields. Marketing claims that a small amount of seed placed fertilizer will result in more rapid growth of 0-till planted corn have further enhanced the interest in starter fertilizers. These types of programs offer the advantage of not requiring additional hardware (planter attachments), but they do increase the potential for early seedling growth problems.
Indiana research has shown that the probability of response to starter fertilizer increases with reduced tillage, particularly 0-till (Table 1). This is true even at soil test levels above those at which response to applied P or K would normally be expected. This work confirmed that most of the response resulted from N in the starter, not from P or K. Dr. Mengel from Purdue further observed that the response to starter was greater when N had been preplant injected or sidedressed than when a preplant surface application was used. Based on these results, it is thought that there should be some N near the seedlings since early season root growth is not adequate to penetrate into the zones of injected ammonia or UAN solutions quickly enough to optimize yield.
Ohio research has shown that yield benefits associated with increasing soil exchangeable K or from the use of starter fertilizer is lessened with increasing mulch levels. This lack of response to starter K was attributed to greater root growth in the surface two inches of soil, this root growth may have allowed for more efficient use of broadcast K fertilizer. In contrast to the Ohio data, Wisconsin work has shown an increased need for K under 0-till systems. These differences in results may be due to differences in early season soil temperature.
The limited research on seed-placed fertilizer has shown that rates of N plus K2O in excess of 10 lb/acre may cause seedling emergence problems. In addition, prior research has shown that it is desirable to use low salt materials and to avoid the use of urea in seed placed materials.
As is evident from the above discussion, there is some confusion about the
need for starter fertilizer for 0-till corn production. In an attempt to identify
conditions under which starter is likely to be an advantage, experiments have
been conducted at four locations in Illinois over the last two years. The objectives
of this project have been to determine the influence of N, P, and K- individually
and in combinations- contained in starter fertilizer on the growth, development,
and yield of 0-till corn grown under different environments and N management
systems, and to determine the influence of N, P, and K rate of application and
nutrient source when placed directly with the seed on the growth, development,
and yield of 0-till corn.
Two separate but related experiments were conducted at four locations in Illinois in 1993 and 1994. While the farms were the same in both years, the field or area within the field was different the second year. The locations were selected to give variation in climatic conditions, soil type, crop rotation, and soil test values (Table 2). In Experiment 1, three main plot treatments consisted of 160 lb N/acre applied as: 1) ammonia injected preplant; 2) UAN broadcast preplant, and 3) ammonia sidedressed when corn was in about the 6-leaf stage. Eight treatments, consisting of factorial combinations of 2 N rates (0 and 25 lb N/acre), 2 P rates (0 and 30 lb P2O5/acre), and 2 K rates (0 and 201b K2O/acre) were applied within each main plot. Following application of the N, corn was planted using a 2-row planter equipped to apply fertilizer in a band 2 inches below and 2 inches to the side of the seed.
Experiment 2 consisted of factorial combinations of 3 N rates (0, 5, and 10 lb N/acre, 2 P rates (0 and 10 lb P2O5/acre), and 2 K rates (0 and 10 lb K2O/acre) applied directly with the seed, and 2 combinations of N-P-K (10-10-10 and 25-30-20) applied in a band 2 inches below and 2 inches to the side of the seed. An additional 13 treatments were applied to compare the effect of N source (urea versus ammonium nitrate), P source (DAP vs MAP), K source (KCI vs. K2SO4), and liquid source (10-34-0 vs 9-18-9) placed directly with the seed on growth and development of 0till corn. In 1994, three additional treatments were added to evaluate the effect of low rates of surface applied N materials on 0-till corn. For the second experiment, preplant ammonia was applied at 160 lb N/acre.
Stand counts were taken 14 and 21 days after planting for Experiment 2. Approximately
one month after planting, uniform stands were established by hand thinning both
experiments. At the V-6 stage of growth, whole plant samples were collected
for determination of plant weight and N and P concentration. Ear leaf samples
were collected at silking for N and P analysis and yield was determined by hand
harvesting at maturity.
Experiment 1
In the first year of the study (1993), both N management system and starter fertilizer treatments significantly influenced several of the crop production parameters (Hoeft et al, 1994). However, there was no interaction between N management system and starter fertilizer; the response to starter fertilizer was independent of N management system. Where there was a difference associated with N management system, it tended to be in favor of UAN. This was especially true for early season plant growth and N concentration. At two of the four locations, this early season advantage for UAN did not carry through to a yield advantage. Corn followed soybean at both of these sites. At a third location where corn followed corn, UAN produced significantly higher yield than did sidedressed ammonia, and comparable yield to preplant ammonia. At the fourth location, a corn soybean rotation, UAN produced significantly lower yield than did either preplant or sidedressed ammonia.
Starter fertilizer consistently increased early season plant growth in 1993. At two of the four locations, most of the increase was due to the N, while at Gridley and Oblong, the greatest increase was due to N and P. At two of the four locations- Gridley and Pana- there was no effect of starter fertilizer on grain yield. At the other two locations, the greatest increase in yield came from the addition of N and P, with most of the increase coming from the N.
Similar to the 1993 results, there appeared to be little interaction between N management system and starter fertilizer in 1994.
In contrast to 1993 when preplant UAN tended to produce larger plants at the V-6 stage of growth, preplant ammonia and UAN produced similar plant sizes at most locations in 1994, with sidedressed ammonia having the smallest plants (Table 3). The fact that UAN provided better early season plant growth in 1993, but did not seem to make much difference in 1994 was likely due to the difference in weather between the two years. The cool soils throughout the early part of the 1993 season that resulted in slow mineralization rates along with shallow root systems probably accounted for the advantage to UAN. Under such conditions, an application of N near the surface early in the growing season (such as was the case with preplant UAN) will result in enhanced growth. In contrast, the 1994 season was warm and dry at most locations. Under these conditions, both mineralization rates and root penetration were likely increased.
In 1994, preplant and sidedressed ammonia produced equivalent yields at all four locations (Table 4). Preplant UAN produced the same yield as ammonia at Ashton and Gridley, but at Pana and Oblong, the yield from preplant UAN was significantly lower than from ammonia. In those cases were UAN did not yield as well, weather records indicate that there were at least 5 rain free days following the UAN application. These results confirm the importance of designing N management programs that will minimize N loss.
Starter fertilizer consistently increased early season plant growth in 1993. The same was true in 1994 (Table 5). In both years the greatest increase was due to the addition of N and P with most of the increase coming from N at three of the locations, and from P at the other location (Gridley). Potassium in the starter was a major contributor to yield increase at the Oblong location in 1994. These latter two responses- the P response at Gridley and the K response at Oblong -occurred on the soils with the lowest P and K soil tests, respectively. In 1993, the Oblong location had a low soil test K, but prior to planting, a broadcast application of 120 lb K2O/acre was made.
In 1993, there was a yield response to starter at two of the four locations. Similar to the early growth response, most of the increase was due to N, but the addition of P resulted in a further increase in yield. In 1994, there was a starter response at all locations, with again the majority of the increase associated with N at two of the locations (Ashton and Pana), with N plus P and/or K at Gridley, and with K at Oblong (Table 6). It is interesting to note that the N response occured more frequently when the rotation was continuous corn rather than a corn-soybean rotation. The response to K in the starter occurred only when soil test K was medium to low and only when no broadcast K had been applied. While P response is associated with soil test P--i.e. the best response occurring at low soil test levels-- we have observed a starter P response at very high soil test P levels at the Ashton location.
Since much of the yield response in 1993 was to N, an experiment was started in 1994 to evaluate the effect of low rates (25 lb N/acre) of UAN dribbled beside the row at planting, UAN broadcast at planting, and DAP broadcast prior to planting. While these treatments appeared to give small increases in early season growth (Table 7) and yield (Table 8) at some locations, they did not produce yield as high as those with the same N rate banded below and to the side of the seed.
Experiment 2
Previous research has indicated that placement of 10 lb N+K2O/acre or more with the seed will result in decreased emergence. While that was the case at 14 days after planting at Ashton and Pana, it did not occur at any of the other locations (Table 9). By 21 days after planting, none of the treatments consistently reduced emergence at any of the locations (Table 10). Inclusion of N in the seed placed fertilizer resulted in significantly larger plants at the V-6 stage of growth at Pana and Oblong (Table 11), but did not increase yield (Table 12). The addition of K with the seed resulted in a significant increase in yield at Oblong and Ashton, and a significant yield decrease at Pana.
Urea was more deleterious to emergence when seed placed than was ammonium nitrate at two of the four locations (Table 13-14). This effect also carried through at the Oblong location in early season plant weight (Table 15). However, by harvest when yields were obtained from plots that had uniform stands, urea actually resulted in higher yield at the Oblong location (Table 16). When compared at similar rate of application, there was no difference in emergence, plant weight, or yield between KCl and K2SO4. Emergence was significantly lower with MAP than with DAP at the Pana location, but the reverse was true at the Oblong location. Neither plant weight nor yield was differentially influenced by either MAP or DAP at any of the locations. Use of the low salt 9-18-9 resulted in better emergence and early season plant growth at the Gridley location as compared to 10-34-0, but this effect was not seen in yield.
Results of this study indicate no serious problem with emergence from seed
placed fertilizer. Plant growth responses to seed placed fertilizer were quite
variable, although higher rates of N + K2O (10-201b/acre) generally
increased plant growth similarly to the 2X2 banded treatments. Because plant
response to seed placed fertilizer were less consistent in our experiments than
were responses from 2X2 placement, seed placed fertilizer should be used with
caution until its effects on germination and plant growth are better understood.
Table 1: Effect of tillage on starter response in Indiana
Table 3: Effect of N management system on early season plant growth. 1994
Table 4: Effect of N management system on grain yield. 1994
Table 5: Effect of starter fertilizer on early season plant growth (1994)
Table 6: Effect of starter fertilizer on corn yield (1994)
Table 7: Effect of source and method of N application on early season plant growth. 1994
Table 8: Effect of source and method of N application on corn grain yield. 1994
Table 9: Effect of seed-placed fertilizer on emergence 14 days after planting. 1994
Table 10: Effect of seed-placed fertilizer on emergence 21 days after planting. 1994
Table 11: Effect of seed-placed fertilizer on plant weight at V-6. 1994
Table 12: Effect of seed-placed fertilizer on corn grain yield. 1994
Table 13: Effect of nutrient source of seed-placed fertilizer on emregence 14 days after planting
Table 14: Effect of nutrient source of seed-placed fertilizer on emregence 21 days after planting
Table 15: Effect of nutrient source of seed-placed fertilizer on plant weights at V-6. 1994
Table 16: Effect of nutrient source of seed-placed fertilizer on corn grain yield. 1994
1R.G. Hoeft, E.D. Nafziger, and W.L. Banwart are Professors, K.B. Ritchie is a Jonathan Baldwin Turner Fellow, and L.C. Gonzini and J.J.Warren are Research Specialists, Dept. of Agronomy, University of Illinois.
