Illinois Fertilizer
Conference Proceedings
January 21-23, 2002
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R.G. Hoeft, E.D. Nafziger, L.C. Gonzini, J.J. Warren,
E.A. Adee, L.E. Paul, and R.E. Dunker1
Strip tillage, a system where residue is removed and small ridges are formed in the fall in the position of next year's rows, has been developed in an attempt to overcome the adverse effects of cool wet soils often observed in 0-till corn production. Ammonia is usually injected into the small ridges at the time of their formation. Several farmers have successfully used this system. This project was designed to determine whether the benefit from the system was due to warmer-drier soils, the presence of nitrogen near the seedbed, or a combination of the two. The impact of starter fertilizer in combination with strip tillage was also evaluated.
To accomplish the objectives, experiments were conducted at DeKalb, Monmouth, and Urbana, Illinois. At each location, a factorial experiment was conducted to evaluate the effect of tillage (conventional, strip till, and 0-till), time (fall versus spring) and placement (under versus between rows) of N, and starter fertilizer on corn yield. Additional treatments were included to determine if surface-applied P and K was equivalent to P and K injected into the strip-till band.
When averaged across all locations, the data showed no difference due to tillage
system, placement or time of N application, or starter fertilizer. One should
not construe the results of these two years of experiments to imply that strip
tillage may not be advantageous. The 1999 and 2000 growing seasons were characterized
with very early warm temperatures, which resulted in nearly identical temperatures
in the seeding zone irrespective of tillage system by the time corn could be
planted. In most years, soil temperatures would be expected to be warmer in
conventional tillage and in the strip-till zones than in 0-till seeding zones.
Under those conditions, emergence and early season plant growth would be expected
to be lessened under 0-till conditions.
Slower germination and early season plant growth of no-till corn have prompted farmers and researchers to look for innovative, low-cost techniques that would allow them to retain the advantage of no-till while overcoming these disadvantages. Earlier work funded by FREC has clearly shown that the addition of an N- and P-containing starter fertilizer will increase no-till corn yield on most fields (Ritchie et al., 1996). However, even with use of this yield-enhancing treatment, early season growth on no-till fields is still slower than on conventionally tilled fields.
Cooler soil temperatures and wetter soils associated with no-till fields are the primary factors responsible for the slower early season growth. In an attempt to overcome these adverse factors, farmers have developed a system called strip tillage that allows them to apply their N in the fall, while at the same time creating an improved environment for spring planting. Special application equipment moves the residue from the row area, applies ammonia, and covers that application band with a small ridge in which next year's crop will be planted. Creation of the ridge allows the seed row area to dry sooner in the spring, and, since the residue has been removed, soil temperatures should approximate those in conventional tillage.
While strip tillage has been successfully used by several farmers, there are still questions that can only be answered through a scientifically designed study. These questions include:
Is the benefit from strip tillage associated with the improved seedbed (warmer and drier seedbed) or from the presence of N in a band near the seed, or both?
Will starter fertilizer in combination with strip tillage result in yield equivalent to that under conventional tillage?
Is placement of ammonia directly under the row a safe and effective method of N application?
While there is considerable data on the impact of ammonia fertilizer placement, only limited data exists on the impact of strip tillage on yield (Peterson et al., 1997), and this project did not explore the impact of ammonia with the strip tillage. Therefore, this research offers an opportunity to provide new research information for no-till producers to use in their decision making process. Refinement of strip tillage techniques offer the potential for producers to obtain the benefits of no-till while overcoming the disadvantage associated with high residue over the row.
The objectives of the project are to evaluate the effect of strip tillage with and without ammonia application in the fall as compared to conventional tillage and 0-till, and to evaluate the effect of starter fertilizer on the three tillage systems.
Experiments were established in the fall of 1998 and 1999 at Urbana, DeKalb, and Monmouth, Illinois. The previous crop at each location was soybean. A split plot experiment with tillage as main plot and a factorial combination of time of ammonia application by ammonia placement as subplot was established. Treatments consisted of conventional till (two-pass tillage in the spring after ammonia application), 0-till, and strip till; two times of ammonia application (fall and spring); and two ammonia placement positions (under row and between row). Each experimental unit was eight rows by 50 feet. When the corn was planted in the spring, four of the eight rows of each plot received a 2 x 2 placed starter application of 21-19-0, and the other four rows received no starter. Two treatments were added to the study to evaluate the effect of P and K injected into the ridge as compared to broadcast over the surface. At Urbana, two additional treatments were established in the spring to evaluate the effect of ammonia placement under the row versus between the rows on spring strip tillage.
Emergence counts and plant height were taken, and all plots were thinned to
a uniform population at approximately the V-4 stage of growth (Table
1). Grain yield was determined at maturity.
In six of the eight site-years of the study, placement of ammonia under the row resulted in significant increases in emergence as compared to injection of the ammonia between the rows. These differences were small, ranging from 1 to 3 percent, and were likely the result of a slight improvement in the seedbed caused by the tillage done by the knife. When averaged over all eight site-years, there was no difference in emergence due to ammonia placement. There were no significant differences in emergence (averaged over eight site-years) due to other treatments such as tillage, starter, or time of ammonia application (Table 2).
We had postulated that the use of strip till might result in somewhat higher soil temperature in the strip as compared to 0-till, and, thus, it might result in increased early season emergence and plant height. Other research has shown substantial soil temperature differences between 0-till and conventional till plots in most years. The three years of this study were unusually warm in the early spring, and, by planting time, there was no difference in soil temperature between tillage systems.
While there was a significant (although not agronomically important) difference in emergence between plots that had received ammonia directly under the row as compared to the middle of the row, we still do not recommend injection of ammonia in the spring directly in the strip till due to the potential for seedling damage. We have observed, on rare occasions, reduction in emergence associated with fall application of ammonia into the strip-till ridge. Conditions under which this may happen appear to be injection of ammonia into a wet soil followed by rapid soil drying and a very dry seedbed in the spring. Under those conditions, the sidewall compaction of the ammonia knife seals the ammonia into a small zone. Upon drying, the soil tends to crack along the knife track, and the ammonia moves up into the seed zone.
The addition of starter fertilizer resulted in increased early season growth, as measured by plant height, at all eight site-years. Overall, there was an 8 percent increase in height (1.1 inches) when starter was used (Table 3).
In a few cases, there was an interaction between starter and ammonia placement, with the starter advantage being greater when the ammonia was injected between the rows as compared to when it was injected under the row. This interaction is probably the result of slightly warmer soils where the ammonia knife had cleared the residue away from the seed row combined with tillage that likely resulted in enhanced mineralization in the area immediately surrounding the roots of the seedlings. The earlier work by Ritchie et al. (1996) demonstrated that nitrogen was the most important element in starter for 0-till corn. That being the case, procedures that release nitrogen in the rooting zone may obviate a portion of the benefit from starter.
In a few cases, tillage had a significant influence on early season plant height. Generally, 0-till had the smallest plants, while those from conventional and strip-till were about the same size.
Very good yields were obtained at all locations in each year of the study (Table 4), with no consistent differences in yield due to tillage (Figure 1), starter fertilizer (Figure 2), N placement (Figure 3), or time of N application (Figure 4). Lack of response to starter fertilizer was not surprising, as initial soil test levels for P and K were adequate for optimum production.
Placement of nitrogen under the row as compared to between the rows could be advantageous in some years if it provides a starter effect. This benefit would be most probable under conditions of cool soil temperatures in the early growth period, conditions that did not exist during the experimental period. Soil drainage at each of the sites was adequate for the amount of precipitation received to prevent the loss of N via denitrification or leaching, and, thus, there was no difference in yields between fall- and spring-applied N. Had precipitation been excessive in the spring at any of these locations, there is a potential that spring-applied N would have produced yields significantly higher than fall-applied N.
Table 1. Characteristics of the experimental sites.
Figure 1. Effect of tillage on average yield across eight site-years of study.
Figure 2. Effect of starter fertilizer on average yield across eight site-years
Figure 3. Effect of ammonia placement relative to corn row on average yield across eight site-years
Figure 4. Effect of time of ammonia application on average yield across eight site-years
1 R.G. Hoeft and E.D. Nafziger are Professors; L.C. Gonzini, J.J. Warren, and E.A. Adee are Senior Research Specialists; and L.E. Paul and R.E. Dunker are Agronomists, Dept. of Crop Sciences, University of Illinois.
Petersen, W.L., R.E. Dunker, C.A. Bradley, D.S. Mueller, and J.C. Siemens. 1997. Evaluation of fall and spring strip-till as an alternative to no-till for corn. Agron. Abstr. p. 111. Amer. Soc. Agron. Madison, WI.
Ritchie, K.B., R.G. Hoeft, E.D. Nafziger, W.L. Banwart, L.C. Gonzini, and J.J. Warren. 1996. N management and starter fertilizers for no-till corn. In R.G. Hoeft (ed.) Illinois Fertilizer Conference Proceedings. Univ. of Il., Urbana, IL. pp 55-65.
