Illinois
Fertilizer Conference Proceedings
January 27-29, 2003
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K.S. Guebert, 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 soil; 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 objective, 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 striptillage band.
When data was run as a complete data set including all years and locations, there were no differences in yield due to tillage system, N timing, or N placement. Starter fertilizer increased yield 2.2 bushel/acre. Emergence differences were observed for tillage, N timing, and N placement. These differences were small (1 to 2 percent). Early height differences were observed for N placement and starter fertilizer (0.5 to 1.5 inches). One should not construe the results of these experiments to imply that strip tillage may not be advantageous. Most locations experienced warm conditions that resulted in 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 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 0-till corn have prompted farmers and researchers to look for innovative, low-cost techniques that would allow them to retain the advantage of 0-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 0-till corn yield on most fields (Ritchie et al., 1996). However, even with use of this yield-enhancing treatment, early season growth on 0-till fields is still slower than on conventionally tilled fields.
Cooler soil temperatures and wetter soils associated with 0-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 several farmers have successfully used strip tillage, questions still exist that can only be answered through a scientifically designed study. These questions include:
1. Is the benefit from strip tillage associated with the improved seedbed (warmer and drier seedbed), from the presence of N in a band near the seed, or both?
2. Will starter fertilizer in combination with strip tillage result in yield equivalent to that under conventional tillage?
3. Is the placement of ammonia directly under the row a safe and effective method of N application?
4. Does fall strip tillage remove the advantage provided by starter fertilizer?
While there is considerable data on the impact of ammonia fertilizer placement, only limited data exist on the impact of strip tillage on yield (Peterson et al., 1997), and this project did not explore the impact of ammonia with strip tillage. Therefore, this research offers an opportunity to provide new information for 0-till producers to use in their decision-making process. Refinement of strip tillage techniques offers the potential for producers to obtain the benefits of 0-till while overcoming the disadvantages associated with high residue over the row.
The objectives of this project were 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, 1999, and 2001 in Urbana, DeKalb, and Monmouth, Illinois and in 2000 in Urbana and Monmouth. The Urbana location established in 2001 was abandoned prior to harvest due to severe lodging. 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 passes in the spring following ammonia application), 0-till, and strip tillage; two times of ammonia application (fall and spring); and two ammonia application placements (under row and between rows). Each experimental unit was eight rows by 50 feet. When corn was planted in the spring, four of the eight rows received a 2x2 placed starter fertilizer 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 heights 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. Data for the 10 site-years of
yield data and 11 site-years of emergence and plant data were analyzed as a
complete set.
Tillage significantly affected emergence at the 0.05 level, N timing at the 0.1 level, N placement at the 0.01 level, and an interaction of tillage by N placement at the 0.1 level. Strip till, 0-till, and conventional tillage had emergence percentages of 90.6, 89.5, and 88.8, respectively. Fall and spring N timings had emergence percentages of 90.0 and 89.3, respectively. Under and between N placements had emergence percentages of 90.5 and 88.7, respectively. Strip till with N placed under the row had the highest emergence percentage at 91.1; conventional tillage with N placed between the rows had the lowest at 88.0 (Table 2).
From an agronomic standpoint, these small differences in emergence are of little significance. In fact, some of them are difficult to explain. For example, there is no logical reason why ammonia placed under the row should provide enhanced emergence, or why there should be higher emergence from fall- rather than spring-applied nitrogen.
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 emergence and plant height. Other research has shown substantial soil temperature differences between 0-till and conventional till plots in most years. The four years of this study were unusually warm in the early spring (Table 3), and, by planting time, there was no difference in soil temperature between tillage systems.
While there was 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 zone due to the potential for
seedling injury. We have observed, on rare occasions, reduction in emergence
associated with fall application 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.
Plant Height
Plant height was significantly affected by N placement, starter, and an interaction of N placement by starter at the 0.01 level in all three cases. Nitrogen placement under the row and starter fertilizer resulted in height increases of 0.6 and 1.5 inches respectively. All combinations of N placement and starter fertilizer were significantly different from one another. Nitrogen placement under the row and starter resulted in the tallest plants on average, and N placement between the rows and no starter fertilizer resulted in shortest plants on average, with a difference of 2.0 inches (Table 4).
The increase in plant heights due to placement of ammonia under the row was
probably the result of slightly warmer soils where the ammonia knife had cleared
residue from the seed row and increased availability of nitrogen in the root
zone. 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. However, starter fertilizer still provided an increase
in plant height even when ammonia was placed under the row. Therefore, starter
fertilizer may be beneficial even when ammonia is placed under the row.
Yield
No significant differences in yield were seen due to tillage (Figure 1), N timing (Figure 2), or N placement (Figure 3). Starter significantly increased yield at the 0.1 level by an average of 2.2 bushels (Figure 4). There was a significant interaction of tillage and N placement at the 0.1 level. N placement between rows yielded 2.7 and 3.5 bushels higher in conventional tillage and 0-till respectively, but no difference was seen in the strip-till treatments (Table 5).
Placement of N under the row as compared to between the rows may 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 generally 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.
Injected P and K
Injecting P and K into the ridge had no effect on yield, emergence, or plant
heights as compared to surface-applied P and K. All sites had adequate soil
test levels for optimum yields. Lower than optimum P and K levels may have resulted
in yield increases.
Spring Strip Tillage
Spring strip tillage did not result in yield that was significantly different
from that of fall strip tillage. Spring strip tillage had significantly higher
emergence than fall strip tillage at the 0.1 level by an average of 1.6 percent.
Fall strip tillage had significantly higher plant heights at the 0.1 level by
an average of 0.9 inches. With the lack of differences in soil temperature between
tillage treatments, it is doubtful that agronomically important differences
could be found between spring and fall strip tillage, unless a growing season
with extreme weather conditions was experienced.
Table 1. Characteristics of the experimental sites
Table 3. Average soil temperatures for one week after planting
Figure 1. Effect of tillage on average yield across 10 site-years
Figure 2. Effect of time of ammonia application on average yield across 10 site-years
Figure 3. Effect of ammonia placement relative to corn row on average yield across 10 site-years
Figure 4. Effect of starter fertilizer on average yield
across 10 site-years
1K.S. Guebert is a graduate student; 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; Department 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 corn. Agron. Abstr. P111. 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.
