Determination of the Effect of Starter Fertilizer on 0-Till Corn in Illinois

Illinois Fertilizer Conference Proceedings
January 24-26, 1994

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Determination of the Effect of Starter Fertilizer on 0-Till Corn in Illinois

R..G. Hoeft, E.D. Nafziger, and W.L. Banwart¹

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Introduction

Rapid adoption, both voluntary and mandatory, of 0-till planting systems has spurred considerable interest in the use of starter fertilizer. This interest has been further enhanced by marketing programs that have claimed that a small amount of seed placed fertilizer will result in more rapid growth of 0-till planted corn. While there have been several research projects that have demonstrated conditions under which starter fertilizer will be beneficial under conventional tillage, there is very little data available in Illinois or surrounding states that defines the parameters farmers should consider when deciding whether to use starter fertilizer under 0-till conditions. The objectives of this project were (1) 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 seed placed fertilizer on the growth, development, and yield of 0-till corn.

Materials and Methods

Two separate but related experiments were established at 5 locations in Illinois. The locations were selected to give a variation in climatic conditions, soil type, and crop rotation (Table 1). In Experiment 1, three main plot treatments consisted of 160 lb N/acre applied as: 1) ammonia injected preplant; 2) UAN broadcast preplant; or 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 20 lb 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, 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, and an additional 13 treatments comparing sources of nutrients applied directly with the seed. For the second experiment, preplant ammonia was applied at 160 lb N/acre.

Stand counts were taken 14 and 21 days after planting. Approximately one month after planting, uniform stands were established by hand thinning. At approximately 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.

Results and Discussion

Experiment 1

Ashton: N rate and source consistently influenced all parameters measured at this site. The data in Table 2 confirmed visual observations in early July: the plants which received preplant UAN were larger than those which received either preplant or sidedress ammonia. While they also appeared to be greener, there was no difference in N concentration between plants receiving UAN and those with preplant ammonia; both had higher N concentration than plants which received sidedress ammonia (Table 3). Sidedressed ammonia resulted in a significantly higher P concentration than did any of the other N sources (Table 4). Although the P concentration was higher, P uptake was lowest on the sidedress ammonia plots as plant size was smaller. Preplant UAN and preplant ammonia produced similar grain yields, both of which were higher than yields produced by sidedress ammonia (Table 5). Inclusion of N in the starter resulted in significant increases in plant weight and grain yield, but starter P and K did not increase either plant weight or grain yield.

Gridley: Preplant UAN resulted in greater plant weight (Table 6) and P concentration (Table 7) than did either of the other two N treatments, and N concentration equal to that produced by preplant ammonia and greater than that from sidedressed ammonia (Table 8). There was, however, no effect of N source on grain yield (Table 9). Addition of P in the starter increased early season plant weight, and P in combination with N increased early season plant P concentration. However, this latter effect was of no practical significance as the treatment without starter had adequate P concentration for optimum yield. The no-starter treatment produced the highest grain yield.

Pana: Nitrogen source had little influence on any of the variables measured except that the plants grown on the preplant N sources contained a higher N concentration than did those grown on sidedress N (Table 10, 11 and 12). Inclusion of N in the starter treatments resulted in greater plant weight and N concentration and inclusion of P in the starter increased the P concentration. The significant interaction of N source and starter treatment on grain yield appears to be the result of a stimulation of yield when N and P were included in the starter on the UAN treatments, but not when they were included with the ammonia treatments (Table 13).

Oblong: Plant weight at the V-6 stage of growth was significantly higher for the plots receiving UAN than for either of the two ammonia application times (Table 14). At that stage of growth there was no difference in N concentration between preplant ammonia and UAN, but both of them resulted in significantly higher N concentrations than did sidedress ammonia (Table 15). Nitrogen source had no significant effect on P concentration in the small plants (Table 16). Even though plants were larger from UAN application, they ended up yielding significantly less than for either the preplant or sidedress ammonia treatments (Table 17). The most likely explanation for the reduced yield associated with the UAN treatments is that N volatilized from the urea contained in the UAN; the soil surface on which the UAN was applied contained considerable residue from the previous year's wheat crop. Inclusion of N in the starter treatment resulted in a significant increase in both early plant growth (Table 14) and grain yield (Table 17). Phosphorus concentration in the small plants was significantly increased when P was included in the starter treatment (Table 16). Despite this increase, there was no associated effect on yield as the P concentration in the plots without P was above that normally considered to be adequate for maximum crop production.

In this first year of the study, both N source (time of application and carrier) and starter fertilizer treatments significantly influenced several of the crop production parameters. Where there was a difference associated with N source, it tended to be in favor of UAN. This was especially true for early season plant growth and N concentration. Cool soils throughout the early season which resulted in slow mineralization rates along with shallow root systems probably account for this differential effect from N sources observed early in the season. Under such conditions, an application of N near the surface early in the growing season (e.g., preplant UAN) likely will result in enhanced growth. The early season advantage for UAN over sidedress ammonia carried through as a yield advantage at Ashton, though preplant ammonia produced yields similar to those with UAN. At Gridley and Pana there was no difference in yield due to N source. At Oblong, both preplant and sidedress ammonia produced higher yields than did UAN. Starter fertilizer consistently increased early season plant growth. In three of the four locations, the effect was due entirely to the N contained in the starter materials, while at Gridley, addition of P to the starter further enhanced early season growth.

Experiment 2

For convenience of interpretation, the results of this experiment have been separated into two parts. First, we will discuss those treatments designed to evaluate the impact of increasing N, P, and K rates of seed placed fertilizer on crop growth and development (Tables 18, 19, and 20). The second group of treatments include those designed to evaluate the impact of seed-placed sources of N, P, and K on crop growth and development (Tables 21, 22, and 23). Treatments consisting of fertilizer banded 2 inches below and to the side of the seed (Tables 18, 19, and 20) are used as a comparison for both sets of treatments.

Previous indications that placement of more than 10 lb N +K₂O with the seed will result in decreased emergence were not supported by our results. Nutrient sources of ammonium nitrate, concentrated super phosphate, and potassium chloride did not consistently reduce emergence, even with rates as high as 20 pounds per acre of N+K₂O (Table 18). The differences in emergence were inconsistent within any location and across locations. The 2 by 2 placement of the fertilizer consistently resulted in the highest weight of plants at the V-6 stage of growth as compared to any of the seed placed treatments or the control (Table 19). Several of the seed placed treatments resulted in significant increase in plant growth at the Ashton and Oblong locations. The addition of 10 lb N/acre in the seed placed treatments resulted in a significant increase in crop yield at the Ashton location (Table 20). At the other locations, neither seed placed nor 2 by 2 placement of the fertilizer resulted in a significant increase in crop yield.

No consistent effect of nutrient source on seedling emergence was observed across locations (Table 21). MAP significantly reduced emergence at the Ashton and Oblong locations, but had no effect at the other locations. At Oblong, the highest rate of DAP significantly reduced emergence. At Springfield, Pana, and Oblong, the combination of urea with potassium chloride resulted in a significant reduction in emergence. At four of the five locations, nearly all of the nutrient sources increased early season plant weight (Table 22). The exception was that none of the 9-18-9 treatments increased plant weight at Ashton, Gridley, or Springfield. At Oblong, all three of the 9-18-9 rates increased plant weight. At the Ashton location, all nutrient sources increased grain yield except for the two low rates of 9-18-9 and the low rate of 10-34-0 (Table 23). At Gridley, application of DAP as well as all liquid materials decreased grain yield as compared to the control. None of the treatments evaluating nutrient source influenced grain yield at Springfield, Pana, or Oblong.

Results from the first year of this study indicate no serious problem with emergence from seed placed fertilizer. However, the lack of consistent yield increases associated with seed placed fertilizer and the occasional indication of decreased yield indicate that seed placed fertilizer should be used with extreme caution.