Illinois Fertilizer
Conference Proceedings
January 24-26, 2005
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E.D. Nafziger, Eric Adee, R.E. Dunker, and L.E. Paul 1
Recent high yields recorded by Francis Childs in Iowa and by others have usually been from fields where corn is grown continuously. This has resulted in support for the idea that such yields may be high because corn follows corn. There is no known research data supporting this idea; our recent work in Illinois shows that in direct comparisons, corn following corn produces 7 to 10 percent less yield than corn following soybean. Still, on the most productive fields, continuous corn can certainly produce high yields. However, inputs needed to produce such yields must be investigated and rationalized.
While we have accumulated a considerable amount of data on the nitrogen response of corn following corn compared to that of corn following soybean, we do not know the effects of some of the "high yield practices" used by some producers, including those producers who are attempting to approach yields of 400 bushels per acre. Such practices typically include deep and thorough fall tillage, high N rates, and high plant populations. Most fields also have high to very high P and K levels, usually as a result of high inputs from fertilizer and/or manure over a period of years.
While this set of practices clearly results in high yields, it is possible, or even likely, that some of these practices may contribute little or nothing to yield. This study is designed as a way to isolate the effects of deep tillage, additional plant nutrient supply, and higher plant population on yield at a number of productive sites in Illinois.
Trials were established in 2004 at at four University of Illinois Research and Education Centers operated by the Department of Crop Sciences:
Treatments were a 2 × 2 × 2, split-split-plot factorial design, arranged in a randomized complete-block design with 4 replications. The previous crop was corn. Main plots consisted of 1) fall chisel plow following corn and 2) deep tillage using a modified mini-moldboard or another tillage tool capable of soil disturbance to a depth of about 15 inches. Subplots consisted of two levels of fertilizer: 1) normal amounts of P and K according to soil test values and 220 lb of N in the spring, and 2) an additional increment of 80 lb P2O5 and 150 lb K2O per acre annually, and an additional 100 lb N in the spring, for a total of 320 lb N. Sub–subplots consist of two final plant populations – 32,000 and 40,000 per acre, established after emergence following planting about 45,000 seeds per acre. Sub-subplots were at least 8 (30–inch) rows wide by 60 ft long. Yields within each sub–subplot will be taken by machine harvest of the center 4 rows.
The 2004 cropping season in Illinois was almost ideal, with very high yields in most areas, and, in general, high yields in corn following corn compared to corn following soybean, at least at higher rates on N (see Nafziger et al., report on FREC project 190 in this Proceedings). The trial at the DeKalb location was lost due to flooding in May 2004, and a planting error at Urbana allowed us to establish only the lower plant population (32,000 per acre), so did not allow us to test the effect of plant population. Yields were high at the t hree locations, however, averaging 201, 239, and 224 bu⁄acre at Monmouth, Urbana, and Perry, respectively.
At Monmouth, deep tillage (with a mini–moldboard plow) increased yield significantly, by 32 bu⁄acre, extra fertilizer increased yield by 7 bu/acre, and raising the population from 32 to 40 thousand per acre decreased yield by 11 bu/acre ( Table 1). All of these (main) effects were significant, but none of the interactions were significant for yield. There was a very large effect of tillage on lodging, with 48% of plants lodged in chisel–plowed plots and only 8% lodged where plots were deep–tilled. Fertility did not affect lodging, but the higher population increased lodging, and this effect was more pronounced in chisel–plowed plots. At Urbana, tillage did not affect yield significantly, while extra fertilizer increased yield by 18 bu/acre (Table 1). At Perry, neither tillage nor plant population had a significant effect on yield, while higher fertilizer rates increased yield by 8 bu⁄acre (Table 1) In contrast to Monmouth, there was little lodging at either Urbana or Perry.
1 E.D. Nafziger is Professor, E. Adee is Principal Research Specialist, and R.E. Dunker and L.E. Paul are Agronomists, Dep. of Crop Sciences, Univ. of Illinois, Urbana, IL.
