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Fluid Journal : Fluid Journal 2002-2004
A combination of laboratory/greenhouse and field experiments offers useful information to dealers, producers, and agronomists. Summary: Starter fertilizer formulation and placement studies in 2002 were: 1) effect on corn growth and grain yield, 2) changes in P bio-availability in the soil, and 3) differences in hybrid response. Formulation and placement generally had no effect on corn emergence in 2002, with a mean of 86 percent and values ranging from 78 to 90 percent. The exception was 21 gal/A of 7-21-7, applied as a 4-inch surface band over the row, which decreased emergence. In 2002, no one N:P2O5 ratio or starter placement consistently outperformed all others; however, the highest yields were produced with starters containing more N relative to P2O5. Measurements of P a vailability within the profile were inconsistent. Highest concentration of bio-available P 43 days after application occurred more than four inches below the surface for 15-30-10 (2x0), while application of 60-30-10 (2x0) had little measurable effect. At 68 days after application, changes in P bio-availability probably reflected differences in root proliferation, rather than the effect of a starter fertilizer application. Finally, preliminary results of a pot experiment suggest that two non-transgenic corn v arieties took better advantage of early growing conditions in Clarion silt loam soil than did transgenic isolines. Starter fertilizer has been a key management tool for corn production in the Midwest for many years. During spring planting, low soil temperatures and high soil water content can inhibit corn root growth. Experience and research have shown that starter applications can alleviate nutrient stress, frequently producing a yield response--- particularly in conservation-till systems. Recent studies suggest that both N and P are responsible for early growth responses and grain yield increases, with specific N:P ratios more effective. Research also has shown that N and P stimulate root growth and enhance uptake. Placing N and P together enhances P uptake. In general, starter effectiveness depends on how well it increases the soil's supply of N and available P and how well corn seedlings respond to this increase. Hybrid selection bears on starter effectiveness. Earlier studies in Florida and Kansas reported that 46 to 60 percent of hybrids tested showed a positive response to starters. However, little research has specifically addressed hybrid-starter interactions of transgenic and non-transgenic hybrids. To investigate the interactions of soil supply characteristics and hybrid selection outlined above, laboratory/ greenhouse and field experiments were conducted. Objectives of this research were to evaluate the effectiveness of 7- 21-7 fluid starters in combination with UAN as a corn starter, determine the effect of N:P2O5 ratio on soil supply of P, and determine if P response is hybrid dependent. Starter effects Plant nutrition. Starters generally had no effect on plant emergence in 2002, with a mean of 86 percent and values ranging from 78 to 90 percent. The exception was 21 gal/A of 7-21-7, applied as a 4-inch surface band over the row, which decreased emergence. At mid-silk, both the N and P contents of ear leaves (Table 1) were in the sufficiency ranges of 2.7 to 4 percent for N and 0.25 to 0.50 percent for P, although some values w ere on the low end of the range. However, K content of the tissue was below the sufficiency range of 1.7 to 3 percent. Given that precipitation once again fell below normal during this part of the 2002 growing season, the soil supply of K via diffusion may have been limited. Although soil strength measurements were not made, it also is possible that soil compaction affected K uptake by the root systems. The very high level (200 ppm) of exchangeable K in the soil certainly did not limit K availability. Yield. In 2002, starters produced variable yield effects (Table 2). When 21 gal/A of 7-21-7 was surface-banded over the row, yield decreased. This Se arching For More Effective Corn Starters In Conservation-Till Dr. John Kovar Early Spring 2003
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