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Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings Publication Acceptance Date: 2/18/2003 Publication Date: 2/18/2003 Citation: KOVAR, J.L. EFFECTIVE STARTER FERTILIZERS FOR CORN IN CONSERVATION TILLAGE SYSTEMS. FLUID FERTILIZER FOUNDATION SYMPOSIUM PROCEEDINGS. 2003. V. 20. P. 230-240. Interpretive Summary: Early in the growing season, cool soil temperatures often limit the ability of corn roots to absorb sufficient nutrients and water. An application of a small amount of fertilizer at the time of planting may overcome this problem, leading to better plant growth and higher grain yields at the end of the season. With a field experiment, we found that nitrogen and phosphorus fertilizers applied in or near the seed furrow had no negative effect on seed germination. Fertilizer mixtures with more nitrogen relative to phosphorus boosted early growth of the crop, as well as corn grain yields. A lack of adequate rainfall during the middle of the growing season probably limited the effect to some extent. Nevertheless, the results suggest that this production practice is an inexpensive and environmental-friendly way to promote maximum soil productivity, which will certainly benefit those involved in production agriculture. Technical Abstract: Recent research has shown that application of starter fertilizer may alleviate nutrient stress associated with poor root growth early in the season, which can result in a yield response. Several studies suggest that both nitrogen (N) and phosphorus (P) are responsible, with specific N:P ratios being more effective. To investigate further, field plots were established on a Canisteo silty clay loam soil in central Iowa. The starter fertilizer treatments were: i) control; ii) 6-20-0 (5 gal/A 10-34-0), in-furrow; iii) 6-20-6 (8.7 gal/A 7-21-7), in-furrow; iv) 14-48-0 (12 gal/A 10-34-0) 4-in. surface band over row; v) 16-48-16 (21 gal/A 7-21-7) 4-in. surface band over row; vi) 15-30-10, dribbled over row and 2x0; vii) 30-30-10, dribbled over row and 2x0; viii) 45-30-10, dribbled over row and 2x0; and ix) 60-30-10, dribbled over row and 2x0. Starter fertilizer generally had no effect on emergence, with a mean of 86% and values ranging from 78% to 90%. The exception was Treatment 5, in which 21 gal/A 7-21-7 applied as a 4-in. surface band over row, decreased emergence. The N, P, and potassium (K) contents of plants at the 4- to 5-leaf stage were in the optimum range; however, at mid-silk, the K content of the ear-leaf tissue was below the sufficiency range of 1.70% to 3.00% for all treatments. Given that precipitation was below normal during this part of the growing season, the soil supply of K via diffusion may have been limited. 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. The overriding yield-limiting factor was likely available soil water. In addition to the crop measurements, movement of bioavailable P from the application band into the soil profile was evaluated at 43 and 68 days after application. The highest concentration of bioavailable P at 43 days after application was found at a depth of more than four inches below the surface for the 15-30-10 (2x0) starter treatment, while application of the 60-30-10 (2x0) starter material had little measurable effect. At 68 days after application, the highest P concentration was measured at a depth of less than two inches below the surface for the 15-30-10 starter treatment, and at a depth of more than three inches below the surface for the 60-30-10 treatment. Finally, preliminary results of a pot experiment suggest that two non-transgenic corn varieties were better able to take advantage of the growing conditions in Clarion silt loam soil than were the transgenic isolines. |
