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Fluid Journal : Fluid Journal 1999-2001
3 Fluid Journal Winter 2000 206 204 202 Starter Starter + 0.58 lbs/A B Starter + SD Boron Starter + 0.58 lbs/A B+ SD Boron Figure 6. Corn response to 2 by 2 banded N (@ lbs/A), P O (@ 30 lbs/A), and K O (@ 30 lbs/A) fluid starter without and with B, plus 2 lbs/A of B sidedressed. 25 2 208 210 212 214 216 218 Yield - bu/A SD = Sidedress 209 NP NPK Figure 7. Corn response to banded N (@ 13 lbs/A),P O (@ 13 lbs/A), and N ( @ 20 lbs/A), PO(@15lbs/A),KO (@ 30 lbs/A) fluid starters. 25 25 2 KO 2 210 211 212 213 214 215 Yield - bu/A low potassium soils. Cause and Effect Some conditions endemic to this region of the United States are worth citing when it comes to the use of starters. NS deficiency. Sometimes we see general yellowing and slow growth associated with N and S deficiencies. Often the deficiencies are related to unfavorable weather, particularly cold- wet or cold-dry conditions. Plants usually grow out of this deficiency symptom (especially if subsoiling is employed under the row where subsoil clay is within reach of the subsoil shank) but not before yields are adversely affected. Low testing soil. The plow layer in coastal plain soils normally tests low before spring fertilization in several nutrient elements, except P. The more mobile nutrients (N, S, B, and K) were moved out of the plow layer by leaching winter rains. The occurrence of nutrient deficiencies is inversely related to the depth required to penetrate to the subsoil clay. Compaction. In addition to depth to clay, there is the problem of surface compaction and lack of seedling root proliferation toward inter-row areas. A compacted layer just below the plowed depth exists on most soil types in South Carolina. It retards root penetration into the subsoil. This is especially serious on soils having thick sandy surfaces. We have observed that applying nutrients such as nitrogen, sulfur, and boron in the inter-row is not as effective as banding materials near the seed or sidedressing close to the plant row. Delayed responses to starter place- ment are related to time lapse before corn roots reach the subsoil clay and to a lack of penetration into the inter-row because of adverse soil physical characteristics and low moisture regime. South Carolina data show that handing N, P, K, and B near the seed at planting, and sidedressing S close to the plant row produce corn yield responses. Dr. Woodruff is professor emeritus, agronomy and soils, Clemson University. !
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