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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Spring 2002 3400 3350 3300 3250 3200 3150 3100 3050 Yield - lbs/A Broadcast Check 20+0+0 20+20+0 20+20+1 20+20+1 N+P+Zn Figure 1. Yield and maturity response of dry beans to starter fertilizer applications, average of two years (1994-1995), two cultivars, four planting dates and four replications. Summary: Numerous studies have documented crop responses to N, P, K, and S in starters. But micronutrients have received less attention as components of starter applications. The purpose of this article is to provide some examples of how starters can be used to enhance the effectiveness of micronutrient fertilizers. Opportunities exist to improve crop response to micronutrients by combining them with starter fertilizer applications. Starters can improve early growth and root development, hasten maturity, and improve yields under a variety of conditions. Crops planted early in cool soils particularly seem to benefit from starters. Studies have demonstrated improved micronutrient response in starters for a variety of reasons. Under soil conditions that potentially reduce nutrient availability from broadcast fertilizers, starter applications may: 1. Produce superior micronutrient response by concentrating nutrients in a band where probability of root interception is greater 2. Produce root exudates that enhance nutrient availability 3. Place nutrients in a chemical environment that favors less rapid fixation. Root interception is a critical factor in uptake because several of the micronutrients are immobile in soils. Early root development of many crops is slow, especially with early plantings in cold, wet soils. Banding close to the row under these environmental conditions greatly increases the chance of roots contacting these balky nutrients. Additionally, banding N and Dr. Alan Blaylock Micronutrient Response Enhanced By Fluid Starters Mixed solutions create intimate contact between nutrient compounds in the various carriers combined. P to stimulate root proliferation in and around the fertilizer band further increases the amount of root length available for nutrient uptake. Many plants secrete compounds from their roots that can solubilize unavailable micronutrient compounds and increase uptake. Band placing micronutrients in the root zone increases the probability of nutrient contact by roots, which also increases the effectiveness of these secreted compounds. Increased solubility caused by the exudates, in turn, in-creases diffusion through the soil by creating a greater concentration gradient around the fertilizer zone and increases the volume of soil enriched by the fertilizer. Zinc response/net return The potential for enhanced micronutrient response through placement with starters was demonstrated in a three-year dry-bean study in Wyoming. Zinc applied with N and P in a 2 x 2 starter produced significant yield increases over N and P without Zn (Figure 1). The same N-P-Zn combination broadcast before planting produced no response. Early growth and development were improved by starter application, leading to greater yield potential and greater partitioning of photosynthates to the seed during pod fill. In spite of the fact that the field had a high DTPA-extractable soil Zn (2.7 to 3.8), other conditions that compounded the probability of response to starter Zn were: 1.SoilpHat7.7to8.0 2. Low soil organic matter (1.1 to 1.6%) 3. High N supply
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