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Fluid Journal : Fluid Journal 1993-1995
Winter 1995 Yield (bu/A) Broadcast Band 140 130 120 110 100 90 80 70 50 100 50 100 N rate --- lbs/A Figure 4. Nitrogen management effects on no-till sorghum yield, Lamond et al., 1991. Dry Matter (lbs/A) Broadcast Band 1,200 1,050 900 750 600 450 300 150 Check 15 45 Phosphate rate --- lbs/A Figure 5. Early no-till winter wheat growth response to phosphate rate and placement, Havlin et al., 1990. Table 2. Nutrient stratification in western Iowa soils. Organic Depth matter NO3N P K S Zn A (0-3") 2.8% 23 84 231 8.0 4.6 B (3-12") 1.7% 7 15 135 0.1 2.0 C (12-24") 2.2% 6 9 146 0.1 2.0 Clay loam, dryland near the surface. A possible solution is the "ABC" method of sampling where three samples are taken from three zones (Figure 3). The "A" zone could be 0 to 3 inches, the "B" 3 to 12 inches, and the "C" 12 to 24 inches. It makes good sense to evaluate at least the A and B zones and knife fluid fertilizer down where the roots grow. Nitrogen. N placement can significantly influence crop growth and yield, espe- cially on high-residue cropping systems. Our no-till studies showed that subsur- face band application of N significantly increased sorghum grain yield compared to broadcast (Figure 4). Although not measured directly, the enhanced yield response was likely due to reduced N immobilization, denitrification, and/or volatilization. Phosphorus. We quantified phosphate rate and placement effects on no-till early winter wheat growth in central Kansas. Compared to broadcast phosphate, the number of tillers, dry matter yield, and phosphate uptake were much greater with band-applied phosphate (Figure 5). The dramatic early growth response to band-applied phosphate was likely due to cool soil temperatures in the fall that reduced phosphate diffusion rate and root growth. Although this early growth response to phosphate placement is critical for maximizing grain yield in areas where the major economic return from winter wheat is realized through grazing, substantially more biomass would be available with band-applied phosphate. Over the last several decades extensive placement research has been conducted with often contrasting results. For example, numerous factors affect crop response to phosphate placement that include a) soil test phosphate level, b) root contact with fertilized soil, c) phosphate concentration in the fertilized soil solution, and d) environmental factors. Root contact with fertilized soil is influenced by total root length, volume of soil fertilized, and location of the fertilized soil in relation to plant roots. In addition to agronomics, the availability of equipment, labor, fertilizer source, and operating capital are other common factors affecting phosphate placement decisions. Groundwater quality. The impact of N fertilizer on groundwater quality has become a major concern for the public and fertilizer industry. Adoption of N fertilizer "best management practices" can significantly minimize NO3- contamina- tion of groundwater. The N management studies in no-till sorghum described earlier showed significantly greater recovery of N fertilizer when applied below the soil surface. Dr. Havlin is associate professor in the Department of Agronomy at Kansas State University and L.W. Lohry chairman of Nutra-Flo Company in Sioux City, IA. !
Fluid Journal 1996-1998