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Fluid Journal : Fluid Journal 2005-2007
18 Fluid Journal SPRING 2007 Seven Year Average (All Crops) Dalhart (1999-2005) Quantity (lb/A) 0 2000 4000 6000 8000 10000 12000 14000 N1 N2 Grain Residue Residue C Texline (1999-2005) Grain Residue Residue C Figure 1. Average annual grain, crop residue, and residue carbon yields at Dalhart and Texline from 1999 through 2005. received no irrigation water in 2005 after corn tasseling. Average grain yield for all crops from 1999 through 2005 is shown in Figure 1. The average amount of corn and wheat residue returned to the soil for the N1 and N2 sites was 8,915 and 8,376 lbs/A, respectively (Figure 1). Adding wheat to the rotation in 2003 resulted in reduced residue production and residue carbon. Residue carbon concentration has averaged 45 percent with a seven- year average above-ground residue carbon and N input to the soil of about 4,004 and 3,732 lbs/A of carbon and 63 and 81 lbs/A of N per year for the N1 and N2 treatments, respectively (Figures 1 and 2). The N concentration of the residue averaged 0.70 and 0.97 percent, respectively. Texline. At Texline, combine- harvested yield for the fields averaged 218 bu/A in 2005. Hand-harvested corn grain yields averaged 258 and 228 bu/A in 2005 for the N1 and N2 sites, respectively. Seven Year Average (All Crops) Dalhart (1999-2005) Units 0 10 20 30 40 50 60 70 80 90 100 N1 N2 C/N ratio Residue N (lb N/A) Residue N (lb N/A) Residue C/N ratio Texline (1999-2005) Figure 2. Average annual residual N content and carbon/nitrogen ratio at Dalhart and Texline from 1999 through 2005. From 1999 to 2005, hand-harvested corn grain yields averaged 226 to 210 bu/A for the N1 and N2 treatments, respectively (Figure 1). The N2 sampling sites are located on a steeper sloping area of the field than the N1 sampling sites. This may have caused the slightly lower grain yields on the N2 sites compared to the N1 sites. Estimated corn residue amounts returned to the soil averaged 11,127 and 10,989 lbs/A for the N1 and N2 sites, respectively (Figure 1) with an
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