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REVIEW

REVIEW. Farmer Practice. N Rich Strip. Response Index variable from year to year in the same field. 2004. 1995. Long term N-P-K Experiment #222 (1969-2004) Dr. Billy Tucker. _. y ±1 δ = 68% of values (2/3 of the population) y ±2 δ = 95% of values y ±3 δ = 99.7% of values . _. _.

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REVIEW

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  1. REVIEW

  2. Farmer Practice N Rich Strip

  3. Response Indexvariable from year to year in the same field 2004 1995 Long term N-P-K Experiment#222 (1969-2004) Dr. Billy Tucker

  4. _ y ±1δ = 68% of values (2/3 of the population)y ±2δ = 95% of valuesy ±3δ = 99.7% of values _ _ = 68% of values -1δ +1δ -2δ +2δ _ y Assume: differences are due to X

  5. Assume: differences are due to X

  6. Gyles Randall, 2006Problems - sidedress N • 1. We have limited equipment for the later SD applications. • 2. We see more and more 20 and 15” rows, which poses a huge problem. • 3. Quick N uptake is problematic, depending on rainfall. • 4. Will yield-drag occur if some “hidden” N deficiency occurs around the VT and R1 stages. • Farmers see these challenges as one big RISK, and risk in today’s environment plays a large role in farmer’s decision making.

  7. Average, 8 Farmer Sites, 04-05 N Rate Yield GP NUE kg/ha kg/ha $/ha % Check 0 2477 293 - SBNRC 43 2644 304 37 RCS 77 2791 303 30 Farmer Practice 127 2911 287 16 SED 379 2005 $0.59 kg N $0.12 kg grain ($0.27/lb N, $3.40/bu)SBNRC (Sensor Based Nitrogen Rate Calculator)

  8. Issues • Corn Weakness - you don't know whether or not this rate will "run out" later in the season.  • Long-term experiments have shown that there are years where the check plot (No N Fertilizer ever applied) produced near maximum yields.  • Have years where the demand for fertilizer N is less (and highly dependent on the environment), and other years where it is cool and dry and the demand for fertilizer N is greater.  • RCS approach can help to determine how much the environment delivers and that is variable year to year  

  9. HISTORY of METHODS for Determining Fertilizer N Rates

  10. 0 50 10 40 20 30 30 N Rate (kg N/ha) 40 N Uptake (kg N/ha) 50 20 60 70 10 80 0 0.2 0.3 0.5 0.6 0.7 0.8 0.4 NDVI Linear NDVI - N rate scale previously used to determine variable N rates based on NDVI. New approach for determining N rate which needs to be further researched.

  11. Red 620-750 nm NIR 750-1x106 nm NDVI = NIR - Red NIR + Red Increased soil background Increased red reflectance Decreased NDVI In this region, NDVI is influenced by (a) color. 0 50 10 20 40 In this region, NDVI is influenced by (a) soil (b) % coverage (c) color 30 N Rate (kg N/ha) 30 40 N Uptake (kg N/ha) 50 20 60 70 10 80 0.2 0.3 0.4 0.5 0.6 0.7 0.8 NDVI

  12. Tipton, January 15, 1998, Feekes 5 Fertilizer N Rate Percent Coverage 35 55 85 NDVI 0.3 0.5 0.7

  13. N Fertilization Strategy Based on Potential Yield (YP0) and Forage N Uptake What about YPN and RI? Fertilizer N Rate ? ? kg/ha kg/ha kg/ha Potential Yield (YP0) 1000 2000 3000 Grain N uptake 25 50 75Forage N uptake 24 35 62Difference 1 15 13Topdress N Rate 1.5 21.4 18.6

  14. Nitrogen Rate Based on RI and Potential Yield RI= high 100 80 60 40 20 0 RI= medium N Rate, kg/ha RI= low 0 1 2 3 4 Potential yield, Mg/ha (INSEY)

  15. 1 3 2001 YPN < YPMAX Predict RI Predict YP0 Predict YPN based on RI Fertilizer N = GNUP-FNUP/0.7 2 2 3 4 1 4

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