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Long-Term N-P-K Experiment Insights: Farmer Practices and Nitrogen Response in Crop Yield

This study analyzes the long-term nitrogen (N) response data from a N-P-K experiment conducted from 1969 to 2004. It highlights the challenges farmers face, such as equipment limitations for later applications, variability in N uptake due to rainfall, and risks associated with hidden nitrogen deficiencies. The findings suggest that fertilizer rates should be adaptable based on environmental conditions and farmer practices, emphasizing the need for further research into new nitrogen rate determination methods using NDVI and response indices.

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Long-Term N-P-K Experiment Insights: Farmer Practices and Nitrogen Response in Crop Yield

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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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