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Why by-plant resolutions will be necessary in precision agriculture. 1992, At What Resolution are there real biological differences. Target plant acquired over 70% of the total depleted 15N fertilizer that was taken up
Target plant acquired over 70% of the total depleted 15N fertilizer that was taken up
data revealed an individual corn plant acquires most of its N from within a radius of less than 0.5 m.
Timely emergence impacts a plant's potential to achieve maximum yield.
Plants lose yield potential by emerging as little as three days after their neighbors.
Large doses of N fertilizer could not increase the yield of late emerging corn plants.
Small spatial resolution N management techniques should be focused on determining the N demand of the early emerging plants.Paul Hodgen, Univ. Nebraska, Dissertation AA13271926, Jan 1, 2007
Plant-to-plant variation, avg. 45 bu/acNebraska, Iowa, Virginia, Oklahoma,
Argentina, Mexico, Ohio
37 ± 9 bu/ac
Farmer fields in the USA, Argentina, and Mexico showed that over all sites, plant-to-plant variation in corn grain yield averaged 2765 kg ha-1 or 44.1 bu ac-1 (Martin et al., 2005).
Hodgen et al. (2007) showed that if corn plants are delayed by as little as four days, the yield depression of that individual delayed plant was as much as 15 percentSummary
2010, 1.54 billion bushels, Nebraska
2009, 159 bu/ac
Days from planting to sensing
•double seed drops
•seed geometry within the furrow
•random soil clods
•soil texture differences
•variable distance between seeds
•variable soil compaction around the seed
•variable surface residue
•variable seed furrow closure
early season root pruning (disease, insect)Causes for Delayed and uneven emergence
Yield increase up to 27.1% and 30.6% (prostrate and erect hybrids respectively at pop 74,100 plants/ha) when compared to random placement
Comprehensive work from transects sampled all over the world have shown that the average difference in corn grain yield when determined by plant, averaged 44 bu/ac. This included corn hybrid data from farmer fields in Nebraska, Ohio, Virginia, Iowa, Mexico, and Argentina (http://nue.okstate.edu/Index_Publications/Plant_toPlant.htm). This exact same result was encountered in high and low yielding environments. Because plant to plant differences in yield are common and incredibly large, there is significant room for improving nutrient management, especially since N demands by plant are equally as variable. Because variable plant to plant N demands can be managed on-the-go using GreenSeeker sensing technology and advanced spraying systems, research programs like that at Oklahoma State University must deliver improved N management practices. This has become more important when considering that nitrogen use efficiencies are so low, all over the world.
Predicting the Potential Response to Applied N
Yield Potential Achievable with Added N Fertilization (YPN)
Generating a Fertilizer N Rate RecommendationCurrent approach of determine sensor-based in-season N fertilization
Lignin and Tannins
Short Wave Infrared
Expression of Variability
Errors Associated with By-Plant Yield
Corn Grain Yields Averaged over Larger Scales
Errors in Corn Grain Yields from Larger ScalesWhy by-plant resolutions will be necessary in precision agriculture
variable depth of planting
double seed drops
seed geometry within the furrow
random soil clods
soil texture differences
variable distance between seeds
variable soil compaction around the seed
variable surface residue
variable seed furrow closure
volunteerearly season root pruning (disease, insect)
The impact of uneven stands takes place prior to the time that irrigation is employed whether using surface/furrow or center pivot systems.Causes for the Large Differences in By-Plant Corn Grain Yields
Of the 159,531,007 hectares of maize in 2009, there were approximately 34,409,010 hectares in the developing world. Of that total, around 60% was planted by hand, representing just over 20,645,000 hectares or 13% of the total maize area in the world (www.faostat.org. Web 24 Sept. 2010).
If single seeds could be planted 14-17 cm apart, much like conventional planters accomplish in the developed world, production levels could easily increase 25%.
Despite the fact that third world maize yields are generally less than 2.0 Mg/ha (Dowswell et al., 1996), this 25% yield increase on 60% of the hand planted maize area in the third world would be worth more than 3 billion dollars/year (corn price at $0.3/kg)
20,000,000 has * 2.0 Mg/ha *0.25 (% increase) *0.3
VARI-TARGET variable rate nozzle bodies, most widely used metering orifice used with GreenSeeker
1992-present67 Graduate Students + Faculty1 week to 4 month study abroad
Because yield and N responsiveness were consistently found to be independent of one another, and since both influence the demand for fertilizer N, estimates of both should be combined to calculate realistic in-season N rates.
Strategy: Have to have experience seeing the different responses from one year to the next
ArgentinaChina (2) El Salvador (2)Ethiopia (3)India (2)IndonesiaIraqKenyaKoreaMexico (2)Philippines Russia (2)Uzbekistan
RI-NFOAYPN=YP0 * RI
INSEY (NDVI/days from planting to sensing)
Nf = (YP0*RI) – YP0))/Ef