Sensor Orientation to maize canopy row and estimating biomass and Nitrogen Status Paul Hodgen, Fernando Solari, Jim Schepers, John Shanahan, Dennis Francis

Objectives: 1) Evaluate effects of sensor orientation on estimating maize biomass and nitrogen uptake. 2) Evaluating if auxiliary information combined with sensor data improves ability of estimate biomass.

Nadir 45 degrees off Nadir Vs.

Seeing what the sensor sees! Nadir 45 degrees off Nadir

Nadir Nadir

Nadir

A few Material and Methods A few Material and Methods Locations: Argentina (February, 2004) GreenSeekers Red and Green Topeka, Kansas (June, 2004) Holland Scientific Amber (595 and 880 nm) Shelton, Nebraska (July, 2004) GreenSeekers GreenSeekers Red and Green Holland Scientific Amber (595 and 880 nm)

Location: Argentina: Data collected over two experiments, three replication (24, 2 linear meter of Row plots) Corn was Planted Dec 29, 2004 Corn was Planted Dec 29, 2004 Seeding rates of 4 or 8 seed m 2 V9 growth stage Three N rates 0, 70, 140 kg N ha -1 No Nitrogen data was available Chlorophyll readings taken from whole plot using a Minolta 502 Spad meter.

NDVI Nadir Maize V9

NDVI 45 degrees Off Nadir Maize V9

GNDVI Nadir Maize V9

GNDVI 45 degrees of Nadir Maize V9

NDVI by itself from the Nadir position is a good predictor of biomass. Off Nadir seemed to Saturate Problems of NDVI Saturates around a leaf area of 2.0 Gitelson et al., 2003 Myneni et al., 1997 GNDVI by itself was a poor indicator of dry matter from the Nadir position. The off Nadir position improved our ability but the relationship was still poor.

GNDVI and Spad R = 0.39 for Nadir R = 0.79 for 45 degrees off Nadir GNDVI from the off Nadir position might tell us more aboutN status of the crop. Why? Believe it is from holding the NIR more constant and difference is in the visible (Green).

Nadir 45 degrees off Nadir Do not see as many gaps

Nadir 45 degrees off Nadir GreenSeeker Light Band

Canopy height and sensor readings. Plant height is important, because nearly half the weight in the vegetative growth is in the stalk. Also leaf area has normal vertical distribution during the growing season. - Boedhram et al., 2001

Sensor output times plant height NDVIht and GNDVIht Plant height does not gives a good estimate of Nitrogen status of the crop.

Maize V9

What happen to the GNDVI off Nadir ? Remember those Gaps? presence or absence of leaves.

Nadir 45 degrees off Nadir Do not see as many gaps

Nitrogen Uptake Since actual Nitrogen data is not available used a pseudo Nitrogen Uptake used a pseudo Nitrogen Uptake Spad time Drymatter Not the real thing but will point us in the right direction. Now we have eliminated GNDVI and NDVI from the 45 degrees off Nadir

Maize V9

NDVI vs. GNDVI

From the Argentina data. NDVI - Had not became insensitive - Prior to Leaf area of approximately 2.0 NDVI should be used. GNDVI - From 45 degrees off Nadir could be a better position for just N status. - Times canopy height is a good predictor of dry matter (Nadir). - GNDVIht Is a good predictor of total N uptake NDVI and GNDVI are not related and are independent, Green does not equal Red. Green does not equal Red. Canopy height is and important piece of auxiliary data to collect along with sensor readings.

Now from Kansas Crop Circle sensor just arrived. Computer problems caused us to lose Green Seeker data. 8 strips, each a different N treatment, 800 ft long Sensors were mounted on a front end loader of tractor.

Back to Nadir vs. 45 degrees off Nadir Crop Circle outputs the values for the NIR (880 nm) and Amber bands (595 nm) Data taken at two distances from the canopy for both positions. 50 and 91 cm

CV’s for Nadir vs. 45 degrees off Nadir 50 cm above canopy ANDVINIR reflectanceAmber (595 nm) Nadir Off Nadir Nadir Off Nadir Nadir Off Nadir PlotCV(%)

CV’s for Nadir vs. 45 degrees off Nadir 90 cm above canopy ANDVINIR reflectanceAmber (595 nm) Nadir Off Nadir Nadir Off Nadir Nadir Off Nadir PlotCV(%)

From Kansas For both distance (50 cm and 91 cm) reflectance values increased going from Nadir to 45 degrees off Nadir. The variability (CV) of the reflectance values increased goingfrom Nadir to 45 degrees off Nadir, more so for visible (Amber) than the NIR, as distance for visible (Amber) than the NIR, as distance increased. increased.

Combing what we learned from Argentina and Kansas. Argentina Nadir was better for dry matter (biomass) in concert with canopy height. Kansas Nadir position had less variability in the mean values. Off Nadir position increases in the mean values and becomes more variable as distance increases.

Applying what we learned for this summer in Nebraska

Neb. V6 Neb. V12 and VT Two maize hybrids, four nitrogen rates, three different dates. three different dates.

Two maize hybrids, four nitrogen rates, three different dates. Neb. V6 Neb. V12 and VT

Crop Circle (ANDVI) from three dates in Nebraska, two maize hybrids, four nitrogen rates.

Plant height continues to explains a large portion of the variability in dry matter (Biomass) during the variability in dry matter (Biomass) during vegetation growth stages. Probably the most important auxiliary piece of information to collect at time of sensor readings Still waiting on lab results for Nitrogen analysis Suspect that the late season cloud will “tighten up” when GINSEY or AINSEY is plotted against total Nitrogen uptake.

Where to next? If biomass, and / or total Nitrogen uptake can be estimated in current vegetation, then we can start to make future prediction about future needs. GNDVI and ANDVI hold promise to detect differences in Nitrogen status post leaf area 2.0. Prior V8 is too early to get a handle on residual plant available Nitrogen in the soil. In addition, V8 up to VT gives a wider window of application than emergence to V8.

That’s our story! Questions???? *