Allen W. Goodwin, Laura E. Lindsey, Steven K. Harrison, and Pierce A. Paul
Between planting in the fall and Feekes 4 growth stage (beginning of erect growth) in the spring, winter wheat is vulnerable to environmental stress such as freezing temperatures with limited snow cover, saturated soils, and freeze-thaw cycles that cause soil heaving (Dickin and Wright, 2008; Fowler and Gusta, 1979). All of which may lead to substantial stand reduction, and consequently, low grain yield. In Ohio, due to poor stands in the spring, an average of 5% of the winter wheat acres are destroyed annually and planted to an alternative crop such as corn or soybean, and as much as 12% of the wheat acres were destroyed in 2014.
However, a stand that looks thin in the spring does not always correspond to lower grain yield. Rather than relying on a visual stand assessment, farmers are encouraged to estimate the yield potential of their winter wheat crop by counting plants or tillers (Weisz et al., 2001), before deciding whether a field should be destroyed and planted to corn or soybean. Despite these recommendations, many farmers do not count wheat plants or tillers in the spring because the measurement is tedious and time consuming. An alternative method to evaluate wheat stand is fractional green canopy cover (FGCC). Fractional green canopy cover can be used to measure the canopy surface area using the mobile device application Canopeo. The app can be downloaded for free here: http://www.canopeoapp.com.
Wheat Stem Count Methods: Wheat stems (main stem plus tillers) should be counted at Feekes 5 growth stage (leaf sheaths strongly erect) from one linear foot of row from several areas within a field (Figure 1).
Fractional Green Canopy Cover Methods: Fractional green canopy cover should be measured at Feekes 5 growth stage using the mobile device application, Canopeo (http://www.canopeoapp.com). The camera should be held to capture three rows of wheat in the image (Figure 2).
After counting the number of wheat stems or measuring FGCC, Table 1 can be used to estimate wheat grain yield. For example, if an average of 51 stems is counted from one foot length of row, the predicted grain yield would be 100 bu/acre. Similarly, if the average FGCC measurement was 35%, the predicted grain yield would be 100 bu/acre.
|Grain Yield (bu/acre)||Stem Count (number/foot of row)||FGCC (%)|
Dickin, E., and D. Wright. 2008. The effects of winter waterlogging and summer drought on the growth and yield of winter wheat (Triticum aestivum L.). Eur. J. Agron. 28:234-244.
Fowler, D.B., and L.V. Gusta. 1979. Selection for winter hardiness in wheat I. Identification of genotypic variability. Crop Sci. 19:769-772.
Weisz, R., C.R. Crozier, and R.W. Heiniger. 2001. Optimizing nitrogen application timing in no-till soft red winter wheat. Agron. J. 93:435-442.
Research funded by Ohio Small Grains Marketing Program.
Salary and research support provided in part by state and federal funds appropriated to the Ohio Agricultural Research and Development Center (OARDC) and The Ohio State University.
Originally published: Goodwin, A.W., L.E. Lindsey, S.K. Harrison, and P.A. Paul. 2018. Estimating wheat yield with normalized difference vegetation index and fractional green canopy cover. Crop Forage and Turfgrass Manage. doi: 10.2134/cftm2018.04.0026