Alfalfa Grass Estimation System
Helping New York State farmers calculate the best time to harvest forages to optimize quality for dairy cattle.
New Harvest

Optimal Harvests

Accurately estimate fiber concentration and optimal harvest timing in spring forage fields in New York State.

Decision Support for Spring Forage Harvests

Accurately estimate fiber concentration and optimal harvest timing in stands of pure grass, pure alfalfa, and alfalfa-grass mixes in New York State.

Required Inputs

Provide forage height measurements, planned stubble height, expected weather, botanical composition (mixed stands), grass species (pure grass) and target NDF at harvest (pure alfalfa and pure grass).

Optimal Harvest

Estimation of current NDF, target harvest height and days to harvest to obtain optimal quality.

Alfalfa Grass Estimation System Tools

Apply these tools to support spring forage harvest decisions. Representative locations in each field (5 or more) should be used for inputs, and average field estimates used to support harvest management decisions.

First, select field composition:


Documentation

Pure alfalfa, pure grass, and alfalfa-grass spring harvest management tools were developed based on multiple years of field research in New York State. Effective use can improve the odds of harvesting high quality forage to make silage for lactating dairy cows. Best experience will be achieved on desktop and smartphones using Google Chrome, Safari, or Mozilla Firefox. Internet Explorer should be avoided.

Instructions

  1. Select New Harvest or scroll down to the Alfalfa Grass Estimation System Tools section.
  2. Select the field composition for the tool you would like to use. Options include: pure alfalfa, pure grass, and alfalfa-grass.
  3. Input required parameters for a sample in the current field.
  4. Click “Add Estimate to Field Average”.
  5. It is recommended to repeat steps (3) and (4) for at least 5 representative locations in the current field.
  6. When you have finished a field, record output parameters and click New Estimate to start a new field from step (2).

Required Inputs

  • Max height of alfalfa (inches): Measure the height of the terminal (highest) alfalfa bud on the tallest stem in the sample. Height should be measured from ground level.
  • Grass canopy height (inches): Measure approximate average height of the grass canopy in the sample with no extension of leaves. Accurate measurement requires stepping back and leaning down to eyeball canopy height (where the upper grass leaves are curving over). Height should be measured from ground level.
  • Planned Stubble height (inches): Enter the planned harvest cutting height above ground level.
  • Estimated weather for next week: Slight adjustments are made in daily accumulation of NDF based on expected weather conditions during the next week. Select normal, warm or cool. Under normal conditions, daily NDF accumulation is assumed to be 0.65% for pure alfalfa, 1% for pure grass, and is calculated proportionally from these values based on botanical composition for mixed stands. Warm weather increases daily change by 0.15% from normal and cool weather decreases daily change by 0.15% from normal.
  • Target harvest NDF: Optimums differ for pure grass (50%) and pure alfalfa (39%). Target harvest NDF is automatically calculated for alfalfa-grass based on botanical composition.
  • Percent Grass in stand: Percentage grass in the stand on a dry matter basis.
    • Upload a photo to estimate this value or enter a manual estimate. Accurate estimation from photos requires: (1) Reasonably good stands that are mostly weed free. If dandelion heads are prevalent in the image area, please remove heads prior to taking the photo. Vegetation coverage should be solid (low percentage of bare soil). (2) Grasses that have not yet headed. (3) Spring stands (1st cutting). (4) A digital or smartphone camera with at least 5-Megapixels resolution.
    • Sample photos should be taken using a digital or smartphone camera held approximately 1 meter (3.3 feet) above the grass canopy. Device should be held level, parallel to the grass canopy and facing the grass canopy (i.e., camera should be pointed straight down) for acquisition of each photo. Lighting should be uniform in the image area; avoid shadows that cut across the image (e.g., shadows generated by your body). Percent grass in the stand is estimated from the sample image.
    • Adjusting the alfalfa maximum height will change the image estimate of percent grass in the stand.
    • Users can choose to manually input percent grass based on a visual estimation or to override the photo-generated estimate. Changing the photo-generated estimate will remove the image and reset the image uploader.

Estimation Results

  • Sample NDF: NDF concentration for parameters entered for the current sample.
  • Average field NDF: The average NDF concentration for all samples added to the current field average.
  • Range in NDF per field: The range in NDF concentration for the current field from minimum to maximum.
  • Estimated days to harvest: Based on average field NDF, target NDF at harvest, and estimated weather conditions, this indicates the number of days to harvest to achieve target NDF.
  • Target AMAX or GCPY at harvest: Target max height of alfalfa or grass canopy height to achieve target harvest NDF.

Abbreviations

  • NDF = neutral detergent fiber
  • AMAX = alfalfa maximum height
  • GCPY = grass canopy height

References

Grass Tool

Parsons, D., McRoberts, K., Cherney, J.H., Cherney, D.J.R., Bosworth, S., Jimenez-Serrano, F. 2012. Preharvest neutral detergent fiber concentration of temperate perennial grasses as influenced by stubble height. Crop Sci. 52(2): 923-931.

Alfalfa Tool

Parsons, D., Cherney, J. H., and Gauch, H. G., Jr. 2006. Estimation of spring forage quality for alfalfa in New York State. Online. Forage and Grazinglands. doi:10.1094/FG-2006-0323-01-RS.

Alfalfa Grass Tool

(1) Parsons, D., Cherney, J.H., and Gauch, H.G., Jr. 2006. Estimation of preharvest fiber content of mixed alfalfa-grass stands in New York. Agron J. 98:1081-1089.

(2) McRoberts, K.C., Benson, B.M., Mudrak, E.L., Parsons, D., Cherney, D.J.R. 2016. Application of local binary patterns in digital images to estimate botanical composition in mixed alfalfa–grass fields. Comput Electron Agric. 123: 95-103.

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