About Us | Help Videos | Contact Us | Subscriptions

Members of ASA, CSSA, and SSSA: Due to system upgrades, your subscriptions in the digital library will be unavailable from May 15th to May 22nd. We apologize for any inconvenience this may cause, and thank you for your patience. If you have any questions, please call our membership department at 608-273-8080.


Institutional Subscribers: Institutional subscription access will not be interrupted for existing subscribers who have access via IP authentication, though new subscriptions or changes will not be available during the upgrade period. For questions, please email us at: queries@dl.sciencesocieties.org or call Danielle Lynch: 608-268-4976.



This article in CS

  1. Vol. 23 No. 5, p. 961-964
    Received: Oct 14, 1982

Request Permissions


Predicting Crude Protein, In Vitro True Digestibility, and Leaf Proportion in Alfalfa Herbage1

  1. David W. Onstad and
  2. Gary W. Fick2



Simple equations to predict alfalfa (Medicago sativa L.) herbage quality are needed for economic analysis of management alternatives. In this study, regression analysis was used to formulate and test prediction equations for leaf proportion (LP), for crude protein (CP), and in vitro true digestibility (IVTD) levels of leaf and stem fractions of standing herbage with canopy age, heat sums with a 5°C base temperature, and daylength sums as independent variables. All data were for pure alfalfa samples collected in central New York State between 1972 and 1980 from established stands with canopies ranging in age from 7 to 66 days. Separate equations were needed to predict LP in first growth and regrowth, but a corresponding distinction was not necessary for leaf and stem CP and IVTD. Heat-sum-based equations gave good fits (R2 from 0.75 to 0.97) for all predicted variables. In few cases, equations with both heat and daylength sums fit equally as well. Canopy age adequately predicted only leaf CP and IVTD. Equation form varied from simple linear to polynomial and logarithmic. Thirteen equations were selected for testing by regressing independent field observations on model predictions of those observations. The r2 values in these tests for the various herbage components were as follows: LP in regrowth, 0.81 to 0.87; leaf CP, 0.55 to 0.59; leaf IVTD, 0.44 to 0.46; stem CP, 0.72 to 0.76; and stem IVTD, 0.89 to 0.92. In general, predicting standing alfalfa herbage quality from heat summation is a promising approach.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © .