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May
25
Posted by:
WCM Staff
5/25/2005 9:00 PM
Many growers are asking about the tradeoffs in yield and quality as they enter quality pricing contracts for hay or haylage. The situation is that premiums are paid for quality but some of the higher price for increased forage quality is offset by lower yields of fields cut earlier for the higher quality.
Change in Yield and Quality of Alfalfa
Dan Undersander, Extension Forage Agronomist
Many growers are asking about the tradeoffs in yield and quality as they enter quality pricing contracts for hay or haylage. The situation is that premiums are paid for quality but some of the higher price for increased forage quality is offset by lower yields of fields cut earlier for the higher quality.
This is difficult to assess since both alfalfa growth and change in forage quality vary considerably depending on environmental conditions. Little data on both yield and quality change over time has existed. The USDA-Dairy Forage Research Center is conducting a detailed study (jointly with the Universities of Pennsylvania) to attempt to get some answers. They have data from this study for 2004. This, combined with some of my studies, can give a few benchmarks and then the grower can decide if the season is proceeding ‘normally’ or not.
First, yield change around harvest time varies considerably and has ranged from 0 to 200 lbs per acre per day. From a number of studies, it seems reasonable to plan on the yield increase of alfalfa being about 100 lbs per acre per day near harvest if growing conditions are ‘average.’ This yield change is consistent across cuttings, exclusive of late fall. Remember that daily yield increase will be less in cool, cloudy weather, and if insects, disease or drought occur. It may be greater in periods of good moisture, sunshine and 75 to 85 degree weather.
We have analyzed forage quality changes over time across cutting of alfalfa for several years. It appears that quality of first cutting changes at the fastest rate and later cuttings change in fiber at a slower rate. We have found that first cutting decreases about 5 pts RFV per day, second cutting decreases 2 to 3 points per day and third and fourth cutting during the growing season decline 1 to 2 points per day. The late fall growth may change little in forage quality during mid to late September and early October. Relative Forage Quality (RFQ) will change about the same as RFV on first cutting and then decline about 3 points per day on 2nd, 3rd and 4th cuttings during the growing season. Factors such as drought and potato leaf hopper will dramatically reduce yield but increase forage quality.
The table at right will allow the grower to calculate changes versus the payment basis for quality of forage. Yield appears to increase by 100 lb/acre/day near harvest regardless of cutting if growing conditions are good. Forage quality declines at a variable rate depending on which cutting is being considered. Remember that the change in quality is on the total forage harvested for the cutting (usually 1.5 to 2 t/a per cutting).
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Alfalfa forage change in yield and quality during the growing season
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Cutting
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Yield (lb)
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RFV
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RFQ
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-------Daily Change-------
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1
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100
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-5
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-5
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2
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100
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-2 to -3
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-4
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3
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100
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-2
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-3
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4
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100
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-1
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-3
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