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Four management limitations (constraints) were inserted into the model, 

 namely, cooling capacity, harvest labor, storage capacity, and replanting 

 acreage. These are described briefly. 



\creage: The planting period for the 50-acre rejuvenated orchard was 10 

 years. Each year 5 acres were removed and replanted. The model also used a 

 20-year period--10 years beyond the end of replant ing--to evaluate consequences 

 of strain/rootstock selections up to the time the orchard readies full produc- 

 tion. For eaiih planting year, the model decided how many acres of each 

 strain/rootstock combination to plant for maximum prof itabli lity, given the 

 following set of conditions. 



Storage. Most orchards divide the marketing of their crop between the 

 fresh market, during and immediately following harvest, and long term storage. 

 However, to simplify the model, we assumed that all fruit produced on the 50 

 acres was placed in long-term storage. 



The storage capacity was set initially at 20,000 bushels. It was increased 

 to 48,500 bushels in year 20 .vh(>n most ,)lantings had reached lull tnat irity. All 

 trees less than 4 years old were considered nonbearing mid u-ed none <jf the 

 storage capacity. Trees older than 4 years were bearing .ind thMr yield used a 

 portion of the total storage capacity. 



Harvest labor. The harvest season was divided into eifrht 3-day picking 

 periods. These extended from September 4 to October 1. A percentage of the 

 total yield for each strain-rootstock combination was harvested during at least 

 4 of these picking periods. Each combination had harvest labor needs specific 

 to its stage of growtJi because yield varies with strain, rootstock, and age of 

 tree. The available labor hours for eacii harvest period were deterrnined by 

 multiplying the number of pickers (set initially at 7) by ivorking hours per day 

 (set constant at 9) and by 3 days per Iiarvest period. For the 50 acres, 189 

 hours were available for each 3-day period. 



Each strain-rootstock (^^mbiiat ion contributed to the use of harvest labor 

 depending on the yield, the tree's ag<!, the percentage of yield harvested during 

 a particular i)icking period, and the picking rate. In year 20, when most 

 plantings were matare, additiotial harvest labor vvas required. To enable the 

 model to operate, harvest labor was increased to 550 hours per picking period 

 (20 pickers) by year 20. 



Cooling capacity. Field heat must be removed from th<i apples after 

 harvest. The (juantity of fruit that can be (tooled is limited by the size of the 

 refrigerating equip-nent. Cooling lapac^ity was evaluated to correspond with the 

 eight 3-day harvest periods. The total capacity was 9,000 bushels for 3 days or 

 3000 bushels per day. 



Each strain-rootstock comoiiat ion contribut:!S to the orchard's returns to 

 management. This contribution dei)<;nds on the difference between revenues and 

 costs. In this study, returns to management covered overhead costs, 

 managernent labor, an<l profit. 



Revenues were dependent on yic^Id, which varies accorcli ig to the trecs's 

 age, the strain-rootstock combiiation, and the (jrice. Price was held constant 

 for all years but varied with fruit gra<le. ^'or all trees, yield was assorted as 

 follows: 75% extra fancy, 15% utility, and 10)6 processing. The busiiel prices 



