01018naa a2200133 a 450000100080000000500110000800800410001910000170006024501460007726000090022352005950023270000140082777300430084116492052000-07-25       1957    bl ---       0--  u    #d1 aMOORE, P. W.  aDeclining yield in oranges appraisai of 220 mature orange orchard in five counties indicates possible causes of downward trend in production.  c1957  aAverage production of southern California oranges dropped from 370 to 265 field boxes per acre - for navels - and from 290 to 265 field boxes per acre - for Valencia - over a 12-year period. Many individual orchards in Los Angeles, San Bernardino, and Orange counties - the three areas most seriously affected - showed a production decline of as much as 100 to 250 field boxes per acre during the period. In order to determine the causes of declining yields, a detailed survey was made of 186 orchards - both Valencia and navel - in Los Angeles, San Bernardno, Orange, and Ventura counties.1 aNAVER, E.  tCalifornia Agriculture, p.13-14, 1957.