The effect of integrated applications of various irrigation and fertilization rates on productivity (yield and size) and returns of the `Hass' avocado (Persea americana Mill.) have been analyzed from 1987 to 1991 in western Riverside County. Eighteen treatment combinations comprised of three irrigation levels [80%, 100%, and 120% crop water use (ETc)], three N fertilizer levels (0.16, 0.7, and 1.4 kg/tree per year), and Zn (0 and 0.2 kg/tree per year) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combination. Costs of treatments, harvesting, hauling, and marketing were subtracted from the value of the crop. The value of the crop was calculated as the sum of crop returns in each size category. Three years of data on the relationship between irrigation and N showed 1) irrigating at 80% ETc would be ineffective even at very high water prices; 2) for groves where 100% ETc is sufficient, its application with either low or medium N would be beneficial; and 3) at higher irrigation (120% ETc), N application should be at or beyond the medium level.
Etaferahu Takele, Jewell L. Meyer, Mary L. Arpaia, David E. Stottlemyer and Guy W. Witney
Etaferahu Takele, John A. Menge, John E. Pehrson Jr., Jewell L. Meyer, Charles W. Coggins Jr., Mary Lu Arpaia, J. Daniel Hare, Darwin R. Atkin and Carol Adams
The effect of various integrated crop management practices on productivity (fruit yield, grade, and sire) and returns of `Washington Navel' oranges [Citrus sinensis (L.) Osbeck] was determined in the San Joaquin Valley of California. Seventy-two combinations of treatments comprised of three irrigation levels [80%, 100%, and 120% evapotranspiration demand (ETc)], three N fertilizer levels (low, medium, and high based on 2.3%, 2.5%, and 2.7% leaf N, respectively), gibberellic acid (±), miticide (±), and fungicide-nematicide (±) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combiition. Costs of treatments, harvesting, packing, and processing were subtracted from the value of the crop. The value of the crop was calculated as the sum of returns of crop in each size and grade category. The overall result indicated that returns after costs were higher for the +fungicide-nematicide treatment and also were generally more with increased irrigation. The combination of 120% ETc, +fungicide-nematicide, medium or high N, -miticide, and -gibberellin showed the highest return of all treatment combinations. Second highest returns were obtained with high N or with miticide and gibberellin used together.