THE EFFECT OF ORCHARD SOIL MANAGEMENT ON SOIL TEMPERATURE AND APPLE TREE NUTRITION

Abstract

Soil temperature was measured from 1981 to 1985 at 0.2- and 1.0-m depths for four soil management treatments which included full ground cover, total vegetation control, shallow tillage and black plastic mulching in a high-density orchard planted to Bisbee Red Delicious (Malus domestica Borkh.) on Mailing 26 rootstock. Ground cover suppression treatments, especially black plastic mulching, increased degree day accumulations above 10 °C in all 5 yr at 0.2-m and in 3 yr at 1.0-m depths relative to full ground cover. However, these treatments also resulted in more extreme temperature fluctuations as characterized by higher summer maximum and lower winter minimum temperatures under black plastic mulching. Despite a potential for more extreme soil temperatures, apple yield was significantly higher under black plastic relative to full ground cover. For these two contrasting temperature treatments, leaf N and Mg concentrations were usually significantly higher under black plastic while leaf P and K were consistently higher and leaf Ca and Zn were occasionally higher under full ground cover. Most of these differences were, with the possible exception of leaf Zn, attributed to the competition for, or recycling of, nutrients by orchard floor vegetation. Mean monthly soil temperatures at the two depths under the four soil management treatments could be predicted by simple linear regression techniques from soil temperature measurements at the Summerland Research Station Meteorological Recording Site. Key words: Bisbee Delicious apples, degree days, ground cover, suppression, black plastic mulching, leaf nutrition