Results are presented of some comparative measurements of air temperature made in spring in 1960 and 1961 in vineyards near Red Cliffs (Victoria) when the soil was subjected to four treatments in separate plots. The treatments used were: (1) Clean cultivation (denoted by O); (2) Rolling (denoted by R); (3) Rolling plus moderate irrigation (denoted by R W); (4) Heavy irrigation (denoted by P).
On nights having 2/s or less of total cloud the average air minimum temperature 3 ft. above clean cultivated soil was 42Β°F (ranging from 22Β°F to 55Β°F) and here the average increase due to treatment R was 0.7Β°F, to treatment R W 1. IΒ°F and to treatment P 0.7 Β° F. In the case of treatments R W and P this temperature difference increased by 0.07-0.08Β°F per degree decrease in air minimum temperature within the stated range so that the expected value of the benefit received from the treatment is 2-2.5Β°F at temperatures below freezing. When all nights during the period of test, rather than nights of little cloud, were considered, the results were, for all practical purposes, the same.
There is some indication, not shown to be statistically significant, that rain may have reduced the observed differences. No decrease in the efficiency of the treatments with time could be proved.