1917] Fowler— Lipman: Optimum Moisture Conditions for Lemon Trees l!;i 



soil moisture percentages within which the young Lisbon trees will 

 grow satisfactorily in the soil studied is, relatively speaking, a wide 

 one, since for practical purposes there is probably Little difference 

 between the growth obtained at moisture percentages varying from 

 16 to 22, both inclusive. This is a fortunate circumstance from the 

 point of view of orchard practice since it allows of considerable leeway 

 in the control of irrigation operations. It docs not follow, however, 

 that as regards fruit production the same wide range of moisture per- 

 centages in the soil would be similarly effective as in the ease of 

 general vegetative growth. On either side of the range of moisture 

 percentages just discussed, there can be no question that conditions 

 are far from proper for good tree growth. This is especially tine, 

 however, for moisture percentages in excess of 22 per cent, at which 

 the light-colored foliage and general lack of vigor, increasing with 

 increase of moisture, accompany the slow growth. In the case of the 

 cylinders receiving less than 16 per cent of moisture while the growth 

 is also slow owing to lack of moisture, the leaves and branches appear 

 to be normal in color and the trees appear to be suffering less from 

 untoward conditions. It seems to be very clear at this stage of the 

 experiment, therefore, that, in practice, there is very much more 

 danger to young lemon trees from too much than from too little 

 moisture in the soil. The harmful effects of the former seem to be 

 always more sharply defined and more intense; small additions of 

 water beyond the optimum produce large and sudden changes, whereas 

 small decreases of moisture below the optimum show their effects only 

 gradually with the continued reduction in the moisture percentage. 



About six months have passed since the measurements and photo- 

 graphs discussed above were obtained. The effects of the different 

 moisture percentages continue to stand out as clearly or more so than 

 ever before, indicating the probability that they may continue so tor 

 a long period of years. It should be mentioned here that small but 

 uniform applications of sulphate of ammonia have been made to all 

 the cylinders during the past year to maintain a more nearly normal 

 growth than is possible without additional nitrogen in such a limited 

 volume of soil as that at the disposal of the trees in the cylinders. 



In the soil under study in this experiment it was found that tin' 

 theoretical wilting point was very close to, if not identical with, the 

 actual wilting point, as both the field moisture determinations and tic 

 10 per cent moisture cylinders have on very dry days attested. It 

 will be observed, moreover, that the moisture equivalenl and the 



