Differential Responses of Slash Pine Progeny Lines to Some Cultural Practices

In three experiments involving intensities of management' slash pine ( Pinus elliottii Engelm. var. elliottii ) progenies of selected lines and crosses varied greatly in their growth rates on unaltered sites and in growth responses to environmental improvements. In three tests, some selections made poor growth in unfertilized soil, but responded well to fertilizer applications, while others made good growth in unfertilized soil, but were little affected by fertilizers. Of greater importance, some progeny lines made good growth in unfertilized soil and at the same time responded to fertilizer treatments. There were greater growth differences within progeny lines due to variations in the immediate environment than there were among lines of different geographic origin. These results emphasize the importance of testing progenies of plus trees on soils as productive and similarly managed as under plantation conditions.