Page:Report of the Puerto Rico Experiment Station (IA CAT31294391015).pdf/23

 the low rate, had somewhat better weed control than those sprayed with Santobrite. The low rate of Santobrite seemed to be as effective in controlling weeds as the highest rate. Likewise, there was no apparent difference in weed control between the high and low rate of 2,4-D, nor was there any noticeable difference in weed suppression between the acid and the salt. Since the experiment was conducted during the rainy season the acid was expected to persist longer, because it is much less soluble than the salt.

The germination of the sugarcane was affected to a certain extent by the 2,4-D, the effect being more pronounced at the higher rate. At the lower rate about 5 percent of the seed pieces failed to grow, and 12 percent failed to grow at the higher rate. Santobrite at the highest rate had no deleterious effect on cane growth. The results of this preemergence weed-control experiment indicate that satisfactory and economical control of weeds, except nutgrass, can be obtained without hand cultivation for a period of 6 weeks to 2 months after the cane is planted.

Sodium pentachlorophenate, sodium trichloroacetate (STA), and the sodium salt of 2,4-dichlorophenoxyacetic acid, alone, and in combination were tested for eradicating grasses and annual weeds. Four weeks after application all treated plots were relatively free of weeds, especially those treated with STA. The 100-pound rate of STA was as effective in suppressing the weeds as the 200-pound rate during the initial period. Also, there was no appreciable difference between plots sprayed with STA + 2,4-D and those sprayed with STA alone. The results to date indicate that sodium trichloroacetate is effective in controlling the hard-to-eradicate perennial grasses like Bermuda and Para. They also indicate that two applications at the rate of 100 pounds per acre are more effective than one application of 200 pounds per acre.

H. R. Cibes and A. J. Loustalot

In the third year of production, vanilla under a lath-shade experiment yielded 495 pounds of green beans per acre; although more than three-fourths of the plants were wilted or dead as a result of disease. The highest mortality occurred in beds with Catalina and Toa mulch, while beds with Soller mulch showed the least damage. The best root development was also obtained in Soller mulch. This experiment demonstrates that vanilla can be grown successfully under lath-shade conditions, but the vines must be maintained separately. The vegetative growth was thrifty beyond all expectation, and this was conducive to the spread of disease. A management experiment now in progress is designed to correct this difficulty.

An experiment was carried out to determine the effect of removal of old mulch and the application of fresh mulch at specific intervals on the growth of vanilla.

The growth data obtained 12 months after planting showed that the control treatment, in which mulch was not removed nor renewed, surpassed the other treatments both in vegetative growth and in the least amount of rotting of seed pieces. Root germination in this treatment ranked second to the treatment in which mulch was removed and renewed every 9 months.