CITRUS CULTURE m PORTO RICO 



21 



may be sown thinly or broadcast, and the trees will develop similarly 

 to annuals. If they are planted 2 to 3 feet apart these trees wiil 

 attain good size and serve as windbreaks as long as they are needed. 

 The main drawback is the poor wind resistance of the gallito, which 

 may result in damage to the citrus trees during heavy winds. 



Several nonleguminous crops may also be used as windbreaks in 

 Porto Rico. Sugarcane makes a desirable windbreak in places where 

 the crop can be disposed of at a profit. (Fig. 11.) The banana is 

 another economic plant that may be used for wind protection 

 wherever the soil moisture is ample for the development of later 

 crops. Corn is not as extensively used as it might be, at least during 

 the first year. A combination of either corn or sunflowers and climb- 

 ing peas or beans is desirable. Pigeon peas, planted thinly so as to 

 produce stout plants, will provide a good support for velvetbeans, 

 and afford one of the best combinations both for wind protection and 

 for soil improvement. The latter factor is very important. The soils 

 of citrus groves in Porto Rico can all be greatly improved by the 

 addition of humus, which must be added while the trees are small 

 enough to allow crops to be grown in the grove. 



For permanent windbreaks the bamboo has been used extensively. 

 It is objectionable because citrus trees do not thrive in proximity to 

 a bamboo hedge. A bamboo windbreak, therefore, entails the loss 

 of two or three rows of citrus trees but is a fairly good insurance 

 against heavy winds. Most of the tall tropical trees are too slow 

 growing for use as windbreaks, and they are usually less wind re- 

 sistant than the citrus trees. The so-called Australian pine (Casua- 

 rina equisetifolia) is promising for the purpose since hedges of it 

 and isolated trees generally withstood the hurricane of September, 

 1928. (Fig. 12.) 



PLANTING AND CULTIVATION 



The method of planting citrus trees with a ball of earth surround- 

 ing the roots is especially desirable where nursery trees are not 

 shipped long distances. Young, vigorous trees taken up with a ball 

 of earth survive the shock of transplanting without the loss of foliage 

 and with very little loss of roots. If the trees are not removed with 

 a ball of earth adhering to the roots, all the leaves should be cut off , 

 the branches should be cut back to within a few inches of the trunk, 

 and a portion of the longest root and all broken ends should be 

 pruned off. Immediately after the roots are pruned they should be 

 dipped in a thin slurry consisting of clay and cow dung and wrapped 

 in wet sacking. The trees should then be kept in a shady place until 

 they are wanted for planting. The method of planting on top of a 

 mound involves the difficulty of conserving the soil moisture. The 

 mounds should, therefore, be mulched with trash cut in the field, or 

 brought from without, if necessary. (Fig. 13,) The soil surround- 

 ing the tree should be well watered at the time planting is clone, and 

 then often enough to maintain a high soil-moisture content until root 

 growth is well advanced. An examination of transplanted trees 

 usually shows that on young vigorous trees with thin roots the root 

 scars heal over in a few months and new roots form rapidly enough 

 to support the leaf growth; and, on the other hand, that on old trees 

 with dormant and thick roots the root scars do not heal quickly. 



