January, 1909.] 



61 



SCIENTIFIC AGRICULTURE. 



WIND-BREAKS FOR ORANGE 

 GROVES IN PORTO RICO. 



Orauge cultivation is an industry of 

 considerable promise in Porto Rico, and 

 numbers of plantations are now being 

 set out. A pest which is causing a good 

 deal of trouble in the citrus groves is 

 the orange mussel scale (Lepidosaphex 

 beckii, (Mytilaspis citricola), and the 1907 

 Report of the Agricultural Experiment 

 Station of the island mentions that 

 xperiments are in progress to determine 

 he best methods of dealing with these 

 insects. Spraying with kerosene has 

 given fairly satisfactory results. It is 

 stated, too, that Porto Rican planters 

 now recognize that wind-breaks on the 

 Avind-ward side of the citrus groves play 

 an important part in checking tlie 

 spread of the scales. The following 

 notes on this point are taken from the 

 report :— 



Wind-breaks are divided into two 

 classes — permanent and temporary. Per- 

 manent wind-breaks are generally plan- 

 ted on the outer borders of the groves, 

 while temporary wind-breaks ar e planted 

 between the rows of trees. There are 

 several plants which grow very quickly, 

 and afford good temporary wind pro- 

 tection, namely : bananas, sugar-cane, 

 pigeon peas, and the China berry or 

 Barbadoes lilac (Melia Azedarach). Tem- 

 porary wind-breaks should not remain 

 between the rows more than three years 

 and in the case of bananas a furrow 

 should be ploughed on each side, thus 

 preventing the roots from sapping the 

 soil around the orange trees. 



For permanent wind-breaks at the 

 present time the mango seems to be the 

 best, but in setting out the young trees 

 they should be headed as low as possible. 

 Bamboo is also being planted, and if the 

 cuttings are set out during the rainy 

 season they start much quicker. These 

 should be planted close together, so as 

 to form a hedge. 



When brush land is being cleared for 

 planting, it is advisable to leave a strip 

 of uncut timber 20 feet wide every 300 to 

 400 feet. The results obtained from 

 wind-breaks are very marked, certain 

 groves which were wind-swept and were 

 not growing at all having been brought 

 into excellent condition. In almost 

 every grove in the island marked im- 

 provements have been observed as the 

 result of planting wind-breaks. In 

 certain areas there may be found trees 

 producing from 1 to 2 boxes of fruit. 



while trees not more than 50 to 70 feet 

 away, and of the same age as the former 

 but without wind protection are fre- 

 uently noticeable, which, from their 

 evelopment, might not be more than 

 a year old. On the latter the branches 

 are blown to one side and covered with 

 scale. Trees protected from the wind 

 require less spraying, and the fruit is 

 free from scars.— A gricultural Netvs, 

 Vol. VII., No. 165, August, 1908. 



GREEN MANURING. 



In India manuring is yet in its empiri- 

 cal stage. The science of manuring, its 

 mode of action, the improvements of 

 the methods available and the return to 

 the soil of all that is taken from it are 

 not sufficiently known. The use of 

 green manures might be especially re- 

 commended to the Indian agriculturist, 

 especially on account of his poverty. 



Green manuring consists of growing 

 a crop of some sort, usually a legumi- 

 nous one, and ploughing it into the soil at 

 the time of flowering. Modern science 

 has up to now determined ten chemical 

 substances in plants, viz., carbon, hydro- 

 gen, oxygen, nitrogen, sulphur, phos- 

 phorus, potassium, calcium, magnesium, 

 and iron. Of thesechemical ingredients, 

 nitrogen, with which organic matter is 

 closely associated, has been generally 

 recognised to be the most important. 

 The growing of leguminous plants be- 

 tween the lines of the staple crop has 

 been found conducive to the accumu- 

 lation in the soil of a sufficient store of 

 organic matter and nitrogen. Nitrogen 

 in its free form is largely present in the 

 atmosphere ; but the plants have not 

 got the power to utilise it. The diffi- 

 culty is that they require a medium to 

 render nitroeen available to themselves. 

 An experienced agriculturist describes 

 the utility of leguminous crop in this 

 respect thus :— " First rains, lightenings 

 and other natural causes tend to unite 

 the free nitrogen with hydrogen, oxy- 

 gen and other substances and com- 

 pounds, which falling down along with 

 rain, enter the soil and mix with the 

 earth ( technically called metallic bases ) 

 and forms salts of nitric acid. Hence 

 the starvation of the plant for nitrogen 

 in the presence of plenty of free nitrogen 

 in the atmosphere. It requires a medi- 

 ator and a process before the nitrogen 



can be of use in its formation 



Of the several thousands of natural 

 orders of plants, modern science has 

 determined that a certain natural order 



:i 



