MODERN RICE CULTURE. , 13 



unaided, can not assimilate any of it. By a wise provision of nature most 

 of the plant food in the soil is stored in the form of insoluble com- 

 pounds, and as such they can not be leached out by rain water. 

 Before the rootlets of the plant can absorb this plant food it is nec- 

 essary that it should be in soluble form, and this chemical operation 

 is performed mostly by low forms of plant life, commonly known as 

 bacteria. As was noted above, however, these special bacteria will thrive 

 only in the presence of oxygen, and as rice lands are under water for a 

 great part of the time the work of the bacteria is suspended, and conse- 

 quently the supply of soluble food in the soil ceases to increase under 

 these conditions, and, unless the young plant is supplied with food from 

 some other source, it can not be expected to reach perfection. 



Irrigation supplies this extraneous food, and although there may be but 

 little fertilizers in the water, such an immense quantity of water is evap- 

 orated during the growth of the rice that a large amount of nitrogen, 

 phosphoric acid, and potash are given up to the plant. 



Another reason why irrigation should be employed in preference to rain 

 water is because its temperature more nearly approaches that of the 

 ground than does the temperature of rain water, and this is a point 

 recognized to be of a good deal of importance. 



Finally, by means of irrigation water two crops of rice could be grown 

 on the same land in the course of a year and the yield of the land thereby 

 doubled. 



DITCHES AND LEVEES. 



The most economical way of digging ditches and constructing levees is 

 to make use of good strong plows, scoops, and grading machines (fig. 9). 

 With a plow, a scoop, and a pair of mules a man can do as much work in 

 a day as he could do in two weeks with a spade. Where the operations are 

 to be conducted on a large scale and the planter can afford to purchase a 



FIG. 9. An ordinary scoop or road scraper. 



road machine, it would be well for him to do so, as it is very useful 

 in making the main channel or canal for conducting the water from the 

 water supply to the field. 



In building the levees around the different cuts the aim should be to 



