1686 



IRRIGATION 



IRRIGATION 



2. Watering by sub-irrigation assures an abundant 

 and uniform supply of water to all parts of the bed. Per- 

 fect construction of the benches is assumed in this case, 

 but with such construction watering becomes almost 

 automatic, the only care necessary being to look after 

 such portions of the beds as may, by position, be sub- 

 ject to unusual conditions of air or sunlight. 



3. Where sub-irrigation is practised in the greenhouse, 

 the surface of the soil does not become compacted, but 

 retains its original loose, friable condition. It is true 

 that where frequent syringing is practised the sur- 

 face of the soil becomes more or less hardened, but not 

 to the extent that occurs in surface-watering, and the 

 condition is easily remedied, whereas in the other case 

 it is not. It follows that a heavier soil may be used for 

 sub-irrigation than with surface-watering. 



Still other considerations might be urged in favor of 

 this method of watering, but many of them would apply 

 to special cases only. Regarding the effect of the method 

 upon insects and diseases, but little can be said. Let- 

 tuce rot is less prevalent upon sub-irrigated plats than 

 upon those which are surface-watered, but in extreme 

 cases plants succumb to the disease, whichever method 

 of watering is practised. Munson found that radishes 

 suffered more from the attacks of millipedes upon sub- 

 irrigated plats than upon plats watered in the usual 

 manner. Nematodes work upon the roots of roses, 

 whichever way the plants are watered. The manner of 

 watering has no apparent effect upon the red-spider. 

 Even in houses watered wholly by sub-irrigation this 

 pest is 'no worse than in houses where the water is 

 applied to the surface of the soil. It may be said, how- 

 ever, that nearly all classes of plants are more easily 

 kept in a healthy growing condition, and are thus better 

 able to resist enemies of all sorts, when sub-irrigated 

 than when supplied with water in the ordinary way. 



This method of applying water to plants in green- 

 house benches has now been sufficiently tested to 

 determine its value. All that now remains is to devise 

 ways and means to utilize what is known concerning it. 

 The adaptation to suit particular cases must be made by 

 individuals, but this will be far easier in the future than 

 in the past, because better methods of construction 

 prevail than formerly. The success of sub-irrigation in 

 the greenhouse is now simply a question of mechanics. 



W. J. GREEN. 



Irrigation for vegetable-growers and other gardeners. 



In this Cyclopedia, it is not the purpose to discuss 

 the general agricultural practice of irrigation but rather 

 those phases that apply particularly to gardening 

 operations. In arid countries, the garden irrigation 

 practice will naturally follow the general methods of 

 the region. In humid countries or regions, the prac- 

 tices may be very special. In the growing of straw- 

 berries and garden vegetables in the eastern United 

 States, special irrigation practices are developing, and 

 these may be briefly considered. 



Success in crop-growing depends on many factors. 

 If one of these factors is deficient to such an extent as 

 to limit the crop in yield or quality, no excess of the 

 other factors will suffice to make up the lack. Thus, 

 if nitrogen is present in the soil in only very minute 

 quantities, no amount of phosphorus or potash will 

 enable the plant to offer the husbandman a worthy 

 harvest. In vegetable-gardening the amounts expended 

 in making the various conditions favorable are rela- 

 tively large. Accordingly, if one factor is deficient, 

 the loss is very heavy. Perhaps the moisture factor is 

 more often to be charged with the responsibility for 

 poor returns than any other single deficiency. 



We are told that 10 inches of rainfall in a year is 

 sufficient for the production of successful crops under 

 the methods of dry-farming. We are told that 20 

 inches of precipitation is sufficient for the production 



of successful crops under ordinary farm methods 

 provided it is well distributed throughout the year. 

 Most places in the eastern states enjoy from 30 to 40 

 inches of rainfall a year. Nevertheless, there is hardly 

 a season in which crops, and especially vegetable 

 crops, do not suffer for lack of moisture during at least 

 a month. The solution of this seeming paradox lies 

 in the fact that our rainfall is poorly distributed through 

 the growing season. We may have as much as 9 inches 

 in a single month, and occasionally less than 1 inch. 

 The total for three months in succession may be as low 

 as 4 inches. Even such a condition as this does not 

 frequently appear upon the weather records; for a 

 period of drought may be followed by torrential rains 

 sufficient to make up the average rainfall after the 

 harm is done. 



In view of these conditions, it is necessary that the 

 vegetable-grower take measures to prevent the loss, 

 through lack of sufficient moisture, of all the time and 

 money that he has invested in land, tillage, fertilizer, 

 seed, planting, cultivation, and care, to say nothing 

 of the loss of the profit which he may reasonably expect. 

 He may accomplish much by so managing his land as 

 to conserve to the utmost the rainfall that is his. He 

 may leave his land rough over winter to prevent run- 

 off, he may harrow frequently till planting time, he 

 may maintain an effective mulch throughout the sea- 

 son; even so through lack of rainfall through absence 

 of moisture to be conserved he may lose his whole 

 crop or so much of it that he might better have left 

 the ground unplanted. 



Within the past ten years, the possibilities of irriga- 

 tion have become apparent to many vegetable-pro- 

 ducers. They have found that the elimination of the 

 moisture factor as one of the obstacles to successful 

 crop-production has made possible larger yields, better 

 quality and early maturity, with all the advantages in 

 economy of management and in returns that accom- 

 pany these gains. Irrigation has proved of especial value 

 when sowings are made in midsummer for autumn 

 maturity, at transplanting time, and as crops approach 

 harvest. 



Surface irrigation is practised to a very limited extent 

 in the East. The method consists in conducting water 

 along the end of the plat to be irrigated and allowing 

 it to flow into furrows between the rows of the crop. 

 It is best to permit the water to reach the far end of the 

 row as soon as possible and then allow it to be absorbed 

 evenly throughout the length. If this is not done, the 

 part of the field next the supply-ditch will receive 

 much more water than the remainder. This form of 

 irrigation is useful on level land where there is abun- 

 dance of water and where the soil is suitable. Light 

 soils drink up the moisture so rapidly that an even 

 distribution of the water is difficult and uniform results 

 may not be secured. 



Boston gardeners employ hose in watering their 

 plantations. A system of underground pipes is installed 

 in such a way that 50 feet of hose will reach all parts of 

 the block. The cost of installation for the first acre is 

 reported in a Massachusetts bulletin as being about 

 $65 and successive acres may be piped for approxi- 

 mately $50. An acre may be given 1 inch of water by 

 one man, using 1 %-inch hose, in five or six hours. Hose 

 irrigation is objectionable on account of the disturbance 

 of plants, the danger of injury to the physical condi- 

 tion of the soil, the amount of labor, and the frequent 

 replacement of hose. 



Sub-irrigation is practised in certain districts of 

 Florida and on some muck land areas in the North. 

 In the Sanford, Florida, district, which is typical, the 

 water-supply is from artesian wells. The land is under- 

 laid with tile which is accessible at both its highest 

 and its lowest points. Thus it serves for both watering 

 and drainage. The impervious bottom which under- 

 lies the soil is essential for the successful operation of 



