Irrigation has been developed to a great extent in arid and semi-arid regions of the West, but not until recent years have intensive growers in the East taken a general interest in the subject. The quickened interest has been due mainly to improved methods and the increased importance of avoiding losses from drouth. Notwithstanding the improvement in implements, production costs more than ever before, and men appreciate more fully the importance of controlling all conditions, thus making every crop a success so far as production is concerned. It seems inconsistent for an intensive grower to spend large sums of money in providing right conditions in every respect except one, which he neglects entirely. Of the factors contributing to the growth of a healthy plant, water is the most important. Scientists have been telling us this for years and it seems strange that practical men have been so slow to grasp the idea. But conditions have changed and vegetable growers in all sections of the United States are giving attention to artificial methods of watering. Hundreds of gardeners every year are installing irrigation systems. The movement is particularly active near the large cities, but it is spreading into all communities where vegetables are grown for commercial purposes.
Throughout the eastern part of the United States there are thousands of opportunities for successful irrigation. Creeks, rivers, ponds and lakes furnish an abundant supply of water, which, in many instances, is available at slight cost. It is not uncommon to find conditions where water might be conducted to the garden by gravity, so there would be no expense for pumping. In many more instances a lift of 5 to 15 feet would put the water on land admirably adapted to garden crops. Near the cities water can usually be secured at reasonable prices, and at some places for as low as 4 or 5 cents a thousand gallons. The late W. W. Rawson, the well-known New England gardener, claimed that an intensive grower could well afford to pump water at a cost of 10 cents a thousand gallons. If it were a matter of saving a crop from almost total loss it might pay to use water at double this cost.
Before entering into a practical discussion of the subject of irrigation the student or the reader should fully realize what an important part water plays in the growth of plants. (1) It is a powerful solvent of plant foods. No matter how fertile a soil may be naturally, or how much manure or fertilizer may be added, such foods are valueless without water to dissolve them. Both stable manures and fertilizers often fail to give increased yields because of insufficient soil moisture. (2) Water not only serves as a solvent, but it holds in solution organic acids which are more powerful solvents than water alone. (3) Water is essential to the life of friendly bacteria. (4) Water serves as a vehicle in the distribution of plant foods in the soil.
Its functions in the plant are equally important. (1) Water enters largely into the composition of all garden products. Many vegetables contain over 90 per cent of water. (2) Water is also a medium in the conveyance of food in the plant, so that enormous quantities transpire from the leaves. Several hundred pounds of water are required to produce every pound of dry matter. It is claimed that a well-developed hill of cucumbers will use half a barrel of water in three days. (3) The transpiration of water has an important relation to the fixation of carbon from the atmosphere.
Irrigation is an insurance, for rainfall is uncertain, and the gardener never knows when it may become necessary to start the pumps or open the water lines to prevent loss. It is a great satisfaction to realize that one can be practically independent of the natural rainfall.
Seeds cannot germinate without moisture. It often occurs that plants do not come up promptly because of a lack of moisture. This trouble may be easily avoided by an up-to-date system of irrigation. Again, transplanting is often an uncertain operation. Hot, drying winds and bright sunshine, after planting, may cause an almost total loss of the plants, while irrigation would save them.
Absolute control of moisture conditions makes it possible to secure large yields, better quality and earlier maturity. These three advantages are of immense importance from a business standpoint. All classes of vegetables should grow unchecked, and this is impossible when moisture is wanting.
Drouths occur in all sections almost every year. They are disastrous to satisfactory returns. It happens not infrequently that $200 or even more an acre is lost during protracted drouth. This would more than pay for the installation of the most approved system and the application of water during the period of drouth.
It has been previously stated that the rate of applying stable manures and commercial fertilizers may be reduced when irrigation can be practiced. This may not be the best business policy, but it is unquestionably true that irrigation is often worth much more than any amount of manure or fertilizer that can be applied.
Numerous experiments have been made that show the value of irrigation. For example, at the Michigan Station an experiment was conducted on a 10-acre plot. Tomatoes and potatoes were irrigated four times and the other vegetables in the test three times, about an inch of water being applied each time, while the same vegetables were grown under natural conditions. "The cabbage crop suffered most of all, perhaps, as where water was not used less than half formed heads of marketable size, and these were small. Of the Early Jersey Wakefield there were 5,000 more marketable heads to the acre obtained by the use of water and the weight was 11,325 pounds greater. Early Summer showed a gain of 4,826 heads and 21,959 pounds in weight. At 2 cents a head the gain to the acre would average nearly $100. A gain of 200 bushels an acre was obtained with the irrigated tomatoes, which at 50 cents a bushel would amount to $100, or ten times the expense of applying the water. Snap beans showed a gain of 300 bushels and early peas of 100 bushels an acre. Four applications of water to potatoes gave a gain of 129 bushels an acre. Marked improvement in quality was also noticeable with peas, beans and cabbage." Such gains, of course, could not be expected in normal seasons.