120 HORTICULTURE, FORESTRY, FLORICULTURE 



of a large apple orchard company in Montana states that no appreci- 

 able effect is noticed on apple trees as a result of growing potatoes, 

 cabbage, beans, onions, and other vegetables between the trees pro- 

 viding the intercrops are well cultivated and irrigated. In the fruit 

 districts of Washington, intercropping is a common practice. In 

 1907 a fruit grower raised on 10 acres of two-year-old trees canta- 

 loupes, tomatoes, peppers, cucumbers, corn, radishes, beans, peas, 

 potatoes and turnips, all of which netted him $2,086.50, or an aver- 

 age of $208.65 an acre. 



While opinions differ regarding the wisdom of growing such 

 crops as have been named between the tree rows, most fruit growers 

 are convinced of the beneficial effects of cover crops. 



The cost of such cover crops as peas, vetch, or clover includes 

 the seed, the labor of sowing it, the water, and the time required to 

 apply it. These items amount to from $2.50 to $3.25 per acre. 

 Twenty tons per acre of green material is perhaps an average crop. 

 In this tonnage there would be about 160 pounds of nitrogen, which 

 at 20 cents per pound represents a value of $32 per acre for a cover 

 crop like vetch. 



When water is used outside of the regular irrigation period or, 

 which is in many cases equivalent, outside of the growing season, it 

 is termed winter irrigation. Over a large part of the arid region the 

 growing season is limited by low temperatures to 150 days, or less, 

 and when the flow of streams is utilized only during this period much 

 valuable water runs to waste. 



It was for the purpose of utilizing some of this waste that the 

 orchardists of the Pacific coast States and Arizona began the prac- 

 tice of winter irrigation. The precipitation usually occurs in winter 

 in the form of rain, and large quantities of creek water are then 

 available. This water is spread over the orchards in January, Febru- 

 ary, and March, when deciduous trees are dormant. The most fa- 

 vorable conditions for this practice are a mild winter climate ; a deep, 

 retentive soil which will hold the greater part of the water applied ; 

 deep-rooted trees ; and a soil moist from frequent rains. 



In the colder part of the arid region winter irrigation is being 

 practiced with satisfactory results. The purpose is not only to store 

 water in the soil but to prevent the winterkilling of trees. Experi- 

 ence has shown that it is not best to apply much water to orchards 

 during the latter part of the growing season, since it tends to produce 

 immature growth which is easily damaged by frost. In many of the 

 orchards of Montana no water is applied in summer irrigation after 

 August 20. Owing, however, to the prevalence of warm chinook 

 winds, which not only melt the snow in a night, but rob the exposed 

 soil of much of its moisture, one or two irrigations are frequently 

 necessary in midwinter. (F. B. 404, 1910.) 



DRAINAGE OP IRRIGATED LANDS. 



Lands 'Needing Drainage. Irrigated lands needing drainage 

 may be divided into three classes: (1) Those injured by excess of 

 water only; (2) Those affected by an excess of both water and alkali ; 

 (S) Those having an excess of alkali only. 



