Relation of Weather to Crops 53 



fields; alfalfa is, therefore, best planted during the cooler weather 

 of fall, winter, or spring, when evaporation is not so great. The 

 conditions are then usually such that the seed may be planted in a 

 moist and well prepared seed bed that will retain its moisture long 

 enough to bring up the plants without further irrigation. When, 

 however, a second irrigation is necessary, the ground does not bake 

 so quickly and the seedlings will, for the most part, get through 

 the surface before a crust is formed. Good stands of alfalfa that were 

 seeded in winter (late November to February 1) are common, but 

 seeding during t^is season is risky on account of frost injury. If 

 a hard freeze occurs soon after the alfalfa gets through the surface, 

 when it has yet but two leaves, and especially when the soil is damp 

 from recent irrigation or winter rains, a large proportion of the young 

 plants may be killed. The writer knows of an instance where a 

 beautiful stand of forty acres was destroyed in this way. After 

 the young plants have three or more leaves, no degree of cold 

 occurring in Arizona is likely to injure them. 



Good stands can be secured during February and March. 

 Spring planting, however, is open to the disadvantage that the 

 young plants go into the hottest and driest parts of the summer 

 (May and June) with poorly developed root systems. Th- tap- 

 roots have not yet penetrated deeply and if a shortage of water 

 should occur, which is more liable at this season than any other, 

 the plants suffer from drought and the stand is apt to be seriously 

 depleted. Moreover, spring-planted alfalfa gives but slight yields 

 the first season and requires more frequent irrigation and greater 

 attention than that which is planted earlier. 



The best time to plant alfalfa is from September to November, 

 inclusive, according to season and locality. Planted at this time, 

 the young seedlings, favored by the mild temperatures of our 

 autumn cHmate, get sufficient start not to be injured by the sharp 

 frosts of December and January. The labor and expense of frequent 

 irrigations are made unnecessary by low evaporation during the 

 cool weather, and this is further reduced by the moisture obtained 

 from whatever winter rains that may occur. While the tops grow 

 but little during the cold season, the root systems are developing 

 steadily. The alfalfa, therefore, goes into the hot, dry period of 

 early summer with wide-spreading and deeply penetrating roots. 

 This enables it to withstand heat and drought and return profitable 

 yields even during the first year of its occupation of the soil. 



Amount to sow. — Plump, well matured alfalfa seed should number 

 about 200,000 to the pound. Where 15 pounds are sown to the 



