272 Bulletin 90 



TOPPING 



The topping of cotton, or the pinching- or cutting off the terminal 

 buds, has been advocated and practiced by many. as a means of pre- 

 venting excessive plant growth and as a means of stimulating the for- 

 mation of bolls. The results secured from this practice have been con- 

 flicting. In some cases, particularly on heavy rich ground, reports 

 state that the practice has been profitable. Up to the present time no 

 reports have been received showing that the practice is profitable on 

 medium or thin lands. Properly grown cotton plants should not re- 

 quire topping. Uncontrollable conditions, such as a high water table 

 or excessive rains, may make topping desirable. If topping is to be 

 practiced at all, it is recommended that it be delayed until about the 

 middle of August. Early topping, instead of checking plant growth, 

 may stimulate the production of vegetative branches if growing con- 

 ditions are favorable, while late topping ought to further the develop- 

 ment of bolls already set. 



FERTILIZING COTTON 



Considerable interest has developed in the last two years in the 

 fertilizing of cotton. For the most part the desert soils in Arizona 

 are deficient in nitrogen, and it is possible that on such soils nitrogen 

 fertilizers may prove beneficial. Experience indicates that desert land 

 that has been plowed and irrigated a number of times and brought 

 into a condition of good tilth will produce better cotton than similar 

 land that has received but little cultivation. This is shown by the fact 

 that the second crop of cotton on desert soil is often better than the 

 first crop. On old lands that have grown legumes for a number of 

 years, if any fertilizer proves profitable, it will be one containing phos- 

 phorus. Nitrogen fertilizers probably will not pay on such lands. 

 It is not advised that farmers buy phosphorus fertilizers or any other 

 fertilizers on an extensive scale until they have first tried them on small 

 plots in their own fields. Applications of 200 to 500 pounds of acid 

 phosphate per acre at the time the cotton is planted promise to give 

 beneficial results ; yet several farmers who have made small tests failed 

 to note appreciable benefits, and tests on the Salt River Valley Experi- 

 ment Station have so far failed to give increases in yield. 



During the last year many questions have been asked regarding 

 the advisability of planting cowpeas in the growing cotton for the pur- 

 pose of increasing the available nitrogen. This recommendation has 

 usually been to the effect that the cowpeas should be planted about 

 thirty days after the cotton is planted, and then destroyed about the 



