1916] HORTICULTURE. 637 



at the rate of 3G0 lbs. per acre increased tlie yield for 1915 to 18.6 bii. on the 

 unlimed land and to 20 bu. on the limed land. One hundred lbs. nmriato of 

 potash added to the acid jihosphate produced a further increase of a bushel 

 per acre for the 22 years in both cases, and tlie complete fertilizer in the same 

 quantities given for the experiments above described increased the yield for 

 1915 to 33 bu. on both unlimed and limed land and to 27.5 bu. for the 22-year 

 average, the nitrate of soda partly taking the place of lime. 



In addition to these plat experiments, a 40-acre field at the station has 

 grown 10 acres of wheat annually for 22 years in a 4-year rotation with corn, 

 oats, and clover. The first 10 years the wheat land was top-dres.sed before 

 seeding with about 10 tons of barnyard manure per acre and the 10-year 

 average yield was 20 bu. Then the manure was reinforced with about 40 ll)s. 

 of acid phosphate per ton and spread on clover sod which was plowed under 

 for corn. The corn received a dressing of about 1.5 tons of limestone per acre 

 and the wheat received 350 lbs. per acre of a fertilizer made up of steamed 

 bone meal, acid phosphate, and .muriate of potash with 50 lbs. of nitrate of 

 soda added in April if the growth was not too rank. The wheat yield on this 

 field for 1915 was nearly 36 bu., and the average yield for the past 10 years 

 34 bu. per acre. 



HORTICULTURE. 



[Seport of horticultural investigations], W. H. Lawrence and S. B. John- 

 son (Arizona Sta. Rpt. 1915, pp. 539-552). — A progress report on various lines 

 of work for the year. 



Studies with processed fabrics prepared for use in protecting citrus trees 

 during injurious low temperatures (E. S. R., 33, p. 48) were continued, and 

 observations reported as to semitransi)areucy, air-tightness of covers, radiation 

 of heat from covers, distribution of heat, and changes of temperature due to 

 wind currents under covers. 



The results are given of fruit-thinning experiments conducted with a number 

 of young date trees. These results, together with observations and study of 

 the influence of thinning fruit on old trees, led to the following conclusions: 



" The date palm is a plant having a natural method of thinning fruit. The 

 fruit begins to drop shortly after pollination takes place and continues long 

 after the reduction to one of the three carpels occurring in each floral cup, some- 

 times continuing into the harvest period. Trees not bearing a maximum crop 

 will mature fruit to size and quality with little or no change in earliness of 

 ripening. Natural methods of thinning fruit early in the season have a greater 

 tendency to increase the size of the berry, in proportion to the number in the 

 bunch, than is induced by artificial removal of a number of berries later in the 

 season following natural thinning. Artificial thinning may be done to ad- 

 vantage only after the bearing capacity of a tree has been determined. 



" Thinning may be done most effectively and quickly by the removal of an 

 entire fruiting branch. This method not only increases the weight of the berry 

 but of the entire bunch, including the brush. Thinning may be done profitably 

 when the tree is carrying in excess of a maximum load. Under these condi- 

 tions bunches with one-half the spikes removed begin to ripen their fruit earlier 

 than the nonpruned bunches, which come second in order, while those with one- 

 half of each spike removed mature the fruit more slowly. In general, fruit of 

 inferior size occurs on the slender-stemmed bunches, bearing weak branches." 



In a cultural test of winter radishes the white varieties gave the best results. 

 For rate of maturity and length of time the roots continue to grow and remain 

 edible, White Icicle was the first choice. 



