FIELD CROPS, 625 



It is Stated that carbou particles and insoluble salts are absolutely harmless 

 to foliage in all its stages, but that leachings of soot, etc., as soluble salts, 

 particularly sulphids and sulphites, cause a degree of injury to the foliage. 



Pine and fir needles, while sensitive to sulphur dioxid, are not injured by 

 sulphur trioxid in a dry medium, and in a damp atmosphere the injury is slow 

 and somewhat limited, as is also the case of tender young foliage, which is more 

 or less moist. Some fluorin compounds tested proved to be injurious. Light 

 access, species, succulence, dilution with air, turgesceuce of guard cells, time 

 of casting leaves, etc., modify the influence of gases on foliage. The time of 

 greatest sensitivity appears not to be in winter or during the most abundant 

 precipitation, but during the greatest activity of the leaves in summer. 



FIELD CROPS. 



Tillage and rotation experiments at Nephi, Utah, P. Y. Caruon (U. S. 

 Dcpt. Agr. Bui. 151 (1915), pp. .'i5, figs. 21). — This bulletin gives results of work 

 carried on jointly by the Utah Station and this Department covering the period 

 from 1908 to 1913, inclusive. See also a previous note (E. S. R., 30, p. 135). 

 A description of the station and of the climatic conditions is included. 



A summary of the tests that deal with time and depth of ])lowing, cultiva- 

 tion of fallow, seeding, cultivation and harvesting of the crop, frequency of 

 cropping, and diversity of crops in rotation is given as follows : " The average 

 results for five years, 1909 to 1913, inclusive, show that spring plowing was 

 better than fall plowing for moisture conservation, in yield of grain, and in 

 cost of producing the crop. Spring plowing gave an average yield of 18.5 bu. 

 per acre, as compared with 16.8 bu. for fall plowing. Owing to this difference 

 in yield and the lower cost of producing the crop, spring plowing gave a net 

 a.cre profit of $3.03 more than fall plowing. 



'• The results of five years show that there was no advantage in deep plowing 

 or subsoiling over shallow plowing so far as moisture conservation is con- 

 cerned. There was no material difference in the yields obtained from plats 

 plowed at different depths, varying from 5 to 18 in. The highest average 

 yield was obtained from plats plowed 10 in. deep, and the lowest average yield 

 was from the plats subsoiled 18 in. deep, while the 5-in. plowing yielded higher 

 than the 15-in. subsoiling. 



" One year's results from a test of deep fall plowing and shallow spring 

 plowing compared with shallow fall plowing and deep spring plowing show no 

 difference in soil moisture and but slight difl'erence in yield. 



"The results of five j-ears' experiments on fall-plowed fallow show that 

 the moisture of the cultivated plats remained practically the same throughout 

 the season, while that of the uncultivated plats rapidly declined, until by 

 fall it was reduced to a comparatively low point. It is probable that weeds 

 and volunteer grain were important factors in this loss of moisture. The aver- 

 age acre j-ield of the cultivated plats was 17 bu., as comparetl with 13 bu. on 

 the uncultivated plats. 



" The results of one season on spring-plowed fallow show no difference in 

 the moisture content of the plats cultivated or not cultivated. The yields, 

 11.9 and 9.5 bu. per acre, favor the noncultivated plat. 



" The results of 10 years show no correlation between the time of sowing 

 winter wheat and the yield, but the best yields have usually been obtained 

 from plats seeded between September 1 and October 15. There was no sig- 

 nificant difference between the average moisture content of the plats for any 

 one or for all years. The chief problem in the time-of-seeding tests of winter 

 wheat now seems to be a mechanical pue involving some improvement of the 



