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MISC. PUBLICATION- 3 6 9, U. S. PEPT. OF AGRICULTURE 



plants varies with the age of the plant are not explainable at the pres- 

 ent time, but a very likely cause is the availability of these elements 

 or the rate at which they become available in the soil. Although it 

 has long been known that forage and other crops must be harvested 

 at certain stages of development so that they will be palatable and so 

 as to obtain maximum yields of dry matter, comparatively little 

 attention has been given to obtaining maximum yields of nutrients. 

 As the plant matures, particularly beyond the bloom stage, the per- 

 centage of digestible nutrients and of available mineral matter may 

 drop so low as to nullify completely the effects of increased yield of 

 total dry matter. 



CLIMATE 



Climate was shown by LeClerc and coworkers (336, 338, 339) to 

 be of greater influence on the protein content and slightly more influ- 

 ence on the phosphorus and potassium contents of wheat grain than 

 was the soil. Unfortunately, their work did not include the com- 

 position of the straw nor of any part of the plant that would respond 

 more accurately to soil deficiencies than does the seed. The work is 

 of interest, however, because of the procedure, which consisted of 

 transporting fairly large amounts of soils from two of three localities 

 (California, Kansas, and Maryland) to the third locality for plot tests. 



In similar experiments with sugarcane, Borden (83) failed to demon- 

 strate the predominance of climate over that of soil as an influence 

 on the mineral composition of the plant. The two localities for this 

 experiment, although only 3 miles apart in Hawaii, differed markedly 

 in climatic conditions, for, although the temperature range is about 

 the same for both places, Manoa receives nearly four times as much 

 rainfall and 40 percent less sunshine than does Makiki. Tubs of 

 soil from both localities were planted with three different varieties of 

 sugarcane, which were allowed to grow at each locality. The results, 

 classified as to soils and as to localities, are given in table 18. The 

 climate at Makiki was apparently quite favorable for the production 

 of sugar, but while the cane grown at Manoa has a slightly higher potas- 

 sium and phosphorus content than has that grown at Makiki, the 

 dominating influence of soils is evident, for the average content of 

 these minerals in the cane grown in the Makiki soil at both localities 

 is much higher than that of cane grown in the Manoa soil. 



Table 18. — Influence of soil and of climate on the sugar, phosphorus, and potassium 



content of sugarcane 



[Borden (83)] 









Items 



Sugar 

 produced 



P in 100 cc. 



of juice 



K in 100 cc. 

 of juice 



Averages by soils: 



Makiki soil. . __ _______ 



Pounds 

 5.41 

 6.26 



8.93 



2.73 



Percent 

 0.044 

 .014 



.027 

 .031 



Percent 

 21 



Manoa soil .: 



10 



Averages by localities: 



Makiki soil ________ 



134 



Manoa soil__ ___ _ 



.172 







Kunze (322) in 1914 determined the phosphorus, potassium, and 

 calcium content of oats grown in normal and dry years in Germany. 

 No significant differences were observed in the phosphorus content 

 of the grain, but about half as much phosphorus was found in the 



